Broad beam transmission data for the shielding of brachytherapy facilities

Dosimetry comparison between TG-43 and Monte Carlo calculations using the Freiburg flap for skin high-dose-rate brachytherapy

Abstract Purpose The purpose of this work was to evaluate whether the delivered dose to the skin surface and at the prescription depth when using a Freiburg flap applicator is in agreement with the one predicted by the treatment planning system (TPS) using the TG-43 dose-calculation formalism. Methods and Materials Monte Carlo (MC) simulations and radiochromic film measurements have been performed to obtain dose distributions with the source located at the center of one of the spheres and between two spheres. Primary and scatter dose contributions were evaluated to understand the role played by the scatter component. A standard treatment plan was generated using MC- and TG-43-based TPS appl…

A dosimetric study of Leipzig applicators.

Purpose: To obtain the absolute dose-rate distribution in liquid water for all six cup-shaped Leipzig applicators by means of an experimentally validated Monte Carlo (MC) code. These six applicators were used in high-dose-rate (HDR) afterloaders with the “classic” and v2 192Ir sources. The applicators have an inner diameter of 1, 2, and 3 cm, with the source traveling parallel or perpendicular to the contact surface. Methods and materials: The MC GEANT4 code was used to obtain the dose-rate distribution in liquid water for the six applicators and the two HDR source models. To normalize the applicator output factors, a MC simulation for the “classic” and v2 sources in air was performed to es…

Monte Carlo calculation of dose rate distributions around 192Ir wires.

Monte Carlo calculations of absolute dose rate in liquid water are presented in the form of away-along tables for 1 and 5 cm 192 Ir wires of 0.3 mm diameter. Simulated absolute dose rate values can be used as benchmark data to verify the calculation results of treatment planning systems or directly as input data for treatment planning. Best fit value of attenuation coefficient suitable for use in Sievert-integrals-type calculations has been derived based on Monte Carlo calculation results. For the treatment planning systems that are based on TG43 formalism we have also calculated the required dosimetry parameters.

Exclusive MRI-based tandem and colpostats reconstruction in gynaecological brachytherapy treatment planning

Purpose: According to the GYN GEC-ESTRO Recommendations, MRI is needed with the modality of T2 weighted. CT-MR compatible tandem Plus colpostats (T/C) (Nucletron) is widely used in cervical brachytherapy. The major challenge of MRI is the lack of dummy catheters. Therefore, an additional imaging modality is usually required. One disadvantage of sliced-based reconstruction is that resolution in longitudinal directions can be affected by the slice thickness. The aim of this study is to present a modified T/C applicator in which the catheter visibility is significantly improved. Methods and materials: A modification to the existing T/C applicator has been made available, increasing the cathete…

A program for the independent verification of brachytherapy planning system calculations

Purpose: In this work a spreadsheet based program is presented that to a large extent independently verifies the calculations of individual plans of brachytherapy treatment planning systems for low dose rate, high dose rate and pulsed dose rate techniques.Material and methods: The verification program has been developed based on workbooks/spreadsheets. The treatment planning system output text files are automatically loaded into the new program, allowing the use of the source coordinates, the desired calculation point coordinates, and the dwell times of a patient plan. The source strength and the reference dates are entered by the user and then dose points calculations are independently per…

Design and evaluation of a HDR skin applicator with flattening filter

The purposes of this study are: (i) to design field flattening filters for the Leipzig applicators of 2 and 3 cm of inner diameter with the source traveling parallel to the applicator contact surface, which are accessories of the microSelectron-HDR afterloader (Nucletron, Veenendaal, The Netherlands). These filters, made of tungsten, aim to flatten the heterogeneous dose distribution obtained with the Leipzig applicators. (ii) To estimate the dose rate distributions for these Leipzig+filter applicators by means of the Monte Carlo (MC) method. (iii) To experimentally verify these distributions for prototypes of these new applicators, and (iv) to obtain the correspondence factors to measure t…

Study of low-lying states of 51V, 50,52,53Cr, 59Co and 63Cu nuclei by α-particle inelastic scattering

Abstract Differential cross sections for inelastic scattering of α -particles to various levels in 51 V, 50,52,53 Cr, 59 Co and 63 Cu have been measured at incident α-particle energy of 25 MeV. Data corresponding to the odd nuclei have been analyzed in terms of the weak-coupling model and the symmetric rotor model. Even-even nuclei data have been analyzed in the framework of the coupled channels formalism in terms of two collective models: the harmonic vibrational model and the symmetric rotor model. Model predictions reproduce quite satisfactorily experimental angular distributions.

On the use of the absorbed depth-dose measurements in the beam calibration of a surface electronic high-dose-rate brachytherapy unit, a Monte Carlo-based study.

PURPOSE To evaluate the use of the absorbed depth-dose as a surrogate of the half-value layer in the calibration of a high-dose-rate electronic brachytherapy (eBT) equipment. The effect of the manufacturing tolerances and the absorbed depth-dose measurement uncertainties in the calibration process are also addressed. METHODS The eBT system Esteya® (Elekta Brachytherapy, Veenendaal, The Netherlands) has been chosen as a proof-of-concept to illustrate the feasibility of the proposed method, using its 10 mm diameter applicator. Two calibration protocols recommended by the AAPM (TG-61) and the IAEA (TRS-398) for low-energy photon beams were evaluated. The required Monte Carlo (MC) simulations w…

Monte Carlo calculation of the TG-43 dosimetric parameters of a new BEBIG Ir-192 HDR source

Background and purpose: High dose rate (HDR) brachytherapy is a highly extended practice in clinical brachytherapy today. Quality dose rate distribution datasets of the HDR sources used in a clinical treatment are required. Because of the different source designs, a specific dosimetry dataset is required for each source model. In the recently published BRAPHYQS-ESTRO Report, an overview of available dosimetric data for all HDR Ir-192 sources is given, pointing out the lack of data for one of the sources that is used by the BEBIG MultiSource afterloading system (BEBIG GmbH, Germany). The purpose of this study is to obtain detailed dose rate distributions in liquid water media around this sou…

Backscatter and Transmission through a Lead Shield Used in Surface and Interstitial HDR Brachytherapy

Dosimetric characteristics of backscattered electrons in lead.

In electron beam therapy, tissue overdose due to electrons backscattered from lead has been profusely studied. To quantify this dose enhancement effect, an electron backscatter factor (EBF) was defined as the ratio of dose at the tissue-inhomogeneity interface with and without the scatterer present. The dependence of the EBF on energy at the scatterer surface is not well known for energies lower than 3 MeV which is the most frequent clinical situation. In this work, we have done Monte Carlo calculations with the GEANT code to study EBF in lead at this energy range. The applicability of this code and the developed procedure for dose estimation has been experimentally verified. The dependence…

Novel simple templates for reproducible positioning of skin applicators in brachytherapy.

Purpose : Esteya and Valencia surface applicators are designed to treat skin tumors using brachytherapy. In clinical practice, in order to avoid errors that may affect the treatment outcome, there are two issues that need to be carefully addressed. First, the selected applicator for the treatment should provide adequate margin for the target, and second, the applicator has to be precisely positioned before each treatment fraction. In this work, we describe the development and use of a new acrylic templates named Template La Fe-ITIC. They have been designed specifically to help the clinical user in the selection of the correct applicator, and to assist the medical staff in reproducing the po…

Calculated organ doses using Monte Carlo simulations in a reference male phantom undergoing HDR brachytherapy applied to localized prostate carcinoma

Purpose : The aim of this study was to obtain equivalent doses in radiosensitive organs (aside from the bladder and rectum) when applying high-dose-rate (HDR) brachytherapy to a localized prostate carcinoma using60Co or 192 Ir sources. These data are compared with results in a water phantom and with expected values in an infinite water medium. A comparison with reported values from proton therapy and intensity-modulated radiation therapy (IMRT) is also provided. Methods : Monte Carlo simulations in Geant4 were performed using a voxelized phantom described in International Commission on Radiological Protection (ICRP) Publication 110, which reproduces masses and shapes from an adult reference…

SU-GG-T-70: A Dosimetric Study of the MicroSelectron HDR Ir-192 Brachytherapy Source

Purpose: Recently the manufacturer of the mHDR‐v2 HDR Ir‐192 brachytherapy source clarified design changes that may alter the existing dosimetric data for this source. The object of this study was to obtain new dose rate tables following the TG‐43 formalism and to provide these data in close proximity to the source with high spatial resolution including the electron dosimetric contributions from Ir‐192 disintegration. Methods and Material: To study the source we used three different Monte Carlo codes: MCNP5, GEANT4, and Penelope. The source was located inside a 40 cm radius water phantom. Dose and kerma were obtained using 0.1 mm thick voxels to provide high‐resolution dosimetry near the so…

Physics Contributions Evaluation of interpolation methods for TG-43 dosimetric parameters based on comparison with Monte Carlo data for high-energy brachytherapy sources

Purpose: The aim of this work was to determine dose distributions for high-energy brachytherapy sources at spa- tial locations not included in the radial dose function gL(r) and 2D anisotropy function F(r,θ) table entries for radial dis- tance r and polar angle θ. The objectives of this study are as follows: 1) to evaluate interpolation methods in order to accurately derive gL(r) and F(r,θ) from the reported data; 2) to determine the minimum number of entries in gL(r) and F(r,θ) that allow reproduction of dose distributions with sufficient accuracy. Material and methods: Four high-energy photon-emitting brachytherapy sources were studied: 60Co model Co0.A86, 137Cs model CSM-3, 192Ir model I…

Determination of consensus kQ values for megavoltage photon beams for the update of IAEA TRS-398

The IAEA is currently coordinating a multi-year project to update the TRS-398 Code of Practice for the dosimetry of external beam radiotherapy based on standards of absorbed dose to water. One major aspect of the project is the determination of new beam quality correction factors, kQ, for megavoltage photon beams consistent with developments in radiotherapy dosimetry and technology since the publication of TRS-398 in 2000. Specifically, all values must be based on, or consistent with, the key data of ICRU Report 90. Data sets obtained from Monte Carlo (MC) calculations by advanced users and measurements at primary standards laboratories have been compiled for 23 cylindrical ionization chamb…

Dosimetric evaluation of internal shielding in a high dose rate skin applicator

Purpose: The Valencia HDR applicators are accessories of the microSelectron HDR afterloading system (Nucletron) shaped as truncated cones. The base of the cone is either 2 or 3 cm diameter. They are intended to treat skin lesions, being the typical prescription depth 3 mm. In patients with eyelid lesions, an internal shielding is very useful to reduce the dose to the ocular globe. The purpose of this work was to evaluate the dose enhancement from potential backscatter and electron contamination due to the shielding. Material and methods: Two methods were used: a) Monte Carlo simulation, performed with the GEANT4 code, 2 cm Valencia applicator was placed on the surface of a water phantom in …

Radiation leakage study for the Valencia applicators

Abstract Introduction and purpose The Valencia applicators which are accessories of the microSelectron-HDR afterloader (Nucletron, Veenendaal, The Netherlands) are designed to treat skin lesions. These cup-shaped applicators are an alternative to superficial/orthovoltage x-ray treatment units. They limit the irradiation to the required area using tungsten-alloy shielding, and are equipped with a tungsten-alloy flattering filter allowing the treatment of skin tumors, the oral cavity, vaginal cuff, etc. The tungsten-alloy thickness to shield radiation is not the same in all parts of the applicators. This fact led us to question whether the leakage radiation differs depending on where it is me…

Monte Carlo calculation of dose rate distributions around 0.5 and 0.6 mm in diameter 192Ir wires

Monte Carlo simulations of absolute dose rate in liquid water are presented in the form of away-along tables for 1 and 5 cm 192 Ir wires of 0.5 and 0.6 mm diameter. Simulated absolute dose rate values can be used as benchmark data to verify the calculation results of treatment planning systems or directly as input data for treatment planning. Best fit value of an attenuation coefficient suitable for use in Sievert integral-type calculations has been derived based on Monte Carlo simulation results. For the treatment planning systems that are based on the TG43 formalism we have also computed the required dosimetry parameters.

SU-E-J-64: Evaluation of a Commercial EPID-Based in Vivo Dosimetric System in the Presence of Lung Tissue Heterogeneity

Purpose: To study the performance of Dosimetry Check (DC), an EPID-based dosimetry software, which allows performing transit dosimetry, in low density medium, by comparing calculations in-phantom, and analysing results for 15 lung patients. Methods: DC software (v.3.8, pencil beam-based algorithm) has been tested, for plans (Eclipse v.10.0 TPS) delivered in two Varian Clinac iX equipped with aS1000 EPIDs.In the CIRS lung phantom, comparisons between DC and Eclipse (Acuros) were performed for several plans: (1) four field box; (2) square field delivered in arc mode; (3) RapidArc lung patient plan medially centred; (4) RapidArc lung patient plan centred in one lung. Reference points analysed:…

Comparison of woods-saxon and double-folding potentials forα-particle scattering from54Fe at 24.5 MeV

Inelastic-scattering data are presented forα-particles of 24.5 MeV from54Fe over the range 15° to 175° in the centre-of-mass system. The real part of the optical potential is calculated microscopically using the M3Y effective interaction of Bertschet al. and the DDM3Y density-dependent interaction. Elastic scattering has been analysed by using as real part of the optical potential M3Y, DDM3Y and Woods-Saxon forms (WS), taking in all three cases as imaginary part a WS potential. To fit the data the double-folding potential needs to be normalized by a factor of ⋍1.6 for the M3Y interaction and of ⋍1.13 for the DDM3Y interaction. By the study of the invariant-point ambiguity it has been observ…

MO-D-AUD B-08: Treatment Planning for Complex Brachytherapy Dose Distributions Using High-Z Shields and Conventional Software

Purpose: Certain brachytherapydose distributions, like for LDR prostate implants, are readily modeled by treatment planningsoftware using the superposition principle of individual seeds to replicate the total dose distribution. However, dose distributions for brachytherapy treatments using high‐Z shields are currently not well‐modeled using conventional software.Method and Materials:Dose distributions from complex brachytherapy plaques determined using Monte Carlo methods were used as input data, and included COMS‐based eye plaques using 125 I , 103 Pd , and 131 Cs ; 4–8cm diameter AccuBoost peripheral breast brachytherapy applicators from Advanced Radiation Therapy; and the 2 and 3cm diame…

Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air

Purpose: For a given radionuclide, there are several photonspectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for I 192 r , I 125 , and P 103 d on the final estimations of kerma and dose. Methods: For I 192 r , I 125 , and P 103 d , the authors considered from two to five published spectra. Spherical sources approximating common brachytherapy sources were assessed. Kerma and dose results from GEANT4, MCNP5, and PENELOPE-2008 were compared for water and air. The dosimetric influence of I 192 r , I 125 , and P 103 d spectral choice was determined. Results…

The necessity of systematic verification of applicator position in brachytherapy treatment of the vaginal cuff

Prescription Depth in Surface Skin Brachytherapy

Graphical interface for designing geometries and processing DICOM images for PENELOPE

One of he most difficult steps when preparing a Monte Carlo calculation is the design of their geometries. Such process is an error-prone, time-consuming, and complex step for any simulation in the field of medical physics. The software VoxelMages has been developed to help the user in this complex task. It allows to design arbitrary geometries and to process DICOM image files for simulations with the general-purpose Monte Carlo code PENELOPE. Its main characteristics are described in the following.

Technique for routine output verification of Leipzig applicators with a well chamber

The H-type Leipzig applicators are accessories of the microSelectron-HDR system (Nucletron, Veenendaal, The Netherlands) for treatment of superficial malignancies. Recently, the dose rate distributions in liquid water for the whole set of applicators using both source models available for the microSelectron-HDR afterloaders have been obtained by means of the experimentally validated Monte Carlo (MC) code GEANT4. Also an output table (cGy/hU) at 3 mm depth on the applicator central axis was provided. The output verification of these applicators by the user, prior to their clinical use, present practical problems: small detectors such as thermoluminescent dosimeters or parallel-plate ionizati…

Urethral Dose Limit in Boost Permanent Prostate 125I Seed Implants Based on Biologically Effective Dose Values

A generic TG-186 shielded applicator for commissioning model-based dose calculation algorithms for high-dose-rate Ir-192 brachytherapy

PurposeA joint working group was created by the American Association of Physicists in Medicine (AAPM), the European Society for Radiotherapy and Oncology (ESTRO), and the Australasian Brachytherapy Group (ABG) with the charge, among others, to develop a set of well-defined test case plans and perform calculations and comparisons with model-based dose calculation algorithms (MBDCAs). Its main goal is to facilitate a smooth transition from the AAPM Task Group No. 43 (TG-43) dose calculation formalism, widely being used in clinical practice for brachytherapy, to the one proposed by Task Group No. 186 (TG-186) for MBDCAs. To do so, in this work a hypothetical, generic high-dose rate (HDR) Ir-19…

Dose Escalation in Permanent Brachytherapy for Prostate Cancer: Preliminary Results

Brachytherapy structural shielding calculations using Monte Carlo generated, monoenergetic data

Purpose: To provide a method for calculating the transmission of any broad photon beam with a known energy spectrum in the range of 20–1090 keV, through concrete and lead, based on the superposition of corresponding monoenergetic data obtained from Monte Carlo simulation. Methods: MCNP5 was used to calculate broad photon beam transmission data through varying thickness of lead and concrete, for monoenergetic point sources of energy in the range pertinent to brachytherapy (20–1090 keV, in 10 keV intervals). The three parameter empirical model introduced byArcher et al. [“Diagnostic x-ray shielding design based on an empirical model of photon attenuation,” Health Phys. 44, 507–517 (1983)] was…

SU-G-201-02: Application of RayStretch in Clinical Cases: A Calculation for Heterogeneity Corrections in LDR Permanent I-125 Prostate Brachytherapy

Purpose: Tissue heterogeneities and calcifications have significant impact on the dosimetry of low energy brachytherapy (BT). RayStretch is an analytical algorithm developed in our institution to incorporate heterogeneity corrections in LDR prostate brachytherapy. The aim of this work is to study its application in clinical cases by comparing its predictions with the results obtained with TG-43 and Monte Carlo (MC) simulations. Methods: A clinical implant (71 I-125 seeds, 15 needles) from a real patient was considered. On this patient, different volumes with calcifications were considered. Its properties were evaluated in three ways by i) the Treatment planning system (TPS) (TG-43), ii) a M…

HDR Valencia skin applicators: A proposed commissioning procedure

Brachytherapy organ dose estimation using Monte Carlo simulations of realistic patient models

Radiation Therapy Planning Systems (RTPS) currently used in hospitals contain algorithms based on deterministic simplifications that do not properly consider electrons lateral transport in the areas where there are changes of density, and as a result, erroneous dose predictions could be produced. According to this, the present work proposes the use of Monte Carlo method in brachytherapy planning systems, which could affect positively on the radiotherapy treatment planning, since it provides results that are more accurate and takes into account the in homogeneities density variations. This paper presents a Monte Carlo (MC) simulation of a brachytherapy prostate treatment with I-125 seeds, us…

TH-C-AUD A-08: Evaluation of Electronic Equilibrium Conditions Near Brachytherapy Sources

Purpose: For high‐energy photon‐emitting brachytherapysources such as 60 Co , 137 Cs , 192 Ir , and 169 Yb , the main contribution of the systematic uncertainty in the dose distributions near the sources is understanding of electronic equilibrium and the contribution of β‐rays due to radioactive disintegration. Thus, it is important to study these effects in detail to accurately depict dose distributions near these brachytherapysources. This work studies the relative importance of β‐ray contributions to total dose (β + γ + x‐ray), and feasibility of using the approximation “collision kerma equals dose in electronic equilibrium conditions.” Method and Materials:Characteristics of kerma and d…

Evaluation of methods of interpolation-extrapolation of g L (r) and F(r,θ) for high-energy brachytherapy sources

Limitations of the TG-43 formalism for skin high-dose-rate brachytherapy dose calculations

Purpose: In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Methods: Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a …

SU-E-T-237: Monte Carlo Dosimetric Characterization of the Mobetron Mobile Linac

Purpose: The aim of this work is to characterize dosimetrically a clinical intraoperative electron beam accelerator, Mobetron (IntraOp Medical, Inc.) in clinical use in our Hospital. Once this first step is completed our purpose is to evaluate shielding requirements for such a device by preparing adequate phase space files. Methods: It is known that electron beam simulation parameters required for state-of-the-art Monte Carlo codes to obtain a good match with measured data, like the mean energy or the FWHM, may not be code-independent due to the different set of process simulated and formalisms involved. Then, to cross-check our results against any issue in the simulation we have compared e…

SU-FF-T-15: Comparison of Various Monte Carlo Codes for Brachytherapy Source Dosimetry

Purpose: Monte Carlo simulations are used for dosimetric evaluation of brachytherapysources. Various investigators had demonstrated good agreement between the measured and simulated data while some others have shown discrepancies between the two methods. These discrepancies were attributed to the errors in cross section data, differences in phantom and source geometry and composition. However, the exact causes of these differences have not yet fully explored. The goal of this project is to verify the differences among the widely available Monte Carlo codes for brachytherapysourcedosimetry.Material and method: These investigations are based on VariSource 192 Ir , Model VS2000, IsoAid Advanta…

Dosimetric characteristics of the CDC-type miniature cylindrical 137Cs brachytherapy sources

The low dose rate CDC-type miniature cylindrical 137 Cs sources are available, with one or three active beads, for use in source trains in automatic and manual afterloading systems for gynecological brachytherapy. Absolute dose rate distributions in water have been calculated around these sources using the Monte CarloGEANT3 code and they are presented as conventional two-dimensional Cartesian lookup tables. The AAPM Task Group 43 formalism for dose calculation has been also applied. The dose rate constant obtained for the one bead source is Λ=1.113±0.003 cGyh −1 U −1 , and the value for the three bead source is Λ=1.103±0.003 cGyh −1 U −1 . Finally, for the treatment planning systems based o…

New HDR Valencia Applicator for Treating Skin Lesions Larger Than 3 cm Size with Either a Co-60 or Ir-192 Source

A Monte Carlo investigation of the dosimetric characteristics of the CSM11 137Cs source from CIS

The purpose of this study is to calculate basic dosimetry data for a CSM11 low dose rate 137Cs source in water. This source is widely used in afterloadable dome cylinders designed to homogeneously irradiate the vaginal cuff alone or additional areas of the vagina in hysterectomized patients. In this study, the Monte Carlo simulation code GEANT, incorporating in detail source geometry, is used to investigate the dosimetric characteristics of the source. The calculated data were analyzed using a fitting procedure that is described in detail. Absolute dose rate distributions in water were calculated around this source and are presented as conventional 2D Cartesian lookup tables (classically al…

Erratum: “Technical note: Monte-Carlo dosimetry of the HDR 12i and Plus 192Ir sources” [Med. Phys. 28 , 2586-2591 (2001)]

Monte Carlo evaluation of kerma in an HDR brachytherapy bunker

In recent years, the use of high dose rate (HDR) after-loader machines has greatly increased due to the shift from traditional Cs-137/Ir-192 low dose rate (LDR) to HDR brachytherapy. The method used to calculate the required concrete and, where appropriate, lead shielding in the door is based on analytical methods provided by documents published by the ICRP, the IAEA and the NCRP. The purpose of this study is to perform a more realistic kerma evaluation at the entrance maze door of an HDR bunker using the Monte Carlo code GEANT4. The Monte Carlo results were validated experimentally. The spectrum at the maze entrance door, obtained with Monte Carlo, has an average energy of about 110 keV, m…

Impact of the Tiloop Bra mesh in CT images and dose delivery in breast radiotherapy

A new titanized breast mesh, TiLOOP Bra, is currently available for implantation in patients who require radiotherapy. The purpose of this work is to study the dosimetric effect of the presence of a TiLOOP Bra mesh on breast radiation treatment and radiographic imaging. The dosimetric effects have been measured for three X‐ray energies: 1.25 MeV, 6 MV and 18 MV, using radiochromic films placed at three different depths. These depths are representative of mesh location in breast during the radiotherapy treatment and hence, are of interest in this study. In order to assess the disturbance in a radiographic image, different computed tomographic (CT) studies of the mesh have been performed. The…

Evaluation of interpolation methods for TG-43 dosimetric parameters based on comparison with Monte Carlo data for high-energy brachytherapy sources.

Purpose The aim of this work was to determine dose distributions for high-energy brachytherapy sources at spatial locations not included in the radial dose function gL(r) and 2D anisotropy function F(r,θ) table entries for radial distance r and polar angle θ. The objectives of this study are as follows: 1) to evaluate interpolation methods in order to accurately derive gL(r) and F(r,θ) from the reported data; 2) to determine the minimum number of entries in gL(r) and F(r,θ) that allow reproduction of dose distributions with sufficient accuracy. Material and methods Four high-energy photon-emitting brachytherapy sources were studied: 60Co model Co0.A86, 137Cs model CSM-3, 192Ir model Ir2.A85…

SU-E-T-508: Monte Carlo Dosimetric Study of the CSM40 Low Dose Rate Source

Purpose: There is a LDR 137Cs brachytherapy source, CSM40, developed by Eckert & Ziegler BEBIG. Fundamental dosimetric datasets to be used on treatment planning systems do not exist for this source. This study aims to obtain quality dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Methods: Penelope2008 and GEANT4 Monte Carlo codes were used to characterize this source dosimetry. Water composition and mass density was that recommended by AAPM. Due to the typical energies of the 137 Cs, dose for small distances can be approximated by collisional kerma. Therefore, we have considered collisional kerma for r<20 cm. To provide adequate spatial resolu…

A dosimetric study on the Ir-192 high dose rate Flexisource

In this work, the dose rate distribution of a new Ir-192 high dose rate source (Flexisource used in the afterloading Flexitron system, Isodose Control, Veenendaal, The Netherlands) is studied by means of Monte Carlo techniques using the GEANT4 code. The dosimetric parameters of the Task Group No. 43 Report (TG43) formalism and two-dimensional rectangular look-up tables have been obtained.

SU-FF-T-365: Practical Reconstruction Method for 3D CT-Based Brachytherapy with Shielded Colpostats

Introduction and purpose.‐ The most extended worldwide HDR and PDR afterloading machines are from Nucletron, using the Plato Treatment Planning System (TPS) to perform the clinical dosimetry. The Fletcher‐Williamson (FW) vaginal colpostat applicators are widely used with these machines, they are made of a very dense material (densimet‐17) which allows shielding up to 50% of the dose. Almost all the TPS have incorporated the CT‐Based Brachytherapy (BT), in which the CT catheters and applicators reconstruction is based on contiguous CT transverse slices where the user points the catheter position. The problem with these applicators is the production of artefacts that makes the reconstruction …

MRI based treatment planning in gynaecological brachytherapy

Interobserver study of countouringbased on ultrasound image in real-time interactive prostate brachytherapy

Study of encapsulated T170m sources for their potential use in brachytherapy

Purpose: High dose-rate (HDR) brachytherapy is currently performed with {sup 192}Ir sources, and {sup 60}Co has returned recently into clinical use as a source for this kind of cancer treatment. Both radionuclides have mean photon energies high enough to require specific shielded treatment rooms. In recent years, {sup 169}Yb has been explored as an alternative for HDR-brachytherapy implants. Although it has mean photon energy lower than {sup 192}Ir, it still requires extensive shielding to deliver treatment. An alternative radionuclide for brachytherapy is {sup 170}Tm (Z=69) because it has three physical properties adequate for clinical practice: (a) 128.6 day half-life, (b) high specific a…

Erratum: “Technique for routine output verification of Leipzig applicators with a well chamber” [Med. Phys. 33, 16-20 (2006)]

A Monte Carlo study of intersource effects in dome-type applicators loaded with LDR Cs-137 sources

In this study, the dose rate distributions produced by low dose rate Cs-137 sources loaded in afterloadable dome applicators are studied using the Monte Carlo method. Dose differences between Monte Carlo results and calculations done using the superposition principle are within 1-3% in front of the applicator and between 3 and 10% near and along the longitudinal source axis. Consequently, the real doses to lateral vaginal wall, rectum and bladder are very close to the doses estimated applying the superposition principle, while the dose to the vaginal cuff has been overestimated by up to 10%.

The use of nomograms in LDR-HDR prostate brachytherapy

Purpose: The common use of nomograms in Low Dose Rate (LDR) permanent prostate brachytherapy (BT) allows to estimate the number of seeds required for an implant. Independent dosimetry verification is recommended for each clinical dosimetry in BT. Also, nomograms can be useful for dose calculation quality assurance and they could be adapt ed to High Dose Rate (HDR). This work sets nomograms for LDR and HDR prostate-BT implants, which are applied to three different institutions that use different implant techniques. Material and methods: Patients treated throughout 2010 till April 2011 were considered for this study. This exam ple was chosen to be the representative of the latest implant tech…

Depth-dose measurement corrections for the surface electronic brachytherapy beams of an Esteya® unit: a Monte Carlo study

Abstract Three different correction factors for measurements with the parallel-plate ionization chamber PTW T34013 on the Esteya electronic brachytherapy unit have been investigated. This chamber type is recommended by AAPM TG-253 for depth-dose measurements in the 69.5 kV x-ray beam generated by the Esteya unit. Monte Carlo simulations using the PENELOPE-2018 system were performed to determine the absorbed dose deposited in water and in the chamber sensitive volume at different depths with a Type A uncertainty smaller than 0.1%. Chamber-to-chamber differences have been explored performing measurements using three different chambers. The range of conical applicators available, from 10 to 30…

Implementation and Validation of an End-to-End Commissioning Process for Model-Based Dose Calculation Algorithms in Brachytherapy

Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions

Purpose: The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a 192Ir source; (ii) to calculate by means of the Monte Carlo(MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. Methods: The penelope2008MC code was used to optimize dwell positions and dwell times. Next, the dose distribution in a water phantom and the leakage dose distribution arou…

SU-FF-T-14: Monte Carlo Derivation of TG-43 Dosimetric Parameters for Radiation Therapy Resources and 3M Cs-137 Sources

Purpose: In clinical brachytherapydosimetry a detailed dose rate distribution of the radioactive source in water is needed to make a quality treatment planning. Two Cs‐137 sources are considered in this study the Radiation Therapy Resources 67–800 source(Radiation Therapy Resources Inc., Valencia, CA) and the 3M model 6500/6D6C source.Material and methods: A complete dosimetric dataset for both sources has been obtained by means of the Monte Carlo GEANT4 code. Results:Dose rate distributions are presented in two different ways, following the TG43 formalism and in a 2D rectangular dose rate table. Conclusion: This 2D dose rate table is helpful for the TPS quality control and it is fully cons…

SU-FF-T-41: Monte Carlo Dosimetric Study of the New BEBIG Co-60 HDR Source

Purpose: The use of high dose rate brachytherapy (HDR) is a highly extended practice today, being the Ir‐192 the most widely extended isotope used for this type of practice although Co‐60 is also available for HDR. The purpose of this study is to obtain the dosimetric parameters of the Co‐60 source used by the BEBIG MultiSource remote afterloader (BEBIG GmbH, Germany) for which there is no dosimetric data available in the literature. It is recommended that accurate dose distribution data, based on a realistic geometry and on the mechanical characteristics of the source, should be obtained by an appropriate method, experimental or Monte Carlo, to be used as input in the HDR Treatment Plannin…

Dosimetric perturbations of a lead shield for surface and interstitial high-dose-rate brachytherapy.

In surface and interstitial high-dose-rate brachytherapy with either (60)Co, (192)Ir, or (169)Yb sources, some radiosensitive organs near the surface may be exposed to high absorbed doses. This may be reduced by covering the implants with a lead shield on the body surface, which results in dosimetric perturbations. Monte Carlo simulations in Geant4 were performed for the three radionuclides placed at a single dwell position. Four different shield thicknesses (0, 3, 6, and 10 mm) and three different source depths (0, 5, and 10 mm) in water were considered, with the lead shield placed at the phantom surface. Backscatter dose enhancement and transmission data were obtained for the lead shields…

Dosimetry characteristics of the Plus and 12i Gammamed PDR 192Ir sources.

In this study a complete set of dosimetric data for the Plus and 12i Gammamed PDR (pulsed dose rate) 192 Ir sources is presented. These data have been calculated using the Monte Carlo simulation code GEANT3. Absolute dose rate distributions in water around these sources were calculated and are presented in form of conventional two dimensional (2D) Cartesian look-up tables. All dosimetric quantities recommended by the AAPM Task Group 43 report have been also calculated. These quantities are dose rate constant, radial dose function, anisotropy function and anisotropy factor. The dose rate distribution of the 12i source was compared with the corresponding data for the microselectron PDR source…

Collision-kerma conversion between dose-to-tissue and dose-to-water by photon energy-fluence corrections in low-energy brachytherapy

The AAPM TG-43 brachytherapy dosimetry formalism, introduced in 1995, has become a standard for brachytherapy dosimetry worldwide; it implicitly assumes that charged-particle equilibrium (CPE) exists for the determination of absorbed dose to water at different locations, except in the vicinity of the source capsule. Subsequent dosimetry developments, based on Monte Carlo calculations or analytical solutions of transport equations, do not rely on the CPE assumption and determine directly the dose to different tissues. At the time of relating dose to tissue and dose to water, or vice versa, it is usually assumed that the photon fluence in water and in tissues are practically identical, so tha…

Technical note: Monte-Carlo dosimetry of the HDR 12i and Plus 192Ir sources.

In this study a complete set of dosimetric data for the GammaMed high dose rate (HDR) 12i and Plus 192 Ir sources are presented. These data have been calculated by means of the Monte Carlo simulation code GEANT3. Absolute dose rate distributions in water are presented as conventional two dimensional (2D) Cartesian look-up tables, and in the TG43 formalism.

A Generic High-Dose-Rate 192Ir Source Model for Model-Based Dose Calculation Methods in Brachytherapy Beyond the TG-43 Formalism

Technical note: Dosimetric study of a new Co-60 source used in brachytherapy

The purpose of this study is to obtain the dosimetric parameters of a new Co-60 source used in high dose rate brachytherapy and manufactured by BEBIG (Eckert & Ziegler BEBIG GmbH, Germany). The Monte Carlo method has been used to obtain the dose rate distribution in the updated TG-43U1 formalism of the American Association of Physicists in Medicine. In addition, to aid the quality control process on treatment planning systems (TPS), a two-dimensional rectangular dose rate table, coherent with the TG-43U1 dose calculation formalism, is given. These dosimetric data sets can be used as input data of the TPS calculations and to validate them.

SU-FF-T-62: Dosimetric Evaluation of An Internal Shielding Used with a HDR Skin Applicator

Purpose: The Valencia HDR skin applicators are accessories of the microSelectron HDR afterloading system (Nucletron) cup shaped to limit the dose to the irradiation area. Applicators sizes are: diameter 2 and 3 cm. The typical prescription depth is 3 mm. This work aims to evaluate the backscatter and electron contamination of an internal shielding used to reduce the dose to the ocular globe when the lesion is located at the eyelid. Monte Carlo(MC) and experimental methods have been used. Method and Materials: The geometry has been: the Valencia applicator (2 cm diameter) on the surface of a solid polystyrene slab phantom; inside, a 2 mm lead slab located at 3 mm depth. MC simulation charact…

SU-FF-T-13: Monte Carlo Calculation of the TG-43 Dosimetric Parameters of a New BEBIG Ir-192 HDR Source

Purpose: High dose rate (HDR) brachytherapy is a highly extended practice in clinical brachytherapy today. Quality dose rate distribution datasets of the HDR sources used in a clinical treatment are required. Because of the different source designs, a specific dosimetry dataset is required for each source model. In the recently published BRAPHYQS-ESTRO Report, an overview of available dosimetric data for all HDR Ir-192 sources is given, pointing out the lack of data for one of the sources, the used by the BEBIG MultiSource afterloading system (BEBIG GmbH, Germany). The purpose of this study is to obtain detailed dose rate distributions in liquid water media around this source. Material and …

SU-E-J-69: Evaluation of the Lens Dose On the Cone Beam IGRT Procedures

Purpose: With the establishment of the IGRT as a standard technique, the extra dose that is given to the patients should be taken into account. Furthermore, it has been a recent decrease of the dose threshold in the lens, reduced to 0.5 Gy (ICRP ref 4825-3093-1464 on 21st April, 2011).The purpose of this work was to evaluate the extra dose that the lens is receive due to the Cone-Beam (CBCT) location systems in Head-and-Neck treatments. Methods: The On-Board Imaging (OBI) v 1.5 of the two Varian accelerators, one Clinac iX and one True Beam, were used to obtain the dose that this OBI version give to the lens in the Head-and-Neck location treatments. All CBCT scans were acquired with the Sta…

SU-FF-T-329: Monte Carlo Dosimetric Study of the Flexisource Ir-192 HDR Source

Purpose:Brachytherapy with high dose rate (HDR) sources of 192 Ir is a usual practice in clinical brachytherapy today. The TG43 U1 update report recommends that accurate dose distribution data of the brachytherapysource in use should be obtained experimentally or by Monte Carlo (MC), to be used as input in the HDR Treatment Planning System (TPS). The purpose of this study is to obtain the dose rate distribution in liquid water media for the Flexisource HDR 192 Ir source (Isodose Control GmbH, Germany) using the Monte Carlo method to obtain the TG43 U1 parameters and the 2‐D rectangular dose rate table. Material and methods: The MC code GEANT4 (7.1 version) was used to estimate dose rate in …

Phantom size in brachytherapy source dosimetric studies

An important point to consider in a brachytherapy dosimetry study is the phantom size involved in calculations or experimental measurements. As pointed out by Williamson [Med. Phys. 18, 776-786 (1991)] this topic has a relevant influence on final dosimetric results. Presently, one-dimensional (1-D) algorithms and newly-developed 3-D correction algorithms are based on physics data that are obtained under full scatter conditions, i.e., assumed infinite phantom size. One can then assume that reference dose distributions in source dosimetry for photon brachytherapy should use an unbounded phantom size rather than phantom-like dimensions. Our aim in this paper is to study the effect of phantom s…

Monte Carlo dosimetric study of the Flexisource Co-60 high dose rate source.

Purpose: Recently, a new HDR 60 Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V. Veenendaal, The Netherlands). This study aims to obtain dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Material and methods: Two Monte Carlo radiation transport codes were used: Penelope2008 and GEANT4. The source was centrally-positioned in a 100 cm radius water phantom. Absorbed dose and collisional kerma were obtained using 0.01 cm (close) and 0.1 cm (far) sized voxels to provide high-resolution dosimetry near (far from) the source. Dose rate distributions obtained with the two Monte Carlo codes were compared. Results and Discussi…

Erratum: “Fitted dosimetric parameters of high dose-rate 192Ir sources according to the AAPM TG43 formalism” [Med. Phys. 28 (4), 654-660 (2001)]

Establishing Universal Test Cases for Benchmarking Model-Based Dose Calculations beyond TG-43

SU-FF-T-180: Dosimetric Characteristics of Tm-170 as a Radionuclide for Its Possible Use in Brachytherapy

In clinical brachytherapy several types of photon sources are used, mainly Cs‐137, Ir‐192, I‐125, and Pd‐103. The Tm‐170 is a promising radionuclide for use in brachytherapy because of the low mean‐energy (46.75 keV or 66.39 keV if the lines below 10 keV are removed) and the possible high specific activity (2.21×1014 Bq/g for a half life of 128.6 days). Tm‐170 is produced in a nuclear reactor by neutron absorption of the natural Tm‐169 and decays mainly via β‐emission. The maximum energies of the β‐rays are 0.290 and 0.323 MeV. These β particles are thus absorbed in the source core and in the encapsulation cover producing bremsstrahlung that contributes significantly to the dose. These fact…

Influence of Photon Energy Spectra from 192Ir and 125I Brachytherapy Sources on Kerma and Dose Rates in Water and Air

Monte Carlo dosimetric study of the BEBIG Co-60 HDR source

Although not as widespread as Ir-192, Co-60 is also available on afterloading equipment devoted to high dose rate brachytherapy, mainly addressed to the treatment of gynaecological lesions. The purpose of this study is to obtain the dosimetric parameters of the Co-60 source used by the BEBIG MultiSource remote afterloader (BEBIG GmbH, Germany) for which there are no dosimetric data available in the literature. The Monte Carlo code GEANT4 has been used to obtain the TG43 parameters and the 2D dose rate table in Cartesian coordinates of the BEBIG Co-60 HDR source. The dose rate constant, radial dose function and anisotropy function have been calculated and are presented in a tabular form as w…

A study of Type B uncertainties associated with the photoelectric effect in low-energy Monte Carlo simulations

The goal of this manuscript is to estimate Type B uncertainties in absorbed-dose calculations arising from the different implementations in current state-of-the-art Monte Carlo codes of low-energy photon cross-sections (&lt;200 keV). Monte Carlo simulations are carried out using three codes widely used in the low-energy domain: PENELOPE-2018, EGSnrc, and MCNP. Mass energy-absorption coefficients for water, air, graphite, and their respective ratios; absorbed dose; and photon-fluence spectra are considered. Benchmark simulations using similar cross-sections have been performed. The differences observed between these quantities when different cross-sections are considered are taken to be a go…

Dosimetric characterization of two radium sources for retrospective dosimetry studies

Purpose: During the first part of the 20th century, Ra-226 was the most used radionuclide for brachytherapy. Retrospective accurate dosimetry, coupled with patient follow up, is important for advan ...

Reply to “Comment on ‘Correspondence factor for Nucletron surface applicators'” [Med. Phys. 39, 2947-2948 (2012)]

Monte Carlo dosimetric study of the medium dose rate CSM40 source

Abstract The 137Cs medium dose rate (MDR) CSM40 source model (Eckert & Ziegler BEBIG, Germany) is in clinical use but no dosimetric dataset has been published. This study aims to obtain dosimetric data for the CSM40 source for its use in clinical practice as required by the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO). Penelope2008 and Geant4 Monte Carlo codes were used to characterize this source dosimetrically. It was located in an unbounded water phantom with composition and mass density as recommended by AAPM and ESTRO. Due to the low photon energies of 137Cs, absorbed dose was approximated by collisional kerma. Add…

Equivalent phantom sizes in Ir-192 source brachytherapy dosimetric studies

Erratum: “TG-43 U1 based dosimetric characterization of model 67-6520 Cs-137 brachytherapy source”

Purpose: Brachytherapy treatment has been a cornerstone for management of various cancer sites, particularly for the treatment of gynecological malignancies. In low dose rate brachytherapy treatments,C137s sources have been used for several decades. A new C137s source design has been introduced (model 67-6520, source B3-561) by Isotope Products Laboratories (IPL) for clinical application. The goal of the present work is to implement the TG-43 U1 protocol in the characterization of the aforementioned C137s source. Methods: The dosimetriccharacteristics of the IPLC137s source are measured using LiF thermoluminescent dosimeters in a Solid Water™ phantom material and calculated using Monte Carl…

Source strength determination in iridium-192 and cobalt-60 brachytherapy : A European survey on the level of agreement between clinical measurements and manufacturer certificates

Background and purpose: Brachytherapy treatment outcomes depend on the accuracy of the delivered dose distribution, which is proportional to the reference air-kerma rate (RAKR). Current societal recommendations require the medical physicist to compare the measured RAKR values to the manufacturer source calibration certificate. The purpose of this work was to report agreement observed in current clinical practice in the European Union. Materials and methods: A European survey was performed for high- and pulsed-dose-rate (HDR and PDR) highenergy sources (Ir-192 and Co-60), to quantify observed RAKR differences. Medical physicists at eighteen hospitals from eight European countries were contac…

GEC-ESTRO ACROP recommendations on calibration and traceability of LE-LDR photon-emitting brachytherapy sources at the hospital level

Prostate brachytherapy treatment using permanent implantation of low-energy (LE) low-dose rate (LDR) sources is successfully and widely applied in Europe. In addition, seeds are used in other tumour sites, such as ophthalmic tumours, implanted temporarily. The calibration issues for LE-LDR photon emitting sources are specific and different from other sources used in brachytherapy. In this report, the BRAPHYQS (BRAchytherapy PHYsics Quality assurance System) working group of GEC-ESTRO, has developed the present recommendations to assure harmonized and high-quality seed calibration in European clinics. There are practical aspects for which a clarification/procedure is needed, including aspect…

Review of clinical brachytherapy uncertainties: Analysis guidelines of GEC-ESTRO and the AAPM

Background and purpose: A substantial reduction of uncertainties in clinical brachytherapy should result in improved outcome in terms of increased local control and reduced side effects. Types of uncertainties have to be identified, grouped, and quantified. Methods: A detailed literature review was performed to identify uncertainty components and their relative importance to the combined overall uncertainty. Results: Very few components (e.g., source strength and afterloader timer) are independent of clinical disease site and location of administered dose. While the influence of medium on dose calculation can be substantial for low energy sources or non-deeply seated implants, the influence…

Broad-beam transmission data for new brachytherapy sources, Tm-170 and Yb-169

The characteristics of the radionuclides (170)Tm and (169)Yb are highly interesting for their use as high dose-rate brachytherapy sources. The introduction of brachytherapy equipment containing these sources will lead to smaller required thicknesses of the materials used in radiation protection barriers compared with the use of conventional sources such as (192)Ir and (137)Cs. The purpose of this study is to determine the required thicknesses of protection material for the design of the protecting walls. Using the Monte Carlo method, transmission data were derived for broad-beam geometries through lead and concrete barriers, from which the first half value layer and tenth value layer are ob…

Fitted dosimetric parameters of high dose-rate 192Ir sources according to the AAPM TG43 formalism

The purpose of this study is to find fitted functional forms to the anisotropy function, F(r,θ), and the radial dose function, g(r), in order to characterize dose-rate distributions around all the high-intensity 192 Ir sources currently in use. Dosimetry data are at present available as tables for: the microSelectron HDR (“classic” and “new” design models), the PDR source, and the VariSource HDR source, expressed in terms of the AAPM Task Group No. 43 recommendations. There is only one paper out which introduces a functional form to fit the anisotropy function, but only for symmetric sources with respect to the transverse axis. However, dosimetric data of the HDR and PDR sources mentioned a…

Flattering filter design for HDR surface applicators

Radiation transmission data for radionuclides and materials relevant to brachytherapy facility shielding

To address the limited availability of radiation shielding data for brachytherapy as well as some disparity in existing data, Monte Carlo simulation was used to generate radiation transmission data for 60Co, 137CS, 198Au, 192Ir 169Yb, 170Tm, 131Cs, 125I, and 103pd photons through concrete, stainless steel, lead, as well as lead glass and baryte concrete. Results accounting for the oblique incidence of radiation to the barrier, spectral variation with barrier thickness, and broad beam conditions in a realistic geometry are compared to corresponding data in the literature in terms of the half value layer (HVL) and tenth value layer (TVL) indices. It is also shown that radiation shielding calc…

Dosimetric study of the 15mm ROPES eye plaque

The main aim of this paper is to make a study of dose-rate distributions obtained around the 15 mm, radiation oncology physics and engineering services, Australia (ROPES) eye plaque loaded with {sup 125}I model 6711 radioactive seeds. In this study, we have carried out a comparison of the dose-rate distributions obtained by the algorithm used by the Plaque Simulator (PS) (BEBIG GmbH, Berlin, Germany) treatment planning system with those obtained by means of the Monte Carlo method for the ROPES eye plaque. A simple method to obtain the dose-rate distributions in a treatment planning system via the superposition of the dose-rate distributions of a seed placed in the eye plaque has been develo…

Monte Carlo study of the dose rate distributions for the Ir2.A85-2 and Ir2.A85-1 Ir-192 afterloading sources

The two most commonly used modalities of cancer treatment in clinical brachytherapy practice today are high dose rate (HDR) and pulsed dose rate (PDR) brachytherapy. In a clinical treatment, quality dose rate distribution data sets of the brachytherapy sources are required for each source model. The purpose of this study is to obtain detailed dose rate distributions around the new BEBIG HDR and PDR Ir-192 brachytherapy sources. These distributions will then be used as input data in the treatment planning systems dedicated to brachytherapy and its calculations can be verified. The Monte Carlo method was used to obtain the dose rate distributions around the sources studied, taking into accoun…

Monte Carlo calculation of dose rate distributions around the Walstam CDC.K-type137Cs sources

Basic dosimetric data for the Walstam CDC.K-type low dose rate 137Cs sources in water have been calculated using Monte Carlo techniques. These sources, CDC.K1 -K3 and CDC.K4, are widely used in a range of applicators and moulds for the treatment of intracavitary and superficial cancers. Our purpose is to improve existing data about these sources using the Monte Carlo simulation code GEANT3. Absolute dose rate distributions in water have been calculated around these sources and are presented as conventional 2D Cartesian look-up tables. Also the AAPM Task Group 43 formalism for dose calculation has been applied. The calculated dose rate constant for the CDC.K1-K3 source is A = 1.106 +/- 0.001…

A Monte Carlo-based dosimetric characterization of Esteya® , an electronic surface brachytherapy unit

PURPOSE The purpose of this work is threefold: First, to obtain the phase space of an electronic brachytherapy (eBT) system designed for surface skin treatments. Second, to explore the use of some efficiency enhancing (EFEN) strategies in the determination of the phase space. Third, to use the phase space previously obtained to perform a dosimetric characterization of the Esteya eBT system. METHODS The Monte Carlo study of the 69.5 kVp x-ray beam of the Esteya® unit (Elekta Brachytherapy, Veenendaal, The Netherlands) was performed with PENELOPE2014. The EFEN strategies included the use of variance reduction techniques and mixed Class II simulations, where transport parameters were fine-tune…

Dosimetric Characteristics of a New Unit for Electronic Skin Brachytherapy

Monte Carlo and experimental derivation of TG43 dosimetric parameters for CSM-type Cs-137 sources

In this study, complete dosimetric datasets for the CSM2 and CSM3 Cs-137 sources were obtained using the Monte Carlo GEANT4 code. The application of this calculation method was experimentally validated with thermoluminescent dosimetry (TLD). Functions and parameters following the TG43 formalism are presented: the dose rate constant, the radial dose functional, and the anisotropy function. In addition, to aid the quality control process on treatment planning systems, a two-dimensional (2D) rectangular dose rate table (the traditional along-away table), coherent with the TG43 dose calculation formalism, is given. The data given in this study complement existing information for both sources on…

A practical MRI-based reconstruction method for a new endocavitary and interstitial gynaecological template

Purpose: There are perineal templates for interstitial implants such as MUPIT and Syed applicators. Their limitations are the intracavitary component deficit and the necessity to use computed tomography (CT) for treatment planning since both applicators are non-magnetic resonance imaging (MRI) compatibles. To overcome these problems, a new template named Template Benidorm (TB) has been recently developed. Titanium needles are usually reconstructed based on their own artifacts, mainly in T1-weighted sequence, using the void on the tip as the needle tip position. Nevertheless, patient tissues surrounding the needles present heterogeneities that complicate the accurate identification of these …

Dosimetry revisited for the HDR I192r brachytherapy source model mHDR-v2

Purpose: Recently, the manufacturer of the HDR I 192 r mHDR-v2 brachytherapysource reported small design changes (referred to herein as mHDR-v2r) that are within the manufacturing tolerances but may alter the existing dosimetric data for this source. This study aimed to (1) check whether these changes affect the existing dosimetric data published for this source; (2) obtain new dosimetric data in close proximity to the source, including the contributions from I 192 r electrons and considering the absence of electronic equilibrium; and (3) obtain scatterdose components for collapsed cone treatment planning system implementation. Methods: Three different Monte Carlo(MC) radiation transport co…

A monte carlo study of dose rate distribution around the specially asymmetric CSM3-a 137Cs source.

The CSM3 137Cs type stainless-steel encapsulated source is widely used in manually afterloaded low dose rate brachytherapy. A specially asymmetric source, CSM3-a, has been designed by CIS Bio International (France) substituting the eyelet side seed with an inactive material in the CSM3 source. This modification has been done in order to allow a uniform dose level over the upper vaginal surface when this `linear' source is inserted at the top of the dome vaginal applicators. In this study the Monte Carlo GEANT3 simulation code, incorporating the source geometry in detail, was used to investigate the dosimetric characteristics of this special CSM3-a 137Cs brachytherapy source. The absolute do…

VoxelMages: a general-purpose graphical interface for designing geometries and processing DICOM images for PENELOPE

The design and construction of geometries for Monte Carlo calculations is an error-prone, time-consuming, and complex step in simulations describing particle interactions and transport in the field of medical physics. The software VoxelMages has been developed to help the user in this task. It allows to design complex geometries and to process DICOM image files for simulations with the general-purpose Monte Carlo code PENELOPE in an easy and straightforward way. VoxelMages also allows to import DICOM-RT structure contour information as delivered by a treatment planning system. Its main characteristics, usage and performance benchmarking are described in detail.

Evaluation of the shielding in a treatment room with an electronic brachytherapy unit.

Esteya® (Elekta Brachytherapy, Veenendaal, The Netherlands) is an electronic brachytherapy (eBT) system based on a 69.5 kVp x-ray source and a set of collimators of 1 to 3 cm in diameter, used for treating non-melanoma skin cancer lesions. This study aims to estimate room shielding requirements for this unit. The non-primary (scattered and leakage) ambient dose equivalent rates were measured with a Berthold LB-133 monitor (Berthold Technologies, Bad Wildbad, Germany). The latter ranges from 17 mSv h-1 at 0.25 m distance from the x-ray source to 0.1 mSv h-1 at 2.5 m. The necessary room shielding was then estimated following US and some European guidelines. The room shielding for all barriers…

Calibration of a thermoluminescent dosimeter worn over lead aprons in fluoroscopy guided procedures

Fluoroscopy guided interventional procedures provide remarkable benefits to patients. However, medical staff working near the scattered radiation field may be exposed to high cumulative equivalent doses, thus requiring shielding devices such as lead aprons and thyroid collars. In this situation, it remains an acceptable practice to derive equivalent doses to the eye lenses or other unprotected soft tissues with a dosimeter placed above these protective devices. Nevertheless, the radiation backscattered by the lead shield differs from that generated during dosimeter calibration with a water phantom. In this study, a passive personal thermoluminescent dosimeter (TLD) was modelled by means of …

Dosimetric characteristics of a new unit for electronic skin brachytherapy

PURPOSE: Brachytherapy with radioactive high dose rate (HDR) (192)Ir source is applied to small skin cancer lesions, using surface applicators, i.e. Leipzig or Valencia type. New developments in the field of radiotherapy for skin cancer include electronic brachytherapy. This technique involves the placement of an HDR X-ray source close to the skin, therefore combining the benefits of brachytherapy with the reduced shielding requirements and targeted energy of low energy X-rays. Recently, the Esteya(®) Electronic Brachytherapy System (Esteya EBS, Elekta AB-Nucletron, Stockholm, Sweden) has been developed specifically for HDR brachytherapy treatment of surface lesions. The system provides rad…

Commissioning and periodic tests of the Esteya® electronic brachytherapy system

A new electronic brachytherapy unit from Elekta, called Esteya(®), has recently been introduced to the market. As a part of the standards in radiation oncology, an acceptance testing and commissioning must be performed prior to treatment of the first patient. In addition, a quality assurance program should be implemented. A complete commissioning and periodic testing of the Esteya(®) device using the American Association of Physicists in Medicine (AAPM), Groupe Europeen de Curietherapie and the European Society for Radiotherapy & Oncology (GEC-ESTRO) guidelines for linacs and brachytherapy units as well as our personal experience is described in this paper. In addition to the methodology, r…

QA of dynamic MLC based on EPID portal dosimetry.

Abstract Purpose Dynamic delivery of intensity modulated beams (dIMRT) requires not only accurate verification of leaf positioning but also a control on the speed of motion. The latter is a parameter that has a major impact on the dose delivered to the patient. Time consumed in quality assurance (QA) procedures is an issue of relevance in any radiotherapy department. Electronic portal imaging dosimetry (EPID) can be very efficient for routine tests. The purpose of this work is to investigate the ability of our EPID for detecting small errors in leaf positioning, and to present our daily QA procedures for dIMRT based on EPID. Methods and materials A Varian 2100 CD Clinac equipped with an 80 …

Brachytherapy treatment planning for complex applicators based on the AAPM TG-43 dosimetry algorithm: Case studies and clinical impact

Technical note: Monte Carlo derivation of TG-43 dosimetric parameters for radiation therapy resources and 3M Cs-137 sources

In clinical brachytherapy dosimetry, a detailed dose rate distribution of the radioactive source in water is needed in order to plan for quality treatment. Two Cs-137 sources are considered in this study; the Radiation Therapy Resources 67-800 source (Radiation Therapy Resources Inc., Valencia, CA) and the 3M model 6500/6D6C source. A complete dosimetric dataset for both sources has been obtained by means of the Monte Carlo GEANT4 code. Dose rate distributions are presented in two different ways; following the TG43 formalism and in a 2D rectangular dose rate table. This 2D dose rate table is helpful for the TPS quality control and is fully consistent with the TG43 dose calculation formalism…

Monte Carlo dosimetric characterization of the Cs-137 selectron/LDR source: evaluation of applicator attenuation and superposition approximation effects.

The purpose of this study is to calculate the dose rate distribution for the Amersham Cs-137 pellet source used in brachytherapy with the Selectron low-dose-rate remote afterloading system in gynaecological applications using the Monte Carlo code GEANT4. The absolute dose rate distribution for the pellet source was obtained and presented as a one-dimensional absolute dose rate table as well as in the Task Group 43 dose-calculation formalism. In this study, excellent agreement was found between the point source theoretical model using fitted polynomial values and Monte Carlo calculations of the dose rate distribution for the pellet source. A comparison study was also made between the dose ra…

Transit dose comparisons for60Co and192Ir HDR sources

The goal of this study is to evaluate the ambient dose due to the transit of high dose rate (HDR) 60Co sources along a transfer tube as compared to 192Ir ones in a realistic clinical scenario. This goal is accomplished by evaluating air-kerma differences with Monte Carlo calculations using PENELOPE2011. Scatter from both the afterloader and the patient was not taken into account. Two sources, mHDR-v2 and Flexisource Co-60, (Elekta Brachytherapy, Veenendaal, the Netherlands) have been considered. These sources were simulated within a standard transfer tube located in an infinite air phantom. The movement of the source was included by displacing their positions along the connecting tube from …

Evaluation of lens absorbed dose with Cone Beam IGRT procedures

The purpose of this work is to evaluate the absorbed dose to the eye lenses due to the cone beam computed tomography (CBCT) system used to accurately position the patient during head-and-neck image guided procedures. The on-board imaging (OBI) systems (v.1.5) of Clinac iX and TrueBeam (Varian) accelerators were used to evaluate the imparted dose to the eye lenses and some additional points of the head. All CBCT scans were acquired with the Standard-Dose Head protocol from Varian. Doses were measured using thermoluminescence dosimeters (TLDs) placed in an anthropomorphic phantom. TLDs were calibrated at the beam quality used to reduce their energy dependence. Average dose to the lens due to …

Towards clinical application of RayStretch for heterogeneity corrections in LDR permanent 125-I prostate brachytherapy

Purpose RayStretch is a simple algorithm proposed for heterogeneity corrections in low-dose–rate brachytherapy. It is built on top of TG-43 consensus data, and it has been validated with Monte Carlo (MC) simulations. In this study, we take a real clinical prostate implant with 71 125I seeds as reference and we apply RayStretch to analyze its performance in worst-case scenarios. Methods and Materials To do so, we design two cases where large calcifications are located in the prostate lobules. RayStretch resilience under various calcification density values is also explored. Comparisons against MC calculations are performed. Results Dose–volume histogram–related parameters like prostate D90, …

Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low-energy surface brachytherapy dosimetry

Purpose: A surface electronic brachytherapy (EBT) device is in fact an x-ray source collimated with specific applicators. Low-energy (<100 kVp) x-ray beam dosimetry faces several challenges that need to be addressed. A number of calibration protocols have been published for x-ray beam dosimetry. The media in which measurements are performed are the fundamental difference between them. The aim of this study was to evaluate the surface dose rate of a low-energy x-ray source with small field applicators using different calibration standards and different small-volume ionization chambers, comparing the values and uncertainties of each methodology. Methods: The surface dose rate of the EBT unit …

SU-E-T-467: Monte Carlo Dosimetric Study of the New Flexisource Co-60 High Dose Rate Source.

Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V.). This study aims to obtain quality dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO.Penelope2008 and GEANT4 Monte Carlo codes were used to dosimetrically characterize this source. Water composition and mass density was that recommended by AAPM. Due to the high energy of the 60Co, dose for small distances cannot be approximated by collisional kerma. Therefore, we have considered absorbed dose to water for r0.75 cm and collisional kerma from 0.75r20 cm. To provide adequate spatial resolution, cells were 0.01 cm in thickness for r2 cm from the sour…

A simple analytical method for heterogeneity corrections in low dose rate prostate brachytherapy

In low energy brachytherapy, the presence of tissue heterogeneities contributes significantly to the discrepancies observed between treatment plan and delivered dose. In this work, we present a simplified analytical dose calculation algorithm for heterogeneous tissue. We compare it with Monte Carlo computations and assess its suitability for integration in clinical treatment planning systems. The algorithm, named as RayStretch, is based on the classic equivalent path length method and TG-43 reference data. Analytical and Monte Carlo dose calculations using Penelope2008 are compared for a benchmark case: a prostate patient with calcifications. The results show a remarkable agreement between …

Monte Carlo calculation of beam quality correction factors for PTW cylindrical ionization chambers in photon beams.

The beam quality correction factor k Q for megavoltage photon beams has been calculated for eight PTW (Freiburg, Germany) ionization chambers (Farmer chambers PTW30010, PTW30011, PTW30012, and PTW30013, Semiflex 3D chambers PTW31021, PTW31010, and PTW31013, and the PinPoint 3D chamber PTW31016). Simulations performed on the widely used NE-2571 ionization chamber have been used to benchmark the results. The Monte Carlo code PENELOPE/penEasy was used to calculate the absorbed dose to a point in water and the absorbed dose to the active air volume of the chambers for photon beams in the range 4 to 24 MV. Of the nine ionization chambers analysed, only five are included in the current version of…

Fetal dose measurements and shielding efficiency assessment in a custom setup of (192)Ir brachytherapy for a pregnant woman with breast cancer.

To assess the radiation dose to the fetus of a pregnant patient undergoing high-dose-rate (HDR) (192)Ir interstitial breast brachytherapy, and to design a new patient setup and lead shielding technique that minimizes the fetal dose.Radiochromic films were placed between the slices of an anthropomorphic phantom modeling the patient. The pregnant woman was seated in a chair with the breast over a table and inside a leaded box. Dose variation as a function of distance from the implant volume as well as dose homogeneity within a representative slice of the fetal position was evaluated without and with shielding.With shielding, the peripheral dose after a complete treatment ranged from 50 cGy at…

SU-E-T-343: Valencia Applicator Commissioning Using a Micro-Chamber Array

Purpose: In the commissioning and QA of surface isotope-based applicators, source-indexer distance (SID) has a great influence in the flatness, symmetry and output. To these purposes, methods described in the literature are the use of a special insert at the entrance of dwell chamber or radiochromic films. Here we present the experience with a micro-chamber array to perform the commissioning and QA of Valencia applicators. Methods: Valencia applicators have been used, the classic and the new extra-shielded version. A micro-chamber array has been employed, 1000 SRS (PTW), with 977 liquid filled, 2.3×2.3×0.5 mm3 sized ion chambers covering 11×11 cm2, which spacing is 2.5 mm in the central 5.5…

Supplement 2 for the 2004 update of the AAPM Task Group No. 43 Report: Joint recommendations by the AAPM and GEC-ESTRO

Since publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (TG-43U1) and its 2007 supplement (TG-43U1S1), several new low-energy photon-emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical purposes and are posted on the Brachytherapy Seed Registry managed jointly by the AAPM and the Imaging and Radiation Oncology Core Houston Quality Assurance Center (IROC Houston). Given increasingly closer interactions among physicists in North America and Europe, the AAPM and the Groupe Europeen de Curietherapie-European Society for Radiotherapy & Oncology (GEC…

An approach to using conventional brachytherapy software for clinical treatment planning of complex, Monte Carlo-based brachytherapy dose distributionsa)

Certain brachytherapy dose distributions, such as those for LDR prostate implants, are readily modeled by treatment planning systems (TPS) that use the superposition principle of individual seed dose distributions to calculate the total dose distribution. However, dose distributions for brachytherapy treatments using high-Z shields or having significant material heterogeneities are not currently well modeled using conventional TPS. The purpose of this study is to establish a new treatment planning technique (Tufts technique) that could be applied in some clinical situations where the conventional approach is not acceptable and dose distributions present cylindrical symmetry. Dose distributi…

Monte Carlo dosimetry of the Buchler high dose rate 192Ir source.

In this study a complete set of dosimetric data is presented for the high dose rate (HDR) source from Amersham used in the Buchler remote afterloading HDR unit. These data have been calculated by means of the Monte Carlo simulation code GEANT taking into account the detailed geometry of the source. Absolute dose rate distributions in water were calculated around this source and are presented as conventional 2D Cartesian look-up tables. All dosimetric quantities recommended by the AAPM Task Group 43 report have been calculated. Quantities determined are: dose rate constant, radial dose function, anisotropy function, anisotropy factor and anisotropy constant. The dose rate distributions of th…

A generic high-dose rate192Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism

Purpose: In order to facilitate a smooth transition for brachytherapy dose calculations from the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) formalism to model-b ...

Correction factors for ionization chamber measurements with the ‘Valencia’ and ‘large field Valencia’ brachytherapy applicators

Treatment of small skin lesions using HDR brachytherapy applicators is a widely used technique. The shielded applicators currently available in clinical practice are based on a tungsten-alloy cup that collimates the source-emitted radiation into a small region, hence protecting nearby tissues. The goal of this manuscript is to evaluate the correction factors required for dose measurements with a plane-parallel ionization chamber typically used in clinical brachytherapy for the 'Valencia' and 'large field Valencia' shielded applicators. Monte Carlo simulations have been performed using the PENELOPE-2014 system to determine the absorbed dose deposited in a water phantom and in the chamber act…

Air-kerma evaluation at the maze entrance of HDR brachytherapy facilities.

In the absence of procedures for evaluating the design of brachytherapy (BT) facilities for radiation protection purposes, the methodology used for external beam radiotherapy facilities is often adapted. The purpose of this study is to adapt the NCRP 151 methodology for estimating the air-kerma rate at the door in BT facilities. Such methodology was checked against Monte Carlo (MC) techniques using the code Geant4. Five different facility designs were studied for (192)Ir and (60)Co HDR applications to account for several different bunker layouts.For the estimation of the lead thickness needed at the door, the use of transmission data for the real spectra at the door instead of the ones emit…

Surface brachytherapy: Joint report of the AAPM and the GEC-ESTRO Task Group No. 253.

The surface brachytherapy Task Group report number 253 discusses the common treatment modalities and applicators typically used to treat lesions on the body surface. Details of commissioning and calibration of the applicators and systems are discussed and examples are given for a risk-based analysis approach to the quality assurance measures that are necessary to consider when establishing a surface brachytherapy program.

TG-43U1-based dosimetric characterization of model 67-6520 137 Cs brachytherapy source

Monte Carlo dosimetric study of Best Industries and Alpha Omega Ir-192 brachytherapy seeds

Ir-192 seeds are widely used in the USA for low dose rate interstitial brachytherapy. There are two commercially available models: those manufactured by Best Industries filtered with stainless steel, and those manufactured by Alpha-Omega seeds filtered with Pt. Newly developed 3D correction algorithms for brachytherapy are based on dosimetry data obtained on unbounded phantom size, allowing corrections for heterogeneities and actual tissue boundaries. Published dosimetric datasets for both seeds have been obtained under bounded conditions. The aim of the present study is to obtain dosimetric datasets for these seeds under full scatter conditions. The Monte Carlo GEANT4 code has been used to…

Dosimetric Deviation of Leipzig and Valencia Skin Applicators When Used without Cap

Dosimetric Uncertainties in the Practice of Clinical Brachytherapy

SU-GG-T-227: Dynamic IMRT Split Beam Technique Verification Using EPID Based Dosimetry

Purpose: On dynamic IMRT plans with Millenium 80 (Varian) fields wider of 15 cm must be splitted. Since the EPIDdosimetry software does not allow to sum splitted subfluences in the same dosimetric portal image they have to be measured separately and compared independently with the subfluences previously calculated by the TPS Eclipse. The purpose of our work is the development of a tool to: 1) analyze the correct match between the two abutted ports for splitted fields. 2) study the effect of gravity and analyze repercussions of possible misalignments and 3) illustrate that the gamma evaluation should be made with the global summed fluence per field instead of with the individual subfluences.…

Erratum: “Supplement 2 for the 2004 update of the AAPM Task Group No. 43 Report: Joint recommendations by the AAPM and GEC-ESTRO” [Med. Phys. Vol 44 (9), e297-e338 (2017)]

Assaying multiple 125 I seeds with the well-ionization chamber SourceCheck 4π 33005 and a new insert

PURPOSE To provide a practical solution that can be adopted in clinical routine to fulfill the AAPM-ESTRO recommendations regarding quality assurance of seeds used in prostate permanent brachytherapy. The aim is to design a new insert for the well-ionization chamber SourceCheck(4π) 33005 (PTW, Germany) that allows evaluating the mean air-kerma strength of up to ten (125)I seeds with one single measurement instead of measuring each seed individually. MATERIAL AND METHODS The material required is: a) the SourceCheck(4π) 33005 well-ionization chamber provided with a PTW insert to measure the air-kerma strength S K of one single seed at a time; b) a newly designed insert that accommodates ten s…

Commissioning and quality assurance procedures for the HDR Valencia skin applicators

The Valencia applicators (Nucletron, an Elekta company, Elekta AB, Stockholm, Sweden) are cup-shaped tungsten applicators with a flattening filter used to collimate the radiation produced by a high-dose-rate (HDR) 192 Ir source, and provide a homogeneous absorbed dose at a given depth. This beam quality provides a good option for the treatment of skin lesions at shallow depth (3-4 mm). The user must perform commissioning and periodic testing of these applicators to guarantee the proper and safe delivery of the intended absorbed dose, as recommended in the standards in radiation oncology. In this study, based on AAPM and GEC-ESTRO guidelines for brachytherapy units and our experience, a set …

Broad beam transmission curves for new radionuclides in brachytherapy

Evaluation of high-energy brachytherapy source electronic disequilibrium and dose from emitted electrons

Purpose: The region of electronic disequilibrium near photon-emitting brachytherapysources of high-energy radionuclides ( C 60 o , C 137 s , I 192 r , and Y 169 b ) and contributions to total dose from emitted electrons were studied using the GEANT4 and PENELOPEMonte Carlo codes. Methods: Hypothetical sources with active and capsule materials mimicking those of actual sources but with spherical shape were examined. Dose contributions due to sourcephotons, x rays, and bremsstrahlung; source β − , Auger electrons, and internal conversionelectrons; and water collisional kerma were scored. To determine if conclusions obtained for electronic equilibrium conditions and electrondose contribution t…

TH-C-AUD A-07: Evaluation of the Correction Factor Due to the Lack of Full Scatter Conditions in Cs-137 and Ir-192 Brachytherapy Dosimetric Studies

Purpose: Use of a finite phantom to derive dose rate distributions around brachytherapysources implies a lack of backscattering material near the phantom periphery. Conventional planning algorithms and newly‐developed 3D correction algorithms are based on physics data under full scatter conditions. Presently, most published Monte Carlodosimetric studies have been obtained using either a spherical phantom (15cm in radius) or a cylinder phantom (40×40cm2). The study objective was to derive a simple relationship to correlate the radial dose function, g(r), obtained for each one of these phantoms to that obtained for an unbounded phantom. Method and Materials: Assuming bare point sources of 137…

Dosimetric characterization of Ir-192 LDR elongated sources

Ir-192 wires have been used in low-dose-rate brachytherapy for many years. Commercially available treatment planning systems approximate the dose rate distribution of the straight or curved wires applying the superposition principle using one of the following methods: (i) The wire is modeled as a set of point sources, (ii) the wire is modeled as a set of small straight segment wires, (iii) the values of the parameters and functions of the American Association of Physicists in Medicine (AAPM) Task Group 43 protocol are obtained for wire lengths between 3 and 7 cm assuming some simplifications. The dose rate distributions obtained using these methods for linear wires of different lengths and …