Search results for "DOSIMETRY"
showing 10 items of 297 documents
EPR/alanine dosimetry for verification in Helical Tomotherapy Stereotactic Radiosurgery (HTSRS) treatments
2018
Introduction Intracranial stereotactic radiosurgery (SRS) is a technique to deliver an ablative radiation dose with an extremely sharp dose gradient to small brain tumors. In this study the accuracy of the dose delivered in SRS by a non conventional radiotherapy machine, the TomoTherapy Hi-Art System, was investigated using an "end-to-end" test using alanine pellets and gafchromic films. Methods Dose verifications were made using alanine dosimeters placed in an antropomorphic head phantom (Alderson Rando Phantom) under different treatment conditions in case of both single and multiple brain tumors. 1.25mm slice kVCT scan of the phantom was used to generate SRS plans on the TomoTherapy Plann…
Generator-Based Radiopharmaceuticals for PET Dosimetry Before, During, and After Endoradiotherapy
2014
Generator-derived radionuclides for PET/CT imaging are promising for optimizing targeted radiotherapy by an individual patient-based approach, applying pre-therapeutic evaluation, dosimetric calculations, and for measuring treatment response after radionuclide therapy. To realize this vision, sophisticated nuclear chemistry and radiopharmaceutical chemistry should coincide with quantitative molecular imaging and dosimetric calculations.
PbS Nanodots Embedded in ZrO2 Thin Films for Ultraviolet Radiation Dosimetry
2011
PbS nanodots embedded in ZrO2 thin film matrix (ZrO2:PbS films) were investigated for UV radiation dosimetry purposes. ZrO2:PbS films were UV irradiated using wavelengths 250 - 400 nm. Photoelectron emission spectra of ZrO2:PbS films were recorded and band structure of the films was calculated. It was found that density of localized states increased with increase in concentration of PbS nanodots which allowed to suggest that PbS nanodots are responsible for creation of localized states. Number of localized states decreased after UV irradiation. The linear correlation between number of localized states and time of UV exposure was observed. Observed changes in band structure of ZrO2:PbS films…
LOW DOSE CHARACTERIZATION OF FRICKE GEL DOSIMETERS BY OPTICAL ABSORBANCE AND MR RELAXATION METHODS
2016
Introduction Fricke gel dosimeters allow measurements of 3D dose distributions and can be an effective tool for dosimetry verifications in radiotherapy. Various authors have reported drawbacks of the gels affecting the accuracy in case of low dose measurements. Purpose This study aims at investigating such drawbacks and at establishing the conditions for an optimal use of the gels. Materials and methods Our dosimeters consist of gels infused with a Fricke ferrous sulphate solution combined with xylenol orange (XO). Two kinds of xylenol orange (XO) and two different gelling agents (gelatin from porcine skin and Agarose) were utilized. Gels are red out by light absorption techniques: images o…
Calculated organ doses using Monte Carlo simulations in a reference male phantom undergoing HDR brachytherapy applied to localized prostate carcinoma
2013
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…
Monte Carlo dosimetric study of the Flexisource Co-60 high dose rate source.
2011
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…
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
2008
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…
WE-C-108-08: Organ Doses in a Male Phantom Undergoing High-Dose-Rate Brachytherapy Applied to the Prostate
2013
Purpose: The aim of this study was to obtain equivalent doses to radiosensitive organs when applying high‐dose‐rate (HDR) brachytherapy to the prostate using60 Co or 192 Ir sources, and in comparison to external‐beam radiotherapy (EBRT) modalities. Methods: Monte Carlo simulations in Geant4 were performed using a voxelized adult reference man described in Publication 110 by the International Commission on Radiological Protection (ICRP). Point sources of 60Co or 192Ir with photon energy spectra corresponding to those exiting their capsules were placed in the center of the prostate. Equivalent doses per therapeutic absorbed dose to the prostate were obtained in several radiosensitive organs. …
Monte Carlo dosimetric study of Best Industries and Alpha Omega Ir-192 brachytherapy seeds
2004
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…
Un sistema digitale innovativo per la caratterizzazione energia-flusso di fasci X diagnostici
2016
La conoscenza della distribuzione energetica e del rateo di fluenza dei fasci X è essenziale nei controlli di qualità in medicina diagnostica, sia in termini dosimetrici che della qualità delle immagini. Gli spettri energetici possono essere utilizzati per stime accurate delle tensioni dei tubi (kVp), per la correzione di distorsioni dovute al beam-hardening e per la corretta implementazione delle nuove tecniche dual-energy [1]. In mammografia, gli spettri energetici possono essere usati per stimare l’esposizione, il kerma in aria e la distribuzione energetica della dose assorbita nei tessuti, superando gli inconvenienti dovuti alla dipendenza energetica della risposta dei dosimetri (a stat…