Phenol compounds as new materials for electron spin resonance dosimetry in radiotherapy

Preliminary magnetic resonance relaxometric analysis of Fricke gel dosimeters produced with polyvinyl alcohol and glutaraldehyde

This work describes the preliminary analysis of Fricke gels dosimeters characterized by a new formulation making use of a matrix of polyvinyl alcohol cross-linked by adding glutaraldehyde and analyzed by means of nuclear magnetic resonance relaxometry. In previous optical studies, these gels have shown promising dosimetric features in terms of photon sensitivity and low diffusion of ferric ions produced after irradiation. In this work, we used a portable nuclear magnetic resonance relaxometer to measure the relaxation times (which are important for dosimetric applications) of these gel materials. For this purpose, we performed a study for optimizing the acquisition parameters with a nuclear…

EPR DOSIMETRY WITH ALANINE FOR TOTAL BODY IRRADIATION USING AN ANTHROPOMORPHIC PHANTOM

The Total Body Irradiation (TBI) is a radiation therapy technique widely used in clinical hemato-oncological treatment of patients that underwent bone marrow transplantation or peripheral stem cell transplantation. Typically, the administration of TBI treatment provides irradiations in 3 consecu-tive days with a double daily fractionation, although other dose fractionation modes have been widely adopted in the clinic procedures. Although this tech-nique allows to irradiate the whole body from head to toes, it has some limitations such as the lack of homogeneity of the dose distribution (which can show varia-tions of 20% in the different areas), irradiation of critical organs such as lungs, …

Phenol compounds as new materials for electron spin resonance dosimetry in radiotherapy

Introduction: Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures. Free radicals are known to be produced when a compound is irradiated with ionizing radiations. The concentration of radiationinduced free radicals is proportional to the absorbed dose and this allows for dosimetric measurements through ESR technique which enables to quantitatively determine the radical concentration. In this work we report the ESR investigation of phenol pellets and thin films exposed to various types of radiation beams (clinical photon and el…

Resting state fMRI as a tool to investigate brain functional connectivity

Diffusion and sensitivity characteristics of a chemically cross-linked PVA-Fricke gel dosimeter

Introduction: Current radiotherapy techniques implement treatment plans based on volumetric distributions of dose with complex shapes and sharp gradients. The agreement between these plans and the dose that is truly delivered is very challenging to verify. Thus, there is the need for a dosimetric system that is truly three dimensional, sensitive to radiation in each point and tissue equivalent. In this framework, great interest is encountered by radio-chromic gel dosimeters. In order to address the limitations of gels based on natural matrices, some investigators have proposed dosimeters based on poly vinyl alcohol (PVA) made by freezing-thawing cycles. Even though these gels have a low dif…

Characterization of phenolic pellets for ESR dosimetry in photon beam radiotherapy

This work deals with the dosimetric features of a particular phenolic compound (IRGANOX 1076 ® ) for dosimetry of clinical photon beams by using electron spin resonance (ESR) spectroscopy. After the optimization of the ESR readout parameters (namely modulation amplitude and microwave power) to maximise the signal without excessive spectrum distortions, basic dosimetric properties of laboratory-made phenolic dosimeters in pellet form, such as reproducibility, dose–response, sensitivity, linearity and dose rate dependence were investigated. The dosimeters were tested by measuring the depth dose profile of a 6 MV photon beam. A satisfactory intra-batch reproducibility of the ESR signal of the …

Characterization of the ESR response of alanine dosimeters to low-energy (1-40 keV) X-rays

The aminoacid L-a-alanine has attracted considerable interest for use in radiation ESR dosimetry and has been formally accepted as a secondary standard for high-dose (kGy) and transfer dosimetry . The accuracy of the method is quite high, largely due to the low dependence of the alanine response on various irradiation parameters (photon energies above 100 keV, dose rate, temperature, etc.). Furthermore, this system presents alinear response to dose, fairly high sensitivity, tissue equivalence, absence of fading, small dimensions, ruggedn ess, and non-destructive readout. In this work, we examined the energy dependence of alanine ESR dosimeters in the low energy X-photon energy range between…

Dosimetria tramite Risonanza Elettronica di Spin (ESR) in Electron Intra-Operative RadioTherapy (IORT): misure di Output Factor e simulazioni Monte Carlo-GEANT4

La Radioterapia IntraOperatoria (IORT) È una modalità di trattamento in cui una singola dose di radiazioni è impartita direttamente al letto tumorale o al tumore durante l'intervento chirurgico, evitando di colpire i tessuti sani circostanti. Nel caso di irraggiamento alla mammella, una singola frazione di 21 Gy impartita al volume neoplastico durante la procedura chirurgica è equivalente ad una dose totale di 60 Gy che solitamente viene somministrata con la radioterapia frazionata. Questo lavoro riporta il confronto tra la risposta ESR di dosimetri di alanina e di camere a ionizzazione Markus per le misurazioni degli Output Factor (OF) di fasci di elettroni prodotti da un acceleratore line…

Phenol compounds as a New Materials for EPR dosimetry in radiation therapy

Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the Electron Paramagnetic Resonance (EPR) arouses increasing interest for applications in various therapy procedures. When a compound is irradiated with ionizing radiations free radicals are produced and their concentration is proportional to the absorbed dose. This allows for dosi-metric measurements through EPR technique which is able to quantitatively de-termine the radical concentration. Our research group has started an investigation of the EPR response of some phenols compounds for possible dosimetric applications. In this work we report the EPR investigation of IRGANOX 1076 …

Testing and linearity calibration of films of phenol compounds exposed to thermal neutron field for EPR dosimetry

This paper reports the preliminary results obtained by Electron Paramagnetic Resonance (EPR) measurements on films of IRGANOX® 1076 phenols with and without low content (5% by weight) of gadolinium oxide (Gd2O3) exposed in the thermal column of the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia (Italy). Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. The dependence of EPR signal as function of neutron dose was investigated in the fluence range between 10(11) cm(-2) and 10(14) cm(-2). Linearity of EPR response was fou…

Dosimetria ESR con alanina per adronterapia per protoni e ioni carbonio

Gamma component dosimetry in the thermal column of the TRIGA reactor in Pavia

This presentation describes the assessment of the gamma rays spectrum and dose. Yhe result have been used to perform dosimetry in cell cultures for in-vitro BNCT studies.

CHARACTERIZATION OF THE GAMMA DOSE COMPONENT IN THE NEUTRON FIELD OF A BNCT IRRADIATION FACILITY

At the University of Pavia, a neutron irradiation facility has been constructed for preclinical in vitro and in vivo studies for BNCT. The facility is a wide channel (40 x 20 x 100 cm3) inside the graphite Thermal Column of the 250 KW research reactor TRIGA Mark II. The neutron field consists in a thermal component ranging from about 1010 and 109 cm-2s-1 along the longitudinal axis of the channel and it is uniform within 10% along the transversal axes. The fast neutron contamination (En > 1.58 keV) is more than 2 orders of magnitude lower. The gamma background coming from the core has been reduced with a 20 cm thick bismuth shield, however in the facility a gamma component is still prese…

Investigation of alanine with gadolinium for ESR dosimetry at TRIGA Mark II reactor of Mainz

In this work we have studied the response of alanine pellets with and without gadolinium exposed to the thermal column of the TRIGA Mark II research reactor at the University of Mainz

PVA gel dosimeters for radiotherapy applications,

Gel dosimeters for three-dimensional mapping of radiotherapy doses were introduced at Yale University in the mid-1980’s. Soon after, research and development in this field also started in Italy. Early work was done at the Istituto Superiore di Sanità, and at the Universities of Pisa and Milan. Several institutes now collaborate on this topic with the goal of developing new formulations of hydrogel matrices with improved characteristics of stability, sensitivity and spatial resolution compared to those of earlier Fricke-gel and polymer-gel systems. Contrary to earlier gels based on natural gelling agents, such as porcine skin gelatin and/or agarose, which suffer from limited batch -to-batch …

Investigation of relaxation times of irradiated Fricke gels by means of nuclear magnetic resonance relaxometry

Fricke gel dosimeters are ideal candidates to provide 3D maps of dose distributions and are particularly useful in the plann ing and verification phase of radiotherapy treatments. One of the most effective experimental techniques to reconstruct dose maps is magnetic resonance imaging (MRI). This measures th e nuclear relaxation times variations induced by irradiation. In this work, we analyzed Fricke gels with and without Xylenol Orange by means of a single side-NMR relaxometer (which is abl e to provide information on both relaxation relaxation times T1 and T2 and is mainly used in the field of diagnostics for Cultural Heritage [1-2] to perform porosimetry meaurements). Our goal was to per…

Resting state FMRI: A tool to investigate functional connectivity modulation induced by transcranial direct current stimulation of the motor network

Introduction: Resting-state functional connectivity (fcMRI) represents a novel fMRI approach that allows detection of temporal correlations in spontaneous BOLD signal oscillations while subjects rest quietly in the scanner. Under resting conditions the brain is engaged in spontaneous activity that causes a low frequencies (<0.1 Hz) BOLD signal fluctuations. Functional connectivity (FC) can be defined as the synchrony of neural activity among spatially distant regions. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that is known to modulate cortical activity and FC among brain regions, as measured by functional magnetic resonance imaging. This st…

ALANINE/EPR DOSIMETRY APPLIED TO THE VALIDATION OF A TOTAL BODY IRRADIATION (TBI) PROTOCOL AND TREATMENT PLANNING DOSE CALCULATION USING A HUMANOID PHANTOM

L’irraggiamento a corpo intero (Total Body Irradiation - TBI) è una tecnica di radioterapia oncologica di largo impiego nella clinica ematoncologica nell’ambito del trattamento di pazienti avviati al trapianto di midollo osseo o al trapianto di cellule staminali periferiche. La TBI da una parte permette di sopprimere il sistema immunitario del ricevente per prevenire il rigetto del midollo del donatore ed eliminare le cellule neoplastiche residue dai trattamenti chemioterapici. In genere, la modalità di somministrazione della TBI prevede irraggiamenti in 3 giorni consecutivi con un bi-frazionamento giornaliero (2 Gy, 2 volte al giorno con intervallo minimo di 6 ore tra le sedute, per 3 gior…

Neutron flux and gamma dose measurement in the BNCT irradiation facility at the TRIGA reactor of the University of Pavia

Abstract University of Pavia is equipped with a TRIGA Mark II research nuclear reactor, operating at a maximum steady state power of 250 kW. It has been used for many years to support Boron Neutron Capture Therapy (BNCT) research. An irradiation facility was constructed inside the thermal column of the reactor to produce a sufficient thermal neutron flux with low epithermal and fast neutron components, and low gamma dose. In this irradiation position, the liver of two patients affected by hepatic metastases from colon carcinoma were irradiated after borated drug administration. The facility is currently used for cell cultures and small animal irradiation. Measurements campaigns have been ca…

Testing and calibration of ESR response of Fricke gel dosimeters in mixed neutron-gamma fields

Advanced techniques in Magnetic Resonance Imaging: characterization of non-gaussian water diffusion using DIFFUSION KURTOSIS IMAGING (DKI)

DOSIMETRIA DI FASCI NEUTRONICI TRAMITE SPETTROSCOPIA DI RISONANZA PARAMAGNETICA ELETTRONICA (EPR)

Functional connectivity modulation induced by transcranial direct current stimulation of the motor network investigated by resting state fMRI

This study is aimed at measuring the variation of functional connectivity between cortical brain regions after tDCS along time. For this purpose we enrolled 20 healthy right-handed subjects.

Fricke gel, electron spin resonance and thermoluminescence for integration and intercomparison of measurements in NCT dosimetry

Correlation between ferrous ammonium sulfate concentration, sensitivity and stability of Fricke gel dosimeters exposed to clinical X-ray beams

Abstract This work describes the characterization of various Fricke-Agarose-Xylenol gels (FXG) dosimeters using NMR relaxometry and MRI analysis. Using X-rays from a clinical linear accelerator (LINAC), the gels were irradiated in the dose range from 0 Gy to 20 Gy. The photon sensitivity of the FXGs was measured in terms of NMR relaxation rates; its dependence on radiation dose was determined as a function of ferrous ammonium sulfate contents (from 0.5 mM to 5 mM). Furthermore, the stability of the NMR signal was monitored over several days after irradiation. These measurements were aided by Magnetic Resonance Imaging (MRI) scans which allowed three-dimensional (3D) dose mapping. In order t…

Use of alanine EPR dosimeters for discriminating neutron and photon components in the thermal column of Pavia Triga reactor

The main gol of the present work is to investigate the response behaviour of alanine EPR pellets in clinical proton anc carbon ion beams. Proton irradiations were carried out at PSI (Switzerland) using both passive and active scattering modality, whereas, C ions irradiation were performed at GSI (Germany) adopting the raster scanning modality.

Characterization of the terminal column of TRIGA Mark II reactor of Mainz through of alanine pellets.

We have studied the ESR response of alanine pellets with and without gadolinium exposed to the thermal column of the TRIGA Mark II research reactor at the University of Mainz (Germany). The choice of Gd as additive nucleus is due to its very high capture cross section to thermal neutrons and to the possibility for secondary particles produced after interaction with thermal neutrons of releasing their energy in the neighborhood of the reaction site. In particular, it was found that low concentration (5% by weight) of Gd brings about a neutron sensitivity enhancement of more than 10 times without heavily reducing tissue equivalence. Monte Carlo (MC) simulations of both response of alanine and…

EPR RESPONSE OF PHENOLIC SOLID STATE PELLETS FOR DOSIMETRY OF RADIO- THERAPEUTIC PHOTON AND ELECTRON BEAMS

Gel di Fricke: studio della risposta NMR in funzione della concentrazione di ferro ed utilizzo dosimetrico in ambito clinico (3D MRI)

Analysis of the response of PVA-GTA Fricke-gel dosimeters with clinical magnetic resonance imaging

Abstract Fricke gel dosimeters produced with a matrix of Poly-vinyl alcohol (PVA) cross-linked with glutaraldehyde (GTA) were analyzed with magnetic resonance imaging (MRI). Previous studies based on spectrophotometry showed valuable dosimetric features of these gels in terms of X-ray sensitivity and diffusion of the ferric ions produced after irradiation. In this study, MRI was performed on the gels at 1.5 T with a clinical scanner in order to optimize the acquisition parameters and obtain high contrast between irradiated and non-irradiated samples. The PVA gels were found to offer good linearity in the range of 0–10 Gy and a stable signal for several hours after irradiation. The sensitivi…

Nuclear Magnetic Resonance investigation of PVA-GTA FRicke gel dosimeters exposed to clinical photon beams

Fricke Xylenol Gel (FXG) dosimetric system is based on the radiation induced oxidation of ferrous (Fe2+) to ferric (Fe3+) ions. The application of Fricke gels for ionizing radiation dosimetry is continuously increasing worldwide due to their many favorable properties. However, one of their shortcomings is that ferrous and ferric ions diffuse in the gel matrix. To maintain the spatial integrity of the dose distribution, Fricke gels must be undergoing measurement within a few hours of their irradiation, so that ferric ions remain close to their point of production. Thus, the spatial integrity of the dose distribution in the Fricke gel is maintained. The gel matrix also contributes to the oxid…

Characterization of Fricke gel dosimeters exposed to gamma rays and neutrons

Spin trapping as tool for investigating radiation induced free radicals in biologically active molecules

Since from the second half of the last century the spin trapping has found wide applications in chemistry, biology and medicine [1]. Of particular interest are the studied of the free radicals induced in biologically active molecules, such as DNA and proteins, when they are exposed to ionizing radiation. Their characterization allows to investigate the radiation-induced primary processes inside living cells. Indeed, ionizing radiations produce many kinds of free radicals through direct action; radicals can be formed also by indirect actions. However, the direct detection of these radicals is hard to obtain as they have a too short lifetime and this makes difficult to record them by conventi…

Sensibilità e stabilità dei dosimetri gel di tipo Fricke esposti ai fotoni nel range clinico in funzione della concentrazione di ferro e degli additivi presenti: 3D MRI per applicazioni dosimetriche

COMPARATIVE EVALUATION OF DATA PREPROCESSING SOFTWARE TOOLS TO INCREASE EFFICIENCY AND ACCURACY IN DIFFUSION KURTOSIS IMAGING

Introduction: Diffusion tensor imaging (DTI) is the most commonly used technique to extract microstructural features from a set of diffusionweighted images. In addition to the metrics obtained with DTI, diffusion kurtosis imaging (DKI) can provide non-Gaussian diffusion measures by means of the kurtosis tensor. DKI has shown to be more sensitive to tissue microstructural changes in both normal and pathological neural tissue. In a clinical setting, however, these benefits are often nullified by numerous acquisition artifacts. The aim of this study was compare two preprocessing software for DTI apply to DKI. Also, the major preprocessing, processing and post-processing procedures applied to D…

Study of optical absorbance and MR relaxation of irradiated Fricke Xylenol Orange Gel Dosimeters

Studies on the optical absorbance spectra of Fricke xylenol orange gel dosimeters were performed, in the wavelength range from 300 nm to 800 nm, in order to highlight some particular characteristics that can affect the achievable precision. The spectra are different mainly due to the different types of xylenol orange that was used and to a lower extent due to the different gelling agents (agarose or gelatine). The characteristic of variation of absorbance spectra versus dose, however, are similar in the various cases and can explain some peculiarities, as apparent effects of dose threshold. Changes of spectral shapes appear over the time after irradiation. Magnetic resonance measurements pe…

Characterization of the ESR response of alanine dosimeters to low-energy Cu-target X-tube photons

Abstract This article describes Electron Spin Resonance (ESR) response measurements of Kodak BioMax alanine films exposed to low-energy X-rays from a Cu-target tube operating at 20 kV. Commercial alanine detectors were used to ensure maximum reproducibility of the results, while the choice of a film was due the low penetration of the soft X-rays. X-ray energy spectra and fluences were determined with an innovative digital semiconductor detector system. These data were used to quantify the irradiation of the alanine films in terms of absorbed dose to water. The alanine films were found to present a stable response, highly linear with dose. To our knowledge, these data have not been previousl…

Investigation of applicability of alanine pellets and films for dosimetry of proton clinical beams

Laser-driven proton has recently gained a great interest as an alternative to conventional and more expensive acceleration techniques. These ion beams have desirable qualities such as small source size, high luminosity and small emittance to be used in different physics fields. This is very promising specially for the future perspective of a new concept of hadrontherapy based on laser-based devices could be developed, replacing traditional accelerating machines. ELIMED (Medical Applications at Extreme Light Infrastructure) is a task-force originally born by an idea of ELI-Beams (Prague) and INFN-LNS (Italian Institute for Nuclear Physics of Catania) researchers. ELIMED main goal is to perfo…

LOW DOSE CHARACTERIZATION OF FRICKE GEL DOSIMETERS BY OPTICAL ABSORBANCE AND MR RELAXATION METHODS

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…

Dosimetria a risonanza di spin elettronico (ESR) tramite composti organici (alanina e tartrato di ammonio) per campi misti neutroni-gamma

Study of optical absorbance and MR relaxation of Fricke xylenol orange gel dosimeters

Abstract Studies on the optical absorbance spectra of Fricke xylenol orange gel dosimeters were performed, in the wavelength range from 300 nm to 800 nm, in order to highlight some particular characteristics that can affect the achievable precision. The spectra are different mainly due to the different types of xylenol orange that was used and to a lower extent due to the different gelling agents (agarose or gelatine). The characteristic of variation of absorbance spectra versus dose, however, are similar in the various cases and can explain some peculiarities, as apparent effects of dose threshold. Changes of spectral shapes appear over the time after irradiation. Magnetic resonance measur…

NUCLEAR MAGNETIC RESONANCE RELAXOMETRY AND IMAGING FOR DOSIMETRY WITH AGAROSE FRICKE GEL

Introduction: Fricke Xylenol Gel (FXG) dosimetric system is based on the radiation induced oxidation of ferrous to ferric ions. In this kind of gels it can occur that ferrous and ferric ions diffuse in the gel matrix. To preserve the spatial distribution of the dose from diffusion, Fricke gels must be undergoing measurement within a few hours of their irradiation. Thus, the spatial integrity of the dose distribution in the Fricke gel is maintained. The oxidation of ferrous ions also causes a reduction of the longitudinal nuclear magnetic relaxation time which can be measured by means of nuclear magnetic resonance (NMR) instrumentation. In this work we performed NMR relaxometry and MR imagin…

I fenoli come nuovi materiali per la dosimetria EPR in campo misto neutroni-gamma

PVA-GTA Fricke gel: studio della risposta NMR in funzione della concentrazione degli additivi e studi preliminari con scanner MRI 7 T

Sono stati analizzati tramite rilassometria NMR ed acquisizioni MRI dosimetri gel di tipo Fricke realizzati utilizzando un'innovativa matrice gel sintetica e tessuto equivalente: Polyvinyl alcohol (PVA) attivando chimicamente il processo di gelificazione tramite l'aggiunta di Glutaraldehyde (GTA). Questi gel sono stati irradiati con fasci di fotoni (LINAC) nel range 0--20 Gy. Per valutare la sensibilità a fotoni è stata studiata la dipendenza dei tempi di rilassamento nucleari dalla dose e dalla concentrazione di ferro nei gel. Inoltre è stata monitorata la stabilità del segnale dopo l'irraggiamento. Acquisizioni preliminari MRI con uno scanner MRI da 7 T sono state affiancate alle misure N…

Nuove frontiere per la dosimetria ESR per fasci clinici di fotoni ed elettroni: i composti fenolici IRGANOX® 1076. (Characterization of phenolic solid state pellets for ESR dosimetry with radio-therapeutic photon and electron beams)

This work deals with the dosimetric features of a particular phenolic compound (IRGANOX 1076®) for dosimetry of clinical photon and electron beams by using Electron Spin Resonance (ESR) spectroscopy. After the optimization of the ESR readout parameters (namely modulation amplitude and microwave power) to maximise the signal without excessive spectrum distortions, basic dosimetric properties of laboratory-made phenolic dosimeters in pellet form, such as reproducibility, dose-response, sensitivity, linearity and dose rate dependence were investigated. The dosimeters were tested by measuring the depth dose profile of a 6 MV photon beam. A satisfactory intra-batch reproducibility of the ESR sig…

ESR dosimeter material properties of phenols compound exposed to radiotherapeutic electron beams

Abstract There is a need for a sensitive dosimeter using Electron Spin Resonance spectroscopy for use in medical applications, since non-destructive read-out and dose archival could be achieved with this method. This work reports a systematic ESR investigation of IRGANOX ® 1076 exposed to clinical electron beams produced by a LINAC used for radiation therapy treatments. Recently, dosimetric features of this material were investigated for irradiation with 6 0Co γ -photons and neutrons in both pellet and film shape and have been found promising thanks to their high efficiency of radiation-matter energy transfer and radical stability at room temperature. Here the analysis of the dosimetric fea…

Sviluppo e Applicazioni di nuovi materiali per la dosimetria delle radiazioni ionizzanti

The Research Activities carried out during the Three-year International PhD Course in Applied Physics of the candidate Salvatore Gallo had two main topics related to dosimetry of ionizing radiations (IR): the analysis of 3D gel dosimeters and the analysis of solid state dosimeters through electron spin resonance. Both these activities are focused on a careful study of new materials for the IR Dosimetry, both in terms of physical characterization of these new materials and of the optimization of readout methods for dosimetric measurements. The study performed through various techniques such as UV-Vis absorption spectroscopy, NMR Relaxometry, Magnetic Resonance Imaging (MRI) and Electron Spin…

DOSIMETRIA ESR CON ALANINA PER ADRONTERAPIA CON IONI CARBONIO

La sicurezza del paziente sottoposto a trattamenti terapeutici con radiazioni ionizzanti e il buon esito degli ultimi sono strettamente legati all’ottimizzazione delle procedure di esposizione alle radiazioni ionizzanti. In particolare è fondamentale arrecare il danno minore possibile ai tessuti sani che circondano la neoplasia da trattare. Rispetto ai campi di radiazione convenzionali utilizzati in radioterapia (fotoni), le particelle cariche pesanti (protoni e ioni carbonio) offrono diversi vantaggi quali la bassa dispersione laterale, l’alta efficacia biologica (RBE) nella regione del picco di Bragg ed un profilo di dose caratteristico in profondità del tutto differente da quello dei fot…

Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging

Abstract This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which …

Caratterizzazione di pigmenti storici singoli e in miscela

Phenol compounds for Electron Spin Resonance (ESR) dosimetry in gamma and neutron field

The use of neutrons for cancer treatments has stimulated the research for beam characterization in order to optimize the therapy procedures in Neutron Capture Therapy (Altieri, 2008). Several research laboratories have shown an increasing interest aimed at extending the applicability of Electron Spin Resonance (ESR) dosimetry to radiotherapy with different types of radiation beams. In particular, ESR spectrometry provides absorbed dose measurements through the detection of the stable free radicals produced by ionizing radiations. The ESR dosimetric method has many advantages such as simple and rapid dose evaluation, the readout procedure is non-destructive, linear response of many organic a…

209 New Fricke gel with high sensitivity and low diffusion for 3D-MRI dosimetry

Purpose Fricke gel (FG) dosimeters are good candidates for 3D dose assessment in biological materials. Their effective atomic number and density are similar to those of soft tissue. In view of their chemical and morphological characteristics, FG serve as dosimeters and as phantoms at the same time. FG dosimeters are obtained by incorporating an acidic aqueous solution of ferrous ions Fe2+ into a gel matrix. In order to address the limitations of gels based on natural matrices, we have studied FG produced with a matrix of poly-vinyl alcohol (PVA) cross-linked with glutaraldehyde (GTA). Materials and methods The proposed gel contains 10% w/v of PVA and GTA of 1%w/v. A common formulation agaro…

Nuclear magnetic resonance relaxometry and imaging for dosimetry with agarose Fricke gel

ESR dosimetry with alanine added with Gadolinium in TRIGA reactor of Mainz

Study of the response of phenol compounds exposed to gamma photons and neutrons for Electron Spin Resonance dosimetry

Caratterizzazione dosimetrica della facility a neutroni termici del reattore TRIGA di Pavia: studio della dose da fotoni mediante rivelatori ESR

EPR/alanine dosimetry for verification in Helical Tomotherapy Stereotactic Radiosurgery (HTSRS) treatments

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…

MRI Characterization of non-Gaussian water diffusion in the brain using Diffusion Kurtosis Imaging (DKI)

Diffusion tensor imaging (DTI) is the most commonly used technique to extract microstructural features from a set of diffusion-weighted images. In addition to the metrics obtained with DTI, diffusion kurtosis imaging (DKI) can provide non-Gaussian diffusion measures by means of the kurtosis tensor. DKI give an dimensionless measure that quantifies the deviation of the water diffusion displacement profile from the Gaussian distribution of unrestricted diffusion, providing a measure of the degree of diffusion hindrance or restriction. DKI has shown to be more sensitive to tissue microstructural changes in both normal and pathological neural tissue. The aim of this work is the description of t…

Dose verification with EPR/alanine dosimeters in Helical Tomotherapy Stereotactic Radiosurgery (HT SRS) treatments

Intracranial stereotactic radiosurgery (SRS) is a technique to deliver an ablative radiation dose with an extremely sharp dose gradient to small brain tumors. This tecnique allows to deliver high doses of radiation to the tumor sparing the surrounding healthy tissue. In this study the accuracy of the dose delivered in a SRS session by a non conventional radiotherapy machine, the TomoTherapy Hi-Art System, was investigated using an "end-to-end" test. This is perfome d by means of alanine Electron Paramagnetic Resonance (EPR) pe llets. The response of these dosimeters is compared to that of gafchromic films which are particularly suitable for two-dimensional dose verification providing accura…

Comparative evaluation of data preprocessing software tools to increase efficiency and accuracy in diffusion kurtosis imaging

Characterization of Fricke gel dosimeters exposed to clinical photons beams and of MRI dosimetrical applications

Dosimetry of Mainz reactors by means of ESR dosimetry with alanine added with gadolinium

Phenol compounds for Electron Spin Resonance dosimetry in gamma and neutron field

The use of neutrons for cancer treatments has stimulated the research for beam characterization in order to optimize the therapy procedures in Neutron Capture Therapy (Altieri, 2008). Several research laboratories have shown an increasing interest aimed at extending the applicability of Electron Spin Resonance (ESR) dosimetry to radiotherapy with different types of radiation beams. In particular, ESR spectrometry provides absorbed dose measurements through the detection of the stable free radicals produced by ionizing radiations. The ESR dosimetric method has many advantages such as simple and rapid dose evaluation, the readout procedure is non-destructive, linear response of many organic a…

ESR response of phenol compounds for dosimetry of gamma photon beams

Abstract In the present paper we investigate the features of IRGANOX® 1076 phenols as a material for electron spin resonance (ESR) dosimetry. We experimentally analyzed the ESR response of pellets of IRGANOX® 1076 phenols irradiated with 60Co photons. The best experimental parameters (modulation amplitude and microwave power) for dosimetric applications have been obtained. The dependence of ESR signal as function of γ dose is found to be linear in the dose range studied (12–60 Gy) and the lowest measurable dose is found to be of the order of 1 Gy. The signal after irradiation is very stable in the first thirty days. From the point of view of the tissue equivalence, these materials have mass…

Dal colore alla caratterizzazione ottica di pigmenti antichi: validità del metodo spettrofotometrico e Teoria di Itten

Studio di assorbanza ottica e rilassometria RM in dosimetri a gel di Fricke

I dosimetri a gel di Fricke con xylenol-orange, analizzati otticamente, presentano alcune limitazioni se impiegati per misure di basse dosi (pochi Gy o meno), per irraggiamenti di lunga durata o per individuare procedure di calibrazione che permettano l'utilizzo in radioterapia. Le difficoltà derivano da variazioni nello spettro di assorbanza verosimilmente dovute a variazioni dei legami degli ioni ferrici con lo xylenol-orange. Sono state effettuate misure: i) di assorbanza ottica, anche spettrometrica, per dosimetri irraggiati a diverse dosi e a diversi tempi rispetto all'irraggiamento; ii) di rilassometria RM per valutare le variazioni dovute al solo aumento del numero di ioni ferrici.

126. Dosimetric analysis of phenolic solid state pellets exposed to radio-therapeutic photon and electron beams through electron spin resonance technique

Abstract Purpose Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures. In this work we report the ESR investigation of particular phenol compounds exposed to clinical photon and electron beams [1] . Materials and methods Pellets were produced by mixing Phenol (IRGANOX 1076® Sigma Aldrich) and paraffin (10% by weight). The irradiations of dosimeters were performed with photon and electron beams with absorbed doses ranging from 0 to 13 Gy. Basic dosimetric properties of phenolic dosimeters, such as reproducibility, dose-response…

ESR response of alanine films exposed to low-energy (1-40 keV) X-rays

Introduction L-a-alanine has aroused considerable interest for use in radiation ESR dosimetry. In this work, we examined the energy response of alanine ESR films in the low energy X-photon energy range between 1 keV and 40 keV. Dose measurements through a reference ionization chamber and a semiconductor detection system were also performed to complement ESR measurements. Methods Commercial alanine ESR films were used. All ESR signal measurements were also done using an XBand (9.7 GHz) Bruker spectrometer. The dosimeters were irradiated at the "Livio Scarsi" Laboratory (LAX) of the University of Palermo, where X-ray beams in the 1–40 keV energy range are produced using a Seifert SN60 tube. R…

Dosimetria EPR con alanina per fasci di protoni per adronterapia

Study of the response of phenol compounds exposed to thermal neutrons beams for Electron Paramagnetic Resonance dosimetry

Abstract This paper reports the results regarding a new organic compound (IRGANOX ® 1076 phenols) with and without low content (5% by weight) of gadolinium oxide (Gd 2 O 3 ) for Electron Paramagnetic Resonance (EPR) dosimetry of neutron beams. The dependence of EPR signal as function of neutron dose was investigated in the fluence range studied between 10 11  cm −2 to 10 14  cm −2 . We evaluated also the effect of gadolinium on 60 Co gamma photon sensitivity of this organic compound. Our analysis showed that a low concentration of gadolinium oxide (of the order of 5% of the total mass of the dosimeter) can enhance the thermal neutron sensitivity more than 10 times with a small reduction of …

Studio e calibrazione della risposta ottica ed NMR di dosimetri gel di tipo Fricke (FXG) in campi misti neutroni-gamma per applicazioni cliniche

Dosimetria tramite Risonanza Elettronica di Spin (ESR) in RadioTerapia IntraOperatoria (IORT): misure di Output Factors e simulazioni Monte Carlo-GEANT4

La RadioTerapia IntraOperatoria (IORT) è una modalità di trattamento in cui una singola dose di radiazioni è impartita direttamente al letto tumorale o al tumore durante l'intervento chirurgico, evitando di colpire i tessuti sani circostanti. La fabbricazione di acceleratori lineari mobili per elettroni dedicati alla IORT ha permesso una grande diffusione di questa tecnica radioterapica. Lo scopo di questo lavoro è il confronto tra la risposta di dosimetri di alanina letti tramite Risonanza Elettronica di Spin (ESR) e di camere a ionizzazione Markus per le misurazioni degli Output Factors (OFs) di fasci di elettroni prodotti da un acceleratore lineare utilizzato per la IORT. Gli OFs dei fas…

Nuovi gel di Fricke ad alta sensibilità e bassa diffusione per dosimetria 3D tramite MRI

One of the most recent and promising developments in radiotherapy dosimetry was the introduction of 3D radiationsensitive gels. These gels present tissue equivalent composition and density, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some gels are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gel). In this work Fricke gel dosimeters produced with a matrix of poly-vinyl alcohol (PVA) cross-linked with glutaraldehyde (GTA) were analyzed with magnetic resonance imaging (MRI). This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GT…

Alanine/ESR dosimetry for electron Intra-Operative RadioTherapy: output factor measurements and Monte Carlo-GEANT4 simulations for IORT mobile dedicate accelerator

Intra-operative radiation therapy (IORT) is a treatment modality where a single high dose of radiation is delivered directly to the tumor bed or to the exposed tumor during the surgical intervention, while avoiding surrounding dose-limiting structures. Mobile electron linear accelerators dedicated to IORT have been manufactured which have promoted a local large diffusion of this radiotherapy modality. For breast irradiation, a single fraction of 21 Gy delivered on the target volume during the surgical procedure is equivalent to the total dosage (60 Gy) usually delivered during 30 external fractionated radiotherapy at 2Gy/fraction. Alternatively, a single dose of 10 Gy can be administered as…

Rare-earth doped silica optical fibres for ionizing radiation detection

Scintillating silica optical fibre sensors have shown interesting results for ionizing radiation monitoring and therefore can be useful for dosimetry applications in medical field. In fact, they enable a remote, punctual and real-time dose assessment (Mones et al., 2008). In addition, the high radiation hardness that characterizes silica optical fibers, makes these systems promising for radiation detection in high energy physics experiments (Chiodini et al., 2014). This work aims to review the recent progresses in the development and characterization of rare-earth doped silica fibres. The radioluminescent and dosimetric properties of Ce, Eu, Yb and Pr-doped silica matrices are described and…

Sensibilità e stabilità dei dosimetri gel di tipo Fricke esposti ai fotoni nel range clinico in funzione della concentrazione di ferro: 3D MRI ed applicazioni dosimetriche

Phenol compounds as new materials for Electron Spin Resonance (ESR) dosimetry in clinical photon and electron beams

In the last decades several research laboratories have shown an increasing interest aimed at extending the applicability of Electron Spin Resonance (ESR) dosimetry to radiotherapy with different types of radiation beams. ESR is a spectroscopic method for investigating the structure and dynamics of such paramagnetic species. Free radicals are known to be produced when a compound is irradiated with ionizing radiations. The concentration of radiation-induced free radicals is proportional to the energy released inside in the medium and this allows for dosimetric measurements through ESR technique which able to quantitatively determine the radical concentration.The use of alanine as a dosimetric…

Determination of gamma component in thermal column of Pavia Triga reactor by using alanine ESR detectors

EPR ANALYSIS OF ALANINE WITH GADOLINIUM FOR DOSIMETRY AT TRIGA MARK II REACTOR OF MAINZ

Negli ultimi anni il crescente interesse verso la radioterapia a cattura neutronica (internazionalmente nota come Neutron Capture Therapy - NCT) per il trattamento di neoplasie ha stimolato diverse attività di ricerca finalizzate alla caratterizzazione del fascio utilizzato e all'ottimizzazione delle procedure radioterapiche. La corretta riuscita del trattamento NCT e il monitoraggio della dose impartita non possono prescindere dalla valutazione delle varie componenti del fascio impiegato (neutronica e fotonica). Infatti, durante le procedure di moderazione dei neutroni, si verifica la produzione di fotoni e la stima dei rischi a cui sono soggetti i tessuti sani sottoposti al campo misto ne…

NMR relaxometry measurements of Fricke gel dosimeters exposed to neutrons

Fricke infused gel matrices offer several features making them suitable for dosimetric applications; among the set here are tissue equivalence, low cost and ease of preparation. Their nuclear magnetic resonance (NMR) relaxation properties can be used as a radiation detector for the dosimetry of beams used in cancer therapy. In recent years neutron capture therapy has been resumed for the treatment of various types of cancer and it requires three-dimensional mapping of the neutron fields. In this work, we investigated this particular application through NMR relaxometry and MR imaging of Fricke gels exposed to neutrons. We analyzed both the R1 and R2 relaxation rates, which relate to the long…

Diffusion and sensitivity characteristics of a chemically cross-linked PVA-Fricke gel dosimeter

Agarose and PVA Fricke gel dosimeters exposed to clinical photons beams: Nuclear Magnetic Resonance Relaxometry and Imaging

Fricke Xylenol Gel (FXG) dosimetric system is based on the radiation induced oxidation of ferrous (Fe2+) to ferric (Fe3+) ions. The application of Fricke gels for ionizing radiation dosimetry is continuously increasing worldwide due to their many favorable properties. However, one of their shortcomings is that ferrous and ferric ions diffuse in the gel matrix. To maintain the spatial integrity of the dose distribution, Fricke gels must be undergoing measurement within a few hours of their irradiation, so that ferric ions remain close to their point of production. Thus, the spatial integrity of the dose distribution in the Fricke gel is maintained. The gel matrix also contributes to the oxid…

Caratterizzazione ESR di composti fenolici: nuovi materiali per la dosimetria in campo misto neutroni-gamma

Sviluppo di un software per l’analisi di immagini di Diffusion Kurtosis Imaging

L’analisi mediante RM del tensore di diffusione (Diffusion Tensor Imaging, DTI) consente di valutare anche in vivo e con modalità non invasive il processo di diffusione delle molecole d’acqua nei tessuti biologici. La peculiare organizzazione di alcuni tessuti biologici (es: muscoli, sostanza bianca del sistema nervoso centrale e tessuti ad alta cellularità) influenza tale fenomeno rendendolo anisotropo e quindi ben valutabile con tali tecniche di studio. Nonostante i grandi vantaggi di tale tecnica, il DTI è basato su un modello molto semplificato che assume che lo spostamento per diffusione segua un profilo gaussiano il che è molto raro in un ambiente variegato come i tessuti biologic…

Dependence of MRI sensitivity of Fricke gel dosimeters exposed to clinical photons beams on ferrous ammonium sulfate content

Comparison of EPR response of alanine and Gd2O3-alanine dosimeters exposed to TRIGA Mainz reactor.

In this work we report some preliminary results regarding the analysis of electron paramagnetic resonance (EPR) response of alanine pellets and alanine pellets added with gadolinium used for dosimetry at the TRIGA research reactor in Mainz, Germany. Two set-ups were evaluated: irradiation inside PMMA phantom and irradiation inside boric acid phantom. We observed that the presence of Gd2O3 inside alanine pellets increases the EPR signal by a factor of 3.45 and 1.24 in case of PMMA and boric acid phantoms, respectively. We can conclude that in the case of neutron beam with a predominant thermal neutron component the addition of gadolinium oxide can significantly improve neutron sensitivity of…

ALANINE/ESR DOSIMETRY FOR TOTAL BODY IRRADIATION USING AN ANTHROPOMORPHIC PHANTOM

Introduction: Total Body Irradiation (TBI) is a technique widely used in the radiation blood-oncology in the treatment of patients that need bone marrow transplantation or peripheral stem cell transplantation. This technique has some limitations such as the lack of homogeneity of the dose distribution (which may show variations of 20% in the different areas), irradiation of critical organs such as the lungs, the liver, the intestine and the eye-lens which can receive a dose comparable to that nominal and require appropriate shielding and a proper evaluation of the dose absorbed by them. The positive outcome of this type of radiation therapy is strictly related to a precise and accurate meas…

Alanine EPR pellets for dosimetry of clinical proton and carbon ion beams

The main gol of the present work is to investigate the response behaviour of alanine EPR pellets in clinical proton anc carbon ion beams. Proton irradiations were carried out at PSI (Switzerland) using both passive and active scattering modality, whereas, C ions irradiation were performed at GSI (Germany) adopting the raster scanning modality.

Functional connectivity modulation induced by transcranial direct current stimulation of the motor network: a Resting-State fMRI study

Resting-state functional connectivity represents a novel fMRI approach that allows detection of temporal correlations in spontaneous BOLD signal oscillations while subjects rest quietly in the scanner. Functional connectivity (FC) can be defined as the synchrony of neural activity among spatially distant regions. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that is known to modulate cortical activity and FC among brain regions. This study is aimed at measuring the variation of functional connectivity between cortical brain regions after tDCS along time. The temporal concatenation group ICA showed that immediately after anodal stimulation the a…

EPR/alanine dosimetry for two therapeutic proton beams

Abstract In this work the analysis of the electron paramagnetic resonance (EPR) response of alanine pellets exposed to two different clinical proton beams employed for radiotherapy is performed. One beam is characterized by a passive delivery technique and is dedicated to the eyes treatment (OPTIS2 beam line). Alanine pellets were irradiated with a 70 MeV proton beam corresponding to 35 mm range in eye tissue. We investigated how collimators with different sizes and shape used to conform the dose to the planned target volume influence the delivered dose. For this purpose we performed measurements with varying the collimator size (Output Factor) and the results were compared with those obtai…

Analysis of response of PVA-GTA Fricke gel dosimeters through magnetic resonance imaging.

The experimental activities here reported are focused on the analysis of the clinical applications of Fricke gel dosimeters produced with a matrix of Polyvinyl alcohol (PVA) cross-linked by adding glutaraldehyde (GTA). The analyses were performed by means of a 1.5 T clinical magnetic resonance imaging (MRI) scanner. The sensitivity of these dosimetric gels to clinical photon beams as well as the signal stability were suitably investigated. Furthermore, the effect of the xylenol orange on the MRI signal was analyzed. The results obtained show that these PVA-GTA gel dosimeters show good dosimetric features for possible future use for 3D dose mapping in clinical applications.

Analisi NMR su gel di tipo Fricke irradiati con fasci routinari per la radioterapia: stabilità e sensibilità in funzione degli additivi

In questo lavoro sono presentate le misure effettuate tramite rilassometria NMR su campioni costituiti da una matrice gelatinosa drogata con ioni ferrosi comunemente chiamati dosimetri gel di tipo Fricke (FXG). La dosimetria con gel Fricke si basa sulla ossidazione degli ioni ferrosi (Fe2+) in ioni ferrici (Fe3+) all’interno di una matrice gelatinosa a seguito di irraggiamento (Schreiner, 2004). Tale processo è fortemente dipendente dalla dose somministrata (Marrale, 2014a). I dosimetri di Fricke sono tessuto-equivalenti, rispondono ad ogni tipo di radiazione ionizzante ed, assumendo la forma del contenitore in cui avviene la gelificazione, possono essere utilizzati per studiare l’effetto d…

Looking into the architecture of the brain with MRI: quantification of non-Gaussian water diffusion by Diffusion Kurtosis Imaging (DKI)

The aim of this work is the definition of an MRI protocol for Diffusion Kurtosis Imaging (DKI) by using a 1.5T clinical scanner and the development of a software for DKI analysis.

Simulazioni numeriche e test di applicabilità clinica della Diffusion Kurtosis Imaging su tomografi RM da 1.5 Tesla

Electron Spin Resonance dosimetry using organic compounds (alanine and ammonium tartrate) for mixed neutron-gamma fields

Alongside with the development of Neutron Capture Therapy (NCT) and the use of thermal neutrons for radiotherapeutic purposes, many efforts have been devoted to the characterization of the beam in order to optimize therapy procedures. Reliable dose measurements should be able to determine the various (neutrons and photonic) components of the mixed beam usually employed for therapy. This paper studies the effect of additives such as boric and gadolinium nuclei on the sensitivity of neutron organic (alanine and ammonium tartrate) dosimeters analyzed through Electron Spin Resonance (ESR) technique (Marrale, 2014). These dosimeters were exposed to a mixed (neutron-gamma) field mainly composed o…

Monte Carlo simulation of energy absorbed in phenolic ESR dosimeters added with gadolinium exposed to thermal, epithermal and fast neutrons

Abstract In this work analyses of the energy released per unit mass in phenolic compound exposed to neutron beams were performed with the aim of predicting the increase in dose achievable by addition of gadolinium (Gd) inside the pellets. In particular, Monte Carlo (MC) simulations were carried out for IRGANOX® 1076 phenolic compound irradiated with neutron beams with different energy spectra at various depths inside a water phantom. The addition of gadolinium increases sensitivity of phenolic ESR (electron spin resonance) dosimeters to neutrons thanks to the high gadolinium cross section for neutron capture and to the large number of secondary particles (mainly Auger and internal conversio…

Ruolo della granulometria sul colore dei pigmenti

Neutron Electron Spin Resonance dosimetry with phenol compounds

Electron Spin Resonance (ESR) characterization of phenol compounds as new materials for dosimetry in radiotherapy

Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures [1]. Free radicals are known to be produced when a compound is irradiated with ionizing radiations. The concentration of radiation-induced free radicals is proportional to the absorbed dos e and this allows for dosimetric measurements through ESR technique which able to quantitatively determine the radical concentration [2]. Our research group has started an investigation of the ESR response of some phenols compounds for possible ESR dosimetric ap plications suitable feature…

Comparison between mercury intrusion porosimetry and nuclear magnetic resonance relaxometry to study the pore size distribution of limestones treated with a new consolidation product

Abstract Pore-space properties, such as pore-size distribution and connected porosity, are relevant factors in the evaluation of the performance of a consolidation treatment. In this study, two different techniques – Mercury Intrusion Porosimetry (MIP) and Nuclear Magnetic Resonance Relaxometry (NMRR) – were adopted to study the compatibility and the efficacy of a new consolidation product for limestones. This work aims at comparing and combining data obtained by MIP and NMRR; to confirm the relationship between the quantitative results of MIP and the qualitative ones of NMRR, a calibration which leads to correlate T2 distribution and pore size distribution has been applied. Experimental re…

New materials for ESR dosimetry in clinical photon and electron beams: Phenol Compounds.

In the last decades several research laboratories have shown an increasing interest aimed at extending the applicability of ESR-dosimetry to radiotherapy with different types of radiation beams. ESR is a spectroscopic method for investigating the structure and dynamics of such paramagnetic species. The concentration of radiation-induced free radicals is proportional to the energy released inside in the medium. Our research group has started an investigation of the ESR response of some phenols compounds for possible ESR dosimetric applications suitable features, such as high efficiency of radiation-matter energy transfer and radical stability at room temperature. In particular, the phenoloct…

Characterization of phenolic solid state pellets for ESR dosimetry with radio-therapeutic photon and electron beams

Introduction Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures. In this work we report the ESR investigation of particular phenol compound (IRGANOX 1076) exposed to clinical photon and electron beams (Gallo et al., 2017). Methods Phenol (IRGANOX 1076 - Sigma Aldrich) pellets were produced also with paraffin (10% by weight). Phenol pellets were exposed to clinical photon and electron beams at various energies produced by a linear accelerator (LINAC) Siemens Primus (Siemens Medical Systems, CA, USA) installed at the Radiother…

Determinazione della componente fotonica all’interno della colonna termica del reattore TRIGA mediante letture ESR di dosimetri di alanina

Phenol compounds for Electron Spin Resonance dosimetry of gamma and neutron beams

Dosimetria per fasci di protoni tramite spettroscopia di risonanza paramagnetica elettronica (EPR)