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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-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. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which is a standard dosimetric gel formulation. The analysis showed that the diffusion process is much slower (more than five times) for PVA-GTA gels than for agarose ones. Furthermore, MRI was performed on the PVA-GTA 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 sensitivity was about 40% higher compared to gels produced with agarose as gelling agent. The effect of xylenol orange (XO) on the MRI signal was also investigated: gel dosimeters made without XO show higher sensitivity to x-rays than those made with XO. The dosimetric accuracy of the 3D gels was investigated by comparing their MRI response to percentage depth dose and transversal dose profile measurements made with an ionization chamber in a water phantom. The comparison of PVA-GTA gels with and without XO showed that the chelating agent reduces the MRI sensitivity of the gels. Depthdose and transversal dose profiles acquired by PVA-GTA gels without XO are more accurate and consistent with the ionization chamber data.

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 oxidation of ferrous ions during irradiation, increasing the chemical yield of ferric ions in aqueous solution and increasing the sensitivity of the dosimeter. The oxidation of ferrous ions also causes a reduction of the longitudinal nuclear magnetic relaxation time T1 which can be measured by means of Nuclear Magnetic Resonance Relaxometry (NMR) and Magnetic Resonance Imaging (MRI). The results presented are related to an experimental investigation conducted on Fricke Gels characterized by gelatinous matrix of Agarose or PVA. The dose calibration curves are reported and discussed from the point of view of the dosimeter use in clinical radiotherapy. This work has highlighted that the optimization of additives inside gel matrix is fundamental for optimizing photon sensitivity of these detectors. We can conclude that FXG dosimeters with optimal ferrous ammonium sulfate content can be regarded as a valuable dosimetric tool to achieve fast information on spatial dose distribution.

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.

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 delle radiazioni su fantocci antropomorfi da essi costituiti. Inoltre, la matrice di gel rallenta la diffusione degli ioni ferrosi (Fe2+) e ferrici (Fe3+) in modo che, se il gel viene analizzato entro un paio di ore dall’irraggiamento, gli ioni ferrici rimangono prossimi al loro punto di produzione. Inoltre, il gel favorisce l’ossidazione degli ioni ferrosi durante l'irraggiamento, in modo da aumentare la resa chimica degli ioni ferrici e quindi la sensibilità dei dosimetri. Lo scopo di questo lavoro è l'analisi tramite risonanza magnetica nucleare (NMR) delle proprietà di rilassamento protonico dei gel dosimetrici da noi preparati al variare della concentrazione dei centri paramagnetici (Fe3+) prodotti al variare della dose di irraggiamento. I gel Fricke sono stati irradiati con fasci di fotoni (LINAC) nel range clinico tra 0 e 20 Gy. Le analisi NMR sono state affiancate da acquisizioni di imaging a Risonanza Magnetica Nucleare (MRI) utilizzata in ambito ospedaliero (Galante, 2008). Per valutare la sensibilità a fotoni, abbiamo studiato la dipendenza dei tempi di rilassamento nucleari dalla dose, dalla concentrazione di solfato di ammonio ferroso contenuto all’interno dei gel e dalla presenza di indicatori ottici degli ioni metallici. Inoltre, è stata monitorata la stabilità del segnale per diversi giorni dopo l'irraggiamento. Le acquisizioni MRI sono state finalizzate alla mappatura 3D della dose su fantocci estesi. Vengono presentati e discussi i risultati ottenuti in relazione ad applicazioni dei dosimetri gel Fricke in ambito radioterapico. Questo lavoro evidenzia come valutazioni dosimetriche non possono prescindere dall’ottimizzazione della concentrazione degli additivi.

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 performed at various times after irradiation only reveal the slow changes due to the auto-oxidation effect, proving therefore that the modality of chelation of ferric ions by xylenol orange can affect the observed changes in the optical absorbance spectra.

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 NMR. Questo lavoro evidenzia come le valutazioni dosimetriche non possono prescindere dall'ottimizzazione della concentrazione degli additivi.

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 1 keV and 40 keV, which was not previously described. Furthermore, we analyzed the response enhancement of alanine loaded with gadolinium oxide. The ESR measurements were complemented by the information provided by a reference ionization chamber and a by semiconductor detection systems.

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 perform a more basic investigation on the MR relaxation features of these gels with and without xylenol orange in order to achieve a deeper understanding of the physical properties of these gels from the relaxation times.

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 imaging investigations of Fricke Xylenol Gel characterized by gelatinous matrix of Agarose for possible applications in clinical photon beams used for radiation therapy. Materials and Methods: NMR relaxometry measurements were performed using an mq-ProFiler single-side relaxometer (Bruker Biospin). MRI imaging was realized on a 1.5 T Achieva scanner (Philips) with an eight channel head coil. The gels were irradiated in the clinical dose range (0– 20 Gy) with a Siemens Primus Low linear accelerator. Results: The main dosimetric features of the NMR signal were investigated. The linearity of the response with dose was observed. In order to assess the photon sensitivity we analyzed the dependence of NMR relaxation time on radiation dose with varying ferrous ammonium sulfate content inside FXG. The ferrous ammonium sulfate content which maximizes sensitivity is 1.75 mM. Furthermore, signal stability was followed for several days after irradiation. Aldo for MRI analysis the dose calibration curves were obtained also with MRI scanner. Moreover, a depth dose profile was reconstructed. Conclusions: We can conclude that FXG dosimeters with optimal ferrous ammonium sulfate content can be regarded as a valuable dosimetric tool to achieve fast information on spatial dose distribution.

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 oxidation of ferrous ions during irradiation, increasing the chemical yield of ferric ions in aqueous solution and increasing the sensitivity of the dosimeter. The oxidation of ferrous ions also causes a reduction of the longitudinal nuclear magnetic relaxation time T1 which can be measured by means of Nuclear Magnetic Resonance Relaxometry (NMR) and Magnetic Resonance Imaging (MRI). The results presented are related to an experimental investigation conducted on Fricke Gels characterized by gelatinous matrix of Agarose or PVA. We performed NMR relaxometry investigations which allow for direct measurements of the relaxation times in samples exposed to clinical photon beams. The main dosimetric features of the NMR signal were investigated. The gels were irradiated in the clinical dose range between 0 and 20 Gy. In order to assess the photon sensitivitywe analyzed the dependence of NMR relaxation time on radiation dose with varying ferrous ammonium sulfate content inside FXGs. Furthermore, signal stability was followed for several days after irradiation. These measurements were preliminary to MRI analysis which can permit 3D dose mapping. In order to optimized the MRI response a systematic study was performed to optimize acquisition sequences and parameters. In particular, we analyzed for inversion recovery sequences the dependence of MRI signal on the repetition time TR and on the inversion time TI . The dose calibration curves are reported and discussed from the point of view of the dosimeter use in clinical radiotherapy. This work has highlighted that the optimization of additives inside gel matrix is fundamental for optimizing photon sensitivity of these POSTERS 355 detectors. We can conclude that FXG dosimeters with optimal ferrous ammonium sulfate content can be regarded as a valuable dosimetric tool to achieve fast information on spatial dose distribution.

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

An integrated analytical approach can be useful to study the effectiveness of preservation treatment for Carrara marble surfaces, carried out for testing commercial products which are based on nano-structured silica oxides. Variation in hydrophobic properties, porosity distribution, and chemical composition of treated surfaces have been studied. With this aim, contact angle evaluation, NMR, XRF measurements have been used. Changes of above mentioned physical and chemical characteristics have been evaluated before and after aging in saline chamber of the treated and untreated samples. Moreover, the effectiveness of ultrasonic treatment in “safe” removal of the products from treated surfaces has been evaluated by XRF measurements, studying results by the PC analysis. Results show that some of tested products enhanced the required properties, while some other do not, hence their use should be avoided in the field of CH. Regarding the analysed stone sample, a “safe” removal of product from treated surfaces is possible by using ultrasound probe.

The use of nanoproducts in the Cultural Heritage (CH) field requires great sensitivity and responsibility and, above all, analytical research and studies evaluating effectively their potential use. In order to evaluate the capability of nanostructured protective in the CH field, limestone materials of historical-artistic interest were treated and then studied. The study focuses on the non-invasive evaluation of samples stone, of interest in the CH field, their surface has been tested with nanostructured products. In particular, samples of limestone of Favara (Sicily) have been studied, before and after artificial aging. The analytical methodology involved X-ray fluorescence measurements, in order to evaluate the elemental composition differences between treated and untreated samples; spectrophotometric measurements to determine the colour changes due to the protective application, contact angle estimations on the untreated/treated surfaces and, finally, evaluation of the amount of the absorbed water by capillarity. The samples were, also, artificially aged inside a microclimate chamber, in order to evaluate how the waterproofer properties of the nanostructured products are affected by temperature and humidity. The investigation, repeated after saline chamber, allowed to evaluate the treatments effectiveness and, in particular, their persistence after aging through Si presence/absence, selected as a XRF marker of nanostructured protective layer.

Most of the artworks constituting the collection of Renaissance statuary of Abatellis Palace in Palermo (Sicily) show evidence of colour layers and fragments of gold foil that probably once covered the whole marble surface. The restoration of some of these statues has allowed to carry out archaeometric studies about the painting technique and to highlight the original materials and inclusion present on the precious marbles by two famous Italian sculptors of the Renaissance, Francesco Laurana and Antonello Gagini. The measurements have been performed in situ through the integrated use of two non-invasive techniques: visible fluorescence stimulated by ultraviolet light and X-ray fluorescence. The ultraviolet-induced fluorescence analysis has provided additional information on the conservation status of marble surfaces by differentiating the pictorial materials and highlighting the presence of gilding and pigment traces through their characteristic fluorescence response. The observation in ultraviolet light has been used as valuable guide for the identification of the significant points to be analysed by X-ray fluorescence to characterise the original materials. X-ray fluorescence measurements have cast light about their chemical composition and stratigraphical structure. Pictorial layers were identified: vermilion for red layers, blue pigment based on copper for blue layers and pure gold leaf for gilding layers. Principal component analysis of the data was capable of clustering the different painting materials, discriminating through their chemical content. The results represent an important scientific support both to the hypotheses about the original look of the artworks and to the resolution of restoration and conservation questions still open. © 2012 John Wiley & Sons, Ltd.

Along with the Neutron Capture Therapy (NCT) development and with the use of thermal neutrons for radiotherapeutic purposes, many efforts have been devoted to the beam characterization in order to optimize the therapy procedures. Reliable dosimetric measurements should be able to determine the various components (neutronic and photonic) of the mixed beam usually employed for therapy. We have studied the effect of the additive such as gadolinium and 10B-boric acid on the neutron sensitivity of alanine ESR dosimeters exposed to a gamma and mixed (n, gamma) field mainly composed by thermal neutrons. We have chosen both this additive nuclei because of their very high capture cross section to thermal neutrons. Furthermore, in the nuclear reaction with thermal neutrons particle, which in turn release their energy in the neighbourhood of the reaction site, are ejected. We completed our study through a Monte Carlo simulation aimed at obtaining information about the reliability of this powerful tool in predicting the response enhancement achievable with the addition of gadolinium and 10B-boric acid in alanine dosimeters. These computational values obtained through simulation are compared with the experimental results.

Along with the Neutron Capture Therapy (NCT) development and with the use of thermal neutrons for radiotherapeutic purposes, many efforts have been devoted to the beam characterization in order to optimize the therapy procedures. Reliable dosimetric measurements should be able to determine the various components (neutronic and photonic) of the mixed beam usually employed for therapy [1]. We have studied the effect of the additive such as gadolinium and 10B-boric acid on the neutron sensitivity of alanine ESR dosimeters exposed to a gamma and mixed (n, gamma) field mainly composed by thermal neutrons. We have chosen both this additive nuclei because of their very high capture cross section to thermal neutrons. Furthermore, in the nuclear reaction with thermal neutrons particles, which in turn release their energy in the neighbourhood of the reaction site, are ejected [2]. We completed our study through a Monte Carlo simulation aimed at obtaining information about the reliability of this powerful tool in predicting the response enhancement achievable with the addition of gadolinium and 10B-boric acid in alanine dosimeters. These computational values obtained through simulation are compared with the experimental results.