Characterisation of a silicon photomultiplier based oncological brachytherapy fibre dosimeter

Source localisation and real-time dose verification are at the forefront of medical research in brachytherapy, an oncological radiotherapy procedure based on radioactive sources implanted in the patient body. The ORIGIN project aims to respond to this medical community's need by targeting the development of a multi-point dose mapping system based on fibre sensors integrating a small volume of scintillating material into the tip and interfaced with silicon photomultipliers operated in counting mode. In this paper, a novel method for the selection of the optimal silicon photomultipliers to be used is presented, as well as a laboratory characterisation based on dosimetric figures of merit. More specifically, a technique exploiting the optical cross-talk to maintain the detector linearity in high-rate conditions is demonstrated. Lastly, it is shown that the ORIGIN system complies with the TG43-U1 protocol in high and low dose rate pre-clinical trials with actual brachytherapy sources, an essential requirement for assessing the proposed system as a dosimeter and comparing the performance of the system prototype against the ORIGIN project specifications

Magnetic resonance imaging in locally advanced rectal cancer : quantitative evaluation of the complete response to neoadjuvant therapy

Purpose: To assess the diagnostic performance of diffusion-weighted imaging (DWI) for the discrimination of complete responder (CR) from the non-complete responder (n-CR) in patients with locally advanced rectal cancer (LARC) undergoing chemotherapy and radiation (CRT). Material and methods: Between December 2009 and January 2014, 32 patients (33 lesions: one patient had two synchronous lesions) were enrolled in this retrospective study. All patients underwent a pre- and post-CRT conventional MRI study completed with DWI. For both data sets (T2-weighted and DWI), the pre- and post-CRT tumour volume (VT2; VDWI) and the tumour volume reduction ratio (ΔV%) were determined as well as pre- and post-CRT apparent diffusion coefficient (ADC) and ADC change (ΔADC%). Histopathological findings were the standard of reference. Receiver operating characteristic (ROC) curves were generated to compare performance of T2-weighted and DWI volumetry, as well as ADC. Results: The area under the ROC curve (AUC) revealed a good accuracy of pre- and post-CRT values of VT2 (0.86; 0.91) and VDWI (0.82; 1.00) as well as those of ΔVT2% (0.84) and ΔVDWI% (1.00) for the CR assessment, with no statistical difference. The AUC of pre- and post-CRT ADC (0.53; 0.54) and that of ΔADC% (0.58) were significantly lower. Conclusions: Both post-CRT VDWI and ΔVDWI% (AUC = 1) are very accurate for the assessment of the CR, in spite of no significant differences in comparison to the conventional post-CRT VT2 (AUC = 0.91) and ΔVT2% (AUC = 0.84). On the contrary, both ADC and ΔADC% values are not reliable

Ultrasuoni: qualità e sicurezza nella diagnostica per immagini.

Qualità e sicurezza sono due aspetti generalmente correlati tra loro nella diagnostica per immagini. Ciò è vero anche in ecografia, anche se la normativa a riguardo non è così puntuale ed articolata come nel campo delle radiazioni ionizzanti o della risonanza magnetica. Per quanto riguarda la sicurezza, la materia è regolamentata da indicazioni di associazioni o istituzioni italiane o internazionali (es. CEI, AIUM) mentre per quanto riguarda la qualità il riferimento italiano è la circolare LR-154 dell’ISPESL ed i documenti SIRM (ultima versione del 2004). Come tutte le apparecchiature radiologiche, anche gli ecografi devono essere quindi sottoposti ad un programma di controlli di qualità. Numerosi sono i parametri che possono essere valutati per esprimere un giudizio di qualità sull’apparecchiatura

Management of electron accelerators for radiotherapy. Data as of 31 December 1984 [La gestione di acceleratori di elettroni per radioterapia. Dati aggiornati al 31 dicembre 1984.]

Several italian radiotherapeutic centers have supplied the data analysed, regarding problems connected with the management of electron accelerators in the years 1982-1983-1984. The data concern 27 out of the 35 accelerators settled in Italy. The average cost of purchase has proved to be of 940 M pounds with an expense of annual allowance of 94 M pounds. We have then analysed the incidences of the allowance of the purchase expenditure of the machine (23%), the allowance of the expenses for the construction of the bunker (22%), the expenses of maintenance of the machine (5%), the cost of the staff (48%) and the cost of the power supply (2%) on the management costs (about pounds 820.000 per each handled patient). The duration of the various phases of the machinery installment, from the purchase to the beginning of the treatment, the charge of work supported in the three considered years, the daily use of the machinery and the problems deriving from days of time out of services due to failures or to periodical maintenance have then been studied. The analysis of the average values of the parameters studied and of the range of their variability allows us to find out the sector in which it is possible, also at present, to intervene in order to ameliorate the employment of a linear accelerator, regarding the costs and the performance

A new method for calculating the distribution of radioactivity in man measured with a whole body counter

A whole-body counter with a scanning bed and two opposite (antero-posterior) probes was used to obtain profiles of count rates of radioactivity held in the whole body. The distribution of the activity in the patient was calculated by solving an over determined system (more equations than unknowns) of linear equations with the Chebyshev method, the least-squares method, and an iterative method. The iterative method gave the best results, especially in the case of distributions with peaks of radioactivity. Some in-vivo applications of the method are presented