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Purpose This study investigated the benefits of implementing a cluster analysis technique to extract relevant information from a computed tomography (CT) dose registry archive. Methods A CT patient dose database consisting of about 12,000 examinations and 29,000 single scans collected from three CT systems was interrogated. The database was divided into six subsets according to the equipment and the reference phantoms in the definition of the dose indicators. Hierarchical (single, average, and complete linkage, Ward) and not hierarchical (K-means) clustering methods were implemented using R software. The suitable number of clusters for each CT system was determined by analysing the dendrogram, the within clusters sum of squares, and the cluster content. Summary statistics were produced for each cluster, and the outliers of the dose indicator distribution were investigated. Results Ward clustering identified the most common combinations of scanning parameters for each group. The optimal number of clusters for each CT equipment system ranged from 5 to 15. The main diagnostic applications were then extracted from each cluster. Outlier analysis of the dose indicator distribution of each cluster revealed potential improper settings that resulted in increased patient dose. Conclusions Clustering methods applied to CT patient dose archives provide a quick and effective overview of the main combinations of currently used exposure parameters and the consequences for dose indicator distributions, also when protocol labels and/or study descriptions are not homogeneous.

Purpose The use of unsealed sources (either in nuclear medicine or in radiochemical bio-laboratories) involves the risk of internal contamination for workers after partial evaporation of the unsealed source during its use. This issue was already addressed in [1] , the aim of this work is to extend that work towards a comprehensive model taking into account also the airborne contamination after radionuclide evaporation from the cumulated surface contamination of the working area. Methods The above mentioned model takes into account the manipulation time (tm, the manipulated activity (A), the frequency of manipulations, the total time the workers spend in the laboratory (on an yearly basis), the air exchange ratio (R) and the half-life of the manipulated radionuclides. According to the actual working conditions, the model evaluates firstly the radionuclide air concentration as a function of time and thereafter the committed effective dose depending on the time spent in the laboratory by the worker. Results During tm the radioisotope manipulation determines both air contamination (AC) and probabilistic surface contamination (SC). After tm AC decreases due to R, whereas surface contamination increases after each manipulation, decreasing only through physical decay, thus leading to an asymptotic SC in the long run. SC is more relevant for long-life radioisotopes. Conclusions Application of the model to an actual bio-laboratory case shows that contribution to inhaled activity from surface contamination may be relevant or even dominant especially for long-life radionuclide (i.e. 3H and 14C). Great care should be used in cleaning the working surfaces after each manipulation to avoid or at last reduce to a reasonable level surface contamination. Smear test looks the test of choice to accurately verify the effective contamination level.

Purpose Daily images from CBCT could deliver significant dose to the patient, which should be considered and evaluated. It is essential to associate the absorbed dose delivered by the imaging procedures to the treatment of each patient. Aim of this work is to calculate organ doses for patients undergoing Cone Beam CT (CBCT) when treated with radiotherapy. Methods The system in use was an Elekta CBCT (XVI) and the protocols analysed were four: head, pelvis, chest and chest 4D with different parameters. The formula for organ dose calculation was obtained from Rampado et al. [1] where dose to organs were evaluated by means of Monte Carlo simulation in phantom; the effect of patient size were also accounted for. Dose to organs involved in CBCT scans is: D T = D W , 1 Ph · ( D T / D W , 1 Ph ) tab · a · e - bx where D W , 1 Ph is the measured dose in a phantom for the specific protocol, x is the effective diameter of the patient, ( D T / D W , 1 Ph ) tab , a and b are tabulated data from the article cited above. Patients were analyzed from March to June 2017. For each case were registered: the effective diameter from simulation CT, CBCT protocol, number of CBCT scans. Results Two hundred patients were considered. For head protocol, the mean CBCT doses were about 20 ± 10 mGy for all organs. Instead, doses of about 400 ± 150 mGy were evaluated for pelvis protocol. CBCT Doses for Chest 4D protocol were lower than other chest ones (about 50 ± 25 mGy vs 400 ± 150 mGy). This difference was due to number of CBCT scans/treatment fractions. Conclusions Doses from CBCT procedures should be accounted for; based on organ doses calculation, a program of dose optimization could be performed.

Introduction The Abdus Salam International Centre for Theoretical Physics (ICTP) and the Trieste University have initiated in 2014 a Master of Advanced Studies in Medical Physics a two-years training programme in Medical Physics. The programme is designated to provide young promising graduates in physics, mainly from developing countries, with a post-graduated theoretical and clinical training suitable to be recognised as Clinical Medical Physicist in their countries. Presently, the 3 cycles of the programme has seen 49 participants from 33 Countries: Africa (19), Asia (11), Central and South America (14), and Europe (5), selected from more than 400 applicants per year. Scholarships are awarded to candidates from developing countries with support of the IAEA, TWAS, KFAS, IOMP, EFOMP and ICTP. Material and methods The programme is developed following the recommendations of IOMP and IAEA for education and clinical training. In the first year 332 lectures and 228 h of exercises are devoted to all main fields of medical physics. The second year is spent in one of the 12 medical physics department of the hospitals’ network for the clinical training in: radiation oncology or diagnostic and nuclear medicine, on a programme developed adapting the IAEA (TCS37, TCS47 and TCS50) and AFRA guidelines. Conclusions IOMP, EFOMP and IAEA are seeing this initiative as an answer to the growing demand of Medical Physicists in developing Countries, representing an important European contribution to the development of medical physics in the developing world.

The Abdus Salam International Centre for Theoretical Physics (ICTP) and the Trieste University have initiated in 2014 a Master of Advanced Studies in Medical Physics (www.ictp.it/programmes/mmp.aspx), a two-years training programme in Medical Physics, co- sponsored by the Academy of Sciences for the Developing World (TWAS).

Dental CT dose evaluations are commonly performed using thermoluminescent dosimeters (TLD) inside anthropomorphic phantoms. Radiochromic films with good sensitivity in the X-ray diagnostic field have recently been developed and are commercially available as GAFCHROMIC XR-QA. There are potential advantages in the use of radiochromic films such as a more comprehensive dosimetry thanks to the adjustable size of the film samples. The purpose of this study was to investigate the feasibility of using radiochromic films for dental CT dose evaluations. Film samples were cut with a width of 5mm and a length of 25 mm (strips), the same size as the Alderson Rando anthropomorphic phantom holes used in this study. Dental CT dose measurements were performed using simultaneously both TLD and radiochromic strips in the same phantom sites. Two equipment types were considered for dental CT examinations: a 16 slice CT and a cone beam CT. Organ equivalent doses were then obtained averaging the measurements from the sites of the same organ and effective doses were calculated using ICRP 103 weighting factors. The entire procedure was repeated four times for each CT in order to compare also the repeatability of the two dosimeter types. A linear correlation was found between the absorbed dose evaluated with radiochromic films and with TLD, with slopes of 0.930 and 0.944 (correlation r>0.99). The maximum difference between the two dosimeter's measurements was 25%, whereas the average difference was 7%. The measurement repeatability was comparable for the two dosimeters at cumulative doses above 15 mGy (estimated uncertainty at 1 sigma level of about 5%), whereas below this threshold radiochromic films show a greater dispersion of data, of about 10% at 1 sigma level. We obtained, using respectively Gafchromic and TLD measurements, effective dose values of 107 μSv and 117 μSv (i.e. difference of 8.6%) for the cone beam CT and of 523 μSv and 562 μSv (i.e. difference of 7%) for the multislice CT. This study demonstrates the feasibility of radiochromic films for dental CT dosimetry, pointing out a good agreement with the results obtained using TLD, with potential advantages and the chance of a more extensive dose investigation.

Gafchromic® XR-R films are a useful tool to evaluate entrance skin dose in interventional radiology. Another dosimetric quantity of interest in diagnostic and interventional radiology is the dose area product (DAP). In this study, a method to evaluate DAP using Gafchromic® XR-R films and a flat-bed scanner was developed and tested. Film samples were exposed to an x-ray beam of 80 kVp over a dose range of 0–10 Gy. DAP measurements with films were obtained from the digitalization of a film sample positioned over the x-ray beam window during the exposure. DAP values obtained with this method were compared for 23 cardiological interventional procedures with DAP values displayed by the equipment. The overall one-sigma dose measurement uncertainty depended on the absorbed dose, with values below 6% for doses above 1 Gy. A maximum discrepancy of 16% was found, which is of the order of the differences in the DAP measurements that may occur with different calibration procedures. Based on the results presented, after an accurate calibration procedure and a thorough inspection of the relationship between the actual dose and the direct measured quantity (net optical density or net pixel value variation), Gafchromic® XR-R films can be used to assess the DAP.