BriXS, a new X-ray inverse Compton source for medical applications.

MariX is a research infrastructure conceived for multi-disciplinary studies, based on a cutting-edge system of combined electron accelerators at the forefront of the world-wide scenario of X-ray sources. The generation of X-rays over a large photon energy range will be enabled by two unique X-ray sources: a Free Electron Laser and an inverse Compton source, called BriXS (Bright compact X-ray Source). The X-ray beam provided by BriXS is expected to have an average energy tunable in the range 20-180 keV and intensities between 1011 and 1013 photon/s within a relative bandwidth ΔE/E=1-10%. These characteristics, together with a very small source size (~20 µm) and a good transverse coherence, will enable a wide range of applications in the bio-medical field. An additional unique feature of BriXS will be the possibility to make a quick switch of the X-ray energy between two values for dual-energy and K-edge subtraction imaging. In this paper, the expected characteristics of BriXS will be presented, with a particular focus on the features of interest to its possible medical applications.

Skin DVHs predict cutaneous toxicity in Head and Neck Cancer patients treated with Tomotherapy.

PURPOSE: To explore the association between planning skin dose-volume data and acute cutaneous toxicity after Radio-chemotherapy for Head and Neck (HN) cancer patients. METHODS: Seventy HN patients were treated with Helical Tomotherapy (HT) with radical intent (SIB technique: 54/66 Gy to PTV1/PTV2 in 30fr) ±â€¯chemotherapy superficial body layer 2 mm thick (SL2) was delineated on planning CT. CTCAE v4.0 acute skin toxicity data were available. Absolute average Dose-Volume Histograms (DVH) of SL2 were calculated for patients with severe (G3) and severe/moderate (G3/G2) skin acute toxicities. Differences against patients with none/mild toxicity (G0/G1) were analyzed to define the most discriminative regions of SL2 DVH; univariable and multivariable logistic analyses were performed on DVH values, CTV volume, age, sex, chemotherapy. RESULTS: Sixty-one % of patients experienced G2/G3 toxicity (rate of G3 = 19%). Differences in skin DVHs were significant in the range 53-68Gy (p-values: 0.005-0.01). V56/V64 were the most predictive parameters for G2/G3 (OR = 1.12, 95%CI = 1.03-1.21, p = 0.001) and G3 (OR = 1.13, 95%CI = 1.01-1.26, p = 0.027) with best cut-off of 7.7cc and 2.7cc respectively. The logistic model for V56 was well calibrated being both, slope and R2, close to 1. Average V64 were 2.2cc and 6cc for the two groups (G3 vs G0-G2 toxicity); the logistic model for V64 was quite well calibrated, with a slope close to 1 and R2 equal to 0.60. CONCLUSION: SL2 DVH is associated with the risk of acute skin toxicity. Constraining V64 < 3cc (equivalent to a 4x4cm2 skin surface) should keep the risk of G3 toxicity below or around 10%.

Comprehensive Intra-Institution stepping validation of knowledge-based models for automatic plan optimization.

PURPOSE: To develop and apply a stepping approach for the validation of Knowledge-based (KB) models for planning optimization: the method was applied to the case of concomitant irradiation of pelvic nodes and prostate + seminal-vesicles bed irradiation in post-prostatectomy patients. METHODS: The clinical VMAT plans of 52 patients optimized by two reference planners were selected to generate a KB-model (RapidPlan, v.13.5 Varian). A stepping-validation approach was followed by comparing KB-generated plans (with and without planner-interaction, RP and only-RP respectively) against delivered clinical plans (RA). The validation followed three steps, gradually extending its generalization: 20 patients used to develop the model (closed-loop); 20 new patients, same planners (open-loop); 20 new patients, different planners (wide-loop). All plans were compared, in terms of relevant dose-volume parameters and generalized equivalent uniform dose (gEUD). RESULTS: KB-plans were generally better than or equivalent to clinical plans. For RPvsRA, PTVs coverage was comparable, for OARs RP was always better. Comparing only-RPvsRA, PTVs coverage was always better; bowel\bladder V50Gy and D1%, bowel\bladder\rectum Dmean, femoral heads V40Gy and penile bulb V50Gy were significantly improved. For RPvsRA gEUD reduction >1 Gy was seen in 80% of plans for rectum, bladder and bowel; for only-RPvsRA, this was found in 50% for rectum/bladder and in 70% for bowel. CONCLUSION: An extensive stepping validation approach of KB-model for planning optimization showed better or equal performances of automatically generated KB-plan compared to clinical plans. The interaction of a planner further improved planning performances.

FDG PET-derived parameters as prognostic tool in progressive malignant pleural mesothelioma treated patients.

PURPOSE: The value of FDG PET-derived parameters in predicting overall survival (OS), local relapse-free survival (LRFS) and distant relapse-free survival (DRFS) in treated patients with malignant pleural mesothelioma (MPM) was evaluated. METHODS: This retrospective evaluation included 55 MPM patients treated between March 2006 and February 2015 with FDG PET/CT-guided salvage helical tomotherapy (HTT) after previous surgery plus chemotherapy. Univariate Cox regression analysis was performed to assess the impact of the following FDG PET-derived parameters: biological target volume (BTV), mean and maximum standardized uptake values (SUVmean/max), metabolic tumour volume (MTV) and total lesion glycolysis (TLG), measured using different uptake thresholds (40%, 50% and 60%). Logistic regression was then performed to identify the best FDG PET-derived parameters for selecting patients with poorer survival. RESULTS: The median OS was 9.1 months (range 0.0 - 69.6 months) after the end of HTT; 54/55 patients were dead at the last follow-up. BTV and TLG40, TLG50 and TLG60 were the most significant predictors of OS (p < 0.005). The median OS was 4.8 months in patients with MTV60 >5 cm3 and TLG40 >334.4, compared with 13.8 months and 16.1 months in patients with smaller values, respectively. The median LRFS and DRFS were 6.2 months (range 1.2 - 39.4 months) and 6.5 months (0.0 - 66.4 months), respectively. TLG40, TLG50 and TLG60 were significantly correlated with LRFS (p < 0.015). Median DRFS was 6.4 months in patients with MTV40 >39.6 cm3 and 6.2 months in patients with TLG40 >334.4, compared with 17 months and 18.8 months in patients with smaller values. BTV, TLG40 and MTV40 were also found to be good predictors in patients with poor OS/LRFS/DRFS (median survival times less than the median values). CONCLUSION: FDG PET-derived parameters effectively discriminated patients with a poor prognosis and may be helpful in the selection of MPM patients for salvage HTT.

Could early tumour volume changes assessed on morphological MRI predict the response to chemoradiation therapy in locally-advanced rectal cancer?

AIM: To investigate the potential role of an additional magnetic resonance imaging (MRI) examination performed during neoadjuvant chemoradiation therapy (CRT) in the prediction of pathological response in locally advanced rectal cancer (LARC). MATERIAL AND METHODS: Forty-eight consecutive patients with LARC underwent neoadjuvant CRT. MRI studies at 1.5 T, including high-resolution T2-weighted sequences that were acquired parallel and perpendicular to the main axis of the tumour were performed before (preMRI), during (midMRI), and 6-8 weeks after the end of CRT (postMRI). Cancer volumes (Vpre, Vmid, Vpost) were drawn manually and the reduction rate calculated (ΔVmid, ΔVpost). According to Rödel's pathological tumour regression grade (TRG), patients were considered non-responders (NR; TRG0-2), partial responders (PR; TRG3), and complete responders (CR; TRG4). Multivariate regression analysis was performed to identify the best MRI predictors of NR, PR, and CR. RESULTS: Twenty-five patients were considered PR (52%), 13 CR (27%), and 10 NR (22%). Tumour shrinkage mainly occurred shortly after CRT (ΔVmid: CR: 80±10% versus PR: 56±19% versus NR: 28±22%, p=2.2×10-16). Vmid, Vpost, ΔVmid, and ΔVpost correlated with TRG (p<0.001). At multivariate analysis, the combined assessment of Vmid and ΔVmid was selected as the best predictor of response to CRT, in that it distinguishes CR, PR, and NR early and accurately (81.5%). CONCLUSION: MidMRI allows final response assessment to neoadjuvant CRT earlier and better than the MRI performed after the end of CRT. MRI findings at midMRI may be useful to tailor patient treatment.

Validation of a method for "dose of the day" calculation in head-neck tomotherapy by using planning ct-to-MVCT deformable image registration.

PURPOSE: The aim of this study was to test the feasibility and dosimetric accuracy of a method that employs planning CT-to-MVCT deformable image registration (DIR) for calculation of the daily dose for head and neck (HN) patients treated with Helical Tomotherapy (HT). METHODS: For each patient, the planning kVCT (CTplan) was deformably registered to the MVCT acquired at the 15th therapy session (MV15) with a B-Spline Free Form algorithm using Mattes mutual information (open-source software 3D Slicer), resulting in a deformed CT (CTdef). On the same day as MVCT15, a kVCT was acquired with the patient in the same treatment position (CT15). The original HT plans were recalculated both on CTdef and CT15, and the corresponding dose distributions were compared; local dose differences <2% of the prescribed dose (DD2%) and 2D/3D gamma-index values (2%-2mm) were assessed respectively with Mapcheck SNC Patient software (Sun Nuclear) and with 3D-Slicer. RESULTS: On average, 87.9%±1.2% of voxels were found for DD2% (on average 27 slices available for each patient) and 94.6%±0.8% of points passed the 2D gamma analysis test while the 3D gamma test was satisfied in 94.8%±0.8% of body's voxels. CONCLUSIONS: This study represents the first demonstration of the dosimetric accuracy of kVCT-to-MVCT DIR for dose of the day computations. The suggested method is sufficiently fast and reliable to be used for daily delivered dose evaluations in clinical strategies for adaptive Tomotherapy of HN cancer.

Deformable registration-based segmentation of the bowel on Megavoltage CT during pelvic radiotherapy.

During pelvic radiotherapy bowel loops (BL) are subject to inter-fraction changes. MVCT images have the potential to provide daily bowel segmentation. We assess the feasibility of deformable registration and contour propagation in replacing manual BL segmentation on MVCT. Four observers delineated BL on the planning kVCT and on one therapy MVCT in eight patients. Inter-observer variations in BLs contouring were quantified using DICE index. BLs were then automatically propagated onto MVCT by a commercial software for image deformation and subsequently manually corrected. The agreement between propagated BL/propagated+manually corrected BL vs manual were quantified using the DICE. Contouring times were also compared. The impact on DVH of using the deformable-registration method was assessed. The same procedures were repeated on high-resolution planning-kVCT and therapy-kVCT. MVCTs are adequate to visualize BL (average DICE: 0.815), although worse than kVCT (average DICE:0.889). When comparing propagated vs manual BL, a poor agreement was found (average DICE: 0.564/0.646 for MVCT/KVCT). After manual correction, average DICE indexes increased to 0.810/0.897. The contouring time was reduced to 15min with the semi-automatic approach from 30min with manual contouring. DVH parameters of propagated BL were significantly different from manual BL (p<0.0001); after manual correction, no significant differences were seen. MVCT are suitable for BL visualization. The use of a software to segment BL on MVCT starting from BL-kVCT contours was feasible if followed by manual correction. The method resulted in a substantial reduction of contouring time without detrimental effect on the quality of bowel segmentation and DVH estimates.

Moderate Hypofractionation with Simultaneous Integrated Boost in Prostate Cancer: Long-term Results of a Phase I-II Study.

AIMS: To report 5 year outcome and late toxicity in prostate cancer patients treated with image-guided tomotherapy with a moderate hypofractionated simultaneous integrated boost approach. MATERIALS AND METHODS: In total, 211 prostate cancer patients, 78 low risk, 53 intermediate risk and 80 high risk were treated between 2005 and 2011. Intermediate- and high-risk patients received 51.8 Gy to pelvic lymph nodes and concomitant simultaneous integrated boost to prostate up to 74.2 Gy/28 fractions, whereas low-risk patients were treated to the prostate only with 71.4 Gy/28 fractions. Daily megavoltage computed tomography (MVCT) image guidance was applied. Androgen deprivation was prescribed for a median duration of 6 months for low-risk patients (for downsizing), 12 months for intermediate-risk and 36 months for high-risk patients. The 5 year biochemical relapse-free survival (bRFS), cancer-specific survival (CSS), overall survival and late gastrointestinal and genitourinary CTCAE.v3 toxicity were assessed. The effect of several clinical variables on both outcome and gastrointestinal/genitourinary toxicity was tested by uni- and multivariate Cox regression analyses. RESULTS: After a median follow-up of 5 years, the late toxicity actuarial incidence was: genitourinary ≥ grade 2: 20.2%; genitourinary ≥ grade 3: 5.9%; gastrointestinal ≥ grade 2: 17%; gastrointestinal ≥ grade 3: 6.3% with lower prevalence at the last follow-up visit (≥ grade 3: genitourinary: 1.9%; gastrointestinal: 1.9%). Major predictors of ≥ grade 3 genitourinary and gastrointestinal late toxicity were genitourinary acute toxicity ≥ grade 2 (hazard ratio: 4.9) and previous surgery (hazard ratio: 3.4). The overall 5 year bRFS was 93.7% (low risk: 94.6%; intermediate risk: 96.2%; high risk: 91.1%), overall survival and CSS were 88.6% (low risk: 90.5%; intermediate risk: 87.4%; high risk: 87%) and 97.5% (low risk: 98.7%; intermediate risk: 95%; high risk: 94.3%), respectively. Risk classes and androgen deprivation were not significantly correlated with either bRFS, overall survival or CSS. Twelve patients experienced a biochemical relapse but none experienced clinically proven local and/or pelvic recurrence. CONCLUSION: A satisfactory 5 year outcome with an acceptable toxicity profile was observed. The combination of image-guided radiotherapy-intensity-modulated radiotherapy, high equivalent 2 Gy dose (EQD2) with a moderate hypofractionated approach and extensive prophylactic lymph node irradiation also leads to very good outcome in high-risk patients.

Quality assurance of rapid arc treatments: performances and pre-clinical verifications of a planar detector (MapCHECK2).

The purpose of this study is to evaluate the use of MapCHECK2 in a patient-specific quality assurance (QA) procedure for Rapid Arc (RA) radiotherapy and to obtain reference values of gamma index (γ) for different irradiation geometries. Dose distributions of 386 patients, optimized with Eclipse treatment planning system for RA on Varian Clinac 2300IX were exported and measured with MapCHECK2 detector array inserted in a MapPHAN dedicated phantom. Gamma index analysis was used to evaluate differences between calculated and delivered doses; collected data were analysed on the basis of complexity of plans and type of disease. Angular dependence and dose drift of detectors were estimated. The overall mean passing rate (percentage of points with γ < 1) was equal to 97.0% ± 3.1%; plan-specific evaluation of %γ < 1 showed significant differences among different treatment protocols (pancreas 98.6% ± 1.5%, prostate 96.6% ± 2.8% and rectum 92.8% ± 5.7%). MapCHECK2 demonstrated a strong angular dependence over a restricted range of angles (90° ± 5° and 270° ± 5°); this condition affected the result of pre-treatment QA only for plans with intense lateral fluence. The drift of diode array response due to the accumulated dose was found to be comparable with the manufacturer's declaration (0.5% per 1000 Gy). MapCHECK2 proved to be a useful and accurate tool in the process of patient-specific QA for RA treatment. Excluding the irradiation geometries with a high contribution of lateral fluence, the mean percentage of cases with γ-index > 95% equal to 90.3% was obtained instead of 81.7% including all plans.

Evaluation of second cancer induction risk by CT follow-up in oncological long-surviving patients.

The goal of establishing prompt localization of the malignant spread or recurrence of a tumor has found a powerful solution in the definition of follow-up protocols, which include the indication for CT scans on an annual or semiannual basis. In the case of long-surviving patients, however, this approach will lead to a considerable integrated dose level over a period of several years after recovery from the illness. Pathologies treated primarily by surgery and/or chemotherapy have been considered, not taking into account cancers treated with adjuvant or radical radiotherapy. Given that the most likely protocols for these cancers often call for total body scans, an estimation of the consequent effective and organ doses can be performed with acceptable accuracy. The data acquired from five centers have been collected and the related effective and organ doses calculated by means of IMPACT software. Use of the effective dose concept, however, has lately become the subject of criticism, and the recently proposed Effective Risk Model has therefore also been applied. The evaluated absolute additional risk of second tumor induction ranges between 0.1% and 10%, depending primarily on age and pathology. These results depict this additional risk as an issue of significant importance for clinical practice. A revision of follow-up and scan parameter protocols, as well as the introduction of new algorithms for dose reduction, could significantly improve the risk-benefit ratio for all the pathologies studied.

Biological optimization of simultaneous boost on intra-prostatic lesions (DILs): sensitivity to TCP parameters.

The aim of this investigation was to explore the potential of biological optimization in the case of simultaneous integrated boost on intra-prostatic dominant lesions (DIL) and evaluating the impact of TCP parameters uncertainty. Different combination of TCP parameters (TD50 and γ50 in the Poisson-like model), were considered for DILs and the prostate outside DILs (CTV) for 7 intermediate/high-risk prostate patients. The aim was to maximize TCP while constraining NTCPs below 5% for all organs at risk. TCP values were highly depending on the parameters used and ranged between 38.4% and 99.9%; the optimized median physical doses were in the range 94-116 Gy and 69-77 Gy for DIL and CTV respectively. TCP values were correlated with the overlap PTV-rectum and the minimum distance between rectum and DIL. In conclusion, biological optimization for selective dose escalation is feasible and suggests prescribed dose around 90-120 Gy to the DILs. The obtained result is critically depending on the assumptions concerning the higher radioresistence in the DILs. In case of very resistant clonogens into the DIL, it may be difficult to maximize TCP to acceptable levels without violating NTCP constraints.

Optical imaging of radioisotopes: a novel multimodal approach to molecular imaging.

In this review there will be presented an overview of the literature about the recent developments on radiotracers imaging using optical methods and their applications. We will begin with a short summary regarding the discovery of Cerenkov radiation (CR) and then focus on the early developments and experimental validation of planar Cerenkov luminescence imaging. A significant improvement in Cerenkov luminescence imaging was given by the development of tomographic methods in order to obtain in vivo whole body 3D images of Cerenkov sources. An interesting and original application discussed in this review is the use of CR as the excitation source of quantum dots and fluorophores. We will also present some recent experimental results on in vivo radio luminescence imaging of alpha and gamma emitters. All these results make optical radioisotopes imaging an interesting cost-effective tool for the screening of new probes for both imaging and therapeutic applications. Other interesting aspects are the uses of Cerenkov radiation for radiotherapy and for radiopharmaceuticals synthesis applications. We will conclude by summarising the most important results and the future challenges.

PP163. Are we using magnesium sulphate excessively for preeclamptic patients?

INTRODUCTION: There is now evidence that magnesium sulfate can prevent and control eclamptic seizures. For women with pre-eclampsia, magnesium sulfate reduces by more than one half the risk of eclampsia. After Magpie Trial [1] our clinical practice has been modified in terms of more liberal use of MgSO4, but the evidence regarding the benefit-to-risk ratio of MgSO4 prophylaxis in mild preeclampsia remains uncertain [2]. Thus we consider important to evaluate whether there are specific characteristics between patients who received the medicine that might signal risk and justify our decisions. OBJECTIVES: To identify in a group of hypertensive patients who used magnesium sulfate, clinical and/or laboratory characteristics that can be defined as specific risk factors and be useful to base clinical decisions. METHODS: The study was conducted at the Maternity School of Vila Nova Cachoeirinha, a public institution located in the north of the city of São Paulo (Baazil) between 01/07 and 31/12/2011. This is a retrospective study of a series of 103 pregnant women with hypertensive disorders, defined according to NHBPEP. We excluded patients admitted in labor. Patients were assigned into two groups according to the use of MgSO4. We compared clinical and laboratory characteristics between the two groups. RESULTS: Of 103 patients included, 31 (30.1%) received MgSO4. Among the outcomes analyzed, there were significant differences in the group that received MgSO4 in terms of blood pressure equal to or greater than 110mmHg, clinical symptoms (eg headache and visual disturbance) and at least some evidence of organ dysfunction (hepatic, renal, haematologic, or central nervous system) (Table 1). Table 1. Variables associated with theuse of magnesium sulfate. CONCLUSION: We can say that in our institution over the years was an increase in the use of magnesium sulfate. Our results support the hypothesis that about one in three patients treated at this institution receive the medication. Although our protocol admits that the decision may be based on subjective criteria, we identified some objective characteristics that supported their application, and that these criteria do not differ from the classic recommendations. We can also conclude that in our clinical experience we do not have identified a clear justification for support the routinely use of magnesium sulphate for all women with preeclampsia.

An automatic contour propagation method to follow parotid gland deformation during head-and-neck cancer tomotherapy.

We developed an efficient technique to auto-propagate parotid gland contours from planning kVCT to daily MVCT images of head-and-neck cancer patients treated with helical tomotherapy. The method deformed a 3D surface mesh constructed from manual kVCT contours by B-spline free-form deformation to generate optimal and smooth contours. Deformation was calculated by elastic image registration between kVCT and MVCT images. Data from ten head-and-neck cancer patients were considered and manual contours by three observers were included in both kVCT and MVCT images. A preliminary inter-observer variability analysis demonstrated the importance of contour propagation in tomotherapy application: a high variability was reported in MVCT parotid volume estimation (p = 0.0176, ANOVA test) and a larger uncertainty of MVCT contouring compared with kVCT was demonstrated by DICE and volume variability indices (Wilcoxon signed rank test, p < 10(-4) for both indices). The performance analysis of our method showed no significant differences between automatic and manual contours in terms of volumes (p > 0.05, in a multiple comparison Tukey test), center-of-mass distances (p = 0.3043, ANOVA test), DICE values (p = 0.1672, Wilcoxon signed rank test) and average and maximum symmetric distances (p = 0.2043, p = 0.8228 Wilcoxon signed rank tests). Results suggested that our contour propagation method could successfully substitute human contouring on MVCT images.

Dosimetric data and radiation risk analysis for new procedures in interventional cardiology.

The purpose of this study was to evaluate radiation doses to the patients and operators during interventional cardiology procedures, with a particular focus on the transcatheter aortic valve implantation (TAVI). Patient doses for 5549 diagnostic and therapeutic procedures and 76 TAVI were examined, as well as occupational doses to Cardiology Department operators. The average patient dose for TAVI was double that of PTCA and six times higher than a simple CA; statistically significant differences were shown in the average patient dose for both transfemoral and transapical access; the measurements show a corresponding increase in the average occupational dose for the cardiologist. Interventional cardiology could increase the collective dose and occupationally exposed worker doses; this increase could be significant if the use of certain procedures is extended to younger people; particular attention in the choice of procedure, optimisation and staff education and organisation is therefore suggested.

Measurements and evaluation of the risks due to external radiation exposures and to intake of activated elements for operational staff engaged in the maintenance of medical cyclotrons.

The aim of this paper is to assess the activation phenomena and to evaluate the risk of external exposure and intake doses for the maintenance staff of two medical cyclotrons. Two self-shielded cyclotrons are currently operating in the facility for the routine production of (11)C and (18)F. Four radiochemistry laboratories are linked to the cyclotrons by means of shielded radioisotope delivery lines. Radiopharmaceuticals are prepared both for the PET Diagnostic Department, where four CT-PET scanners are operating with a mean patient workload of 40 d(-1) and for [(18)F]FDG external distribution, to provide radiopharmaceuticals for other institutions. In spite of the fact that air contamination inside the radiochemistry laboratories during the synthesis represents the largest 'slice of the pie' in the evaluation of annual intake dose, potential contamination due to the activated particulate, generated during cyclotron irradiation by micro-corrosion of targets and other components potentially struck by the proton beam and generated neutrons, should be considered. In this regard, the most plausible long-lived (T(1/2) > 30 d) radioisotopes formed are: (97)Tc, (56)Co, (57)Co, (58)Co, (60)Co, (49)V, (55)Fe, (109)Cd, (65)Zn and (22)Na. The results for the operating personnel survey has revealed only low-level contamination for (65)Zn in one test, together with minor (18)F intake, probably due to the environmental dispersion of the radioisotope during the [(18)F]FDG synthesis.

Measurement and control of the air contamination generated in a medical cyclotron facility for PET radiopharmaceuticals.

The aim of this paper is to report the data concerning the contamination of the exhausted air from the hot cells dedicated to the large-scale synthesis of positron emission tomography (PET) radiopharmaceuticals. Two cyclotrons are currently operating in Ospedale San Raffaele for the routine production of C and F. They are linked with four radiochemistry laboratories by means of shielded radioisotope delivery lines. The above labs are dedicated both to the large scale preparation and to the research and development of PET radiopharmaceuticals. The department hosts four CT-PET scanners, which operate with a mean patient workload of 40 per day. Radiosyntheses are performed using automated modules located in 10 hot cells. The air outlets are monitored online by a 2-inch NaI(Tl) counter in a Marinelli geometry counting volume. Contamination values up to 10(5) Bq L(-1) have been measured at the hot cell exit point during the synthesis. The corresponding concentrations at the point of release in atmosphere are largely above the threshold of 1.29 Bq L(-1), defined by national regulations as the limit for free environmental release. A shielded gas storage system controlled by a dedicated, customized software program has thus been installed to prevent the potentially hazardous release of gaseous radioactive contaminants. The system has allowed us to maintain the effective dose to neighboring population groups below the limit of 10 muSv y(-1).

Decommissioning procedures for an 11 MeV self-shielded medical cyclotron after 16 years of working time.

The present article describes the decommissioning of a compact, self-shielded, 11 MeV medical cyclotron. A Monte Carlo simulation of the possible nuclear reactions was performed in order to plan the decommissioning activities. In the course of the cyclotron dismantling, cyclotron components, shields, and floor concrete samples were measured. Residual activities were analyzed with a Ge(Li) detector and compared with simulation data. Doses to staff involved in the decommissioning procedure were monitored by individual TL dosimeters. The simulations identified five radioactive nuclides in shields and floor concrete: 55Fe and 45Ca (beta emitters, total specific activity: 2.29 x 10(4) Bq kg) and 152Eu, 154Eu, 60Co (gamma emitters, total specific activity: 1.62 x 10(3) Bq kg-1). Gamma-ray spectrometry confirmed the presence of gamma emitters, corresponding to a total specific activity of 3.40 x 10(2) Bq kg-1. The presence of the radioisotope 124Sb in the lead contained in the shield structure, corresponding to a simulated specific activity of 9.38 x 10(3) Bq kg-1, was experimentally confirmed. The measured dose from external exposure of the involved staff was <20 muSv, in accordance with the expected range of values between 10 and 20 muSv. The measured dose from intake was negligible. Finally, the decommissioning of the 11 MeV cyclotron does not represent a risk for the involved staff, but due to the presence of long-lived radioisotopes, the cyclotron components are to be treated as low level radioactive waste and stored in an authorized storage area.

Seed migration in prostate brachytherapy: a re-implant case report.

Seed embolisation to the lung is a possible risk following permanent prostate brachytherapy. The purpose of this work is to analyse a seed migration case and to suggest methods to reduce such occurrences. With this aim, the clinical history of the patient who experienced seed migration, the implant technique and the pre- and post-plan procedures have been investigated. The massive seed migration has been detected in the patient by means of a pelvic X-ray and a CT-scan of the thorax. The use of loose seeds, the implant technique and the presence of unfavourable anatomical characteristics, have been recognised as possible causes of this event. The use of linked seeds embedded in vicryl sutures for the peripheral portions of prostate, and the development of an implant technique based on both transverse and longitudinal ultrasound guidance are proposed in order to reduce seed migration.