Microdosimetric investigations at the fast neutron therapy facility at Fermilab

Microdosimetry was used to investigate three issues at the neutron therapy facility (NTF) at Fermilab. Firstly, the conversion factor from absorbed dose in A-150 tissue equivalent plastic to absorbed dose in ICRU tissue was determined. For this, the effective neutron kerma factor ratios, i.e., oxygen tissue equivalent plastic and carbon to A-150 tissue equivalent plastic, were measured in the neutron beam. An A-150 tissue equivalent plastic to ICRU tissue absorbed dose conversion factor of 0.92 {+-} 0.04 was determined. Secondly, variations in the radiobiological effectiveness (RBE) in the beam were mapped by determining variations in two related quantities, e{sup *} and R, with field size and depth in tissue. Maximal variation in e{sup *} and R of 9% and 15% respectively were determined. Lastly, the feasibility of utilizing the boron neutron capture reaction on boron-10 to selectively enhance the tumor dose in the NTF beam was investigated

Microdosimetric investigations at the Fast Neutron Therapy Facility at Fermilab

Microdosimetry was used to investigate three issues at the neutron therapy facility (NTF) at Fermilab. Firstly, the conversion factor from absorbed dose in A-150 tissue equivalent plastic to absorbed dose in ICRU tissue was determined. For this, the effective neutron kerma factor ratios, i.e. oxygen tissue equivalent plastic and carbon to A-150 tissue equivalent plastic, were measured in the neutron beam. An A-150 tissue equivalent plastic to ICRU tissue absorbed dose conversion factor of 0.92 {+-} 0.04 determined. Secondly, variations in the radiobiological effectiveness (RBE) in the beam were mapped by determining variations in two related quantities, e{sup *} and R, with field size and depth in tissue. Maximal variation in e{sup *} and R of 9% and 15% respectively were determined. Lastly, the feasibility of utilizing the boron neutron capture reaction on boron-10 to selectively enhance the tumor dose in the NTF beam was investigated. In the unmodified beam, a negligible enhancement for a 50 ppm boron loading was measured. To boost the boron dose enhancement to 3% it was necessary to change the primary proton energy from 66 MeV and to filter the beam by 90 mm of tungsten

An endorectal balloon reduces intrafraction prostate motion during radiotherapy.

Item does not contain fulltextPURPOSE: To investigate the effect of endorectal balloons (ERBs) on intrafraction and interfraction prostate motion during radiotherapy. METHODS AND MATERIALS: Thirty patients were treated with intensity-modulated radiotherapy, to a total dose of 80 Gy in 40 fractions. In 15 patients, a daily-inserted air-filled ERB was applied. Prostate motion was tracked, in real-time, using an electromagnetic tracking system. Interfraction displacements, measured before each treatment, were quantified by calculating the systematic and random deviations of the center of mass of the implanted transponders. Intrafraction motion was analyzed in timeframes of 150 s, and displacements >1 mm, >3 mm, >5 mm, and >7 mm were determined in the anteroposterior, left-right, and superoinferior direction, and for the three-dimensional (3D) vector. Manual table corrections, made during treatment sessions, were retrospectively undone. RESULTS: A total of 576 and 567 tracks have been analyzed in the no-ERB group and ERB group, respectively. Interfraction variation was not significantly different between both groups. After 600 s, 95% and 98% of the treatments were completed in the respective groups. Significantly fewer table corrections were performed during treatment fractions with ERB: 88 vs. 207 (p = 0.02). Intrafraction motion was significantly reduced with ERB. During the first 150 s, only negligible deviations were observed, but after 150 s, intrafraction deviations increased with time. This resulted in cumulative percentages of 3D-vector deviations >1 mm, >3 mm, >5 mm, and >7 mm that were 57.7%, 7.0%, 0.7%, and 0.3% in the ERB-group vs. 70.2%, 18.1%, 4.6%, and 1.4% in the no-ERB group after 600 s. The largest reductions in the ERB group were observed in the AP direction. These data suggest that a 5 mm CTV-to-PTV margin is sufficient to correct for intrafraction prostate movements when using an ERB. CONCLUSIONS: ERB significantly reduces intrafraction prostate motion, but not interfraction variation, and may in particular be beneficial for treatment sessions longer than 150 s

Feasibility of couple-based expanded carrier screening offered by general practitioners

Expanded carrier screening (ECS) aims to inform couples’ reproductive choice, preferably before conception. As part of an implementation study in which trained general practitioners (GPs) offered a population-based ECS couple-test, we evaluated the feasibility of the test-offer and degree of participant informed choice (IC). Trained GPs from nine practices in the northern Netherlands invited 4295 female patients aged 18–40 to take part in couple-based ECS. Inclusion criteria were having a male partner, planning for children and not being pregnant. We evaluated the feasibility of the organizational aspects, GP competence and the content of the pre-test counselling. Participant satisfaction, evaluation of pre-test counselling and degree of IC were measured using a longitudinal survey. We explored GP experiences and their views on future implementation through semi-structured interviews. 130 consultations took place. All participating GPs were assessed by genetic professionals to be competent to conduct pre-test counselling. Most (63/108 (58%)) consultations took place within the planned 20 min (median 20, IQR 18–28). GPs considered couples’ prior knowledge level an important determinant of consultation length. 91% of patients were (very) satisfied with the GP counselling. After pre-test counselling, 231/237(97%) participants had sufficient knowledge and 206/231(88%) had a positive attitude and proceeded with testing. Our pilot demonstrates that offering couple-based ECS through trained and motivated GPs is feasible. Future large-scale implementation requires a well-informed general public and a discussion about appropriate reimbursement for GPs and health care coverage for couples. Providing (more) test information pre-appointment may help reduce average consultation time

Toward an effective exome-based genetic testing strategy in pediatric dilated cardiomyopathy

Genetics of disease, diagnosis and treatmen