42 Deposited dose measurement using bremsstrahlung X-rays

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Beam monitoring and dosimetry tools for radiobiology experiments at the cyclotron ARRONAX

International audienceThe ARRONAX (Accélérateur pour la Recherche en Radiochimie et Oncologie à Nantes Atlantique) cyclotron in Saint Herblain - France is a facility delivering alpha particles at 68 MeV (1). One of its purposes is to become a platform for radiobiological studies. The radiobiological studies evolvearound two axes: the low energy range (<10MeV) in order to optimize radio-immunotherapy (RIT) treatments, and the high energy range (30-68 MeV) in order to puzzle out the fundamental mechanisms generated by cells in response to ionizing radiations.The ARRONAX platform for radiobiology is currently preparing to use a time lapse fluorescence confocal microscope suitable for the irradiation of cell wells. This platform should contain tools for beam intensity checks to enable accurate and repeatable irradiation conditions and a device to monitor thedelivered dose

FLASHMOD : vers une plateforme d’irradiation préclinique en protonthérapie FLASH à ARRONAX

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New beam monitoring tool for radiobiology experiments at the cyclotron ARRONAX

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Investigation of energy dependance for EBT3 response to irradiation with alpha beams

International audienceThe response of EBT3 radiochromic film to ionizing radiation has been investigated for alpha beams. An experiment has been performed at the ARRONAX cyclotron to measure the net optical density (net OD) of EBT3 films as a function of the deposited doses of an alpha beam at different energies. A stack of 4 films was irradiated, therefore the beam energy is changed as a function of the film position between 45 MeV and 22 MeV. No differences in the film responses were observed in function of the alpha beam energy. The same calibration (Dose vs net OD) can be used for EBT3 film in this range of alpha beam energy. It is necessary to extend this study at lower energy down to the Bragg peak region

Preliminary results of 68Ga-PSMA PET/CT prospective study in prostate cancer occult recurrence patients : diagnostic performance and impact on therapeutic decision-making

International audienceIntroduction: The aim of this prospective study was to investigate the impact of 68Ga-PSMA-11 PET/CT on current management of prostate cancer patients with occult biochemical recurrence (BCR). Subjects & Methods: 130 hormone-naïve occult BCR (PSA from 0.05 to 1.6 ng/mL) patients were enrolled in a prospective study (NCT03443609). All patients received a radical treatment (prostatectomy +/- radiotherapy) which allowed to an undetectable PSA level. Before PSMA PET/CT, patients were screened by conventional imaging as mpMRI and bone scan (+ trunk SPECT/ CT) and enrolled only if conventional imaging was doubtful or normal. PET images were recorded 1 and 2 hours after injection of 150 MBq of tracer and images interpreted by 2 nuclear physicians. Referring patient physician completed 2 questionnaires to assess PSMA PET imaging influence on therapeutic strategy: one prior and one after PSMA PET/CT indicating treatment plan without and with PSMA PET/CT information respectively. Six months after the end of treatment, a PSA assay was requested to evaluate therapeutic efficacy. Results: Currently, we have complete data analysis of the first 52 patients. After pre-screening, 7 patients were excluded due to positive MRI (5 pts) or bone scan (2 pts). The median time from radical prostatectomy or radiotherapy to BCR was 4.92y (0.6-15.46). Thirty-eight among the 52 patients (73%) had a positive PSMA PET/CT. Ninety-four lesions were detected, 53/94 in lymph nodes (56.4%) predominantly dispatched on pelvic area (75.5%), 25/94 in bone (26.6%) (mostly on axial skeleton) and 12/94 into prostate bed (12.7%). Detection rates were 56 %, 87 % and 74% for patients with PSA value ranging from 0.05 to 0.3, 0.3 to 0.6 and 0.6 to 1.6 ng/ml respectively. Thanks to PSMA PET/CT, therapeutic management changed in 35/52 patients (67.3%). PSMA-positive patients had undetectable PSA level after stereotaxic radiotherapy or focal surgery based on PSMA results in 30.7% (16/52). In this particular hormone naïve patient population, Rauscher’s nomogram (1) was not validate, may be due a too small population. Conclusion: Preliminary results of this prospective study showed, in more than half of patients, a major impact of PSMA PET/CT on treatment management allowing them to benefit very early from focal therapy with the great result for 30% of them of PSA complete response. Reference: (1) Rauscher I., et al: doi:10.1016/j.eururo.2018.01.00