Behavior of CVD diamond-based TL dosimeters in radiotherapy environments using photon and electron beams from treatment accelerators

Article associé : https://hal.archives-ouvertes.fr/hal-00740867 DOI:10.1016/j.diamond.2011.02.004International audienceChemical Vapor Deposited (CVD) diamond has great advantages for use as thermoluminescent dosimeters in radiotherapy environment because of the reproducible high quality and controlled doping. This study compares CVD diamond Thermally Stimulated Luminescence response to that of a classical ionization chamber. Clinically-relevant features like the depth-dose distributions as well as the absorbed dose profile are investigated for a 6 MV photon beam and a 6 MeV electron beam. Moreover electron beam cartography and one beam Intensity-Modulated Radiation Therapy (IMRT) treatment planning have been controlled by means of CVD diamonds. Reproducibility and repeatability of TL measurements are satisfying and a good TL sensitivity to both electron and photon beams is clearly shown. Comparing the TL responses presented here to the ionization chamber underline the very promising behavior of CVD diamonds, particularly in high dose gradient areas

Does gap-free intensity modulated chemoradiation therapy provide a greater clinical benefit than 3D conformal chemoradiation in patients with anal cancer?

Abstract Background Chemoradiation is the standard treatment for anal cancer. 3D conformal radiotherapy (3D-CRT) is usually split in 2 sequences with a therapeutic break (gap) in between. Intensity-modulated radiation therapy (IMRT) makes it possible to reduce treatment time by abandoning this gap. The purpose of this study was to compare outcomes and toxicities in patients treated with either IMRT or 3D-CRT. Methods Between 2004 and 2011, the data of 51 patients treated with exclusive radiotherapy with or without concomitant chemotherapy for non-metastatic anal carcinoma were retrospectively analyzed. Twenty-seven patients were treated with 3D-CRT and 24 patients with IMRT, with a median dose delivered to the tumor of 59.4Gy [30.6-66.6], whatever the radiotherapy technique (p= 0.99). The median follow-up was 40 months [26.4-51.6]. Results There was no difference between the two groups for response to treatment (p= 0.46). Two-year overall survival, locoregional relapse-free survival and colostomy-free survival rates were 88.5%, 63% and 60.3%, respectively for the IMRT group and 81%, 76.5% and 81.1% for the 3D-CRT group (all NS). Ten patients (37%) in 3D-CRT and 11 patients (45.8%) in IMRT (p= 0.524) had grade 3 acute toxicity. No grade 4 toxicity occurred. Conclusions Our study suggests that further investigations concerning the use of IMRT to treat cancer of the anus are warranted. IMRT makes it possible to remove the gap, but with no impact on the prognosis. Nonetheless, a longer follow-up is essential to determine whether or not IMRT has an impact on late toxicity, local control and survival compared with conventional 3D-CRT.</p

Inferring postimplant dose distribution of salvage permanent prostate implant (PPI) after primary PPI on CT images

International audiencePURPOSE:To evaluate the dose distribution of additional radioactive seeds implanted during salvage permanent prostate implant (sPPI) after a primary permanent prostate implant (pPPI).METHODS AND MATERIALS:Patients with localized prostate cancer were primarily implanted with iodine-125 seeds and had a dosimetric assessment based on day 30 postimplant CT (CT1). After an average of 6 years, these patients underwent sPPI followed by the same CT-based evaluation of dosimetry (CT2). Radioactive seeds on each CT were detected. The detected primary seeds on CT1 and CT2 were registered and then removed from CT2 referred as a modified CT2 (mCT2). Dosimetry evaluations (D90 and V100) of sPPI were performed with dedicated planning software on CT2 and mCT2. Indeed, prostate volume, D90, and V100 differences between CT2 and either CT1 or mCT2 were calculated, and values were expressed as mean (standard deviation).RESULTS:The mean prostate volume difference between sPPI and pPPI over the 6 patients was 9.85 (7.32) cm3. The average D90 and V100 assessed on CT2 were 486.5 Gy (58.9) and 100.0% (0.0), respectively, whereas it was 161.3 Gy (47.5) and 77.3% (25.2) on mCT2 (p = 0.031 each time). The average D90 the day of sPPI [145.4 Gy (11.2)] was not significantly different from that observed on mCT2 (p = 0.56).CONCLUSION:Postimplant D90 and V100 of sPPI after pPPI can be estimated on CT images after removing the primary seeds.Copyright © 2018 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved