Biomedical subjects

Claude Malet

Publications and source records attributed to Claude Malet.

4 recordsLinked to original sources

PubMed2007

Active breathing control for Hodgkin's disease in childhood and adolescence: feasibility, advantages, and limits.

PURPOSE: The challenge in early Hodgkin's disease (HD) in children is to maintain good survival rates while sparing organs at risk. This study assesses the feasibility of active breathing control (ABC) in children, and compares normal tissue irradiation with and without ABC. METHODS AND MATERIALS: Between May 2003 and June 2004, seven children with HD with mediastinal involvement, median age 15, were treated by chemotherapy and involved-field radiation therapy. A free-breathing computed tomography simulation scan and one additional scan during deep inspiration using ABC were performed. A comparison between planning treatment with clinical target volume including supraclavicular regions, mediastinum, and hila was performed, both in free breathing and using ABC. RESULTS: For a prescription of 36 Gy, pulmonary dose-volume histograms revealed a mean reduction in lung volume irradiated at more than 20 Gy (V20) and 30 Gy (V30) of 25% and 26%, respectively, using ABC (p = 0.016). The mean volume of heart irradiated at 30 Gy or more decreased from 15% to 12% (nonsignificant). The mean dose delivered to breasts in girls was small in both situations (less than 2 Gy) and stable with or without ABC. Considering axillary irradiation, the mean dose delivered to breasts remained low (<9 Gy), without significant difference using ABC or not. The mean radiation dose delivered to thyroid was stable using ABC or not. CONCLUSIONS: Using ABC is feasible in childhood. The use of ABC decreases normal lung tissue irradiation. Concerning heart irradiation, a minimal gain is also shown. No significant change has been demonstrated concerning breast and thyroid irradiation.

Adolescent↗

PubMed2005

Exclusive brachytherapy for T1 and T2 squamous cell carcinomas of the velotonsillar area: results in 44 patients.

PURPOSE: To evaluate the role of interstitial brachytherapy as an exclusive radiotherapy modality for primary T1-T2 squamous cell carcinomas (SCC) of the velotonsillar area. METHODS AND MATERIALS: Between 1992 and 2000, 44 patients with T1-T2 SCC of the tonsil (n = 36) and soft palate (n = 8) were treated to the primary with brachytherapy alone (37 patients) or after a limited resection (7 patients). Eight patients had prior external beam radiation therapy (EBRT) for previous head-and-neck carcinoma. Nineteen patients had initial neck dissection. The mean brachytherapy dose was 58.7 Gy, and the mean reference dose rate and Ir-192 linear activity were 58.2 cGy/h and 1.51 mCi/cm respectively. RESULTS: With a 75-month median follow-up, 1 patient recurred locally. Isolated nodal relapses occurred in 4 patients, none of whom had initial neck dissection, and salvage therapy was successful in 2. Five-year overall and progression-free survival rates were 76% and 68%, respectively. Full-course radiation therapy was possible in 7 of 12 patients who developed a second primary head-and-neck carcinoma. Late toxicity was limited to 6 mild soft-tissue necroses, and was significantly associated with previous surgery to the primary and high linear activity. CONCLUSIONS: Exclusive brachytherapy for T1-T2 velotonsillar carcinomas is safe and effective, and permits definitive reirradiation for a second head-and-neck cancer. Initial neck dissection should be performed for optimal selection for exclusive brachytherapy.

Adult↗

PubMed2003

Three-dimensional conformal radiotherapy for paranasal sinus carcinoma: clinical results for 25 patients.

PURPOSE: To assess local control, survival, and clinical and dosimetric prognostic factors in 25 patients with locally advanced maxillary or ethmoid sinus carcinoma treated by three-dimensional conformal radiotherapy (RT). MATERIALS AND METHODS: Surgery was performed in 22 patients and was macroscopically complete in 16. Seven patients received chemotherapy (concomitant with RT in four). The following quality indexes were defined for the 95% and 90% isodoses: tumor conformity index, normal tissue conformity index, and global conformity index. RESULTS: The median radiation dose to the planned treatment volume was 63 Gy, with a minimal dose of 60 Gy, except in 2 patients whose cancer progressed during RT. The maximal doses tolerated by the structures involved in vision were respected, except for tumors that involved the optic nerve. After a median follow-up of 25 months, 14 local tumor recurrences developed. The major prognostic factors were central nervous system involvement by disease and the presence of nonresectable tumors. The radiation dose and tumor conformity index value were not significant prognostic indicators. Two patients died of acute infectious toxicity, and two developed late ipsilateral ocular toxicity. CONCLUSIONS: Improving local control remains the main challenge in RT for paranasal tumors.

Adenocarcinoma↗

PubMed2003

Patient setup error measurement using 3D intensity-based image registration techniques.

PURPOSE: Conformal radiotherapy requires accurate patient positioning with reference to the initial three-dimensional (3D) CT image. Patient setup is controlled by comparison with portal images acquired immediately before patient treatment. Several automatic methods have been proposed, generally based on segmentation procedures. However, portal images are of very low contrast, leading to segmentation inaccuracies. In this study, we propose an intensity-based (with no segmentation), fully automatic, 3D method, associating two portal images and a 3D CT scan to estimate patient setup. MATERIALS AND METHODS: Images of an anthropomorphic phantom were used. A CT scan of the pelvic area was first acquired, then the phantom was installed in seven positions. The process is a 3D optimization of a similarity measure in the space of rigid transformations. To avoid time-consuming digitally reconstructed radiograph generation at each iteration, we used two-dimensional transformations and two sets of specific and pregenerated digitally reconstructed radiographs. We also propose a technique for computing intensity-based similarity measures between several couples of images. A correlation coefficient, chi-square, mutual information, and correlation ratio were used. RESULTS: The best results were obtained with the correlation ratio. The median root mean square error was 2.0 mm for the seven positions tested and was, respectively, 3.6, 4.4, and 5.1 for correlation coefficient, chi-square, and mutual information. CONCLUSIONS: Full 3D analysis of setup errors is feasible without any segmentation step. It is fast and accurate and could therefore be used before each treatment session. The method presents three main advantages for clinical implementation-it is fully automatic, applicable to all tumor sites, and requires no additional device.

Anthropometry↗