[Oligodendrogliomas and radiosurgery]. / Place de la radiochirurgie dans le traitement des oligodendrogliomes.

Radiosurgery of oligodendrogliomas is not specific. It must be integrated into the overall treatment scheme for gliomas which remains to be strictly defined. Nevertheless, empirically, and in light of the limited constraints for the patient and the encouraging radiological and clinical benefits, radiosurgical teams usually propose this technique in the event of recurrence of malignant gliomas, as a second line treatment. Exceptionally radiation can be used for some small benign gliomas which could not be treated by open surgery and accurately defined radiologically. Radiosurgery can achieve local control of the lesion, mostly transitionally, with 15 to 18 Gy at the reference isodose. One of the key problems is the definition of the glioma boundaries. Despite progress in neuroimaging techniques most the limits of malignant forms are still not accessible. In routine practice, the nodular area, considered as the most active on MRI, i.e. the contrast enhanced area, is accepted as the target. Its widest dimension must be about 35-40 mm. Only patients with minimal disability can benefit from radiosurgery. Optimization of the target definition (in particular the most active zone) and prospective randomized studies should be helpful in clarifying indications for this technique.

[Pulmonary nodules: dosimetric and clinical studies at low dose multidetector CT]. / Evaluation dosimétrique en exploration TDM thoracique multibarrette faible dose dans la détection des nodules pulmonaires.

PURPOSE: To measure breast radiation dose from multidetector CT using three different low dose protocols and compare it to a standard two view chest examination. To compare the number of pulmonary nodules detected at low and standard dose. MATERIALS AND METHODS: Thermoluminescent dosimetry was used to measure the absorbed dose on a phantom (Rando) and 10 patients. Then, we compared the standard dose to the low dose examinations. The Wilcoxon rank test and the kappa test were used to assess differences in the detection of nodules. RESULTS: The absorbed dose of these low dose protocols correspond to the radiation dose for the acquisition of two to ten chest radiographs (two views). This study suggests that only the 30 mA protocol is sufficient for the detection of all pulmonary nodules; nodules smaller than 5 mm were overlooked at 10 mA. CONCLUSION: A good image quality can be obtained with low dose protocols at multidetector CT (correspond to 2 to 10 chest radiographs).

[An assessment of low-dose high resolution CT in the detection of benign asbestos-related pleural abnormalities]. / Exploration tomodensitométrique des sujets exposés à l'amiante: validation des coupes millimétriques haute résolution à faible dose.

PURPOSE: To assess the reliability of low-dose high-resolution computed tomography (HRCT) in the detection of benign asbestos-related pleural abnormalities. METHODS: Fourty-one patients exposed to asbestos were imaged on two occasions; the first time with conventional HRCT parameters: 140kVp, 220mAs; the second time with low-dose HRCT parameters: 120kVp, 60mAs. RESULTS: The qualitative assessment dit not show any difference in the visibility of benign pleural abnormalities from one technique to the other in 98% cases. CONCLUSION: The detection of pleural plaques and thickening did not vary with the two scanning protocols and, when compared with conventional HRCT, low-dose HRCT allows reduced radiation exposure by at least 76.5%, with an absorbed dose close to that delivered when using conventional chest radiography. Nevertheless, low-dose HRCT is a complementary study to helical acquisitions.

[Long-term results of cobalt 60 curietherapy for uveal melanoma]. / Résultats à long terme de la curiethérapie par le cobalt 60 des mélanomes de l'uvée.

PURPOSE: To analyze 65 patients with uveal melanomas treated with cobalt plaque therapy with regards to mortality, visual results and complications. PATIENTS AND METHODS: Most of the melanomas were large (T3: 52.5%), with a mean largest dimension of the base of 11 mm, and a mean thickness of 6 mm. Most of the tumors were located in the choroid (95%), with an anterior margin behind the equator (65%), and a posterior margin at less than 3 mm of the disc and/or of the macula (69%). The plaque radiotherapy delivered a mean dose of 95 Gy to the tumor apex, either with a cobalt plaque alone (51 cases), or in association with a ruthenium plaque (14 cases). The mean follow up period was over 8 years. RESULTS: The local control was achieved initially in 86% of the eyes. The estimated melanoma specific survival rate was 83% after 5 years and 74% after 10 years. The main parameter associated with the metastases was the largest dimension of the base (p < 0.01). The eye was retained in 83% of the cases. The probability of keeping a vision better than or equal to 0,1 was 39% after 5 years and 27% after 10 years. The main parameter associated with the visual loss was the tumor size (p < 0.01). The complications included cataract (39%), radiation retinopathy (34%), with maculopathy (19%) and/or papillopathy (13.5%), vitreous hemorrhages (22%), neovascular glaucoma (15%) and retinal detachment (12%). CONCLUSION: These results supported the value of cobalt plaque radiotherapy in the management of uveal melanomas.

[Comparative study of beta irradiation (106Ru/106Rh) and gamma irradiation (125I) on the rabbit eye]. / Etude comparative de l'irradiation bêta (106Ru/106Rh) et de l'irradiation gamma (125I) sur l'oeil du lapin.

We compared beta irradiation (106Ru/106Rh) to gamma irradiation (125I) on the normal rabbit eye, using ophthalmic plaques to deliver doses similar to those recommended in man for choroidal melanoma treatment. A detailed dosimetry was performed and the animals were followed up by clinical and histological examinations during 1 year. The mean total doses were either comparable, or larger with iodine-125, but the globes treated with ruthenium-106 exhibited more damaging effects: total destruction of the chorioretina on the plaque site, abnormalities of the retinal vessels and of the close nerve fiber layers, cavernous atrophy of the optic nerve. In the eyes treated with iodine-125, only the external retinal layers were destroyed.

Radioresistance induced by the high molecular forms of the basic fibroblast growth factor is associated with an increased G2 delay and a hyperphosphorylation of p34CDC2 in HeLa cells.

The basic fibroblast growth factor-(bFGF) mediated signal transduction pathway has been implicated in cellular resistance to ionizing radiation. bFGF is synthesized from the same mRNA in four isoforms resulting from alternative initiations of translation at three CUG start codons (24, 21.5, and 21 kDa) and one AUG start codon (18 kDa). We analyzed the implication of high- and low-molecular forms of bFGF in radioresistance acquisition. For this, we transfected HeLa cells with retroviral vector containing either the CUG-initiated 24-kDa molecular form (HeLa 3A cells), the AUG-initiated 18-kDa molecular bFGF form (HeLa 5A cells), or the vector alone (HeLa PINA cells). A significantly increased radioresistance was obtained only in HeLa 3A cells (Dq = 810 +/- 24 cGy) compared with wild-type cells (Dq = 253 +/- 49 cGy) or HeLa PINA cells (Dq = 256 +/- 29 cGy; P < 0.001). This radioprotective effect was independent of an inhibition of radiation-induced apoptosis but related to an increased G2 duration after irradiation and to an hyperphosphorylation of p34cdc2 kinase. Knowledge of the high-molecular bFGF form-induced radioresistance pathway could offer novel targets for decreasing the radioresistance phenotype of tumors expressing high amounts of bFGF, such as glioblastoma.

[Brachytherapy of ocular melanoma: physical and dosimetric aspects of 125I plaques]. / Curiethérapie des mélanomes oculaires: aspects physiques et dosimétriques des applicateurs d'iode 125.

Off-axis absorbed dose distribution of ophthalmic plaques is a useful parameter for the explanation of some observed biological effects. From a specific dosimetric software, developed in our brachytherapy department, and from our measurements around 125I eye plaque, we studied the dose distribution effects on the spread of activities inside the plaques. After analysis of experimental data, we observed also that the dose distribution in the penumbra area may be described easily with decrement lines.

[Evaluation of radiation doses during radiological tests]. / Evaluation des doses délivrées au cours d'examens radiologiques.

The purpose of this document is to provide radiologists with a simple, but realistic means of determining the individual dose delivered to a patient during a radiological examination both in the region under investigation and at any other particularly sensitive organs. Fourteen types of examinations were considered corresponding to those most frequently carried out in France. The choice of examinations and methods of taking the films approaches as closely as possible, the average situations, and the frequency of different techniques is influenced by the results of a national study of radiodiagnostic examinations carried out in France in 1982. In the first section, the influence on the radiation dose of varying different physical parameters and techniques is analysed, with an aim of defining the limits of validity of the presented dosimetric values and the possible adaptation of these values to any individual situation, which is slightly different from these considered in this study. The second section describes the model used for determining the absorbed dose presented in the tables, concerning each type of examination, as well as bibliographic references referring to methods and results of determining the dose. The suggested calculation model may be used as a base for dose estimation for other types of examination.

[Ureteral dosimetry during gynecological curietherapy. Possible effects on the occurrence of postoperative ureteral complications]. / La dosimétrie urétérale en curiethérapie gynécologique. Incidence possible sur la survenue des complications urétérales postopératoires.

The dosage of radiations delivered during gynaecological brachytherapy is usually calculated for the bladder and the rectum. A new technical approach is described in order to known the dose of radiation received by the terminal portion of the ureter. During placement of the Fletcher suit one of the ureters is catheterized by a special stent which appears on the X-rays control used for dosimetry. Data of 16 pre-operative brachytherapies for carcinoma of the cervix were studied. In half of the cases, the dose debit was higher on the ureter than on the bladder and the rectum. In 7 cases, the dose delivered was also higher on the ureter rather than on the bladder and the rectum. And in 3 cases this dose was higher than 50 grays. It is concluded that the ureter is frequently the most irradiated organ in the pelvis during brachytherapy for carcinoma of the cervix. This may be a physiopathologic explanation for some ureterovaginal fistulas occurring after radical hysterectomy.