[In vivo dosimetry study of semi-conductors EPD-20 in total body irradiation technique]. / Etude de la dosimétrie in vivo par semi-conducteurs EPD-20 dans les conditions de l'irradiation corporelle totale.

PURPOSE: The objective of this work was the study of in vivo dosimetry performed in a series of 54 patients receiving total body irradiation (TBI) at the Salah-Azaiz Institute of Tunis since 2004. In vivo dosimetry measurements were compared to analytically calculated doses from monitor units delivered. PATIENTS AND METHOD: The irradiation was conducted by a linear accelerator (Clinac 1800, Varian, Palo Alto, USA) using nominal X-rays energies of 6 MV and 18 MV, depending on the thickness of the patient at the abdomen. The dose was measured by semi-conductors p-type EPD-20. These diodes were calibrated in advance with an ionization chamber "PTW Farmer" type of 0.6cm(3) and were placed on the surface of plexiglas phantom in the same TBI conditions. A study of dosimetric characteristics of semi-conductors EPD-20 was carried out as a function of beam direction and temperature. Afterwards, we conducted a comparative analysis of doses measured using these detectors during irradiation to those calculated retrospectively from monitor units delivered to each patient conditioned by TBI. RESULTS: Experience showed that semi-conductors are sensitive to the angle of beam radiation (0-90 degrees ) and the temperature (22-40 degrees C). The maximum variation is respectively 5 and 7%, but in our irradiation conditions these correction factors are less than 1%. The analysis of the results of the in vivo dosimetry had shown that the ratio of the average measured doses and analytically calculated doses at the abdomen, mediastina, right lung and head are 1.005, 1.007, 1.0135 and 1.008 with a standard deviation "type A" respectively of 3.04, 2.37, 7.09 et 4.15%. CONCLUSION: In vivo dosimetry by semi-conductors is in perfect agreement with dosimetry by calculation. However, in vivo dosimetry using semiconductors is the only technique that can reflect the dose actually received instantly by the patient during TBI given the many factors that calculation can not take into account: patient and organs motions and the heterogeneity of the targets.

[Radiotherapy in the treatment of retinoblastoma: about 40 cases]. / Place de la radiothérapie dans le traitement du rétinoblastome : à propos de 40 cas.

PURPOSE: The aim of this study is to analyze the results and the complications of radiotherapy in the treatment of retinoblastoma. PATIENTS AND METHODS: Between 1994 and 2004, 40 children received radiotherapy for a retinoblastoma in Salah Azaiz Institute. The average age of the patients was 36 months (four to 132 months). There were 16 girls and 24 boys. Sixteen children presented a bilateral disease and 24 children a unilateral disease. Twenty eyes and thirty-six orbital cavities in 40 children with retinoblastoma were treated by radiotherapy. One child with a unilateral anterior retinoblastoma was treated with 106 ruthenium brachytherapy. External radiotherapy has been used to treat the 39 patients. In 20 cases the irradiation was conservative and in 36 cases postoperatively. The latter (n=36) presented at least one risk factor of relapses noted in the histological examination. The average dose was 44 Gy (1.8 to 2 Gy per fraction, five fractions weekly). This radiotherapy was associated with chemotherapy in 24 cases. RESULTS: Thirty-five children were followed with an average follow-up of 53 months (3-108 months). The average delay of relapses was of 10 months (two to 26 months). We found four orbital relapses and seven metastasis in nine children. The conservation of the eye with a useful visual field was noted in 18 cases among the 20 conservative irradiated eyes. The major therapeutic complication was the growth defect of the bones face. A femoral bone sarcoma was noted five years after the end of the irradiation and chemotherapy in one case. CONCLUSION: If the radiotherapy offers the advantage of the functional conservation and the improvement of the local control, its indications are more and more restricted in favor of the other therapeutic methods (chemotherapy, thermochemotherapy) and this considering the iatrogene risk. The development of new techniques of brachytherapy and the progresses of the conformational radiotherapy appear to reduce considerably this risk.

[Gingival metastasis from the lung through a needle and a pin: a case report]. / Un carcinome pulmonaire métastasé à la gencive via une aiguille de couture: a propos d'un cas.

Gingival metastases are very rare. We report the case of a 47 year-old man presenting with a gingival metastasis from a non small cell lung carcinoma. According to the literature, the most probable way of spread of such metastasis is haematogenous. Local implantation of cancer cells, present in patient's expectorations, in a fragile gingiva may be an other pathway of lung cancer metastasizing in this region as we will try to describe in this case report. Cytological and/or histological investigation is needed to assess the malignant and the metastatic character of these gingival lesions. A rapid regression is observed after a flash of external beam radiation; nevertheless metastasis prognosis depends on the primary tumour progress.

Brachytherapy for primary and recurrent nasopharyngeal carcinoma: treatment techniques and results.

PURPOSE: Nasopharyngeal cancer is the commonest head and neck cancer in Tunisia treated with radiotherapy. A dose effect relationship is established in this tumor. The aim of this study is to describe our Low-dose-rate endocavitary brachytherapy using a personalized mold called Tunis applicator. PATIENTS AND METHODS: Seven patients (4 males and 3 females) with histologically confirmed undifferentiated nasopharyngeal carcinoma (UCNT) were treated between 2002 and 2005. Five patients with primary cancer and 2 with recurrent disease received external beam radiation followed by endocavitary brachytherapy. The mean applied dose of endocavitary brachytherapy was 5.5 Gy for primary site after external beam radiation (70-74 Gy) and 30 Gy for recurrent disease after external beam radiation (38 Gy). We have developed a personalized applicator with a balloon to optimize the placement of sources and a better conformity using the computer tomography scanning. Critical normal structures were identified on orthogonal radiographs and the dose was optimized to avoid excessive doses to these structures. RESULTS: With a follow up of 18 months (8-41), only one local failure was observed, 3 years after external beam radiation therapy for a recurrent disease. Moderate grade mucositis was seen in most patients. One patient was diagnosed with bulb necrosis. CONCLUSION: Endobrachytherapy can provide effective treatment for nasopharyngeal carcinoma with an easy application of the brachytherapy procedure.