Monte Carlo calculation of charge collection efficiencies in ionization chambers.

Collection efficiency is an important quantity in dosimetry with ionization chambers. It can be calculated by solving a hyperbolic system of partial differential equations. This system can be solved only in few, simple, idealized geometries, but for more realistic designs an analytical resolution is no longer possible. In the present work a Monte Carlo scheme that could permit to calculate the collection efficiency for any ionization chamber geometry is proposed. This scheme has been tested against Boag's approach for three chambers with plane-parallel, cylindrical and spherical geometries, operated in the recombination regime. The results obtained in the full Monte Carlo simulation closely agree with the Boag's ones for the three ideal geometries considered. The largest relative difference, ∼0.3%, has been found for the plane-parallel chamber in case of 50 V, the lowest potential difference investigated in this study. Results appear to be stable against changes in the chamber volume, the ion mobility and the recombination constant. The method proposed could be a useful tool to calculate collection efficiencies of ionization chambers, provided the electric field inside them is known.

[Pneumothorax surgery]. / Chirurgie des pneumothorax.

Surgery remains the mainstay treatment of recurrent pneumothorax. We recall the therapeutic modalities and indications of surgery in case of pneumothorax. We then compare postoperative outcome, recurrence rate and chronic pain with regard to techniques and surgical approach. Current video-thoracoscopic or axillary thoracotomy procedures for bullous disease with pleurodesis allow a low rate of morbidity and recurrence after primary or secondary spontaneous pneumothorax.

[Efficacy and tolerability of fraxiparine in the prevention of thromboembolic complications in oncologic thoracic surgery]. / Efficacité et tolérance de Fraxiparine dans la prévention des accidents thrombo-emboliques en chirurgie thoracique oncologique.

A French multicentre, open, randomized trial was conducted in lung cancer surgery in order to test the optimal dosage regimen: Fraxiparine 3075 IU AXa (fixed dosage) and Fraxiparine 4100 or 6150 IU AXa (dosage adjusted for body weight only), over a period of 8 days. 75 patients were allocated to each group. Efficacy (Doppler ultrasonography at D0 and D8, controlled by bilateral ascending phlebography when positive) and safety, i.e. perioperative blood loss and postoperative bleeding complications were the main assessment criteria. The efficacy of the two treatment regimens was confirmed = no deep vein thrombosis and/or pulmonary embolism. No significant difference of safety was observed between the two groups: nevertheless fewer patients developed major bleeding complications in the Fraxiparine fixed dosage group (2 patients) than in the Fraxiparine adjusted dosage group (6 patients). Blood loss was comparable in the 2 groups; a statistical difference (p = 0.09) was showed between D0 and D2 in favour of Fraxiparine fixed dosage group. The results of this trial indicate that Fraxiparine administered at fixed dosage represents an effective and safe prophylaxis against fatal thromboembolism in patients undergoing oncologic thoracic surgery.

[Closure of bronchopleural fistula by video-assisted mediastinal surgery after pneumonectomy]. / Fermeture d'une fistule broncho-pleurale après pneumonectomie par chirurgie médiastinale vidéo-assistée.

Disruption of a mainstream bronchus is a rare but dreaded complication of pneumonectomy. When the bronchial tump measures at least 15 mm, the conventional therapeutic strategy is to drain the pleural cavity followed by closure of the fistula via trans-mediastinal sternotomy. After an experimental study on cadavers to test the technical feasibility of main bronchus closure via a cervical approach using a video-mediastinoscope, we used video-assisted mediastinal surgery successfully in a patient with a left main bronchus fistula.

Closure of a postpneumonectomy main bronchus fistula using video-assisted mediastinal surgery.

Disruption of a mainstem bronchus is a rare but dreaded complication of pneumonectomy. After an anatomic study on cadavers, we successfully used a video mediastinoscope to close a postpneumonectomy main bronchus fistula via a cervical incision.

[Peri-operative chemotherapy during resection of pulmonary metastases of sarcoma]. / Chimiothérapie périopératoire lors des résections de métastases pulmonaires de sarcomes.

The objective of this prospective study was to evaluate the mortality and morbidity of sarcoma pulmonary metastasis resection with continuous chemotherapy. Ifosfamide was administered at the daily dose of 1200 mg/m2/24 h. Twenty-six resections of pulmonary sarcoma were performed from December 1990 to April 1992. The primary lesion was already resected in all patients. Peri-operatory chemotherapy was started 30 minutes before surgery and continued for 6 days. Chemotherapy was associated with an uroprotector, antiemetic drugs and adequate hydration. Patients had a mean age of 30.6 years. The delay between initial and thoracic surgery was 81 months. The following was performed: tumorectomy (32), wedge (18), lobectomy (7), diaphragm resection (1), left pneumectomy (1). All patients had the 6-days chemotherapy course. None of the patients died. Respiratory failure following superinfection, but not necessitating assisted ventilation, was observed in one case. The following adverse events were noted: nausea (34.6%), uncomplicated cystitis (15.4%), leucopenia (7.6%), fever (3.8%). Mean duration of hospitalization was 11.8 days. Chemotherapy adverse effects did not result in significant morbidity. Bronchial fistula was not observed. Following the results of this pilot study, we feel that perioperatory chemotherapy can be added to sarcoma pulmonary metastasis resection surgery without increasing patient morbidity and mortality.