Linear accelerator radiosurgery in treatment of central neurocytomas.

OBJECTIVES: The purpose of this report was to review our experience with stereotactic radiosurgery in the management of patients with residual neurocytomas after initial surgery. METHODS: Between October 1996 and December 2001, four patients with central neurocytoma were treated by surgery and subsequently underwent linear accelerator (LINAC) radiosurgery. RESULTS: Two of the patients were cured, one exhibited a significant reduction in tumour size and the fourth remains stable. All four patients are alive and well. CONCLUSIONS: In cases of small residual tumours or recurrences radiosurgery allows open surgery to be avoided and is a safe and potentially effective approach.

Calculation of airborne radioactivity in a Technegas lung ventilation unit.

Airborne contamination by 99Tcm has been monitored in the Nuclear Medicine Department in our hospital to assess the risk of internal contamination to occupational workers exposed to Technegas studies. An air sampler fitted with a membrane filter was used. The optimum time for air absorption for obtaining the maximum activity in the filter was calculated. Maximum activity in the membrane filter ensures minimum uncertainty, which is especially important when low-level activities are being measured. The optimum time depends on air absorption velocity, room volume and filter efficiency for isotope collection. It tends to 1/lambda (lambda = disintegration constant for 99Tcm) for large volume and low velocity. Room activity with the air pump switched on was related to filter activity, and its variation with time was studied. Free activity in air for each study was approximately 7 x 10(-4) the activity used, and the effective half-life of the isotope in the room was 13.9 min (decay and diffusion). For a typical study (630 MBq), the effective dose to staff was 0.01 microSv when in the room for 10 min.