Intraluminal irradiation for the palliation of lung cancer with the high dose rate micro-Selectron.

Fifty patients with inoperable, symptomatic endobronchial carcinoma were treated by a single exposure of intraluminal radiotherapy. A high dose rate afterloading system (the micro-Selectron-HDR) was used to minimise radiation exposure for staff. Haemoptysis was relieved in 24 of 28 patients, breathlessness in 21 of 33 patients, and cough in nine of 18 patients. Radiological collapse resolved in 11 of 24 patients. Treatment was given on an outpatient basis and was well tolerated. Intraluminal radiotherapy appears to offer an effective alternative to conventional fractionated external beam radiotherapy.

Geometry adopted by Manchester radium applicators and Selectron afterloading applicators in intracavitary treatment for carcinoma cervix uteri.

Twenty-eight patients with early-stage carcinoma of the uterine cervix were treated using one standard Manchester radium application and one afterloading Selectron application. In each case, radiographs were analysed to determine differences in geometry of applicators relative to each other, or to the bony pelvis. During the Selectron treatment the applicators lay significantly more anterior in the pelvis, with a reduced angulation between the axes of the uterus and the vagina. The separation between the ovoids was increased. An identical analysis of 25 patients who had received two radium applications showed that the uterine tube lay significantly more anterior in the pelvis during the second application. Reasons for these differences and their possible clinical importance in terms of increased dose rate to critical tissue are discussed.

Bladder base dosage in patients undergoing intracavitary therapy.

The maximum dose rate being delivered to the base of the bladder during intracavitary therapy was assessed in 20 patients by CAT scanning during treatment. This value was compared with the I.C.R.U. bladder reference point dose rate calculated from lateral radiographs taken after insertion. The ratio of the maximum bladder base dose rate to the I.C.R.U. reference dose rate varied from 1.01 to 3.59. In ten patients the maximum bladder dose rate was not in the midline. Re-examination of five patients revealed significant changes in bladder base dose rate in two due to changes in applicator positioning and packing. The bladder base dose rate on the vertical plane through the middle of the vaginal ovoids was within +/- 25% of the maximum bladder base dose rate in 22/25 examinations.

Cost benefit analysis of radiological protection: a case study of remote after-loading in gynaecological radiotherapy.

The ICRP system of dose limitation requires radiation exposures to be kept "as low as reasonably achievable" (ALARA). The International Commission on Radiological Protection (ICRP) advocates a form of cost benefit analysis for this purpose, in which a comparison is made between the costs of protective measures and the benefits of reduced radiation exposure. In the UK, the National Radiological Protection Board (NRPB) has been developing a framework for the practical application of cost benefit techniques to aid the evaluation of investments in radiological protection. One such investment, being undertaken at a number of radiotherapy centres, concerns remote after-loading equipment to replace the use of radium in the treatment of gynaecological cancers. The introduction of such equipment can offer a complete solution to the radiological protection problems associated with manual radium insertions but involves large capital expenditures on equipment and shielded treatment rooms. This paper describes a cost benefit analysis of introducing remote after-loading equipment at the Christie Hospital and Holt Radium Institute in Manchester. In accordance with the NRPB framework, it is shown that the introduction of after-loading equipment, when housed in appropriately protected rooms, should result in a substantial net benefit and would therefore be justified on radiological protection grounds according to the ALARA principle.

The use of Selectron afterloading equipment to simulate and extend the Manchester System for intracavitary therapy of the cervix uteri.

When Selectron afterloading machines were introduced in the Christie Hospital the first aim was to reproduce, as closely as possible, the isodose distributions achieved with the traditional Manchester Radium System. This resulted in the establishment of standard pellet loading patterns, and standard treatment times, for programming the Selectron channels. However, the availability of whole-body CT scanning facilities provides a method of accurately locating the source positions with respect to the local anatomy and hence the possibility of dosage control based on doses to specific pelvic structures. Various computer programs have been written to extract source position data from the CT images, to allow the operator to propose pellet loading patterns and treatment times, and ultimately to display the resultant isodose distribution superposed on the cross-sectional scans. The effects on the dose distribution arising from changing the number of pellets, the pellet positions within the applicators, and the treatment times, are briefly discussed.