Evaluation of the Therac 6 linear accelerator for radiation therapy

The Therac 6 is new generation of low-energy linear accelerator. It incorporates a PDP-11/05 computer for beam control, treatment-factor input, and beam shutdown in the event of failure of the system. The performance of the unit has not been hindered by computer or software malfunction, and the computer has provided an excellent means for preventive maintenance and repair. Dosimetry parameters are similar to other 6 MV x-ray beams, and comparison to 60Co therapy beams shows that this unit may be more like 60Co units in penumbra and absence of off-axis peaking than other low-energy accelerators.

Use of auxiliary collimating devices in the treatment for breast cancer with 60Co teletherapy units. I. Dosimetric considerations

The dosimetry of tangential field treatment for breast cancer using an auxiliary collimating device on 60Co teletherapy machines is reviewed. The position of the device with respect to the source axis has negligible effect on either the dose rate or the dose distribution. Measurements with thermoluminescent dosimeters in an anatomic phantom verify the accuracy of the method of correction of isodose distributions for sloping skin. Possible systematic errors in dosimetry are identified.

Use of axiliary collimating devices in the treatment for breast cancer with 60Co teletherapy units. II. Dose to the skin

Special auxiliary collimating devices are often used in radiation therapy for breast cancer in order to treat the chest wall with tangential 60Co fields. Some of these devices are manufactured with a permanently attached Lucite end plate which increases the skin dose due to electron contamination. The relative surface dose was measured on a 60Co irradiator utilizing the collimating device with and without the Lucite plate. A parallel plate extrapolation chamber was used. The surface dose was measured as a function of the distance from the end of the device, the position in the field, and the angle of incidence for typical chest wall fields. These results are used to compare the dose to the skin of the chest wall for several treatment regimes. The data indicate that if the Lucite end plate is permanently attached, the skin dose may be enhanced to the extent that the use of additional bolus may be neither necessary nor desirable.

Calibration instrumentation used by the AAPM Radiological Physics Center

The Keithley model 602 electrometer-Farmer ionization chamber combination has served as the standard dosimetry system for calibration measurements made by the AAPM Radiological Physics Center at 156 different institutions. The constancy of this system is compared to that for the Baldwin-Farmer Secondary Standard Dosemeter type 2502, and is based on measurements made over a 3-yr period on a Cobalt-60 gamma-ray source. A Strontium-90 check source is also shown to be a reliable standard, and frequent checks with such a source can prevent serious calibration errors.

Bilateral renal cortical necrosis: a report of 2 cases

Two cases of renal cortical necrosis, one of which occurred after an obstetric complication (abruptio placentae) and the other after postpartum haemorrhage, are described. The diagnosis was made by percutaneous renal biopsy, intravenous pyelography and selective nephro-angiography. Immunofluorescence studies of the kidney showed no abnormality in one patient, but showed the presence of IgM in the glomerular basement membrane in the second patient. Hypotension was not observed when anuria occurred. Both patients survived. The importance of prolonged haemodialysis is stressed, since one patient was oliguric for 57 days and required intermittent haemodialysis for 5 months, while the second patient was oliguric for 17 days, required haemodialysis for 5 months and now has established hypertension.

Postoperative radiation therapy for residual Wilm's tumor. Review of Group III patients in the National Wilm's Tumor Study

Fifty-eight patients with residual abdominal disease (Group III) are reviewed from National Wilm's Tumor Study "1. The totap III) are reviewed from National Wilm's Tumor Study No. 1. The total number of abdominal recurrences is relatively low (eight cases). Local irradiation of the renal fossa would seem to be sufficient treatment for disease believed to be limited to that region, including cases of local spillage. Whole abdominal irradiation is recommended for gross, diffuse peritoneal contamination.

Surface dose from megavoltage therapy machines

To determine the cause of increased skin reactions near the edges of the field the authors measured doses at and near the surface of the skin with an extrapolation chamber for the gamma-ray beam of an AECL Eldorado 8 60Co irradiator and the x-ray beams of a Varian Clinac 4 linear accelerator, a Varian Clinac 6 linear accelerator, and an ARCO Mevatron 8 linear accelerator. Buildup curves were measured on each machine to locate the depth of the maximum dose (Dmax). The surface dose of the central axis was measured as a function of field size. Off-axis surface doses were measured on the Clinac 4 linear accelerator and on the Eldorado 8 60Co therapy unit. No measurable increase in surface dose was found leading the authors to believe that the observed skin reaction in the axilla for the Clinac 4 linear accelerator is due to a combination of increased dose at Dmax from the anterior mantle field and an increase in exit dose from the posterior mantle field when compared to similar treatments for 60Co.

Lymphography--technique, indications and principles of interpretation

The findings in 277 patients investigated by ethiodol lymphography are reviewed, and the applications and limitations of the procedure are presented. The non-specificity of findings is the principal reason for the lack of acceptance of this procedure, and the confusing entity of tuberculous lymphadenitis is discussed.

International dosimetry: an evaluation of treatment planning in clinical trials

A tissue-equivalent phantom containing thermoluminescent dosimeters was mailed in succession to Mount Vernon Hospital, Northwood, Middlesex, England, to Groote Schuur Hospital, Capetown, South Africa, and to Winnipeg General Hospital, Winnipeg, Canada, to determine the accuracy and consistency in treatment for carcinoma of the cervix under hyperbaric oxygen conditions. (Protocol of the Medical Research Council's Working Party on Radiotherapy and Hyperbaric Oxygen.) The data were analysed by the Radiological Physics Center, Houston, Texas, and substantiate uniformity at and between the participating institutions.

Klippel-Trenaunay syndrome. A case report and review of the literature

Clinical and radiological assessment of a female patient suffering from varicose veins revealed many of the features first described by Klippel and Trenaunay. The findings are presented in detail and the lymphographic features are illustrated. The previous literature is briefly reviewed.