Modification of Fletcher Ovoid System for Afterloading, Using Standard-Sized Radium Tubes (Milligram and Microgram)

Abstract

Intracavitary radium therapy has been proved highly effective in treating squamous carcinoma of the uterine cervix. This is evident in the results at the M. D. Anderson Hospital and Tumor Institute (Houston, Texas), where the absolute five-year disease-free survival rate for Stage I cases is 93 per cent (1). These results were achieved under a treatment policy which emphasized intracavitary radium. The radium treatments were performed with the Fletcher ovoid and tandem applicators, which must be loaded with the radium tubes before being brought into the operating room and inserted into the patient. Some 265 new cases of carcinoma of the uterine cervix are treated annually in this hospital, and as the average case has two radium insertions, approximately 530 insertions are performed per year. This involves the handling of about 30 gm. of radium by the radium curators (loading and unloading the applicators), radiotherapist (inserting and removing loaded applicators), operating room nurses, anesthesiologist and assistant, recovery-room staff, diagnostic x-ray technician and assistant, transportation service, and ward nurses. In order to reduce radiation exposure to these various persons we have developed applicators which can be “afterloaded” with standard radium tubes. That is, the insertion and packing of the ovoids and tandem becomes a separate and independent procedure from placing the radium in the applicators. Thus, no radium need be handled until the patient has returned to her bed and has completed the period requiring special nursing care. This procedure has been found to eliminate radiation exposure to operating room, anesthesiology,recovery room, diagnostic x-ray, and transportation personnel. In addition, radiation exposure of the radiation therapist, radium curators, and ward nurses has been substantially reduced. Design of Ovoids and Tandems The applicators have been developed with two design restrictions: that the radiation dose around the ovoids and tandem be the same as for the preloaded applicators and that standard radium tubes be used. This has meant that the external dimension of the ovoid and the position in it of the radium tube must be the same as in the Fletcher design. In Figure 1 are shown two exterior views of the ovoids and tandems, while in Figures 2 and 3 radiographs of the ovoids, tandems, and the radium tube carriers are presented to demonstrate structural details. Compared to the preloaded applicators, the afterloaded ovoids are the same in diameter and 1 mm. greater in length. In order that the ovoid outside height be kept to this limit, i.e., 4 mm. greater than the length of the radium tube, no cap can be fitted over the cylindrical radium carrier. A double-hinge mechanism was therefore required, and this was attached to the side of the carrier. Consequently, the stem of the ovoids had to accommodate two thicknesses of tube carrier.