Illustration of isodose curves with the application of the Sabattier effect.

I T HAS been recognized that intracavi-tary irradiation is essential in the treatment of carcinoma of the uterine cervix. Since the beginning of the present century3 many applicators have been used to irradiate the uterus and vagina and later several afterloading techniques have been de-scnibed. " 4 Some of the techniques involve the use of remote control5 " and linear distribution of the sources.6'8 In our Hospital we have adopted an afterloading linear applicator: the source of radiation is cesium 137. It is the purpose of this report to present a qualitative illustration of the distribution ofradiation around the applicator using the photographic phenomenon of solanization. MATERIAL The applicator consists of a plastic tube with a curvature of2o#{176},and graduated each centimeter on the exterior surface. This tube is inserted into the cervico-utenine cavity after it has been expanded to accommodate a No. 8-9 Hegan dilator. A plastic ring with 2 metallic markers is used as a reference at the external os. A plastic ap-plicaton consisting of 2 cylinders with a lead shield oriented to shield the rectum and the bladder is then inserted into the vagina. \Vith this applicator there is little need for extra packing. The plastic tube is large enough to protrude through the vulva. The whole system is supported by means of a lucite penineal bar which has 2 holes to allow for a Foley catheter and the plastic tube; the ban is in turn secured to an abdominal belt (Fig. I). METHOD A wax phantom was constructed with the applicator located at its center. In this position it was possible to simulate the distribution of radiation within a patient. An industrial radiographic film was irradiated in the phantom. This film was placed in proximity to the applicator on the plane where we wanted to know the distribution of the radiation. It was then irradiated using different source loadings during an irradiation time sufficient to have a good darkening; call this the film " patron. " The film " patron, " after developing, was placed in contact with an unexposed film, and the combination was exposed to a luminous source of 40 watts at a 50 cm. distance for a relatively long time, depending on the transparent curve we wanted (15-900 sec.). The second film was developed partially (one-half of the total time) and then was exposed totally to the same source of light for a shorten …