A simple, inexpensive applicator for irradiation of localized areas of the vagina with intracavitary brachytherapy.

PURPOSE: To describe the construction of a simple, inexpensive applicator for irradiation of localized areas of the vagina with intracavitary brachytherapy. METHODS AND MATERIALS: It was desirable to avoid an interstitial implant in an elderly patient with a stage T2 vaginal cancer. The final phase of radiation therapy was delivered with a custom made intracavitary cylinder that allowed the high-dose area to be limited to the portion of the vagina at high risk for residual disease. The applicator was fabricated from a clear cast acrylic (Lucite) rod with dimensions 3.5 cm diameter x 5.0 cm long. The applicator contained 11 parallel grooves, each 1.8 mm deep x 2.2 mm wide, machined along the surface of the cylinder parallel its long axis at 1.0 cm increments. Plastic needles (15 gauge) were inserted into the grooves along the surface of the acrylic cylinder and held in place with heat shrink tubing. The applicator was easily inserted and positioned without anesthesia. Standard low dose rate 192Ir ribbons were inserted into the plastic needles after positioning the applicator in the vagina. RESULTS: Construction of this applicator system requires a few weeks notice and approximately $150. Fabrication of the grooved cylinder is a routine task for a workshop with a milling machine. A step-by-step description of how to construct and use the applicator is provided along with the telephone numbers of commercial vendors to call to order all necessary materials. CONCLUSION: This article describes a simple, inexpensive method for constructing a customized vaginal applicator that can be used to treat a limited area of the vagina with intracavitary brachytherapy.

Arytenoid sparing during irradiation of early stage vocal cord cancer.

PURPOSE: Optimal position of the posterior field border when irradiating early stage vocal cord cancer is controversial. Several experts recommend moving the posterior field border 5-15 mm anteriorly after 50-60 Gy to decrease the chance of arytenoid edema. This article will evaluate the effect of field position on arytenoid dose. METHODS AND MATERIALS: 5 x 5 cm opposed lateral fields centered on the glottis were set up on a patient with typical anatomy. Isodose profiles were obtained with equally weighted 6 MV photon beams attenuated with 15 degree wedge filters using contours from an axial CT scan. Profiles with the posterior field border overlaying, 5, and 10 mm posterior to the posterior edge of the thyroid cartilage are presented. RESULTS: With the posterior field border 10 mm posterior to the thyroid cartilage, the arytenoids are included in the 95% isodose volume. Reducing the field by 5 mm has no significant effect on the position of the 95 and 90% isodose lines relative to the arytenoids. A field reduction of 10 mm places the arytenoids in the beam penumbra and leaves approximately 10 mm between the 95% isodose line and the midpoint of the true vocal cord. CONCLUSION: To achieve a significant dose differential between the arytenoids and the anterior portion of the vocal cord when using opposed lateral 6 MV photon beams the posterior field border must be at, or anterior to, the posterior edge of the thyroid cartilage. In view of the excellent results reported from institutions that include the arytenoids in the high-dose volume throughout treatment, it would seem appropriate to limit the use of arytenoid-sparing techniques to patients in whom there is no ambiguity about tumor location and in whom the treatment setup is very reproducible.