Interstitial Vaginal Needle Implantation in Gynecological Tumors: Design and Construction of Applicator

Kang, Seunghee; Chun, Mison; Kang, Haejin; Jung, Chil; Son, Jeong Hyae

Abstract

PURPOSE: It is not a simple task to achieve the ideal isodose curve with a standard vaginal applicator or single plane needle impant in the paravaginal tissue when primary or recurrent gynecological neoplasms (cervical cancers, vaginal cancers and vulvar cancers) are treated as a boost following external beam radiotherapy. The authors introduce the development and construction of a simple, inexpensive, customized applicator for volume implant to maximize the radiation dose to the tumor while minimizing the dose to the rectum and the bladder.
MATERIALS AND METHODS
Nine patients underwent Ir-192 transperineal interstitial implantation for either recurrent (5 cases) or primary (3 cases) cervical cancers or primary vaginal cancer (1 case) between August 1994 and February 1998 at Ajou university hospital. First 3 cases were performed with a single plane implant guided by digital palpation. Because of inadequate isodose coverage in the tumor volume in first 3 cases, we designed and constructed interstitial vaginal applicator for volume implant to improve tumor dose distribution and homogeneity while sparing the surrounding normal tissue. Our applicators consist of vaginal obturator and perineal template that made of the clear acrylamide and dental mold material (Provil ). The applicators were customized individually according to the tumor size and its location. Both HDR and LDR irradiation were given with these applicators accomodating 6 Fr needles (Microselectron, Nucletron). The pretreatment planning prior to actual implant was performed whenever possible.
RESULTS
Needles can be inserted easily and evenly into the tumor volume through the holes of templates, requiring less efforts and time for the implant prodecure. Our applicators made of materials available from commercial vendors. These have an advantage that require easy procedure, and spend relatively short time to construct. Also it was possible to fabricate applicators to individualize according to the tumor size and its location and to achieve the ideal isodose coverage. We found an accurate needle arrangement and ideal dose distribution through the CT scan that was obtained in 3 cases after needle implant. Three patients with primary cervical and vaginal cancers were controlled locally at final follow up. But all recurrent cases failed to do so.
CONCLUSION
The authors introduce inexpensive, simple interstitial vaginal templates which were self-designed and constructed using materials available from commercial vendors such as acrylamide and dental mold material (Provil ).