Localization of the apex of the vagina: Implications for radiation therapyplanning

PURPOSE: To evaluate (a) the displacement of the vaginal apex by a rod duri ng radiation therapy simulation for gynecologic malignancy and (b) apical l ocalization Implanted radiopaque markers. MATERIALS AND METHODS: Metallic markers were implanted in the cervix or cuf f in nine patients with cervical or endometrial carcinoma who underwent In all, but one patient, radiographs were obtained with and then without of th e markers relative to bone landmarks was measured. The total displacement w as the square root of the sum of the squares of displacement in each axial direction. RESULTS: All patients showed displacement of the cervical markers by the va ginal rod (mean total displacement, 1.9 cm; range, 0.6-3.6 cm). The greates t displacement, was cephalic (mean, 1.5 cm; range, 0.5-2.4 cm). Anteroposte rior displacement occurred in all patients but was not as predictable as ce phalic displacement. Displacement was anterior in five of the eight patient s, posterior in three patients, and lateral in four patients. CONCLUSION: Displacement of the vaginal apex and/or cervix with placement o f the vaginal rod during simulation was marked in all patients, Use of impl anted cervical markers to localize the vaginal apex or the cervix during si mulation is more accurate than use of a vaginal rod.