AbstractID: 9693 Title: Geometric Tool to Facilitate Placement of a Virtual Syed-Neblett
Template for CT Preplanning
Pretreatment planning for interstitial implants provides many benefits. The practice has gained acceptance for permanent prostate implants. Preplanning requires the virtual placement of delivery needles and the accompanying seeds.
For interstitial GYN implants, we desired to take advantage of the CT-compatible Syed-
Neblett templates by placing intracavitary the template and its attached vaginal cylinder during a preimplant CT study. We have developed a geometric tool that allows us to transform from the actual template placed at time of CT to a virtual template by rotating all coordinates while maintaining the same vaginal orientation vector.
Several days prior to surgery, a vaginal cylinder is placed in the patient along with an attached Syed-Neblett template. A CT of the patient’s pelvis is acquired with the insertion of this intracavitary device. Two points-of-interest aligned with the cylinder axis. The line joining these points defines a vector of the implant. A virtual template whose axis is aligned to the real applicator is then placed within the CT study. We are able to rotate this virtual template around the real vector axis to any desired orientation.
We create virtual interstitial needles and tandem in the patient whose bases correspond to the template base needle-hole locations and whose tips are generated for a desired length. From the preplan we are able to determine the number and activity of seeds to order and can assist needle placement in the OR guaranteeing complete placement into the target volume while avoiding pubic bone and perforation of the bladder and rectum.