AbstractID: 7119 Title: Optimization System for Temporary Interstitial Gynecological Implant with Syed
Template and Ir-192 Ribbons
Patients with advanced gynecological cancer are often treated with temporary interstitial
implant using Syed template and Ir-192 ribbons at Memorial Sloan-Kettering Cancer
Center. Urgency in planning is tremendous, since the patient has to bear the pain of
needle insertion until the end of implant. We describe a computer optimization system for
Syed temporary gynecological implant, which optimize the ribbon strengths instantly
after catheter digitization. Optimization is achieved with simulated annealing. The cost
function is the sum of squares of the differences between delivered and prescribed dose
for all optimization points. Even if the new cost function is higher, the new solution may
still be chosen with a finite probability that provides a way to jump out of a local
minimum. As the number of iterations increases, the probability drops gradually to zero,
and the final cost function converges to the true global minimum. For optimization
points, we draw the target volume on every slice, and the optimization points are
generated evenly along the contours. We evaluate the optimized plans based on target
coverage, conformity index (volume contained in the prescription isodose / target
volume), and visual inspection of isodose distributions on transverse slices. The
optimized plans compare favorably with manual plans.