Fractionated Brachytherapy: Catheter Insertion and Dosimetry

摘要

The incorporation of the Omnitron device, a robotic isotope handling system, into a program of brachytherapy for glial tumors has made it possible to hyperfractionate treatment in 15-20 sessions over a 2- to 3-week period, which offers considerable theoretical advantage over conventional single dose regimens. Stereotactic catheter placement is by contrast-enhanced MR guidance, and takes advantage of the three-dimensional planning offered by voxel orientation. Initial placement is based on orientation to the three customary planes, with oblique planes added to define intercatheter placement more accurately. Catheters may be placed asymmetrically through the tumor or even at different angles of insertion to get the optimal conformation. Dosimetry is based on three-dimensional reconstruction in the Omnitron planning console, and takes advantage of the optimized localization of each catheter position. High-dose isotope insertion is performed robotically, with isotope position and dwell times controlled by computer. The phase I study demonstrates a wide safety margin and suggests better survival than would be expected with conventional management.