Sci-Wed PM: Delivery-01: Clinically Viable Treatment Times with Dual-slice Co-60 Tomotherapy

Abstract

In the present study, we attempt to estimate clinical treatment times that might be achieved with dual‐slice Co‐60 tomotherapy delivery through an investigation of the advantages gained by reduced thread effect and pitch. The helical thread effect (off‐axis ripple), was simulated using a 30 wide cylindrical phantom in our PinnacleTM treatment planning system for various slice widths and pitch values. A cylindrical Co‐60 source of 2 cm diameter was studied along with a typical linac source for both single‐ and dual‐slice delivery. Treatment times were estimated based on a clinical Hi‐ARTTM tomotherapy head and neck treatment but with consideration of reduced output from the Co‐60 source, dual slice collimator and variation in slice width. We determine that dual‐slice tomotherapy delivery provides not only a reduction in treatment time due to an increase in the number of slices but also a reduction in the thread effect and effective pitch which may lead to improved modulation in the S‐I direction with larger slice widths. The net effect is a clinically viable treatment time that may be comparable with linac‐based IMRT with a conventional MLC. This initial study provides the impetus to support further investigations of plan quality and treatment times using dual‐slice Co‐60 tomotherapy.