Quality assurance of treatment plans for interstitial and intracavitary high-dose-rate brachytherapy

Das, Rupak K.; Bradley, Kristin A.; Nelson, Ian A.; Patel, Rakesh; Thomadsen, Bruce R.

doi:10.1016/j.brachy.2005.11.002

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Volume 5, Issue 1 , Pages 56-60, January 2006

Quality assurance of treatment plans for interstitial and intracavitary high-dose-rate brachytherapy

Department of Human Oncology, University of Wisconsin, Hospitals and Clinics, Madison, WI, USA

Received 6 September 2005; received in revised form 11 November 2005; accepted 18 November 2005.

Abstract

Purpose

Quality assurance for complex high-dose-rate (HDR) treatment planning has always been a challenge to the physics community because of the time constraint between HDR planning and the delivery of the treatment. This study proposes an efficient, precise, and easy method for checking the complex computer calculation.

Methods and materials

Posttreatment, three-dimensional dose–volume study was performed for 98 patients with 128 new treatment plans along with 30 library plans. Volumes covered by the 100% isodose line, source activity (Ci), total dwell time (s), and the prescription dose (100%) were recorded. Variation of R_V defined as (irradiated time×activity/elongation factor×prescribed dose) with volume was studied for different catheter systems.

Results

Parametric fit of R_V with volume for three different systems that cover most of the interstitial and intracavitary brachytherapy implants agrees within ±6%.

Conclusions

The excellent agreement of R_V derived from this simplistic point source model with three-dimensional dose calculations for individual HDR treatment plans clearly establishes that for an implant with known number of catheters, the time needed to deliver a prescribed dose to a given prescription volume can be easily predicted.

Keywords: Quality assurance, Accelerated partial breast irradiation, Interstitial implant, Intracavitary implant, Treatment time