RapidArc Radiation Therapy: First Year Experience at the University of Alabama at Birmingham
Received 20 May 2009; received in revised form 10 August 2009; accepted 1 September 2009. published online 08 March 2010.
Purpose
To evaluate treatment planning and delivery for patients treated during our initial year of experience with RapidArc™ radiation therapy.
Methods and Materials
RapidArc was used to treat 52 patients at The University of Alabama at Birmingham between May 2008 and April 2009. A single ionization chamber phantom with film and a two-dimensional ionization chamber array were used for quality assurance measurements. Of the 52 patients, 44 had a static gantry dynamic multileaf collimated (SG-DMLC) IMRT treatment plan, seven of which had quality assurance (QA) measurements.
Results
The mean difference between ionization chamber measurement and calculation was 1.2% ± 0.9% (1 standard deviation). For film, the mean fraction of pixels with γ > 1 (3%/3 mm criterion) was 4.6% and for the two-dimensional chamber array was 1.4%. For the seven corresponding SG-DMLC plans, the results were similar. Differences in important dosimetric indicators were typically within 1% relative to SG-DMLC. The volume of nontarget tissue that received >20 Gy was less for RapidArc compared with SG-DMLC, whereas the volume that received more than 10 Gy was larger. The mean difference between the measured and planned leaf positions and the monitor units obtained from machine log files was 0.0 ± 0.5 mm and 0.4 ± 0.3 MU, respectively. Mean delivery times were 1.5 ± 0.2 and 3.3 ± 0.4 min for one- and two-arc plans, respectively. On average, SG-DMLC delivery took 4.4 min longer.
Conclusions
RapidArc plans have quality comparable to our standard SG-DMLC IMRT technique, and are delivered with similar accuracy in shorter time.
Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, Alabama
Reprint requests to: Richard A. Popple, Ph.D., 121A Wallace Tumor Institute, 1824 6th Avenue South, Birmingham, AL 35233. Tel: (205) 934-1762; Fax: (205) 975-2564
Conflict of interest: The University of Alabama at Birmingham has an agreement with Varian Medical Systems for evaluation of the RapidArc™ technology, for which R.A. Popple is the principal evaluator. R.A. Popple also has a research grant with Varian Medical Systems that is unrelated to RapidArc™. R.A. Popple, J.B. Fiveash, and J.A. Bonner are speaking consultants for Varian Medical Systems. J.A. Bonner is a consultant for Bristol-Myers-Squibb, Imclone Systems, and Lilly Corporation.
ABSTRACT