MATERIALS AND METHODS: Treatment plans were calculated for 15 patients - three plans for each patient using: geometrical optimization (GO), inverse optimization (IO) and blind inverse optimization (BIO). For each patient, PTV and OAR volumes, number of needles and geometry of the implant were set equal. Differences between dose distributions were tracked using: D90, V100, V200, Dmax (for prostate); D10, Dmax (for urethra); D10, V100, Dmax (for rectum).
RESULTS: The analysis of mean values of D90 and V100 in the prostate showed that inverse algorithms gave the best results (mean D90 was 12.1% for BIO and 9.3% for IO better than for GO, mean V100 was 8.2% for BIO and 6.3% for IO better than for GO). From a clinical point of view, GO diminished the doses in the PTV and urethra in all analyzed parameters. The lowest mean doses in the rectum were achieved for plans optimized with IO and BIO (mean D10: 61.2% for GO, 58.1% for IO, 58.0% for BIO; mean Dmax: 92.8% for GO, 85.1% for IO, 83.6% for BIO).
CONCLUSIONS: Application of the blind inverse optimization (BIO) algorithm led to clinically best dose parameters for PTV and the rectum. Use of geometrical optimization (GO) led to smaller doses in the urethra, which was however associated with a certain dose decrease also in PTV.
Written by:
Adamczyk M, Zwierzchowski G, Malicki J, Skowronek J. Are you the author?
Department of Medical Physics, Greater Poland Cancer Centre, 15 Garbary St., 61-866 Poznan, Poland.
Reference: Phys Med. 2012 Jan 3. Epub ahead of print.
doi: 10.1016/j.ejmp.2011.12.005
PubMed Abstract
PMID: 22221470
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