An optimization algorithm of dose distribution using attraction-repulsion model (application to low-dose-rate interstitial brachytherapy).
OBJECTIVE
To optimize dose distribution for prostate cancer in low-dose-rate interstitial brachytherapy, we have developed a new algorithm named the Attraction-Repulsion Model. The purpose was to find the optimal source configuration.


METHODS
The Attraction-Repulsion Model is used to optimize the dose distribution by finding the best seed configuration. We arranged grids at intervals of a certain space inside and established target and critical organs as areas of interest. We can make an attribute for grids, and the grids show attraction or repulsion depending on dose delivered from source. Source position is changed by the forces that the grids impose to the sources. A calculation was done repeatedly until the attraction and repulsion forces reached a balance. The optimal configuration was established when the sources reached a stable distribution in time. To evaluate the optimization plan, dose-volume histograms were used.


RESULTS
Source configuration can be optimized automatically. The calculation time was approximately 5 min. The V100, V150, V200, and D90 of the target were 95%, 39%, 9%, and 157 Gy, respectively. V150 of the urethra and V80 of the rectum were 2% and 0%, respectively.


CONCLUSIONS
This method can optimize the dose distribution objectively.
Sumida
Iori
I
Division of Multidisciplinary Radiotherapy, Osaka University Graduate School of Medicine (D10), 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan. sumida@radonc.med.osaka-u.ac.jp
Shiomi
Hiroya
H
Oh
Ryoong-Jin
RJ
Tanaka
Eiichi
E
Isohashi
Humiaki
H
Inoue
Takehiro
T
Inoue
Toshihiko
T
D000465:Algorithms; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D055585:Physical Phenomena; D010825:Physics; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage