Low-dose-rate prostate brachytherapy is a common procedure for treating prostate cancer through interstitial implantation of small radioactive seeds throughout the prostate. Numerous regimens exist where radioactive seed implant has been used as either a monotherapy or in conjunction with external beam radiotherapy for the treatment of various stages of prostate cancer. Distribution of about 60-100 radioactive iodine seeds in prostate can be efficiently planned by using optimization algorithms with no user intervention.
Genetic algorithms are from the class of stochastic algorithm. They use concepts based on principles of Darwinian Natural Selection. Using probabilities on an initial population of n random seed distributions, operators such as elitism, roulette wheel selection, singlepoint crossover, and single-point mutation are applied.
The elitism ensures the optimal solution of an iteration is not lost by allowing it to pass unaltered to the next generation.
Roulette wheel determine which parent seed distributions will be used to create the new offspring for next iteration. A parent is selected due to its fitness score; the offspring then are formed by singlepoint crossover and mutation process.
The single-point crossover picks a crossover point between a two parents and exchanges the portion of the gene after the crossover point. The single-point mutation works by randomly selecting a point of mutated by altering (adding or subtracting a seed) a base in a parent.
The user-defined objective function then calculates radiation dose and a fitness score for each of the seed distributions and using the objective function before proceeding on to next generation.