Dose-volume histograms computation comparisons using conventional methods and optimized fast Fourier transforms algorithms for brachytherapy

In anatomy based optimization procedures for large volume implants the calc ulation of dose-volume histograms (DVH) accounts for the major part of the time involved and can be as long as a few hours. This time is proportional to the number of seeds or source dwell positions required for the implant. A procedure for the calculation of brachytherapy seed dose distribution cal culation employing fast Fourier transforms (FFT) and the convolution theore m has been described by others and was supposed to significantly improve th e speed of the dose distribution computation. Using new significantly impro ved FFT algorithms and various other optimization techniques we have compar ed the calculated differential and integral DVHs in high dose rate (HDR) br achytherapy with a single stepping source using actual clinical implants. T his is so that we could assess the efficiency and accuracy of the FFT metho d with that of conventional methods. Our results showed that the FFT based method of calculating DVHs in brachytherapy is comparable in speed with con ventional dose calculation methods, but only for implants with more than 28 7 sources. It is therefore of limited practical use even for large implants . This result is in direct opposition to the claim by other authors. (C) 20 00 American Association of Physicists in Medicine. [S0094-2405(00)02410-X].