Source of Support: None, Conflict of Interest: None
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A method that combines radiographic localization of seeds in brachytherapy implant with CT images has been developed to provide accurate seed location and dose distribution data, in relation to the three dimensional localization of target volume and critical organs at risk. The accurate determination of radioactive seed locations in permanent implants from computed tomography (CT) scans is limited by the magnitude of the pixel size and the slice thickness. The image of a single seed may appear in more than one consecutive CT image. A method of removing this artifact using a tolerance diameter about a seed center determined in the previous CT slice is described. To improve further the accuracy of defining the seed positions and orientations, the reconstructed seed coordinates derived from the three film technique were transformed into CT coordinates for dose distribution computations. The differences between this technique and the technique of using CT scans to reconstruct seed coordinates directly were assessed. This method has been applied in the case of prostate implants. It allows for the generation of dose volume histograms for the prostate, bladder and the rectum.
