3-DIMENSIONAL DOSIMETRY FOR INTRALESIONAL RADIONUCLIDE THERAPY USING MATHEMATICAL-MODELING AND MULTIMODALITY IMAGING

A method of dosimetry is described that quantifies the three-dimension al absorbed-dose distribution resulting from an intralesional administ ration of a radiolabeled monoclonal antibody, allowing for both spatia l and temporal heterogeneity of distribution of the radionuclide and w ithout the need for a calibration scan. Methods: A mathematical model was developed to describe the distribution of activity as a function o f time resulting from infusion at a single point within the solid comp onent of a tumor. The parameters required for this model are either kn own directly or may be obtained from SPECT image data registered to co mputed tomography. Convolution of this distribution with a point-sourc e dose kernel enabled the three-dimensional absorbed-dose distribution to be obtained. Results: This method was applied to a set of patient data acquired in the course of a clinical study performed at our cente r, and dose profiles and dose-volume histograms were produced. It was shown the three-dimensional distribution of dose was significantly non uniform. Conclusion: Initial results suggest that this method offers a means of determining the absorbed dose distribution within a tumor re sulting from intralesional infusion. This method extends the Medical I nternal Radiation Dose computation, which, in these circumstances, wou ld make erroneous assumptions. Furthermore, it will enable individual patient treatment planning and optimization of the parameters that are within the clinician's control.