A method of dosimetry is described that quantifies the three-dimensional absorbed-dose distribution resulting from an intralesional administration of a radiolabeled monoclonal antibody, allowing for both spatial and temporal heterogeneity of distribution of the radionuclide and without the need for a calibration scan.
Methods: A mathematical model was developed to describe the distribution of activity as a function of time resulting from infusion at a single point within the solid component of a tumor. The parameters required for this model are either known directly or may be obtained from SPECT image data registered to computed tomography. Convolution of this distribution with a point-source 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 center, and dose profiles and dose-volume histograms were produced. It was shown that the three-dimensional distribution of dose was significantly nonuniform.
Conclusion: Initial results suggest that this method offers a means of determining the absorbed dose distribution within a tumor resulting from intralesional infusion. This method extends the Medical Internal Radiation Dose computation, which, in these circumstances, would make erroneous assumptions. Furthermore, it will enable individual patient treatment planning and optimization of the parameters that are within the clinician's control.