pseudomyxomas were treated with radioimmunotherapy. with single photon emission computed tomography (SPECT) at 3, 10, and 24 days after the therapeutic infusion. Treatment-planning software has been developed 2 Laboratory of Biomedical Engineering, Helin which functional information obtained from SPECT is integrated with anatomic sinki University of Technology, Espoo, Finland. METHODS.information obtained from computed tomography (CT). The activity distribution 3 Department of Oncology, Helsinki University from SPECT images is converted to absorbed dose distributions using a point Central Hospital, Helsinki, Finland.source kernel convolution dose calculation. The absorbed dose calculation requires 4 Department of Radiology, Helsinki University a radionuclide specific dose kernel. The activity map is divided into equally sized Central Hospital, Helsinki, Finland.source voxels from which the distribution is calculated for the target voxels that cover the patient volume. The resulting three dimensional (3D) absorbed dose distribution is viewed as isodose contours superimposed on the CT images or as 3D isodose surfaces. RESULTS.The measured activity distribution shows that the cumulated activity and biologic half-life vary in the patient's body. The developed planning system provides a method for calculating patient specific absorbed dose distributions. CONCLUSIONS. The variation of biologic clearance indicates that a 3D dose calcula-Presented at the Sixth Conference on Radioimtion method incorporating measured activity distributions is needed to quantify munodetection and Radioimmunotherapy of absorbed dose distribution. of management for cancer. 1There is a lack of accurate dosimetry in clinical RIT.

The variation of biologic clearance indicates that a 3D dose calculation method incorporating measured activity distributions is needed to quantify absorbed dose distribution.

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