Physical approach for the reduction of dual radionuclide image subtraction artefacts in immunoscintigraphy

Investigations have been undertaken into methods for reducing the artefacts resulting from the subtraction of images during immunoscintigraphy. The image subtraction techniques have been assessed using simple phantoms and the results applied to the image processing of clinical studies. Subtraction images were viewed for artefacts and the changes in target-to-nontarget ratios measured. Subtraction artefacts were reduced considerably using a combination of radionuclides with similar photopeak energies. In the case of 131I-labelled antibodies a blood pool subtraction with 113Inm was applied. When the images of radionuclides having very different photopeak energies were subtracted as in the case of 131I and 99Tcm, a preliminary background thresholding of the iodine image prior to 99Tcm subtraction reduced the artefacts due to the differential septal penetration and scatter components.