Evaluation of diagnostic composit imaging obtained by superimposition of emission and X-ray CT in abdominal diseases

A diagnostic composit imaging obtained by optically superimposing emission CT (ECT) on X-ray CT (XCT) film-image at an even section was evaluated as to methodological and clinical usefulness and limitation in 173 cases with various abdominal diseases. This composit imaging was an easy and convenient procedure for clinical practical purposes. However, this imaging had some disadvantages inherent in black-and-white X-ray-film images. Of note, the most serious problem in composit imaging was that the original XCT images had some positional or morphological deviation from the original ECT images due to respiratory movement of the abdominal organs. It was the first clinical application to provide anatomical informations in the original XCT images for the ECT images. By means of these informations an abnormal focal accumulation of radiopharmaceuticals on the ECT images could be easily discriminated from the surrounding back-ground and the anatomical location was precisely specified. Furthermore, diagnostic accuracy for detecting and localizing mass lesions on ECT imaging was improved in 20 % of total cases. Another useful application was to provide some informations about tissue characteristics or function of a lesion in the original ECT image for the XCT image and able to identify the information with its anatomical area. And, activities of inflammation or malignant neoplasm, blood flow of vascular lesion, existence of ectopic lesion, and function of an organ or tissue, those were unknown to XCT image, were able to be precisely evaluated. However, these clinical applications of this imaging were limited in the cases whose lesions had a low affinity with radio-pharmaceuticals. (author)