Real time 3D display of gated blood pool tomograms

Gated radionuclide blood pool tomograms offer the possibility of evaluating the shape, size and function of the cardiac chambers. A modified form of the back-to-front display algorithm has been implemented on a conventional nuclear medicine computer, enabling real time display of three-dimensional shaded surface images of the heart. A surface model was created from conventional blood pool tomograms, and then displayed using depth shading. The mean time required to process 40 tomographic sections was 45 s, and subsequently the heart could be inspected from any aspect with a refresh rate of 2-4 Hz, giving the effect of real time rotation. Rapid oscillation between end-diastolic and end-systolic images allowed wall motion to be assessed, and was combined with interactive selection of the viewing direction using a trackerball. For hard copy images, a surface orientation shading algorithm was used. Kinetic information was incorporated by creating composite hidden surface images from end-diastolic and end-systolic objects, using colour to indicate which surface was visible. It is suggested that these techniques are of value in the visual interpretation of the large amount of data obtained by gated blood pool tomography.