Method for Determining Tomographic Plane Separation and Detector Distances for Use with the

Use of the Anger rectilinear tomographic scanner provides. such benefits u.s better information density, superior resolution away from the geometric focal plane, and opportunities to assess lesion depth and reduce confusion and error by virtue of its ability to separate pathology from surrounding normal variance. To reap these benefits, the technologist must have a thorough working knowledge of the tomop/anes. This allows him to distribute the planes throughout the organ being scanned in a fashion that best utilizes tomographic imaging and optimizes re.solution. In working with the new breed of rectilinear scanner with tomographic multiplane imaging capabilities, the technologist needs to distribute the tomoplanes (focal planes) accurately and evenly throughout the organ being scanned. This paper discusses ways of best utilizing tomographic planes and optimizing resolution between them. Methods and Materials The Searle Pho / Con tomographic multi plane scanner produces six images per detector on a transparency film. Each image represents a selected tomoplane. These six tomoplanes are evenly spaced, three above and three below the geometric focal plane (Fig. I). Gamma emissions occurring in a given tomoplane are recorded as sharply focused dots. Emissions from all other planes are recorded as blurred points of much lower intensity. The space between tomoplanes, the total spread of the six tomoplanes, and their distance from the face of the collimator vary depending on format size, collimator used, and setting of the tomographic selector. Ideally, the tomographic planes should be evenly spaced throughout the organ being scanned. Tomoplanes should not be uselessly spaced outside the organ or needlessly overlap in the organ, thereby leaving other areas unexamined (Fig. 2). This ideal cannot always be realized when scanning the whole body because of th