Display of Hemispheric Local Metabolic Rates from Human Brain

Abstract

Positron tomography, a technique that employs the concepts of computerized tomography in combination with specific molecules labelled with positron emitters, is now making possible the direct regional measurement of blood flow and energy requirements or the mapping of the distribution of molecules such as neurotransmitters and the drugs that affect the central nervous system. This technique allows accurate recovery of the distribution of the labelled molecules in thicknesses of grey and white matter in cross sections through the brain. Although sixteen to twenty different levels are routinely examined during a typical study, the data in each tomographic section is usually considered in isolation. A major problem with this approach is that it does not consider the major subdivisions of the brain, the various lobes and gyri, in their entirety. These structures often overlap many tomographic sections, and are not always easily traceable from section to section. We describe an approach that maps the distribution of radioactivity, and hence of the process being studied, over the whole of the cortical mantle from a knowledge of the distribution in the transaxial sections. Our approach allows a more accurate localization of defects in the brain, and a more accurate quantification of the extent of the deficit in the cortical mantle.