A METHOD OF 2-DIMENSIONAL MAPPING OF CORTICAL PERFUSION BY CYLINDRICAL TRANSFORMATION OF HMPAO SPET DATA

In order to synthesize three-dimensional information on relative regio nal blood flow (rCBF) from the cortical grey matter in Tc-99(m)-hexame thylpropyleneamine oxime (HMPAO) single photon emission tomographic (S PET) images into a single two-dimensional 'cortical peel' (CP) image, we developed a program that performs cylindrical transformation of SPE T data. A sub-routine of this program performs measurements of cortex- to-cerebellum rCBF ratios for 54 cortical regions in the CP image. Thi s program was used to establish a normative database derived from 30 y oung normal control subjects aged 28.7 +/- 6.9 years. The database was then used to express cortex-to-cerebellum rCBF ratios in four colour- coded ranges of normal standard deviation of the mean rCBF ratio acros s the cortical regions in the CP image. This CP method was implemented for 30 clinical HMPAO SPET studies in patients (n = 30, aged 71.8 +/- 4.2 years) with suspected dementia as well as several studies in aged healthy subjects (n = 8, aged 67 +/- 9.8 years). In 25/30 (83%) patie nts, all abnormalities seen on the tomographic display were evident on the corresponding CP image. No aged healthy subjects showed abnormali ties on either the tomographic display or the corresponding CP image. An advantage of this technique is that the extent and severity of rCBF abnormalities are readily appreciated in one single image. This techn ique, in conjunction with the conventional multi-slice tomographic dis play, was a useful tool in identifying various patterns of rCBF abnorm alities in the patients with clinically suspected dementia.