BAUMKUCHEN MAP ANALYSIS TO DETECT POSTURAL CEREBRAL HYPOPERFUSION WITH UPRIGHT TC-99(M)-HMPAO BRAIN SPET

We have evaluated a polar cortical flow Baumkuchen map (BK map), const ructed from projection data by inwardly layering cortical flow stripes from the base to the apex, to detect postural cerebral hypoperfusion using Tc-99(m)-HMPAO brain SPET. A circular cortical perfusion outline was constructed from sinogram data at a 20% threshold; a ring was the n formed by constructing an inner line with a radius equal to half tha t of the outer line. This ring on the transaxial image was superimpose d onto the cortical image, then divided into 60 portions at 6 degrees intervals from the centre. The maximal number of counts per pixel with in each sector was determined, translated into polar coordinate profil es and displayed as a polar map. We studied 11 patients with unilatera l stenosis of the internal carotid artery or middle cerebral artery (M CA) and 7 patients without stenosis, using upright and supine (rest) T c-99(m)-HMPAO brain SPET. Cerebral perfusion was visibly altered on th e BK maps of all 11 patients with arterial stenosis and on the transax ial images of 8 of them. A semi-quantitative analysis of the BK maps u sing a ratio of the counts in the regions of interest over the right a nd left MCA areas, showed that the mean of the ratios was significantl y lower in the upright images than in the upright + rest and rest imag es (P = 0.0044 and 0.0033, respectively). Although the difference in t he means of the ratios between the upright and upright + rest images w as significant for both the BK map and transaxial image data (P = 0.00 44 and 0.0051, respectively), the BK map was accurate in detecting cha nges in perfusion in the upright position. We conclude that BK map ana lysis is useful for detecting changes in patients examined using uprig ht brain SPET. ((C) 1998 Lippincott-Raven Publishers).