Use of significance image to determine patterns of cortical blood flow abnormality in pathological and at-risk groups

The purpose of this work was to determine whether certain pathological groups and other groups at risk for neurological damage exhibited distinctive patterns of regional cerebral blood flow (rCBF) abnormality. HMPAO SPECT images obtained from six groups of subjects were compared with a normal cortical rCBF atlas, based on multivariate, voxel-by-voxel methods. In each case, a significance image was outputted, highlighting voxels with deficits of > or =3 s.d. of normal. Abnormal patterns were examined for the six groups, which comprised a further 40 normal volunteers, 18 diver controls, 50 divers with decompression illness (DCI), 34 boxers, 23 schizophrenics and 21 subjects with Alzheimer's disease. The percentages of abnormal cortical voxels for each group were 0.41%, 0.53%, 1.38%, 1.05%, 0.56% and 2.24%, respectively. The percentages of images in each group with at least one lesion of 10 or more connected abnormal voxels and at least 10 lesions of two or more connected voxels, respectively, were 8% and 8% (normal volunteers), 17% and 11% (diver controls), 38% and 38% (divers with DCI), 41% and 29% (boxers), 26% and 13% (schizophrenics) and 90% and 48% (subjects with Alzheimer's disease). This suggests that multiple small lesions are as common as single large lesions for divers with DCI but not for patients with Alzheimer's disease or schizophrenia. Large lesions are located predominantly in the parietal and inferior temporal regions for Alzheimer's disease, in the parietal and occipital regions for divers with DCI and boxers and in the inferior frontal region for schizophrenia. It appears that the groups considered here do have different rCBF patterns and that the significance image is a useful way of demonstrating this fact.