Normal cerebral perfusion of ^99mTc-HMPAO brain spect - Evaluation by an anatomical standardization technique

Single photon labeled tracer ^99mTc-hexamethylpropylene amine oxime (HMPAO) has been used for rCBF studies by SPECT. However, normal perfusion pattern of this agent still remains unclear. The purpose of this study was to investigate normal ^99mTc-HMPAO SPECT image voxel by voxel. Eighteen male subjects without any prior or present history of medical illness participated in this study. All SPECT images were globally normalized to 100 count/voxel. Each subject had an X-ray CT scan at the same day of SPECT measurement. All subjects had normal X-ray CT scans. The standard anatomical structures of the computerized brain atlas of Roland et al. were fitted to X-ray CT images ill a subject by linear and non-linear parameters. These parameters were subsequently used to transform SPECT images of the subject. After the anatomical standardization, mean and SD images of eight standardized images were calculated voxel-by-voxel basis. In the mean image, following structures showed relatively higher radioactivity; the putamen, the cerebellum, and the frontal lobe. In addition, the occipital lobe, parietal lobe, frontal lobe, and the putamen showed large degree of SD. Anatomical standardization of SPECT images may be useful as a reference to diagnose and evaluate various brain disorders.