Research article

A statistical investigation of normal regional intra-subject heterogeneity of brain metabolism and perfusion by F-18 FDG and O-15 H₂O PET imaging

Ching-yee Oliver Wong¹ , Joseph Thie² , Marianne Gaskill¹ , Richard Ponto¹ , Jack Hill³ , Hai-yan Tian³ , Helena Balon¹ , Dafang Wu¹ , Darlene Fink-Bennett¹ and Conrad Nagle¹

¹  Nuclear Medicine, William Beaumont Hospital, Royal Oak, MI, USA

²  Graduate School of Medicine, University of Tennessee Medical Center, Knoxville, TN, USA

³  Medical Information Services, William Beaumont Hospital, Royal Oak, MI, USA

author email corresponding author email

BMC Nuclear Medicine 2006, 6:4doi:10.1186/1471-2385-6-4

Published:	12 July 2006

Abstract

Background

The definite evaluation of the regional cerebral heterogeneity using perfusion and metabolism by a single modality of PET imaging has not been well addressed. Thus a statistical analysis of voxel variables from identical brain regions on metabolic and perfusion PET images was carried out to determine characteristics of the regional heterogeneity of F-18 FDG and O-15 H₂O cerebral uptake in normal subjects.

Methods

Fourteen normal subjects with normal CT and/or MRI and physical examination including MMSE were scanned by both F-18 FDG and O-15 H₂O PET within same day with head-holder and facemask. The images were co-registered and each individual voxel counts (Q) were normalized by the gloabl maximal voxel counts (M) as R = Q/M. The voxel counts were also converted to z-score map by z = (Q - mean)/SD. Twelve pairs of ROIs (24 total) were systematically placed on the z-score map at cortical locations 15-degree apart and identically for metabolism and perfusion. Inter- and intra-subject correlation coefficients (r) were computed, both globally and hemispherically, from metabolism and perfusion: between regions for the same tracer and between tracers for the same region. Moments of means and histograms were computed globally along with asymmetric indices as their hemispherical differences.

Results

Statistical investigations verified with data showed that, for a given scan, correlation analyses are expectedly alike regardless of variables (Q, R, z) used. The varieties of correlation (r's) of normal subjects, showing symmetry, were mostly around 0.8 and with coefficient of variations near 10%. Analyses of histograms showed non-Gaussian behavior (skew = -0.3 and kurtosis = 0.4) of metabolism on average, in contrast to near Gaussian perfusion.

Conclusion

The co-registered cerebral metabolism and perfusion z maps demonstrated regional heterogeneity but with attractively low coefficient of variations in the correlation markers.