Clinical impact of CT attenuation correction by SPECT/CT in brain perfusion images

Objectives To elucidate the regional differences between brain perfusion single photon emission computed tomography (SPECT) images reconstructed with a uniform attenuation correction using Chang’s method (AC-Chang) and a non-uniform attenuation correction with CT in the SPECT/CT instrument (AC-CT).

Methods Twenty-eight consecutive patients with brain disease examined by SPECT/CT brain perfusion imaging were selected and images were reconstructed with AC-Chang and with AC-CT. The AC-Chang and AC-CT reconstructed images were then compared by voxel-based analysis using three-dimensional stereotactic surface projections.

Results Counts in the frontal area of the AC-Chang images were significantly higher than in the AC-CT images, while the counts in the margin of the frontal lobe and posterior margin of the parietal, occipital cortices and cerebellum of the AC-Chang images were significantly lower than those of the AC-CT images. Relative frontal perfusion was 5.0% higher and relative cerebellar perfusion was 4.6% lower in the AC-Chang image relative to the AC-CT image, on average.

Conclusions We have demonstrated the frontal dominant hyper-perfusion and parieto-occipital and cerebellar hypo-perfusion in brain SPECT images reconstructed with AC-Chang compared to those reconstructed with AC-CT. We suggest that to obtain an accurate attenuation-corrected brain perfusion SPECT image, attenuation correction by Chang’s method is inadequate and should be performed by CT using a SPECT/CT instrument