Assessment of the impact of applying attenuation correction on the accuracy of activity recovery in Tc99m-ECD brain SPECT of healthy subject using Statistical Parametric Mapping (SPM)

Introduction: Photon attenuation in tissues is the primary physical degrading factor limiting both visual qualitative interpretation and quantitative analysis capabilities of reconstructed Single Photon Emission Computed Tomography (SPECT) images. The aim of present study was to investigate the effect of attenuation correction on the detection of activation foci following statistical analysis with SPM. Methods: The study population consisted of twenty normal subjects (11 male, 9 female, and age 30-40 years). SPECT images were reconstructed using filter back projection and attenuation correction was done by the Chang method. The SPECT imagings was obtained 20 min after intravenous injection of 740-1110 MBq (20-30 mCi) of Tc99m-ECD and were acquired on 128×128 matrices with a 20% symmetric energy window at 140 keV. These data publicly distributed by the Society of Nuclear Medicine of Toronto Hospital. The data was standardized with respect to the Montreal Neurological Institute (MNI) atlas with a 12 parameter affine transformations. Images were then smoothed by a Gaussian filter of 10 mm FWHM. Significance differences between SPECT images were estimated at every voxel using statistical t-test and p-value as the significant criteria was set at 0.05. Results: The contrast comparing non attenuation corrected to attenuation corrected images suggest that regional brain perfusion activity increase in the cerebrum, frontal (T-value 12.06) , temporal (T-value 10.63) and occipital (T-value 9.31) lobe and decrease in the sub-lobar, extra-nuclear (T-value 17.46) and limbic lobe, posterior cingulate (T-value 17.46) before attenuation correction compare with attenuation correction. Conclusion: It can be concluded that applying attenuation correction in brain SPECT can effectively improve the accuracy of the detection of activation area (p<0.05).

Keywords:

SPM , SPECT , Attenuation correction , Activation foci