Purpose Attenuation correction (AC) based on low-dose computed tomography (CT)
could be more accurate in brain single-photon emission computed tomography
(SPECT) than the widely used Chang method, and, therefore, has the potential
to improve both semi-quantitative analysis and visual image interpretation.
The present study evaluated CT-based AC for dopamine transporter SPECT with
I-123-ioflupane. Materials and methods Sixty-two consecutive patients in whom
I-123-ioflupane SPECT including low-dose CT had been performed were recruited
retrospectively at 3 centres. For each patient, 3 different SPECT images were
reconstructed: without AC, with Chang AC and with CT-based AC. Distribution
volume ratio (DVR) images were obtained by scaling voxel intensities using the
whole brain without striata as reference. For assessing the impact of AC on
semi-quantitative analysis, specific-to-background ratios (SBR) in caudate and
putamen were obtained by fully automated SPM8-based region of interest (ROI)
analysis and tested for their diagnostic power using receiver-operator-
characteristic (ROC) analysis. For assessing the impact of AC on visual image
reading, screenshots of stereotactically normalized DVR images presented in
randomized order were interpreted independently by two raters at each centre.
Results CT-based AC resulted in intermediate SBRs about half way between no AC
and Chang. Maximum area under the ROC curve was achieved by the putamen SBR,
with negligible impact of AC (0.924, 0.935 and 0.938 for no, CT-based and
Chang AC). Diagnostic accuracy of visual interpretation also did not depend on
AC. Conclusions The impact of CT-based versus Chang AC on the interpretation
of I-123-ioflupane SPECT is negligible. Therefore, CT-based AC cannot be
recommended for routine use in clinical patient care, not least because of the
additional radiation exposure
