To determine whether there is stability of cerebral blood flow (CBF) measures using single photon emission computed tomography (SPECT) imaging in healthy controls in a test–retest split-dose paradigm. Such a paradigm is frequently used in the clinical and research setting to assess various brain states.
Five healthy volunteers underwent two brain SPECT scans after the administration of low and high doses of 99mTc-exametazime. The first SPECT scan was acquired approximately 30 min after the intravenous injection of approximately 259 MBq of 99mTc-exametazime. The second SPECT scan was acquired approximately 30 min after the intravenous injection of 925 MBq of 99mTc-exametazime. Both scans were acquired over approximately 30–45 min and the images were reconstructed using filtered backprojection, a low-pass filter and Chang's first-order attenuation correction. Values were obtained for regions of interest (ROIs) in major brain structures and normalized to whole brain activity. Counts on the second SPECT scan were also decay corrected for activity from the first scan.
The results demonstrated a strong correlation between the low-dose and high-dose scans for all regions (r=0.86, P<0.0001). Symmetries were preserved with a strong correlation between low-dose and high-dose scans (r=0.70, P<0.0001). Finally, most regions demonstrated less than a 5% difference between the low-dose and high-dose scans.
The results of this study demonstrate that the split-dose technique can be employed for clinical and research applications to measure CBF in different brain states using two SPECT scans on the same day.
aDivision of Nuclear Medicine, Department of Radiology
bDepartment of Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
Correspondence to Dr Andrew B. Newberg, Division of Nuclear Medicine, 110 Donner Building, H.U.P., 3400 Spruce Street, Philadelphia, PA 19104, USA
Tel: 215-662-3092; fax: 215-349-5843;
Received 19 January 2005 Accepted 24 January 2005