The patients was an 73 year old man who had a progressive memory loss
without other illness, and who had worsened over a the 3 years prior to
imaging. A functional MR technique was used in which a bolus of gadoteridol contrast agent was injected rapidly during the collection of image data, resulting in contrast-induced signal loss in proportion to cerebral blood volume. The resulting maps are a reflection of cerebral function because blood volume is coupled to
flow. Relatively high function in the cortical ribbon can be clearly seen, here as white or high signal, because the data represent integrated signal loss.
The following is a published abstract on the method.
Perfusion SPECT and functional MRI in Alzheimer's disease
K.A.Johnson, P.F.Renshaw, J.A.Becker, A. Satlin, C.D.English, B.L.Holman
Brigham and Women's Hospital, McLean Hospital, Harvard Medical School, Boston, MA.
Functional MRI is potentially useful for the evaluation of brain function in Alzheimer's disease (AD). We compared fMRI and perfusion SPECT in 16 probable AD patients (NIH criteria), and 10 normal age-matched controls. The MR system (GE Signa 1.5T) was equipped with an Advanced NMR Systems Inc. echo planar coil. We used an axial spin echo technique, and injected gadoteridol (Bracco Inc) as a bolus over 6 sec at 20 sec into the scanning sequence. Calculation of CBV maps was performed by the method of Belliveau et al. SPECT was obtained with a digital annular system (DSI Inc) 20 minutes after a 20 mCi injection of Tc99m HM
-PAO. Each SPECT dataset was superposed (registered) to its corresponding MR image dataset, using a computerized iterative surface fitting algorithm. A polar grid system was used to divide a mid-axial fMRI or SPECT slice into 120 regions. The correlation of mean regional activity (counts/pixel) on SPECT and mean signal intensity on fMRI, assessed with Pearson's product moment correlation coefficient, was 0.78 +/- 0.10 across 26 subjects. Regions which included large vascular structures were least correlated. We conclude that dynamic susceptibility contrast fMRI is highly correlated with SPECT perfusion in elderly subjects and may prove useful in the clinical assessment of dementia.