2-D Chemical-Shift Imaging of white matter hyperintensities in Alzheimer’s Disease – a qualitative analysis
CANADIAN JOURNAL OF GERIATRICS
Background: Magnetic resonance spectroscopy (MRS) is an increasingly popular tool for investigating the cellular health of brain tissues. This is especially relevant in conditions such as Alzheimer’s Disease (AD) where the exact pathological processes underlying changes such as the formation of white-matter hyperintensities (WMH) has yet to be fully elucidated (Kantarci et al.,2007).
Little study specifically examining WMH in AD subjects has been performed (Firbank et al.,2003). One qualitative method to compare spectra is to observe “Hunter’s Angle” (HA), which is the angle formed by the peaks of myoinositol and N-acetyl-aspartate (Lin et al.,2005). An angle close to 45o indicates relatively healthy tissues, while angles substantially smaller imply that metabolic processes have deviated from normal.
METHODS: Spectra of 7 AD subjects with extensive WMH, 8 AD subjects without extensive WMH, and 15 age-matched normal controls were compared. Both normal-appearing tissue and WMH were examined in the AD subjects and compared to normal-appearing tissue in controls. 2D-CSI/MRS (acquired on a GE 3T Signa scanner) from 4 voxels from each subject, were averaged giving a total of 28 data points for each tissue class. The mean age of AD subjects was 80.5 and 75.5 years respectively, and 72 years for controls.
RESULTS: A clear dissociation between the spectra of the tissue classes was visible. In voxels which predominantly contained WMH in AD subjects, a noticeable decrease in HA was shown (mean 23o). In voxels which predominantly contained normal-appearing tissue in both AD subjects and controls, a normal HA was visible (mean 38o and 44o respectively).
CONCLUSIONS: This qualitative method clearly demonstrated the differences in spectral profiles between WMH and normal-appearing tissue in AD patients and in normal controls. However, “eyeballing” Hunter’s Angle makes spectroscopy/2D-CSI more user friendly and could be useful for examining WMH when applied in a clinical setting.
Scott C.J.M., Chavez S., Graham S.J., Ganda A. & Black S.E.
5th Canadian Conference on Dementia (CCD) Toronto 2009
Toronto, ON, Canada (October 1-3, 2009)