Quantitation of rCBF by 99mTc-hexamethylpropyleneamine oxime single photon emission computed tomography combined with 133Xe CBF

Quantitative characterization of hemodynamic properties and vasculature dysfunction of high-grade gliomas

Aberrations in tumor and peritumoral vasculature may not be distinguishable by cerebral blood flow (CBF) or cerebral blood volume (CBV) alone. The relationships between CBF and CBV were examined to estimate vasculature-specific hemodynamic characteristics. Twenty glioma patients were studied with dynamic susceptibility T2*-weighted MRI [(dynamic contrast-enhanced magnetic resonance imaging (DSC-MRI)] before and during week 1 and 3 of radiotherapy (RT). CBF and CBV were calculated from DSC-MRI, and relationships between the two were evaluated: the physiological measure of mean transit time (MTT) = CBV/CBF; empirical fitting using the power law CBV = constant x (CBF)(beta). Three different tissue types were assessed: the Gd-enhancing tumor volume (GEV); non-enhanced abnormal tissue located beyond GEV but within the abnormal hyperintense region on FLAIR images (NEV); normal tissue in the hemisphere contralateral to the tumor (CNT). The effects of tissue types, CBV magnitudes (low, medium and high), before and during RT, on MTT and beta were analyzed by analysis of variance (ANOVA). The MTT and beta for the three tissue types were significantly different (p < 0.009). MTT increased from CNT (1.60 s) to NEV (1.93 s) to GEV (2.28 s) (p < 0.0005). beta was significantly greater in GEV (1.079) and NEV (1.070) than in CNT (1.025). Beta increased with increasing CBV magnitude while MTT was independent of CBV magnitude. There was a significant decrease in MTT of NEV and GEV during week 3 of RT compared with pre-RT values for all CBV magnitudes. There was a significant increase in beta during RT in the tumor and peritumor. Progressive abnormalities in vasculature and hemodynamic characteristics of the vascular bed were delineated, with significant disorder in the tumor but mild abnormality in peritumoral tissue.

Cerebral hemodynamics in a healthy population measured by dynamic susceptibility contrast MR imaging

PURPOSE

To establish reference data and to study age-dependency for cerebral perfusion in various regions of the brain in a healthy population.

MATERIAL AND METHODS

Eighty healthy subjects of both genders from 22 to 85 years of age were studied with spin echo echo-planar dynamic susceptibility contrast MR imaging (DSC MRI) at 1.5 T. Cerebral blood volume (CBV), cerebral blood flow (CBF), and contrast agent mean transit time (MTT) were calculated bilaterally for 20 distinct neuroanatomic structures.

RESULTS

In gray matter, the following values were found (mean +/- SD): CBV (4.6 +/- 1.0 ml/100 g), CBF (94.2 +/- 23.0 ml/100 g/min), and MTT (3.0 +/- 0.6 s), and in white matter: CBV (1.3 +/- 0.4 ml/100 g), CBF (19.6 +/- 5.8 ml/100 g/min), and MTT (4.3 +/- 0.7 s). The perfusion parameters did not change with age, except for a tendency to an increase in gray matter MTT and CBV. Males exhibited higher MTT and CBV than females. No hemispheric difference was found in either gender.

CONCLUSION

Cerebral hemodynamics can be assessed with DSC MRI. Age itself seems to have only a marginal effect on cerebral perfusion in healthy population.

The role of neuroimaging in dementia

Potential new therapies for the treatment of Alzheimer's disease demand early and accurate diagnosis. Although clinical evaluation is generally sufficient when the disease is well established, neuroimaging tools are helpful to detect the earliest changes of Alzheimer's disease or differentiate Alzheimer's disease from the other forms of dementia. This article reviews the basic concepts of brain imaging and clinical application. It concludes with a brief discussion of future directions in neuroimaging for the diagnosis and longitudinal follow-up of Alzheimer's disease.