Comparative evaluation of cerebral blood volume and cerebral blood flow in acute ischemic stroke by using perfusion-weighted MR imaging and SPECT

Risk Factors of Impaired Perfusion in Patients With Symptomatic Internal Carotid Artery Steno-Occlusive Disease

Objective

To quantitatively evaluate the impaired perfusion status of patients with symptomatic internal carotid artery (ICA) steno-occlusive disease and to explore the risk factors of impaired perfusion with computed tomography perfusion (CTP).

Methods

The clinical and imaging data of 187 patients with ICA steno-occlusive disease were retrospectively analyzed. The ICA stenosis rate was divided into Grades I–IV (70–79%; 80–89%; 90–99%; 100%), and the circle of Willis was classified as four types (types I–IV). According to the literature, the value of cerebral blood flow/cerebral blood volume (CBF/CBV) of 7.55/min was used as cut-off to predict symptomatic patients. All patients were categorized into two groups: those with impaired perfusion [n = 99 (52.9%)] and those without impaired perfusion [n = 88 (47.1%)]. Symmetrical bilateral internal watershed areas were selected as the regions of interest (ROIs). Statistical analysis was made on the status of impaired perfusion and the risk factors of impaired perfusion.

Results

Univariate analysis revealed that systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), types of the circle of Willis, and clinical features at admission differed between the two groups (patients with or without impaired perfusion) (p < 0.05). Multiple logistic stepwise regression analysis showed that MAP [odds ratio (OR) = 0.946, 95% confidential interval (CI) = 0.917–0.974, p < 0.001] and type IV (type I vs. IV: OR = 4.987, 95% CI = 1.955–12.723, p = 0.001) at admission were independently associated with impaired perfusion in the internal watershed areas.

Conclusion

MAP and the type of circle of Willis at admission are independent risk factors associated with the impaired perfusion in patients with ICA steno-occlusive disease.

Comparison of cerebral blood volume maps generated fromT2* andT1weighted MRI data in intra-axial cerebral tumours

We compared parametric maps, measured values and value distributions of cerebral blood volume (CBV) derived from (1) first pass T1 weighted dynamic contrast-enhanced (DCE) data (T1-CBV) using the recently described leakage profile model and (2) conventional T2* weighted DCE data (T2*-CBV) using a conventional curve fitting technique, in nine patients with intraaxial tumours. Regions of interest were defined around enhancing tumour tissue on matched slices. Median tumour values and conspicuity indexes of CBV from the two techniques were compared, demonstrating good correlation (r = 0.667,p<0.05) in enhancing tumour and no significant difference in conspicuity. Pixel-by-pixel scattergrams of values in normal brain in a representative matched slice were produced for each case, which showed excellent correlation (r = 0.96,p<0.001). Distortion of blood vessels around susceptibility interfaces was evident on T2* CBV but not on T1 CBV maps. Leakage-free T1 CBV maps do not suffer from the susceptibility artifacts seen in T2* CBV maps, although they present comparable biological information.

Correlation of magnetic resonance imaging findings with hexamethylpropyleneamine oxime brain single photon emission computed tomography in ischemic stroke patients in the subacute stage

PURPOSE

To evaluate the correlation between magnetic resonance imaging (MRI) findings and 99mTc-hexamethylpropyleneamine oxime (HMPAO) brain single photon emission computed tomography (SPECT) during the subacute stage in ischemic stroke patients.

MATERIAL AND METHODS

The T1 and T2-weighted images and brain SPECT findings of 84 patients (mean age 60.69 +/- 12.47 years) with subacute cerebral ischemia during the period 1998-2004 were reviewed. All HMPAO SPECT and MRI studies were performed between 3 and 7 days (mean time delay 4.76 +/- 1.29 days) after the onset of stroke symptoms.

RESULTS

An ischemic lesion was seen both in T1 and T2-weighted images with perfusion defects above 60% (severe defect) according to count/pixel data of the lesion in HMPAO SPECT studies in 30 (90.9%) of 33 patients. Otherwise, the ischemic lesion was seen only on T2-weighted images with perfusion defects between 30% and 60% (moderate defect) in HMPAO SPECT studies in 25 (89.3%) of 28 patients. In 20 (87%) of 23 patients who had perfusion defects below 30% (mild defect) on HMPAO SPECT, only non-specific findings such as cerebral atrophy and/or periventricular ischemic-gliotic lesions could be seen in MRI. The difference between these ratios was statistically significant (P < 0.01).

CONCLUSION

Brain 99mTc-HMPAO SPECT findings indicate good correlation with MRI findings. When the ischemic lesions could be seen in both T1 and T2-weighted images, the patients frequently had severe perfusion defects. When only seen in T2-weighted images, the perfusion defect was moderate. When only non-specific findings were revealed by MRI, only mild perfusion defects were found by SPECT.

Cerebral Haemodynamic Disturbances in Patients with Moderate Carotid Artery Stenosis

OBJECTIVE

Dynamic MR perfusion imaging can detect cerebral perfusion deficits resulting from severe internal carotid artery (ICA) stenosis. It is unknown, however, whether moderate ICA stenosis (50-69%) also causes haemodynamic disturbance. We investigated whether cerebral perfusion deficits were detectable in patients with moderate ICA stenosis.

METHODS

Eighteen patients underwent T2* weighted cerebral MR perfusion imaging with a gadolinium based contrast agent. Differences in mean time to peak (mTTP) and relative cerebral blood volume (rCBV) between cerebral hemispheres were calculated for middle cerebral artery territory regions by a reader blinded to the angiographic and clinical findings.

RESULTS

There were significant differences in mTTP between cerebral hemispheres in 15 patients with a mean inter-hemispheric delay in mTTP of 0.49 s (95% confidence intervals, 0.25 and 0.72 s) which was statistically significant ( p <0.001). In 1 patient with bilateral moderate stenosis there was no difference in mTTP.

CONCLUSIONS

Moderate ICA stenosis results in significant ipsilateral cerebral perfusion delays detectable by dynamic susceptibility MRI. Follow-up studies might reveal whether these delays improve following carotid endarterectomy.