M. van Osch

Quantitative cerebral perfusion MRI and CO2 reactivity measurements in patients with symptomatic internal carotid artery occlusion

Quantitative perfusion MRI is a promising new technique capable of offering information on cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, it is still unclear how these perfusion parameters relate to the underlying physiological indicators and how they compare to conventional techniques. The purpose of this study was to investigate how quantitative perfusion MRI is related to the cerebrovascular reactivity as measured by transcranial Doppler ultrasonography (TCD) in combination with a CO2 stimulus in patients with a symptomatic occlusion of the internal carotid artery (ICA). Thirty-nine patients with transient or minor disabling retinal or hemispheric ischemic symptoms and an occlusion of the ICA underwent quantitative perfusion MRI and CO2 reactivity measurements by TCD. Perfusion parameters were correlated with cerebrovascular reactivity measurements and compared with measurements of control subjects. The results of this study show a negative correlation between the cerebrovascular reactivity and the time to bolus peak (TBP) both for gray (r = -0.26, P = 0.035) and white matter (r = -0.28, P = 0.026). No correlation between resting CBV, CBF, or MTT and cerebrovascular reactivity was found. Our results indicate that an increase in TBP reflects a poor development of collateral flow, which is supported by a relatively low CO2 reactivity in these patients.

Repeated quantitative perfusion and contrast permeability measurement in the MRI examination of a CNS tumor

Abstract. This study reports on the results of quantitative MRI perfusion and contrast permeability measurement on two occasions in one patient. The measurements were separated 81 days in time. The tumor grew considerably in this period, but no change was found with respect to perfusion and contrast permeability. Non-involved white matter values were reproduced to demonstrate repeatability. The presented approach to dynamic susceptibility contrast MRI allows fast and repeatable quantitative assessment of perfusion and is easily integrated in a conventional brain tumor protocol.

Two-Step Registration of Subacute to Hyperacute Stroke MRIs

In the use of MRI in acute stroke patients, determination of the perfusion-diffusion (PWI-DWI) mismatch is highly important, since it indicates possible enlargement of the ischemic lesion or deterioration of the patient. When quantitative measures are used such as the ADC of CBF to predict ischemic damage, accurate registration of the ischemic lesion on follow-up MRI to the results obtained in the first MRI is essential. Problems in the registration of stroke images include differences in patient orientation and/or low cooperativeness of the patient in the hyperacute stage of stroke. The aim of the present study is to develop a robust method of stroke image registration.