Juho Nuutinen

Cerebral Hemodynamics in Human Acute Ischemic Stroke: A Study with Diffusion- and Perfusion-Weighted Magnetic Resonance Imaging and SPECT

Nineteen patients with acute ischemic stroke (<24 hours) underwent diffusion-weighted and perfusion-weighted (PWI) magnetic resonance imaging at the acute stage and 1 week later. Eleven patients also underwent technetium-99m ethyl cysteinate dimer single-photon emission computed tomography (SPECT) at the acute stage. Relative (ischemic vs. contralateral control) cerebral blood flow (relCBF), relative cerebral blood volume, and relative mean transit time were measured in the ischemic core, in the area of infarct growth, and in the eventually viable ischemic tissue on PWI maps. The relCBF was also measured from SPECT. There was a curvilinear relationship between the relCBF measured from PWI and SPECT (r = 0.854; P < 0.001). The tissue proceeding to infarction during the follow-up had significantly lower initial CBF and cerebral blood volume values on PWI maps (P < 0.001) than the eventually viable ischemic tissue had. The best value for discriminating the area of infarct growth from the eventually viable ischemic tissue was 48% for PWI relCBF and 87% for PWI relative cerebral blood volume. Combined diffusion and perfusion-weighted imaging enables one to detect hemodynamically different subregions inside the initial perfusion abnormality. Tissue survival may be different in these subregions and may be predicted.

The Real Estate Factor Quantifying the Impact of Infarct Location on Stroke Severity

Background and Purpose— The severity of the neurological deficit after ischemic stroke is moderately correlated with infarct volume. In the current study, we sought to quantify the impact of location on neurological deficit severity and to delineate this impact from that of volume. Methods— We developed atlases consisting of location-weighted values indicating the relative importance in terms of neurological deficit severity for every voxel of the brain. These atlases were applied to 80 first-ever ischemic stroke patients to produce estimates of clinical deficit severity. Each patient had an MRI and National Institutes of Health Stroke Scale (NIHSS) examination just before or soon after hospital discharge. The correlation between the location-based deficit predictions and measured neurological deficit (NIHSS) scores were compared with the correlation obtained using volume alone to predict the neurological deficit. Results— Volume-based estimates of neurological deficit severity were only moderately correlated with measured NIHSS scores (r=0.62). The combination of volume and location resulted in a significantly better correlation with clinical deficit severity (r=0.79, P=0.032). Conclusions— The atlas methodology is a feasible way of integrating infarct size and location to predict stroke severity. It can estimate stroke severity better than volume alone.

Automated perfusion‐weighted MRI using localized arterial input functions

To investigate the utility of an automated perfusion‐weighted MRI (PWI) method for estimating cerebral blood flow (CBF) based on localized arterial input functions (AIFs) as compared to the standard method of manual global AIF selection, which is prone to deconvolution errors due to the effects of delay and dispersion of the contrast bolus.

Apolipoprotein E polymorphism and acute ischemic stroke: a diffusion- and perfusion-weighted magnetic resonance imaging study.

Diffusion- and perfusion-weighted magnetic resonance imaging (MRI) was used to study the putative effects of apolipoprotein E (ApoE) polymorphism in stroke. Thirty-one patients with acute stroke, comparative for age and gender were scanned, nine of whom were ApoE allele ***ε4 carriers. Initially, less than 24 hours from the onset of stroke, the ε4 carriers had significantly smaller volumes of hypoperfusion on relative cerebral blood volume map (P = 0.001), and smaller infarct volumes (P = 0.008) compared with the noncarriers. By day 8, this difference in the infarct volumes had disappeared, suggesting relatively enhanced infarct growth. On average, the total infarct volume increased 145% of the initial infarct volume in the ε4 carriers, and 84% in the noncarriers. There were strong correlations between the imaging findings and clinical status initially and with the outcome 3 months after the stroke in the ε4 noncarriers, but, with a single exception at acute phase, a lack thereof in the ε4 carriers. These patterns were virtually similar in a subgroup of patients with middle cerebral artery stroke. These data support the hypothesis of increased general vulnerability of the brain in the e4 carriers. Thus, the effects of ApoE polymorphism should be accounted for when interpreting diffusion- and perfusion-weighted MRI studies, particularly if predicting lesion growth.

Effect of using local arterial input functions on cerebral blood flow estimation.

To investigate a previously developed method for perfusion‐weighted MRI (PWI) cerebral blood flow (CBF) estimation that uses local arterial input functions (AIFs) in stroke patients, and determine its ability to correct delay and/or dispersion (D/D) errors.

Crossed cerebellar diaschisis in acute ischemic stroke: a study with serial SPECT and MRI

This study evaluated the relationship between crossed cerebellar diaschisis (CCD) and (1) lesion volume and location in the acute phase and 1 week after stroke onset and (2) clinical outcome. Twenty-two patients with cerebral ischemic stroke underwent single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) within 48 h and on day 8 from onset. Interhemispheric asymmetric indices (AI) on SPECT were calculated for medial, intermediate, and lateral zones of the cerebellum. Lesion volumes and locations were obtained from diffusion-weighted MRI. Neurological status and 3-month clinical outcome were evaluated. Within 48 h, lesion locations in the temporal association cortex and pyramidal tract of the corona radiata were independent determinants for the AI of the medial zone (R2 = 0.439). Lesion locations in the primary, premotor, and supplementary motor cortices, primary somatosensory cortex, and anterior part of the posterior limb of the internal capsule were determinants for the AI of the intermediate zone (R2 = 0.785). Lesions in the primary motor cortex, premotor, and supplementary motor cortices and in the genu of the internal capsule were determinants for the AI of the lateral zone (R2 = 0.746). On day 8, the associations were decreased. The AIs of the intermediate and lateral zones and lesion location in the parietal association cortex were independently associated with the 3-month clinical outcome (R2 > 0.555). Acute CCD is a result of functional deafference, while in the subacute phase, transneuronal degeneration might contribute to CCD. CCD in the intermediate and later zones is a better indicator than that in the medial zone.

Diffusion and perfusion MR imaging in acute ischemic stroke : a comparison to SPECT

Diffusion (DWI) and perfusion (PWI) magnetic resonance imaging are relatively new methods of clinical imaging that probably can detect infarcted (DWI) and hypoperfused but still salvageable tissue (PWI) in acute human stroke. Forty-six acute stroke patients were imaged within 24 h of ictus, on the second day and after a week. SPECT was also performed on 23 patients in the acute phase (first or second day). On the first day, mean volume of hypoperfused tissue was significantly greater (P<0.001) than the infarcted tissue. The initial hypoperfusion volume correlated significantly with the final infarct size (P<0.001). The initial perfusion-diffusion mismatch correlated significantly with the infarct growth (P< or =0.001). The hypoperfusion volumes measured from PWI and SPECT correlated significantly (P<0.001). In conclusion, combined DWI and PWI is a powerful tool in evaluating the hemodynamics of acute ischemic stroke and can predict the infarct growth during 1 week.

Physiological noise in MR images: An indicator of the tissue response to ischemia?

To determine whether measuring signal intensity (SI) fluctuations in MRI time series data from acute stroke patients would identify ischemic tissue.

ApoE polymorphism and acute stroke : a study with diffusion- and perfusion-weighted MRI and MR angiography

Objectives –  We examined whether the apolipoprotein E (ApoE) allele ɛ4 influences imaging findings in stroke as assessed by diffusion‐ (DWI) and perfusion‐weighted (PWI) magnetic resonance imaging, and MR angiography (MRA).

Cerebellar apparent diffusion coefficient changes in patients with supratentorial ischemic stroke.

Liu Y, Nuutinen J, Laakso MP, Karonen JO, Könönen M, Vanninen E, Kuikka JT, Vanninen RL. Cerebellar apparent diffusion coefficient changes in patients with supratentorial ischemic stroke.
Acta Neurol Scand: 2010: 122: 316–322.
© 2009 The Authors Journal compilation