Aart Spilt

Reproducibility of total cerebral blood flow measurements using phase contrast magnetic resonance imaging

To evaluate reproducibility of total cerebral blood flow (CBF) measurements with phase contrast magnetic resonance imaging (pcMRI).

Interaction of medial temporal lobe atrophy and white matter hyperintensities in AD

The authors investigated the interaction between medial temporal lobe (MTL) atrophy and white matter hyperintensities (WMH) in Alzheimer disease (AD). They measured the MTL and WMH on MRI in 58 AD patients and 28 controls. MTL atrophy was associated with an increased risk of AD (OR = 6.2), but there was no significant association between WMH and AD. Moreover, there was an interaction between MTL and WMH (p = 0.045). These results suggest that vascular and Alzheimer-type pathology act in synergy in the clinical syndrome of AD.

Cerebral Hemodynamics and White Matter Hyperintensities in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small-vessel disease caused by mutations in the NOTCH3 gene on chromosome 19. On magnetic resonance imaging (MRI), subcortical white matter hyperintensities and lacunar infarcts are visualized. It is unknown whether a decrease in cerebral blood flow or cerebrovascular reactivity is primarily responsible for the development of white matter hyperintensities and lacunar infarcts. The authors used phase-contrast MRI in 40 NOTCH3 mutation carriers (mean age 45 ± 10 years) and 22 nonmutated family members (mean age 39 ± 12 years), to assess baseline total cerebral blood flow (TCBF) and cerebrovascular reactivity after acetazolamide. Mean baseline TCBF was significantly decreased in NOTCH3 mutation carriers. In young subjects, baseline TCBF was significantly lower than in nonmutation carriers (mean difference 124 mL/min). Furthermore, baseline TCBF did not differ significantly between mutation carriers with minimal and mutation carriers with moderate or severe white matter hyperintensities. No significant difference in mean cerebrovascular reactivity was found between mutation carriers and nonmutation carriers. This study suggests that a decrease in baseline TCBF in NOTCH3 mutation carriers precedes the development of white matter hyperintensities.

Cognitive decline in AD and mild cognitive impairment is associated with global brain damage.

ObjectiveTo investigate the relationships between structural damage in the whole brain, the temporal lobes, and the frontal lobes and cognitive decline at old age. The authors hypothesized that widespread brain damage as quantified using magnetization transfer imaging (MTI) is related to global cognitive decline, whereas regional damage to the temporal lobes is related to memory impairment, and regional damage to the frontal lobes is related to executive dysfunctioning. Methods Cognitive function of 22 patients with probable AD, 13 patients with mild cognitive impairment (MCI), and 28 elderly controls was assessed using an extensive neuropsychological test battery. Structural damage in the whole brain, the temporal lobes, and the frontal lobes was estimated using volumetric MTI analysis. Associations between MTI measures and neuropsychological tests were investigated using Pearson correlation analysis. Results MTI measures of the whole brain, as well as the temporal and the frontal lobes, were strongly associated with global cognitive deterioration and impairment in memory, orientation, language, praxis, gnosis, and executive functioning. However, there were no specific cognitive correlates of regional brain damage to the temporal and frontal lobes. Conclusions Using whole brain volumetric magnetization transfer imaging, the authors demonstrated that cognitive decline in patients with mild cognitive impairment and AD is associated with widespread structural brain damage. As there were no specific relationships between regional brain damage and impairment of specific cognitive functions, pathology in AD and mild cognitive impairment is much more generalized than was expected.

Comparison of Imaging Strategies with Conditional Contrast-enhanced CT and Unenhanced MR Imaging in Patients Suspected of Having Appendicitis: A Multicenter Diagnostic Performance Study

PURPOSE To compare the diagnostic performance of imaging strategies with magnetic resonance (MR) imaging and computed tomographic (CT) imaging in adult patients suspected of having appendicitis. MATERIALS AND METHODS Institutional review board approval was obtained prior to study initiation, and patients gave written informed consent. In a multicenter diagnostic performance study, adults suspected of having appendicitis were prospectively identified in the emergency department. Consenting patients underwent ultrasonography (US) and subsequent contrast-enhanced CT if US imaging yielded negative or inconclusive results. Additionally, all patients underwent unenhanced MR imaging, with the reader blinded to other findings. An expert panel assigned final diagnosis after 3 months. Diagnostic performance of three imaging strategies was evaluated: conditional CT after US, conditional MR imaging after US, and immediate MR imaging. Sensitivity and specificity were calculated by comparing findings with final diagnosis. RESULTS Between March and September 2010, 229 US, 115 CT, and 223 MR examinations were performed in 230 patients (median age, 35 years; 40% men). Appendicitis was the final diagnosis in 118 cases. Conditional and immediate MR imaging had sensitivity and specificity comparable to that of conditional CT, which resulted in 3% (three of 118; 95% confidence interval [CI]: 1%, 7%) missed appendicitis, and 8% (10 of 125; 95% CI: 4%, 14%) false-positives. Conditional MR missed appendicitis in 2% (two of 118; 95% CI: 0%, 6%) and generated 10% (13 of 129; 95% CI: 6%, 16%) false-positives. Immediate MR missed 3% (four of 117; 95% CI: 1%, 8%) appendicitis with 6% (seven of 120; 95% CI: 3%, 12%) false-positives. Conditional strategies resulted in more false-positives in women than in men (conditional CT, 17% vs 0%; P = .03; conditional MR, 19% vs 1%; P = .04), wherease immediate MR imaging did not. CONCLUSION The accuracy of conditional or immediate MR imaging was similar to that of conditional CT in patients suspected of having appendicitis, which implied that strategies with MR imaging may replace conditional CT for appendicitis detection.

Basal cerebral blood flow is dependent on the nitric oxide pathway in elderly but not in young healthy men

OBJECTIVE Brain perfusion is tightly regulated over a wide range of blood pressures by local regulation of cerebral blood flow (CBF). Ageing is associated with impaired CBF and impaired nitric oxide mediated vasodilator responses. The role of nitric oxide in the regulation of basal CBF in young and older subjects was investigated, using the nitric oxide synthase inhibitor L-NMMA as pharmacological tool. METHODS We used a gradient echo phase-contrast magnetic resonance imaging technique to investigate the role of nitric oxide in the regulation of cerebral blood flow in young (25+/-7.1 years; n=8) and old (78+/-6.6 years; n=7) volunteers. The study was performed in a double-blinded fashion and consisted of two study days. On one day the effects of the intravenously infused L-NMMA on CBF and blood pressure was measured and on the other day the effects of a matching placebo. RESULTS Basal CBF was significantly lower in old compared to young subjects (590+/-20 vs 704+/-20 ml/min), while the cerebral vascular resistance (CVR) levels were significantly higher (0.15+/-0.01 (arbitrary units) vs 0.12+/-0.01, respectively). Infusion of L-NMMA significantly increased mean arterial pressure in both groups (2.8+/-1.2 mmHg; p=0.02 in the young and in the old subjects 5.6+/-1.1 mmHg; p<0.001). Infusion of L-NMMA significantly decreased CBF (49+/-12 ml/min; p<0.001) and increased CVR (0.02+/-0.004; p<0.001) in the old subjects but did not significantly influence cerebral circulation in the young subjects. CONCLUSION We conclude that compared to young subjects, in old people CBF is impaired, and dependent on the intactness of the nitric oxide pathway.

Automatic model-based contour detection and blood flow quantification in small vessels with velocity encoded magnetic resonance imaging.

Rationale and Objectives:The quantitative assessment of blood flow in peripheral vessels from phase-contrast magnetic resonance imaging studies requires the accurate delineation of vessel contours in cross-sectional magnetic resonance images. The conventional manual segmentation approach is tedious, time-consuming, and leads to significant inter- and intraobserver variabilities. The aim of this study was to verify whether automatic model-based segmentation decreases these problems by fitting a model to the actual blood velocity profile. Methods:In this study 2 new fully automatic methods (a static and a dynamic approach) were developed and compared with manual analyzes using phantom and in vivo studies of internal carotid and vertebral arteries in healthy volunteers. The automatic segmentation approaches were based on fitting a 3D parabolic velocity model to the actual velocity profiles. In the static method, the velocity profiles were averaged over the complete cardiac cycle, whereas the dynamic method takes into account the velocity data of each cardiac time bin individually. Materials consisted of the magnetic resonance imaging data from 3 straight phantom tubes and the blood velocity profiles of 8 volunteers. Results:For the phantom studies, the automatic dynamic approach performed significantly better than the manual analysis (intraclass correlations [ICC] of 0.62–0.98 and 0.30–0.86, respectively). For the assessment of the total cerebral blood flow in the in vivo studies, the automatic static method performed significantly better than the manual 1 (ICC of 0.98–0.98 and 0.93–0.95, respectively). However, the automatic dynamic method was not significantly better than the manual 1 (ICC = 0.92–0.96) but had the advantage of providing additional parameters. Conclusion:Blood flow in magnetic resonance images of small vessels can be assessed accurately, rapidly, and fully automatically using model-based postprocessing by fitting a first approximation of the velocity profile to the actual flow data.

MR assessment of cerebral vascular response: a comparison of two methods.

To compare the results and reproducibility of two MR‐based methods of measuring the cerebrovascular response (CVR).

Choosing radiological modalities in patients with head trauma

Abstract A survey among Dutch neurologists demonstrated that there was no consensus on the diagnostic strategy to be pursued in patients with a blunt head trauma. In the Leiden University Medical Center, an algorithm was designed on the basis of the literature, describing a strategy in patients with head trauma.