Effects of bolus injection duration on perfusion estimates in dynamic CT and dynamic susceptibility contrast MRI.

Estimates of cerebral blood flow (CBF) and tissue mean transit time (MTT) have been shown to differ between dynamic CT perfusion (CTP) and dynamic susceptibility contrast MRI (DSC-MRI). This study investigates whether these discrepancies regarding CBF and MTT between CTP and DSC-MRI can be attributed to the different injection durations of these techniques. Five subjects were scanned using CTP and DSC-MRI. Region-wise estimates of CBF, MTT, and cerebral blood volume (CBV) were derived based on oscillatory index regularized singular value decomposition. A parametric model that reproduced the shape of measured time curves and characteristics of resulting perfusion parameter estimates was developed and used to simulate data with injection durations typical for CTP and DSC-MRI for a clinically relevant set of perfusion scenarios and noise levels. In simulations, estimates of CBF/MTT showed larger negative/positive bias and increasing variability for CTP when compared to DSC-MRI, especially for high CBF levels. While noise also affected estimates, at clinically relevant levels, the injection duration effect was larger. There are several methodological differences between CTP and DSC-MRI. The results of this study suggest that the injection duration is among those that can explain differences in estimates of CBF and MTT between these bolus tracking techniques.

Endoscopic versus open microsurgery for colloid cysts of the third ventricle.

PURPOSE: The surgical approach for colloid cysts of the third ventricle mainly consists of endoscopic or microscopic approach but few studies compare the neurologic outcomes and complications related to the different approaches. We retrospectively reviewed our results after resection of colloid cysts of the third ventricle using endoscopic surgery (ES) compared to open microsurgery (OS). METHODS: Fifty-one patients were included in the study of which 17 patients underwent ES. Colloid cyst size and Evans' index were evaluated on CT or MRI scans. Presenting symptoms, neurologic outcomes and complications were compared between the two groups and analysed using Fisher's exact test. Operative time and days of hospital stay were compared between the two groups, using independent sample t-test. The median follow-up time was 96 days and did not differ significantly between the groups. RESULTS: Shorter mean operative time (p = 0.04) and fewer days of hospital stay (p < 0.01) were found in the endoscopic group compared to the open microsurgical group. Presenting symptoms, neurological outcomes and postoperative complications were similar in the two groups. CONCLUSIONS: ES showed similar neurologic outcomes and complications compared to OS for colloid cysts of the third ventricle. ES showed significantly shorter operative times and hospital stays compared to OS.

Validity and reliability of the medial temporal lobe atrophy scale in a memory clinic population.

BACKGROUND: Visual rating of medial temporal lobe atrophy (MTA) is often performed in conjunction with dementia workup. Most prior studies involved patients with known or probable Alzheimer's disease (AD). This study investigated the validity and reliability of MTA in a memory clinic population. METHODS: MTA was rated in 752 MRI examinations, of which 105 were performed in cognitively healthy participants (CH), 184 in participants with subjective cognitive impairment, 249 in subjects with mild cognitive impairment, and 214 in patients with dementia, including AD, subcortical vascular dementia and mixed dementia. Hippocampal volumes, measured manually or using FreeSurfer, were available in the majority of cases. Intra- and interrater reliability was tested using Cohen's weighted kappa. Correlation between MTA and quantitative hippocampal measurements was ascertained with Spearman's rank correlation coefficient. Moreover, diagnostic ability of MTA was assessed with receiver operating characteristic (ROC) analysis and suitable, age-dependent MTA thresholds were determined. RESULTS: Rater agreement was moderate to substantial. MTA correlation with quantitative volumetric methods ranged from -0.20 (p< 0.05) to -0.68 (p < 0.001) depending on the quantitative method used. Both MTA and FreeSurfer are able to distinguish dementia subgroups from CH. Suggested age-dependent MTA thresholds are 1 for the age group below 75 years and 1.5 for the age group 75 years and older. CONCLUSIONS: MTA can be considered a valid marker of medial temporal lobe atrophy and may thus be valuable in the assessment of patients with cognitive impairment, even in a heterogeneous patient population.

In Patients With Idiopathic Normal Pressure Hydrocephalus Postoperative Cerebral Perfusion Changes Measured by Dynamic Susceptibility Contrast Magnetic Resonance Imaging Correlate With Clinical Improvement.

OBJECTIVE: To explore relationships between clinical improvement and relative cerebral blood flow (rCBF) changes after shunt-insertion in idiopathic normal pressure hydrocephalus (iNPH) as measured by dynamic susceptibility contrast magnetic resonance imaging. METHODS: In 20 idiopathic normal pressure hydrocephalus patients rCBF was measured preoperatively and 3 months postoperatively. Because of shunt-induced right-sided artefacts, evaluation was restricted to 12 left-sided cortical, subcortical, and periventricular regions of interest. Correlations between rCBF and clinical symptoms were analyzed in shunt responders. RESULTS: In responders, the postoperative regions of interest-based rCBF increase of 2% to 9% was significant in the parenchyma, the hippocampus, and the anterior periventricular white matter. Perfusion improvement in the cingulus, caudate head, and thalamus correlated with decreased disturbance in one or more of the domains neuropsychology, gait, balance, and total performance. CONCLUSIONS: Apparently, dynamic susceptibility contrast magnetic resonance imaging can measure postoperative perfusion changes in responders. Postoperatively, perfusion increase in some grey matter structures seems to determine the degree of clinical improvement.

Cerebral perfusion measured by dynamic susceptibility contrast MRI is reduced in patients with idiopathic normal pressure hydrocephalus.

PURPOSE: To demonstrate in idiopathic normal pressure hydrocephalus (iNPH) patients by dynamic susceptibility contrast MRI a reduced preoperative cerebral blood flow (CBF) which correlates with the severity of clinical symptoms and predicts shunt outcome. MATERIALS AND METHODS: In cortical, subcortical, periventricular regions and along peri-and paraventricular profiles absolute perfusion values were estimated by multi-slice DSC MRI in 21 iNPH patients and 16 age-matched healthy individuals (HI). Relative CBF (rCBF), calculated with the occipital cortex as internal reference, was used for comparison between groups and for correlation analysis between regional rCBF and symptoms or outcome. RESULTS: iNPH patients showed significantly decreased rCBF in the basal medial frontal cortex, hippocampus, lentiform nucleus, periventricular white matter (PVWM), central grey matter and the global parenchyma as compared to HI. iNPH patients with higher preoperative rCBF in the PVWM performed better in clinical tests. A lower overall preoperative function resulted in a more obvious recovery after shunt insertion. Shunt-responders had higher rCBF values in the basal medial frontal cortex than non-responders. CONCLUSION: DSC MRI perfusion is a potentially useful diagnostic tool in iNPH and perfusion based criteria might be possible predictors of shunt response.

Evaluation of a Fully Automated Method for Ventricular Volume Segmentation Before and After Shunt Surgery in Idiopathic Normal Pressure Hydrocephalus.

BACKGROUND: Determination of the ventricle size in idiopathic normal pressure hydrocephalus (iNPH) is essential for diagnosis and follow-up of shunt results. Fully automated segmentation methods are anticipated to optimize the accuracy and time efficiency of ventricular volume measurements. We evaluated the accuracy of preoperative and postoperative ventricular volume measurements in iNPH by a magnetic resonance imaging (MRI)-based licensed software for fully automated quantitative assessment. METHODS: Forty-eight patients diagnosed with iNPH were retrospectively analyzed. All patients received a ventriculoperitoneal shunt and had symptom grading and routine MRI preoperatively and 3-6 months postoperatively. Ventricular volumes, generated by fully automated T1-weighted imaging volume sequence segmentation, were compared with semiautomatic measurements and routine radiologic reports. The relation of postoperative ventricular size change to clinical response was evaluated. RESULTS: Fully automated segmentation was achieved in 95% of the MRIs, but showed various rates of 8 minor segmentation errors. The correlation between both segmentation methods was very strong (r >0.9) and the agreement very good using Bland-Altman analyses. The ventricular volumes differed significantly between semiautomated and fully automated segmentations and between preoperative and postoperative MRI. The fully automated method systematically overestimated the ventricles by a median 15 mL preoperatively and 14 mL postoperatively; hence, the magnitudes of volume changes were equivalent. Routine radiologic reports of ventricular size changes were inaccurate in 51% and lacked association with treatment response. Objectively measured ventricular volume changes correlated moderately with postoperative clinical improvement. CONCLUSIONS: A fully automated volumetric method permits reliable evaluation of preoperative ventriculomegaly and postoperative ventricular volume change in idiopathic normal pressure hydrocephalus.

Prevalence of Possible Idiopathic Normal Pressure Hydrocephalus in Sweden: A Population-Based MRI Study in 791 70-Year-Old Participants

BACKGROUND AND OBJECTIVES: Very divergent prevalence rates for idiopathic normal pressure hydrocephalus (iNPH) are reported, probably due to differences in study sample selection and diagnostic criteria. This MRI-based study aimed to determine the prevalence of iNPH and iNPH-specific radiologic changes and their association with clinical symptoms in a large, 70-year-old population-based cohort (Gothenburg H70). METHODS: In this cross-sectional study, disturbances in gait and balance, cognition, and urinary continence were assessed using clinical examination and self-report. MRI was evaluated for iNPH-specific imaging markers. iNPH was diagnosed according to International Guidelines (I.G.). Based on radiologic findings, participants were allocated to 1 of 4 groups: (A) Evans index (EI) ≤0.3 (reference), (B) EI >0.3 without other iNPH-typical radiologic findings, (C) radiologically probable iNPH according to I.G., and (D) radiologically holistically probable (h-probable) iNPH fulfilling radiologic criteria according to I.G. plus highly iNPH-specific changes according to an experienced neuroradiologist. RESULTS: The Gothenburg H70 Studies include 791 individuals (377 men, 414 women) born in 1944 who underwent brain MRI. The prevalence of iNPH was 1.5% (2.1% for men, 0.96% for women) according to I.G. Ninety participants (11%) had EI >0.3 without other iNPH-typical radiologic findings, 29 (3.7%) fulfilled the I.G. radiologic probable iNPH criteria alone, and 11 (1.4%) were classified as radiologically h-probable iNPH. Forty participants (5.1%) had I.G. radiologic features of iNPH (70% men vs 30% women, p = 0.005). Gait disturbances were more common in participants with EI >0.3 without other radiologic iNPH features (B) (33%) compared with the reference group (A) (19%) (p = 0.006). All clinical symptoms were more common in participants with I.G. radiologic features of iNPH (C + D) than they were in the reference group (A) (p < 0.03). DISCUSSION: The iNPH prevalence of 1.5% among 70-year-olds, which is considerably higher than earlier reported in this age group, suggests that iNPH may be more common than previously assumed. This is supported by the 5.1% total prevalence of imaging signs of iNPH. Ventriculomegaly without other iNPH-typical radiologic findings may be an early sign of developing iNPH in some patients.

Changes in relative cerebral blood volume 1 month after radiation-temozolomide therapy can help predict overall survival in patients with glioblastoma.

PURPOSE: To evaluate perfusion parameter changes in patients with glioblastoma multiforme by comparing the perfusion magnetic resonance (MR) imaging measurements obtained before combined radiation and temozolomide therapy (RT-TMZ) with the follow-up MR imaging measurements obtained 1 month after completion of this treatment. MATERIALS AND METHODS: Institutional review board approval was obtained, and HIPAA guidelines were followed. The data of 36 patients (24 male [median age, 63 years]; 12 female [median age, 59 years]) with glioblastoma multiforme who were treated with RT-TMZ were retrospectively reviewed. The hypothesis was that a change in relative cerebral blood volume (rCBV) 1 month after RT-TMZ is predictive of overall survival. Linear regression analysis was performed to correlate changes in tumor size and perfusion parameters with overall survival. Receiver operating characteristic (ROC) curves were evaluated for 1-year survival. Overall survival was assessed with Kaplan-Meir survival curves and log-rank testing. RESULTS: Percentage change in rCBV at 1 month after RT-TMZ correlated with overall survival. Increased rCBV after treatment was a strong predictor of poor survival (median survival, 235 days versus 529 days with decreased rCBV) (P < .008, log-rank test). The ROC curves for 1-year survival showed a greater area under the curve (0.806; 95% confidence interval [CI]: 0.698, 0.970) (P = .005) with rCBV than with tumor size (0.556; 95% CI: 0.342, 0.729) (P = .382). The overall survival for patients with increased tumor size, based on Macdonald criteria, was shorter than that for patients who showed no progression (stable or partial response), but the difference was not significant (median survival, 442 days versus 598 days) (P = .761, log-rank test). CONCLUSION: Change in rCBV after RT-TMZ appears to correlate with overall survival.

MRI diffusion and perfusion alterations in the mesencephalon and pons as markers of disease and symptom reversibility in idiopathic normal pressure hydrocephalus.

INTRODUCTION: Core symptomatology in idiopathic normal pressure hydrocephalus (iNPH) points at dysfunction in the mesencephalon and pons indicating pathological changes in these regions, but only a few studies have addressed the issue. The aim of this study was to investigate diffusion (ADC) and perfusion patterns pre- and postoperatively in these areas in iNPH. METHODS: Twenty iNPH patients and 15 healthy controls were included. Patients underwent a clinical examination and brain MRI pre- and 3-6 months postoperatively. The MRI-scan included diffusion and dynamic susceptibility contrast perfusion weighted sequences. Regions of interest in the mesencephalon and pons were drawn on a FLAIR sequence and co-registered to ADC maps and perfusion data. RESULTS: There were no significant differences in pre or postoperative ADC compared to the control group, however postoperative ADC increased by 10% (p = 0.026) in the mesencephalon and 6% (p = 0.016) in the pons in all patients and also in the subgroup of shunt responders by 11% (p = 0.021) and 4% (p = 0.020), respectively. Preoperative relative cerebral blood flow (rCBF) was similar in iNPH patients and controls. Postoperatively, rCBF increased in shunt responders by 6% (p = 0.02) in the mesencephalon and 11% (p = 0.004) in the pons. This increase correlated with the degree of clinical improvement (rs = 0.80, p = 0.031 and rs = 0.66, p = 0.021, respectively). CONCLUSION: The postoperative increase in ADC and the correlation between postoperative increase in rCBF and clinical improvement in the mesencephalon and pons shown in this study point at an involvement of these areas in the core pathophysiology and its reversibility in iNPH.

Absolute quantification of cerebral blood flow in neurologically normal volunteers: dynamic-susceptibility contrast MRI-perfusion compared with computed tomography (CT)-perfusion.

To improve the reproducibility of arterial input function (AIF) registration and absolute cerebral blood flow (CBF) quantification in dynamic-susceptibility MRI-perfusion (MRP) at 1.5T, we rescaled the AIF by use of a venous output function (VOF). We compared CBF estimates of 20 healthy, elderly volunteers, obtained by computed tomography (CT)-perfusion (CTP) and MRP on two consecutive days. MRP, calculated without the AIF correction, did not result in any significant correlation with CTP. The rescaled MRP showed fair to moderate correlation with CTP for the central gray matter (GM) and the whole brain. Our results indicate that the method used for correction of partial volume effects (PVEs) improves MRP experiments by reducing AIF-introduced variance at 1.5T.

Three-Dimensional Volumetric Segmentation of Pituitary Tumors: Assessment of Inter-rater Agreement and Comparison with Conventional Geometric Equations.

Background The assessment of pituitary tumor (PT) volume is important in the treatment and follow-up of patients with PT. Previously, PT volume estimation has been performed by conventional geometric equations (CGE) such as abc/2 (simplified ellipsoid volume equation) and 4πr 3 /3 (sphere), both presuming a symmetric tumor shape, which occurs uncommonly in patients with PT. In contrast, three-dimensional (3D) voxel-based software segmentation takes the irregular and asymmetric shapes that PTs often possess into account and might be a more accurate method for PT volume segmentation. The purpose of this study is twofold. (1) To compare 3D segmentation with CGE for PT volume estimation. (2) To assess inter-rater reliability in 3D segmentation of PTs. Methods Nineteen high-resolution (1mm slice thickness) T1-weighted MRI examinations of patients with PT were independently analyzed and manually segmented, using the software ITK-SNAP, by two certified neuroradiologists. Concurrently, the volumes of the PTs were estimated with abc/2 and 4πr 3 /3 by a clinician, and the results were compared with the corresponding segmented volumes. Results There was a significant decrease in PT volume attained from the segmentations compared with the calculations made with abc/2 ( p < 0.001, mean volume 18% higher than segmentation) and 4πr 3 /3 ( p < 0.001, mean volume 28% higher than segmentation). The intraclass correlation coefficient (ICC) for the two sets of segmented PTs was 0.99. Conclusion CGE ( abc/2 and 4πr 3 /3 ) significantly overestimates PT volume compared with 3D volumetric segmentation. The inter-rater agreement on manual 3D volumetric software segmentation is excellent.

Persistent regional frontotemporal hypoactivity in violent offenders at follow-up.

Since cross-sectional brain-imaging studies demonstrating frontotemporal cerebral hypoactivity in violent offenders have generally been carried out around the time of trial and sentencing, the findings might be influenced by the stressful situation of the subjects. It seems that no group of offenders with this finding has yet been followed longitudinally. We have re-examined nine offenders convicted of lethal or near-lethal violence in whom single photon emission tomography (SPECT) previously had demonstrated frontotemporal hypoperfusion. The mean interval between the initial and the follow-up examination was 4 years. The initially observed hypoactivity was found to have remained virtually unchanged at follow-up: no mean change in the group exceeded 5% in 12 assessed regions of interest. Although preliminary due to the small sample size, this study suggests that frontotemporal brain hypoactivity is a trait rather than a state in perpetrators of severe violent crimes.

Pre-and postoperative cerebral blood flow changes in patients with idiopathic normal pressure hydrocephalus measured by computed tomography (CT)-perfusion.

In idiopathic normal pressure hydrocephalus (iNPH), the cerebral blood flow (CBF) is of pathophysiological interest and a potential biomarker. Computed tomography perfusion (CTP), an established technique with high spatial resolution and quantitative measurements, has not yet been used in the iNPH context. If CTP were sensitive to the CBF levels and changes in iNPH, this technique might provide diagnostic and prognostic absolute perfusion thresholds. The aim of this work was to determine the applicability of CTP to iNPH. CBF measurements of 18 patients pre- and 17 three months postoperatively, and six healthy individuals (HI) were evaluated in 12 cortical and subcortical regions of interest. Correlations between CBF and symptomatology were analyzed in shunt-responders. Compared to HI, the preoperative CBF in iNPH was significantly reduced in normal appearing and periventricular white matter (PVWM), the lentiform nucleus and the global parenchyma. No CBF differences were shown between responders and non-responders. In responders, the CBF recovered postoperatively by 2.5-32% to approximately the level of HI, but remained significantly decreased in the PVWM of non-responders. The pre- and postoperative CBF of cortical and subcortical regions correlated with the intensity of symptoms. In spite of limited spatial coverage, CTP can measure CBF changes in iNPH.