Association between preoperative white matter hyperintensities and postoperative new ischemic lesions on magnetic resonance imaging in patients with cognitive decline after carotid endarterectomy.

Although cognitive decline after carotid endarterectomy (CEA) is mainly related to postoperative cerebral hyperperfusion, approximately 30% of patients with cognitive decline do not have postoperative cerebral hyperperfusion. In patients with acute ischemic events, the development of cognitive decline after such events is associated with the presence of chronic cerebral white matter hyperintensities (WMHs). The present prospective observational study aimed to determine whether preoperative WMHs and postoperative new ischemic lesions (PNILs) are associated with cognitive decline after CEA in patients without cerebral hyperperfusion after CEA. Brain magnetic resonance imaging (MRI) was performed preoperatively, and WMHs were graded according to the Fazekas scale in patients undergoing CEA for severe stenosis of the ipsilateral internal carotid. Diffusion-weighted MRI was performed before and after CEA to determine the development of PNILs. Neuropsychological testing was performed preoperatively and at 2 months postoperatively to determine the development of postoperative cognitive decline (PCD). In 142 patients without postoperative cerebral hyperperfusion, logistic regression analysis revealed that preoperative Fazekas scale of periventricular WMHs (PVWMHs) (95% confidence interval [CI]: 1.78-28.10; P = 0.0055) and PNILs in the eloquent areas (95% CI: 7.42-571.89; P = 0.0002) were significantly associated with PCD. The specificity and positive-predictive value for the prediction of PCD were significantly greater for the combination of preoperative Fazekas scale 2 or 3 of PVWMHs and PNILs in the eloquent areas than for each individually. Preoperative PVWMHs, PNILs in the eloquent areas, and the combination of both were associated with PCD in patients without cerebral hyperperfusion after CEA.

Assessment of Impaired Cerebrovascular Reactivity in Chronic Cerebral Ischemia using Intravoxel Incoherent Motion Magnetic Resonance Imaging.

BACKGROUND: The severity of chronic cerebral ischemia can be assessed using cerebrovascular reactivity (CVR) to acetazolamide (ACZ) challenge, which is measured by single-photon emission computed tomography (SPECT); however, this is an invasive method. We investigated whether intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) can assess impaired CVR in preoperative patients with chronic cerebral ischemia and compared it to SPECT-CVR. METHODS: Forty-seven patients with unilateral cervical carotid artery stenosis underwent diffusion-weighted MRI with 11 b-values in the range of 0-800 s/mm2 and cerebral perfusion SPECT with the ACZ challenge. The perfusion fraction (f) and diffusion coefficient (D) of the IVIM parameters were calculated using a bi-exponential model. The f and D values and these ratios of the ipsilateral middle cerebral artery territory against the contralateral side were compared with the CVR values of the affected side calculated from the SPECT data. RESULTS: The IVIM-f and D values in the affected side were significantly higher than those in the unaffected side (median: 7.74% vs. 7.45%, p = 0.027; 0.816 vs. 0.801 10-3mm2/s, p < 0.001; respectively). However, there were no significant correlations between the f or D values and SPECT-CVR values in the affected side. In contrast, the f ratio showed a moderate negative correlation with the SPECT-CVR values (r = -0.40, p = 0.006) and detected impaired CVR (< 18.4%) with a sensitivity/specificity of 0.71/0.90. CONCLUSION: The IVIM perfusion parameter, f, can noninvasively assess impaired CVR with high sensitivity and specificity in patients with unilateral cervical carotid artery stenosis.

Differentiation of schizophrenia using structural MRI with consideration of scanner differences: A real-world multisite study.

AIM: Neuroimaging studies have revealed that patients with schizophrenia exhibit reduced gray matter volume in various regions. With these findings, various studies have indicated that structural MRI can be useful for the diagnosis of schizophrenia. However, multisite studies are limited. Here, we evaluated a simple model that could be used to differentiate schizophrenia from control subjects considering MRI scanner differences employing voxel-based morphometry. METHODS: Subjects were 541 patients with schizophrenia and 1252 healthy volunteers. Among them, 95 patients and 95 controls (Dataset A) were used for the generation of regions of interest (ROI), and the rest (Dataset B) were used to evaluate our method. The two datasets were comprised of different subjects. Three-dimensional T1-weighted MRI scans were taken for all subjects and gray-matter images were extracted. To differentiate schizophrenia, we generated ROI for schizophrenia from Dataset A. Then, we determined volume within the ROI for each subject from Dataset B. Using the extracted volume data, we calculated a differentiation feature considering age, sex, and intracranial volume for each MRI scanner. Receiver-operator curve analyses were performed to evaluate the differentiation feature. RESULTS: The area under the curve ranged from 0.74 to 0.84, with accuracy from 69% to 76%. Receiver-operator curve analysis with all samples revealed an area under the curve of 0.76 and an accuracy of 73%. CONCLUSION: We moderately successfully differentiated schizophrenia from control using structural MRI from differing scanners from multiple sites. This could be useful for applying neuroimaging techniques to clinical settings for the accurate diagnosis of schizophrenia.

Detection of impaired cerebrovascular reactivity in patients with chronic cerebral ischemia using whole-brain 7T MRA.

BACKGROUND: Cerebrovascular reactivity (CVR) to acetazolamide (ACZ) on single-photon emission computed tomography (SPECT) can be used to assess the severity of chronic cerebral ischemia; however, this is an invasive method. We examined whether whole-brain magnetic resonance angiography (MRA) at 7T could non-invasively detect impaired CVR in patients with chronic cerebral ischemia by demonstrating the leptomeningeal collaterals (LMCs). METHODS: Fifty-seven patients with symptomatic unilateral cervical stenosis underwent whole-brain time-of-flight MRA at 7T and cerebral perfusion SPECT before/after the ACZ challenge. MRA images were visually assessed based on 6-point grading systems to evaluate the development of LMCs toward the middle cerebral artery (MCA) and antegrade flow of MCA. CVR of the affected side was calculated from the SPECT data. Subsequently, we compared the LMC grades on MRA with CVR on SPECT. RESULTS: CVR was significantly lower in grades ≥ 2 of LMCs than in grades 0-1 (P < 0.05) when applying LMCs from the anterior cerebral artery (ACA) and/or posterior cerebral artery (PCA). These differences were more evident than those in the grading of the antegrade MCA flow. The LMC grades from ACA/PCA readily detected reduced CVR (< 18.4%) with a sensitivity/specificity of 0.79/0.82. CONCLUSION: The development of LMCs on whole-brain MRA at 7T can non-invasively detect reduced CVR with a high sensitivity/specificity in patients with unilateral cervical stenosis.

Computational Fluid Dynamics Analysis of Lateral Striate Arteries in Acute Ischemic Stroke Using 7T High-resolution Magnetic Resonance Angiography.

BACKGROUND: Infarcts in the lateral striate artery (LSA) territory can be caused by several pathological changes, including lipohyalinosis and microatheroma. However, fluid dynamic effects on these changes remain unknown. Thus, we investigated whether the fluid dynamic metrics of the LSAs were altered in patients with acute ischemic stroke using computational fluid dynamics (CFD) analysis. METHODS: Fifty-one patients with acute ischemic stroke confined in the basal ganglia and/or corona radiata underwent high-resolution magnetic resonance angiography (HR-MRA) at 7T. We performed CFD analyses to obtain indices including the wall shear stress (WSS), WSS gradient (WSSG), and flow velocity (FV) and compared these values between the ipsilesional and contralesional sides in the patients with infarcts in the LSA or non-LSA territories. RESULTS: In patients with LSA-territory infarcts, the WSS, WSSG, and FV values were significantly lower in the ipsilesional LSAs than in the contralesional LSAs (P = .01-.03), while these values in the proximal middle cerebral arteries showed no significant lateralities. In contrast, in patients with non-LSA-territory infarcts, there were no significant lateralities in the metrics between the ipsilesional and contralesional sides. CONCLUSIONS: The CFD analyses using HR-MRA revealed significantly low WSS and WSSG values of the ipsilesional LSAs compared with that of the contralesional side in patients with LSA-territory infarcts, suggesting that fluid dynamic factors of LSAs can be one of the risk factors for LSA-territory infarctions.

Supervised multiblock sparse multivariable analysis with application to multimodal brain imaging genetics.

This article proposes a procedure for describing the relationship between high-dimensional data sets, such as multimodal brain images and genetic data. We propose a supervised technique to incorporate the clinical outcome to determine a score, which is a linear combination of variables with hieratical structures to multimodalities. This approach is expected to obtain interpretable and predictive scores. The proposed method was applied to a study of Alzheimer's disease (AD). We propose a diagnostic method for AD that involves using whole-brain magnetic resonance imaging (MRI) and positron emission tomography (PET), and we select effective brain regions for the diagnostic probability and investigate the genome-wide association with the regions using single nucleotide polymorphisms (SNPs). The two-step dimension reduction method, which we previously introduced, was considered applicable to such a study and allows us to partially incorporate the proposed method. We show that the proposed method offers classification functions with feasibility and reasonable prediction accuracy based on the receiver operating characteristic (ROC) analysis and reasonable regions of the brain and genomes. Our simulation study based on the synthetic structured data set showed that the proposed method outperformed the original method and provided the characteristic for the supervised feature.

Indirect MRI of 17 o-labeled water using steady-state sequences: Signal simulation and preclinical experiment.

BACKGROUND: Few studies have been reported for T2 -weighted indirect 17 O imaging. PURPOSE/HYPOTHESIS: To evaluate the feasibility of steady-state sequences for indirect 17 O brain imaging. STUDY TYPE: Signal simulation, phantom measurements, and prospective animal experiments were performed in accordance with the institutional guidelines for animal experiments. POPULATION/SUBJECTS/PHANTOM/SPECIMEN/ANIMAL MODEL: Signal simulations of balanced steady-state free precession (bSSFP) were performed for concentrations of 17 O ranging from 0.037-1.600%. Phantom measurements with concentrations of 17 O water ranging from 0.037-1.566% were also conducted. Six healthy beagle dogs were scanned with intravenous administration of 20% 17 O-labeled water (1 mL/kg). FIELD STRENGTH/SEQUENCE: Dynamic 3D-bSSFP scans were performed at 3T MRI. 17 O-labeled water was injected 60 seconds after the scan start, and the total scan duration was 5 minutes. ASSESSMENT: Based on the result of signal simulation and phantom measurement, signal changes in the beagle dogs were measured and converted into 17 O concentrations. STATISTICAL TESTS: The 17 O concentrations were averaged for every 15 seconds, and compared to the baseline (30-45 sec) with Dunnett's multiple comparison tests. RESULTS: Signal simulation revealed that the relationships between 17 O concentration and the natural logarithm of relative signals were linear. The intraclass correlation coefficient between relative signals in phantom measurement and signal simulations was 0.974. In the animal experiments, significant increases in 17 O concentration (P < 0.05) were observed 60 seconds after the injection of 17 O. At the end of scanning, mean respective 17 O concentrations of 0.084 ± 0.026%, 0.117 ± 0.038, 0.082 ± 0.037%, and 0.049 ± 0.004% were noted for the cerebral cortex, cerebellar cortex, cerebral white matter, and ventricle. DATA CONCLUSION: Dynamic steady-state sequences were feasible for indirect 17 O imaging, and absolute quantification was possible. This method can be applied for the measurement of permeability and blood flow in the brain, and for kinetic analysis of cerebrospinal fluid. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1373-1379.

Improvement of the repeatability of parallel transmission at 7T using interleaved acquisition in the calibration scan.

BACKGROUND: Respiration-induced phase shift affects B0 /B1+ mapping repeatability in parallel transmission (pTx) calibration for 7T brain MRI, but is improved by breath-holding (BH). However, BH cannot be applied during long scans. PURPOSE: To examine whether interleaved acquisition during calibration scanning could improve pTx repeatability and image homogeneity. STUDY TYPE: Prospective. SUBJECTS: Nine healthy subjects. FIELD STRENGTH/SEQUENCE: 7T MRI with a two-channel RF transmission system was used. ASSESSMENT: Calibration scanning for B0 /B1+ mapping was performed under sequential acquisition/free-breathing (Seq-FB), Seq-BH, and interleaved acquisition/FB (Int-FB) conditions. The B0 map was calculated with two echo times, and the B1+ map was obtained using the Bloch-Siegert method. Actual flip-angle imaging (AFI) and gradient echo (GRE) imaging were performed using pTx and quadrature-Tx (qTx). All scans were acquired in five sessions. Repeatability was evaluated using intersession standard deviation (SD) or coefficient of variance (CV), and in-plane homogeneity was evaluated using in-plane CV. STATISTICAL TESTS: A paired t-test with Bonferroni correction for multiple comparisons was used. RESULTS: The intersession CV/SDs for the B0 /B1+ maps were significantly smaller in Int-FB than in Seq-FB (Bonferroni-corrected P < 0.05 for all). The intersession CVs for the AFI and GRE images were also significantly smaller in Int-FB, Seq-BH, and qTx than in Seq-FB (Bonferroni-corrected P < 0.05 for all). The in-plane CVs for the AFI and GRE images in Seq-FB, Int-FB, and Seq-BH were significantly smaller than in qTx (Bonferroni-corrected P < 0.01 for all). DATA CONCLUSION: Using interleaved acquisition during calibration scans of pTx for 7T brain MRI improved the repeatability of B0 /B1+ mapping, AFI, and GRE images, without BH. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2017.

The Effect of Single-Scan and Scan-Pair Intensity Inhomogeneity Correction Methods on Repeatability of Voxel-Based Morphometry With Multiple Magnetic Resonance Scanners.

OBJECTIVE: The aim of this study was to investigate the effects of single-scan and scan-pair intensity inhomogeneity correction methods on the repeatability of voxel-based morphometry (VBM) using images acquired with multiple magnetic resonance (MR) scanners. METHODS: Three-dimensional T1-weighed MR images of the brain were obtained from 22 healthy participants using each of 5 MR scanners, yielding 110 images (5 scanners × 22 subjects) in total. Six patterns of intensity inhomogeneity corrections (no correction, single-scan corrections, and scan-pair correction, and their combinations) were applied in the VBM procedure to investigate the effect of the corrections on the repeatability of gray and white matter volume measurements. RESULTS: Single-scan and scan-pair intensity inhomogeneity corrections significantly reduced the variance in spatially normalized gray and white matter volumes. However, combining the 2 methods did not significantly improve the repeatability when evaluated as whole brain. CONCLUSIONS: Single-scan and scan-pair intensity inhomogeneity corrections improved the repeatability of gray and white matter volumes obtained by multiple MR scanners and assessed by VBM.

Noninvasive Assessment of Oxygen Extraction Fraction in Chronic Ischemia Using Quantitative Susceptibility Mapping at 7 Tesla.

BACKGROUND AND PURPOSE: The oxygen extraction fraction (OEF) is an effective metric to evaluate metabolic reserve in chronic ischemia. However, OEF is considered to be accurately measured only when using positron emission tomography (PET). Thus, we investigated whether OEF maps generated by magnetic resonance quantitative susceptibility mapping (QSM) at 7 Tesla enabled detection of OEF changes when compared with those obtained with PET. METHODS: Forty-one patients with chronic stenosis/occlusion of the unilateral internal carotid artery or middle cerebral artery were examined using 7 Tesla-MRI and PET scanners. QSM images were obtained from 3-dimensional T2*-weighted images, using a multiple dipole-inversion algorithm. OEF maps were generated based on susceptibility differences between venous structures and brain tissues on QSM images. OEF ratios of the ipsilateral middle cerebral artery territory against the contralateral side were calculated on the QSM-OEF and PET-OEF images, using an anatomic template. RESULTS: The OEF ratio in the middle cerebral artery territory showed significant correlations between QSM-OEF and PET-OEF maps (r=0.69; P<0.001), especially in patients with a substantial increase in the PET-OEF ratio of 1.09 (r=0.79; P=0.004), although showing significant systematic biases for the agreements. An increased QSM-OEF ratio of >1.09, as determined by receiver operating characteristic analysis, showed a sensitivity and specificity of 0.82 and 0.86, respectively, for the substantial increase in the PET-OEF ratio. Absolute QSM-OEF values were significantly correlated with PET-OEF values in the patients with increased PET-OEF. CONCLUSIONS: OEF ratios on QSM-OEF images at 7 Tesla showed a good correlation with those on PET-OEF images in patients with unilateral steno-occlusive internal carotid artery/middle cerebral artery lesions, suggesting that noninvasive OEF measurement by MRI can be a substitute for PET.

Detection of changes in the periaqueductal gray matter of patients with episodic migraine using quantitative diffusion kurtosis imaging: preliminary findings.

INTRODUCTION: The periaqueductal gray matter (PAG) is considered to play an important role in generating migraine, but findings from imaging studies remain unclear. Therefore, we investigated whether diffusion kurtosis imaging (DKI) can detect changes in the PAG of migraine patients. METHODS: We obtained source images for DKI from 20 patients with episodic migraine and 20 healthy controls using a 3 T magnetic resonance imaging scanner. Mean kurtosis (MK), fractional anisotropy (FA), and mean diffusivity (MD) maps were generated, and the values of the PAG and other deep gray and white matter structures were automatically measured using an atlas-based region-of-interest analysis. The metrics of these structures were compared between the patients and controls. RESULTS: The MK and MD values of the PAG were significantly increased in the migraine patients compared with the controls (p < 0.05). The FA values were not significantly different. There were no significant differences in the metrics of the other structures between the patients and controls. The MK values of the PAG were significantly positively correlated with both age and the untreated period in the patient group under univariate analysis (r = 0.53 and 0.56, respectively; p < 0.05) but not multivariate analysis. CONCLUSIONS: DKI detected significant increases in the MK and MD values of the PAG in patients with migraine, which suggests that structural changes in the PAG are associated with the pathophysiological mechanisms of migraine.

Genome-wide association study identifies HLA-DP as a susceptibility gene for pediatric asthma in Asian populations.

Asthma is a complex phenotype influenced by genetic and environmental factors. We conducted a genome-wide association study (GWAS) with 938 Japanese pediatric asthma patients and 2,376 controls. Single-nucleotide polymorphisms (SNPs) showing strong associations (P<1×10(-8)) in GWAS were further genotyped in an independent Japanese samples (818 cases and 1,032 controls) and in Korean samples (835 cases and 421 controls). SNP rs987870, located between HLA-DPA1 and HLA-DPB1, was consistently associated with pediatric asthma in 3 independent populations (P(combined) = 2.3×10(-10), odds ratio [OR] = 1.40). HLA-DP allele analysis showed that DPA1*0201 and DPB1*0901, which were in strong linkage disequilibrium, were strongly associated with pediatric asthma (DPA1*0201: P = 5.5×10(-10), OR = 1.52, and DPB1*0901: P = 2.0×10(-7), OR = 1.49). Our findings show that genetic variants in the HLA-DP locus are associated with the risk of pediatric asthma in Asian populations.

Noninvasive evaluation of collateral blood flow through circle of Willis in cervical carotid stenosis using selective magnetic resonance angiography.

BACKGROUND: Preoperative assessment of intracranial collateral circulation is helpful in predicting cerebral ischemia during surgical procedures for cervical internal carotid artery (ICA) stenosis. However, magnetic resonance angiography (MRA) and other less-invasive techniques cannot evaluate collateral blood flow because these techniques are nonselective. Hence, by using a newly developed selective MRA technique, we attempted to visualize collaterals via the circle of Willis in patients with ICA stenosis. METHODS: Twelve patients who underwent carotid endarterectomy were prospectively examined with a 1.5-T MR scanner. Both selective and nonselective MRA were obtained using a 3-dimensional time-of-flight technique, with or without a cylindrical saturation pulse that suppresses the flow signal from the region of the target ICA. Maximum intensity projection MRA images were generated and compared with digital subtraction angiography (DSA) images. RESULTS: In all patients, the distal flow signal of the ipsilateral ICA was completely suppressed on selective MRA compared with nonselective MRA. In addition, collateral blood flow through the anterior and posterior communicating arteries was visualized in 5 and 2 patients, respectively. These findings corresponded well with the DSA imaging. CONCLUSIONS: Selective MRA techniques can readily suppress signals from the distal blood flow of the target artery and visualize the presence of collateral flows through the circle of Willis in patients with cervical ICA stenosis.

Uniformly positive or negative correlation of cerebral gray matter regions with driving safety behaviors of healthy older drivers.

This study investigated the relationship between cerebral gray matter (GM) regions and driving safety behaviors (DSBs) of 98 older drivers without dementia (mean age, 77.72 ± 3.677 years). Their DSBs were evaluated on actual vehicles running on a closed-circuit course. The DSB was scored in six categories: DSB1, visual search behavior; DSB2, speeding; DSB3, signaling of the indicator; DSB4, vehicle stability; DSB5, positioning; and DSB6, steering. The scores were calculated by a single driving instructor; larger scores indicated safer driving performances. Regional GM volumes were measured with voxel-based morphometry by magnetic resonance imaging (MRI). Out of 56 GM regions, 18 were correlated with DSB categories except for DSB4. When a single GM region was correlated with multiple DSB categories, a positive or negative response was uniformly determined for the respective region despite clear differences in the DSB categories. This result suggests the possible existence of two contradictory mechanisms in the brain for DSB. The left postcentral gyrus may largely function in regulating DSBs because it was negatively correlated with five of six DSB categories. Thus, MRI's measurement of regional GM volumes may help deepen the understanding of the diversity and complexity inherent in brain functions for DSBs.

Association Between Serum NT-proBNP and Gray Matter Atrophy Patterns in an Older Japanese Population: The Hisayama Study.

Several population-based studies have reported that higher serum N-terminal pro-brain natriuretic peptide (NT-proBNP) levels are associated with brain morphological changes. However, no population-based studies have examined the relationship between serum NT-proBNP and various regional brain volumes in detail. We here analyzed the brain MRI data of 1 201 community-dwelling Japanese aged ≥65 years. Regional gray matter volumes (GMV) and intracranial volume (ICV) were estimated by applying voxel-based morphometry (VBM) methods. The associations of serum NT-proBNP with regional GMV/ICV were examined by analysis of covariance. The regional gray matter atrophy patterns associated with elevated serum NT-proBNP levels were investigated using VBM without a priori regions of interest. The multivariable-adjusted means of the frontal, temporal, hippocampal, parahippocampal, and entorhinal GMV/ICV decreased significantly with elevated serum NT-proBNP levels (all p for trend and q values of false discovery rate correction < .05). In VBM, elevated serum NT-proBNP levels were correlated with atrophy of the bilateral hippocampi, bilateral amygdalas, bilateral parahippocampal gyri, bilateral entorhinal areas, bilateral fusiform gyri, left middle temporal gyrus, left inferior temporal gyrus, right central operculum, right posterior orbital gyrus, bilateral middle frontal gyri, anterior cingulate gyrus and bilateral medial frontal cortices. In a sensitivity analysis excluding 254 participants with mild cognitive impairment or dementia, serum NT-proBNP levels were correlated with atrophy of the bilateral hippocampi, bilateral amygdalas, bilateral parahippocampal gyri, bilateral fusiform gyri, and left middle frontal gyrus. Our data suggest that elevated serum NT-proBNP levels are associated with gray matter atrophy in brain regions that play an important role in cognitive function.

Association between milder brain deformation before a shunt operation and improvement in cognition and gait in idiopathic normal pressure hydrocephalus.

We investigated the association between the degree of deformation of the brain before shunt operation and improvement of gait and cognitive impairment after shunt operation in 16 patients with idiopathic normal pressure hydrocephalus (iNPH). We evaluated gait and cognitive impairment and measured the cerebrospinal fluid volume in the ventricles/sylvian fissure (vVS) and the subarachnoid space at high convexity/midline areas (vHCM) using MR images with voxel-based morphometry before and 3 months after shunt operation. We used the ratio of vVS to vHCM (vVS/vHCM) as an index of the severity of brain deformation. After shunt operation, improvements were observed in gait, as shown by the Timed Up and Go (TUG) test and 10-meter reciprocating walking test (WT), and in cognitive function, as shown by the Mini-Mental State Examination, Alzheimer Disease Assessment Scale, Frontal Assessment battery (FAB), and Trail Making test A (TMT-A). The vVS/vHCM ratio was negatively correlated with improvement of the FAB, TMT-A and TUG. Preoperative vVS/vHCM was not significantly correlated with preoperative clinical assessments. The rate of change of vVS/vHCM was positively correlated with improvement in the WT. The improvements of gait and cognitive function were larger in iNPH patients with milder deformation of the brain before shunt operation.

Assessment of the accuracy of a Bayesian estimation algorithm for perfusion CT by using a digital phantom.

INTRODUCTION: A new deconvolution algorithm, the Bayesian estimation algorithm, was reported to improve the precision of parametric maps created using perfusion computed tomography. However, it remains unclear whether quantitative values generated by this method are more accurate than those generated using optimized deconvolution algorithms of other software packages. Hence, we compared the accuracy of the Bayesian and deconvolution algorithms by using a digital phantom. METHODS: The digital phantom data, in which concentration-time curves reflecting various known values for cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and tracer delays were embedded, were analyzed using the Bayesian estimation algorithm as well as delay-insensitive singular value decomposition (SVD) algorithms of two software packages that were the best benchmarks in a previous cross-validation study. Correlation and agreement of quantitative values of these algorithms with true values were examined. RESULTS: CBF, CBV, and MTT values estimated by all the algorithms showed strong correlations with the true values (r = 0.91-0.92, 0.97-0.99, and 0.91-0.96, respectively). In addition, the values generated by the Bayesian estimation algorithm for all of these parameters showed good agreement with the true values [intraclass correlation coefficient (ICC) = 0.90, 0.99, and 0.96, respectively], while MTT values from the SVD algorithms were suboptimal (ICC = 0.81-0.82). CONCLUSIONS: Quantitative analysis using a digital phantom revealed that the Bayesian estimation algorithm yielded CBF, CBV, and MTT maps strongly correlated with the true values and MTT maps with better agreement than those produced by delay-insensitive SVD algorithms.

Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra provides reduced effect of scanner for cortex volumetry with atlas-based method in healthy subjects.

INTRODUCTION: This study aimed to investigate whether the effect of scanner for cortex volumetry with atlas-based method is reduced using Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra (DARTEL) normalization compared with standard normalization. METHODS: Three-dimensional T1-weighted magnetic resonance images (3D-T1WIs) of 21 healthy subjects were obtained and evaluated for effect of scanner in cortex volumetry. 3D-T1WIs of the 21 subjects were obtained with five MRI systems. Imaging of each subject was performed on each of five different MRI scanners. We used the Voxel-Based Morphometry 8 tool implemented in Statistical Parametric Mapping 8 and WFU PickAtlas software (Talairach brain atlas theory). The following software default settings were used as bilateral region-of-interest labels: "Frontal Lobe," "Hippocampus," "Occipital Lobe," "Orbital Gyrus," "Parietal Lobe," "Putamen," and "Temporal Lobe." RESULTS: Effect of scanner for cortex volumetry using the atlas-based method was reduced with DARTEL normalization compared with standard normalization in Frontal Lobe, Occipital Lobe, Orbital Gyrus, Putamen, and Temporal Lobe; was the same in Hippocampus and Parietal Lobe; and showed no increase with DARTEL normalization for any region of interest (ROI). CONCLUSION: DARTEL normalization reduces the effect of scanner, which is a major problem in multicenter studies.

Penumbral imaging by using perfusion computed tomography and perfusion-weighted magnetic resonance imaging: current concepts.

Perfusion computed tomography and perfusion-weighted magnetic resonance imaging are used to evaluate the extent of the area with ischemic penumbra; however, different parameters, algorithms, and software packages show significant discrepancies in the size of perfusion abnormalities, which should be minimized. Recently, cross-validation studies were performed using digital phantoms and have elucidated the precision and reliability of various penumbral imaging techniques. These research initiatives can promote further multicenter trials on recanalization therapies by providing accurate inclusion/exclusion criteria for appropriate patient selection.

Reversibility of brain morphology after shunt operations and preoperative clinical symptoms in patients with idiopathic normal pressure hydrocephalus.

AIM: Brain deformations might prevent clinical symptoms from worsening in patients with idiopathic normal pressure hydrocephalus (iNPH). We investigated the relationship between reversibility of brain morphology after shunt operations and preoperative clinical symptoms in iNPH patients. METHODS: Using head magnetic resonance images with voxel-based morphometry, we measured the cerebrospinal fluid volume in the combined areas of the lateral and third ventricles and Sylvian fissure (the volume of the ventricles and Sylvian fissure (vVS)) and the volume of the subarachnoid space at high convexity and midline areas (vHCM) before and 1 year after lumboperitoneal shunt operations in 12 patients with shunt-responsive iNPH. We used the ratio of normalized vVS to normalized vHCM (nvVS/nvHCM) as an index of the severity of the brain deformation. The degree of reversibility of the brain morphology after the shunt operation was defined as the change ratio of the preoperative nvVS/nvHCM to the postoperative nvVS/nvHCM (CR-nvVS/nvHCM). Higher CR-nvVS/nvHCM values indicated more improvement in the brain deformation. In addition, we rated the severity of the white matter lesions on the preoperative magnetic resonance images based on the Fazekas scale. Dependency in activities of daily living, gait and cognition were evaluated before and 1 year after the shunt operations. RESULTS: After the shunt operations, the nvVS/nvHCM and nvVS decreased significantly, and nvHCM increased significantly. The CR-nvVS/nvHCM negatively correlated with the preoperative severity of dependency in activities of daily living, gait and cognitive impairments. The CR-nvVS/nvHCM negatively correlated with the Fazekas scale, but not with age, duration of the disease and cerebrospinal fluid pressure. CONCLUSIONS: Reversibility of brain morphology, which varied among iNPH patients, would prevent clinical symptoms from worsening in iNPH patients. The presence of white matter lesions reduced the degree of reversibility of the brain deformations in iNPH patients.