Shinsuke Narumi

Detection of changes in cerebrospinal fluid space in idiopathic normal pressure hydrocephalus using voxel-based morphometry

IntroductionWe attempted to detect alterations in the cerebrospinal fluid (CSF) space in patients with idiopathic normal pressure hydrocephalus (iNPH) using voxel-based morphometry (VBM).MethodsWe obtained sagittal volume images of the entire head by three-dimensional T1-weighted magnetic resonance imaging and compared the regional distribution of CSF in 12 patients with iNPH, 14 patients with Alzheimer’s disease (AD), and 17 healthy individuals using VBM with automatically extracted CSF objects.ResultsVBM demonstrated significant widening at the lateral ventricles and Sylvian fissures and narrowing of the CSF space at the high convexity/midline areas in iNPH patients, compared to the AD patients and healthy controls (p < 0.05, after correction with a false-discovery rate). In addition, the ratio of the CSF volume in the lateral ventricle/Sylvian fissure area to that in the high convexity/midline area in iNPH patients (3.9 ± 1.2) was remarkably greater than that in AD patients (1.2 ± 0.3) and controls (0.9 ± 0.3; one-way ANOVA, p < 0.001; post hoc Tukey’s test, p < 0.001); we could discriminate iNPH patients from those in the other two groups without any overlap, when using a cutoff level of 1.9.ConclusionVBM using CSF objects can be used to delineate the characteristic alteration of the CSF space in iNPH patients, which has been evaluated by visual interpretation.

Evaluating Middle Cerebral Artery Atherosclerotic Lesions in Acute Ischemic Stroke Using Magnetic Resonance T1-weighted 3-Dimensional Vessel Wall Imaging

BACKGROUND Atherosclerotic lesions in intracranial arteries are a leading cause of ischemic stroke. Magnetic resonance angiography (MRA) is often used to assess atherosclerotic changes by detecting luminal narrowing, whereas it cannot directly visualize atherosclerotic lesions. Here, we used a 3-dimensional vessel wall imaging (3D-VWI) technique to evaluate intracranial arterial wall changes in acute stroke. METHODS Eighteen consecutive patients with acute noncardioembolic stroke in the middle cerebral artery (MCA) territory who were prospectively examined with a 1.5-T magnetic resonance scanner were studied. T1-weighted (T1-W) 3D-VWI was obtained using a flow-sensitized 3D fast-spin echo technique. Wall thickening of MCA that suggests atherosclerotic plaques was visually evaluated and the contrast ratio (CR) of signal intensity of the lesions to that of the corpus callosum was calculated and compared with stenotic changes by MRA. RESULTS Wall thickenings of the MCA ipsilateral and contralateral to the lesion were observed in almost all patients on 3D-VWI (94.4% and 94.4%, respectively), whereas MRA showed stenotic changes of 50% only in 1 patient (5.9%; P < .001). The CR of the thickened wall in the ipsilateral MCA was significantly higher than that in the contralateral MCA (median, .53 and .45, respectively; P = .028), suggesting of unstable plaques consisting of hemorrhage or lipid. CONCLUSIONS The T1-W 3D-VWI can provide direct visualization of atherosclerotic lesions of the intracranial arteries in stroke patients, and it can detect signal change suggestive of unstable plaque.

Carotid plaque signal differences among four kinds of T1-weighted magnetic resonance imaging techniques: A histopathological correlation study

IntroductionSeveral magnetic resonance (MR) imaging techniques are used to examine atherosclerotic plaque of carotid arteries; however, the best technique for visualizing intraplaque characteristics has yet to be determined. Here, we directly compared four kinds of T1-weighted (T1W) imaging techniques with pathological findings in patients with carotid stenosis.MethodsA total of 31 patients who were candidates for carotid endarterectomy were prospectively examined using a 1.5-T MRI scanner, which produced four kinds of T1W images, including non-gated spin echo (SE), cardiac-gated black-blood (BB) fast-SE (FSE), magnetization-prepared rapid acquisition with gradient echo (MPRAGE), and source image of three-dimensional time-of-flight MR angiography (SI-MRA). The signal intensity of the carotid plaque was manually measured, and the contrast ratio (CR) against the adjacent muscle was calculated. CRs from the four imaging techniques were compared to each other and correlated with histopathological specimens.ResultsCRs of the carotid plaques mainly containing fibrous tissue, lipid/necrosis, and hemorrhage were significantly different with little overlaps (range: 0.92–1.15, 1.22–1.52, and 1.55–2.30, respectively) on non-gated SE. However, BB-FSE showed remarkable overlaps among the three groups (0.89–1.10, 1.07–1.23, and 1.01–1.42, respectively). MPRAGE could discriminate fibrous plaques from hemorrhagic plaques but not from lipid/necrosis-rich plaques: (0.77–1.07, 1.45–2.43, and 0.85–1.42, respectively). SI-MRA showed the same tendencies (1.01–1.39, 1.45–2.57, and 1.12–1.39, respectively).ConclusionAmong T1W MR imaging techniques, non-gated SE images can more accurately characterize intraplaque components in patients who underwent CEA when compared with cardiac-gated BB-FSE, MPRAGE, and SI-MRA images.

Prediction of carotid plaque characteristics using non-gated MR imaging: correlation with endarterectomy specimens.

BACKGROUND AND PURPOSE: Electrocardiographic gating, commonly used in MR carotid plaque imaging, can negatively affect intraplaque contrast if the TR is inappropriate. The present study aimed to determine whether a non-gated technique with appropriate TRs can accurately evaluate intraplaque characteristics in specimens excised by CEA. MATERIALS AND METHODS: We prospectively examined 40 consecutive patients who underwent CEA (59–82 years of age) by using a 1.5T scanner. Axial T1WI with a TR of 500 ms and PDWI and T2WI with a TR of 3000 ms with a self-navigated rotating-blade scan instead of cardiac gating were obtained. Signal intensities of the plaque and adjacent muscle were measured, and the CR on T1WI, PDWI, and T2WI as well as the gray-scale median on US were correlated with the pathologic findings of the CEA specimens. RESULTS: On T1WI, the CRs of the carotid plaques differed significantly among groups in which the main components were histologically confirmed as fibrous tissue, lipid/necrosis, and hemorrhage (0.54–1.17, 1.16–1.53, and 1.40–2.29, respectively). The sensitivity and specificity for discriminating lipid/necrosis/hemorrhage from fibrous tissue were 96% and 100%, respectively. On T2WI, the CRs of plaques with lipid/necrosis were significantly higher than those of other groups, but the CRs on PDWI and the gray-scale median on US were not significantly different among the groups. CONCLUSIONS: Non-gated MR plaque imaging, particularly T1WI, can readily predict the intraplaque main components of the carotid artery with high sensitivity and specificity.

1H-magnetic resonance spectroscopy indicates damage to cerebral white matter in the subacute phase after CO poisoning

Objective The authors examined whether 1H-magnetic resonance spectroscopy (MRS) can identify damage to the centrum semiovale in the subacute phase after CO exposure. Methods Subjects comprised 29 adult patients who were treated with hyperbaric oxygenation within a range of 4–95 h (mean 18.7 h) after CO exposure. Subjects were classified into three groups according to clinical behaviours: Group A, patients with transit acute symptoms only; Group P, patients with persistent neurological symptoms; and Group D, patients with ‘delayed neuropsychiatric sequelae’ occurring after a lucid interval. MRS of bilateral centrum semiovale was performed 2 weeks after CO inhalation for all patients and 13 healthy volunteers. The mean ratios of choline-containing compounds/creatine (meanCho/Cr) and N-acetylaspartate/Cr (meanNAA/Cr) for bilateral centrum semiovale were calculated and compared between the three CO groups and controls. Myelin basic protein (MBP) concentration in cerebrospinal fluid was examined at 2 weeks to evaluate the degree of demyelination in patients. Results MBP concentration was abnormal for almost all patients in Groups P and D, but was not abnormal for any Group A patients. The meanCho/Cr ratios were significantly higher in Groups P and D than in Group A. No significant difference in meanNAA/Cr ratio was seen between the three pathological groups and controls. A significant correlation was identified between MBP and meanCho/Cr ratio. Conclusions These results suggest that the Cho/Cr ratio in the subacute phase after CO intoxication represents early demyelination in the centrum semiovale, and can predict chronic neurological symptoms.

Predicting Carotid Plaque Characteristics Using Quantitative Color-Coded T1-Weighted MR Plaque Imaging: Correlation with Carotid Endarterectomy Specimens

BACKGROUND AND PURPOSE: MR plaque imaging is used to evaluate the risk of embolic complications during carotid endarterectomy and carotid artery stent placement. However, its performance for characterizing intraplaque components has varied across studies and is generally suboptimal. Hence, we correlated MR imaging results with histologic findings to determine whether a combination of high-contrast T1-weighted imaging and quantitative image analysis could readily determine plaque characteristics. MATERIALS AND METHODS: We prospectively examined 40 consecutive patients before carotid endarterectomy by using a 1.5T scanner and axial T1-weighted spin-echo images under optimized scanning conditions. The percentage areas of intraplaque fibrous tissue, lipid/necrosis, and hemorrhage were calculated automatically by using the software with previously reported cutoff values and were compared with those of the specimens. The thickness of the fibrous cap was also measured manually. RESULTS: The percentage areas of fibrous, lipid/necrotic, and hemorrhagic components were 5.7%–98.7%, 1.3%–65.7%, and 0%–82.0%, respectively, as determined by the MR images, whereas the corresponding values were 4.8%–92.3%, 7.0%–93.8%, and 0%–70.4%, respectively, as determined by histologic examination. Significant positive correlation and agreement were observed between MR images and histologic specimens (r = 0.92, 0.79, and 0.92; intraclass correlation coefficients = 0.91, 0.67, and 0.89; respectively). Thickness of the fibrous caps on MR images (0.21–0.87 mm) and in the specimens (0.14–0.83 mm) also showed positive correlation and agreement (r = 0.61, intraclass correlation coefficient = 0.59). CONCLUSIONS: Quantitative analysis of high-contrast T1-weighted images can accurately evaluate the composition of carotid plaques in carotid endarterectomy candidates.

Visual discrimination among patients with depression and schizophrenia and healthy individuals using semiquantitative color-coded fast spin-echo T1- weighted magnetic resonance imaging

IntroductionFast spin-echo (FSE) T1-weighted (T1W) magnetic resonance imaging (MRI) at 3T, which is sensitive to neuromelanin-related contrast, can quantitatively detect signal alterations in the locus ceruleus (LC) and the substantia nigra pars compacta (SNc) of depressive and schizophrenic patients; however, its qualitative diagnostic performance remains unknown. We investigated whether visual interpretation of semiquantitative color maps can be used for discriminating between depressive and schizophrenic patients and healthy individuals.MethodsWe retrospectively examined 23 patients with major depression, 23 patients with schizophrenia, and 23 age-matched healthy controls by using a FSE-T1W MRI technique. Semiquantitative color maps of sections through the LC and SNc were visually interpreted by nine raters using a continuous confidence rating scale for receiver operating characteristic (ROC) analysis.ResultsThe area under the ROC curve (Az), which reflects the performance in differentiating between depressive patients and controls, was 0.88, and the sensitivity and specificity at the maximum likelihood were 76% and 83%, respectively. In contrast, the Az value, sensitivity, and specificity values between schizophrenics and controls and between depressives and schizophrenics were 0.66 and 0.69, 42% and 48%, and 82% and 84%, respectively.ConclusionSemiquantitative, color-coded FSE-T1W MRI at 3T can be used for visually differentiating depressive patients from healthy individuals with a substantially high likelihood, but this technique cannot be applied to distinguish schizophrenic patients from the other two groups.

Carotid Plaque Characterization Using 3D T1-Weighted MR Imaging with Histopathologic Validation: A Comparison with 2D Technique

BACKGROUND AND PURPOSE: 3D FSE T1WI has recently been used for carotid plaque imaging, given the potential advantages in contrast and spatial resolutions. However, its diagnostic performance remains unclear. Hence, we compared the ability of this technique to readily assess plaque characteristics with that of conventional images and validated the results with histologic classification. MATERIALS AND METHODS: We prospectively examined 34 patients with carotid stenosis who underwent carotid endarterectomy by using 1.5T scanners and obtained 3D-FSE T1WI and 2D spin-echo T1WI scans. After generating reformatted images obtained from the 3D-FSE T1-weighted images, we calculated the contrast ratios for the plaques and the adjacent muscles and compared these findings with the pathologic classifications. RESULTS: Carotid plaques were histologically classified as types VII, VIII, IV–V, or VI. With 3D-FSE T1WI, the range of contrast ratios for each classification was the following: 0.94–0.97 (median, 0.95), 0.95–1.29 (median, 1.10), 1.33–1.54 (median, 1.42), and 1.53–2.12 (median, 1.80), respectively. With 2D imaging, the range of contrast ratios for each classification was the following: 0.79–1.02 (median, 0.90), 0.88–1.19 (median, 1.01), 1.17–1.46 (median, 1.23), and 1.55–2.51 (median, 2.07), respectively. Results were significantly different among the 4 groups (P < .001). Sensitivity and specificity for discriminating vulnerable plaques (IV–VI) from stable plaques (VII, VIII) were both 100% for the 3D technique and 100% and 91%, respectively, for the 2D technique. CONCLUSIONS: 3D-FSE T1WI accurately characterizes intraplaque components of the carotid artery, with excellent sensitivity and specificity compared with those of 2D-T1WI.

Detection of Vessel Wall Lesions in Spontaneous Symptomatic Vertebrobasilar Artery Dissection Using T1-weighted 3-dimensional Imaging

BACKGROUND Spontaneous intracranial vertebrobasilar artery dissection (iVBD) is a cause of ischemic stroke and subarachnoid hemorrhage in young adults that can be detected noninvasively by using multisequence magnetic resonance imaging (MRI). However, MRI findings are sometimes difficult to interpret, and its accuracy tends to be suboptimal, especially during the acute period. Therefore, we investigated whether 3-dimensional (3D) vessel wall imaging (VWI) technique could readily detect iVBD lesions in acute phase patients. METHODS Sixteen consecutive patients with acute ischemic stroke caused by iVBD were prospectively examined with a 1.5-T magnetic resonance scanner. T1-weighted (T1W) 3D-VWI was obtained using a flow-sensitized 3D fast spin-echo technique. In addition, multisequence MRI comprising magnetic resonance angiography (MRA), basiparallel anatomical scanning (BPAS), and axial T1W imaging (T1WI) were also examined. Presence of luminal stenosis, aneurysmal dilatation, intramural high signal, and intimal flap/double lumen of the vertebral and basilar arteries were visually assessed using each technique. RESULTS On 3D-VWI, luminal stenosis, aneurysmal dilatation, intramural high signal, and intimal flap were observed in 16 (100%), 11 (68.8%), 16 (100%), and 1 (6.3%) patients, respectively. In contrast, on conventional techniques, these findings were observed in 15 (93.8%, MRA with BPAS), 12 (75.0%, MRA with BPAS), 12 (75.0%, T1WI), and 12 (75.0%, MRA) patients, respectively. CONCLUSIONS The T1W 3D-VWI can directly visualize vessel wall iVBD lesions during the acute period of stroke compared with multisequence MRI.

Optimal MR Plaque Imaging for Cervical Carotid Artery Stenosis in Predicting the Development of Microembolic Signals during Exposure of Carotid Arteries in Endarterectomy: Comparison of 4 T1-Weighted Imaging Techniques

BACKGROUND AND PURPOSE: Preoperative identification of plaque vulnerability may allow improved risk stratification for patients considered for carotid endarterectomy. The present study aimed to determine which plaque imaging technique, cardiac-gated black-blood fast spin-echo, magnetization-prepared rapid acquisition of gradient echo, source image of 3D time-of-flight MR angiography, or noncardiac-gated spin-echo, most accurately predicts development of microembolic signals during exposure of carotid arteries in carotid endarterectomy. MATERIALS AND METHODS: Eighty patients with ICA stenosis (≥70%) underwent the 4 sequences of preoperative MR plaque imaging of the affected carotid bifurcation and then carotid endarterectomy under transcranial Doppler monitoring of microembolic signals in the ipsilateral middle cerebral artery. The contrast ratio of the carotid plaque was calculated by dividing plaque signal intensity by sternocleidomastoid muscle signal intensity. RESULTS: Microembolic signals during exposure of carotid arteries were detected in 23 patients (29%), 3 of whom developed new neurologic deficits postoperatively. Those deficits remained at 24 hours after surgery in only 1 patient. The area under the receiver operating characteristic curve to discriminate between the presence and absence of microembolic signals during exposure of the carotid arteries was significantly greater with nongated spin-echo than with black-blood fast spin-echo (difference between areas, 0.258; P < .0001), MPRAGE (difference between areas, 0.106; P = .0023), or source image of 3D time-of-flight MR angiography (difference between areas, 0.128; P = .0010). Negative binomial regression showed that in the 23 patients with microembolic signals, the contrast ratio was associated with the number of microembolic signals only in nongated spin-echo (risk ratio, 1.36; 95% confidence interval, 1.01–1.97; P < .001). CONCLUSIONS: Nongated spin-echo may predict the development of microembolic signals during exposure of the carotid arteries in carotid endarterectomy more accurately than other MR plaque imaging techniques.