Shunrou Fujiwara

Variability in Absolute Apparent Diffusion Coefficient Values across Different Platforms May Be Substantial: A Multivendor, Multi-institutional Comparison Study

PURPOSE To determine whether and to what degree absolute apparent diffusion coefficient (ADC) values vary between different imagers, vendors, field strengths, and intraimager conditions. MATERIALS AND METHODS Informed consent and institutional review board approval were obtained. Diffusion-weighted (DW) images with nearly identical parameters were obtained at 1.5 and 3.0 T from 12 healthy volunteers at seven institutions by using 10 magnetic resonance (MR) imagers provided by four different vendors. ADC maps were generated from isotropic DW maps, and images with a b value of 0 sec/mm(2) were generated by using in-house software. The mean pixel values for the brain tissues were calculated for evaluating the differences among coil systems, imagers, vendors, and magnetic field strengths. RESULTS The absolute ADC values of gray and white matter from the same vendor varied substantially: 4%-9% at 1.5 and 3.0 T. With the exception of one vendor, the intervendor variability at 1.5 T was as high as 7%. Moreover, there was substantial intraimager variability, up to 8%, depending on the coil systems in certain imagers. CONCLUSION There is significant variability in ADC values depending on the coil systems, imagers, vendors, and field strengths used for MR imaging. The relative ADC values may be more suitable than absolute ADC values for evaluating diffusion abnormalities in patients enrolled in multicenter acute ischemic stroke trials.

High-resolution diffusion tensor imaging for the detection of diffusion abnormalities in the trigeminal nerves of patients with trigeminal neuralgia caused by neurovascular compression.

To detect diffusion abnormalities in the trigeminal nerves of patients with trigeminal neuralgia (TN) caused by neurovascular compression (NVC) by using a high‐resolution diffusion tensor imaging (HR‐DTI) technique.

Postoperative Cerebral White Matter Damage Associated with Cerebral Hyperperfusion and Cognitive Impairment after Carotid Endarterectomy: A Diffusion Tensor Magnetic Resonance Imaging Study

Background: Cerebral hyperperfusion after carotid endarterectomy (CEA), even when asymptomatic, often impairs cognitive function. However, conventional magnetic resonance (MR) imaging rarely demonstrates structural brain damage associated with postoperative cognitive impairment. MR diffusion tensor imaging (DTI) is potentially more sensitive for detection of white matter damage. Among the common parameters derived by DTI, fractional anisotropy (FA) is a marker of tract integrity, and mechanical disruption of axonal cylinders and loss of continuity of myelin sheaths may be responsible for reduced FA in white matter. The purpose of the present study was to determine whether postoperative cerebral white matter damage that can be detected by FA derived by DTI is associated with cerebral hyperperfusion after CEA and correlates with postoperative cognitive impairment. Methods: In 70 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), cerebral blood flow (CBF) was measured using single-photon emission computed tomography (SPECT) before and immediately after CEA and on postoperative day 3. FA values in cerebral white matter were assessed using DTI before and 1 month after surgery. These values were normalized and analyzed using statistical parametric mapping 5. In each corresponding voxel in the pre- and postoperative normalized FA maps of each patient, a postoperative FA value minus a preoperative FA value was calculated, and a voxel with postoperatively reduced FA was defined based on data obtained from healthy volunteers. The number of voxels with postoperatively reduced FA was calculated and defined as the volume with postoperatively reduced FA. Neuropsychological testing, consisting of the Wechsler Adult Intelligence Scale Revised, the Wechsler Memory Scale and the Rey-Osterreith Complex Figure test, was also performed preoperatively and after the first postoperative month. Postoperative cognitive impairment on neuropsychological testing in each patient was defined based on data obtained from patients with asymptomatic unruptured cerebral aneurysms. Results: Post-CEA hyperperfusion on brain perfusion SPECT (CBF increase ≥100% compared with preoperative values) and postoperative cognitive impairment on neuropsychological testing were observed in 11 (16%) and 9 patients (13%), respectively. The volume with postoperatively reduced FA in cerebral white matter ipsilateral to surgery was significantly greater in patients with post-CEA hyperperfusion than in those without (p < 0.0001). This volume in cerebral white matter ipsilateral to surgery was also significantly associated with postoperative cognitive impairment (95% confidence interval, 1.559–8.853; p = 0.0085). Conclusions: Cerebral hyperperfusion after CEA results in postoperative cerebral white matter damage that correlates with postoperative cognitive impairment.

Brain Temperature Measured Using Proton MR Spectroscopy Detects Cerebral Hemodynamic Impairment in Patients With Unilateral Chronic Major Cerebral Artery Steno-Occlusive Disease Comparison With Positron Emission Tomography

Background and Purpose— Brain temperature is determined by the balance between heat produced by cerebral energy turnover and heat removed by cerebral blood flow. The purpose of the present study was to investigate whether brain temperature measured noninvasively using proton MR spectroscopy can detect cerebral hemodynamic impairment in patients with unilateral chronic internal carotid or middle cerebral artery occlusive disease when compared with positron emission tomography. Methods— Brain temperature, cerebral blood flow, and metabolism were measured using proton MR spectroscopy and 15O-positron emission tomography, respectively, in 21 normal subjects and 37 patients. Positron emission tomography images were coregistered with MR images and resliced automatically using image analysis software. Regions of interest placed in both cerebral hemispheres on MR images were automatically superimposed in these resliced positron emission tomography images. Results— A significant correlation was observed between brain temperature difference (affected hemisphere–contralateral hemisphere) and both cerebral blood volume and oxygen extraction fraction ratio (affected hemisphere/contralateral hemisphere; r=0.607; P=0.0004 and r=0.631; P=0.0002). With abnormally elevated cerebral blood volume or oxygen extraction fraction ratio defined as higher than the mean +2 SDs obtained from normal subjects, brain temperature difference provided 86% or 92% sensitivity and 87% or 84% specificity with 80% or 73% positive and 91% or 95% negative predictive values for detecting abnormally elevated cerebral blood volume or oxygen extraction fraction ratios, respectively. Conclusions— Brain temperature measured using proton MR spectroscopy can detect cerebral hemodynamic impairment in patients with unilateral chronic major cerebral artery steno-occlusive disease.

Central benzodiazepine receptor binding potential and CBF images on SPECT correlate with oxygen extraction fraction images on PET in the cerebral cortex with unilateral major cerebral artery occlusive disease.

Oxygen extraction fraction (OEF) is a key predictor of stroke recurrence in patients with symptomatic major cerebral arterial occlusive disease. The purpose of the present study was to compare central benzodiazepine receptor binding potential (BRBP) and cerebral blood flow (CBF) images on SPECT with OEF images on PET in patients with chronic unilateral middle cerebral artery (MCA) or internal carotid artery (ICA) occlusive disease. Methods: OEF, CBF, and BRBP were assessed using 15O PET and N-isopropyl-p-123I-iodoamphetamine and 123I-iomazenil SPECT, respectively, in 20 healthy subjects and in 34 patients with unilateral MCA or ICA occlusive disease. All images were transformed into the standard brain size and shape by linear and nonlinear transformation using statistical parametric mapping for anatomic standardization. A region of interest (ROI) was automatically placed according to the arterial supply using a 3-dimensional stereotactic ROI template, and the ratio of the value in the affected side to that in the contralateral side was calculated in each image. Results: Among patients with occlusive disease, a significant positive correlation was observed between PET OEF and SPECT BRBP/CBF ratios in 3 cerebral cortical regions (r = 0.851, P < 0.0001, for anterior cerebral artery [ACA] ROI; r = 0.807, P < 0.0001, for MCA ROI; and r = 0.774, P < 0.0001, for posterior cerebral artery [PCA] ROI), but there were no correlations between these 2 parameters in the basal ganglia or the cerebellum. When an abnormally elevated PET OEF ratio was defined as a value greater than the mean + 2 SDs obtained in healthy subjects, sensitivity and specificity were, respectively, 100% and 96% for the ACA ROI, 100% and 89% for the MCA ROI, and 100% and 93% for the PCA ROI for the SPECT BRBP/CBF ratio for detecting an abnormally elevated PET OEF ratio. Conclusion: BRBP/CBF images on SPECT correlate with OEF images on PET in a specific clinical setting—that is, in the cerebral cortex of patients with chronic unilateral MCA or ICA occlusive disease.

Intentional Hypertension During Dissection of Carotid Arteries in Endarterectomy Prevents Postoperative Development of New Cerebral Ischemic Lesions Caused by Intraoperative Microemboli

BACKGROUND:Low blood flow velocity in the middle cerebral artery (MCA) correlates with the development of postoperative cerebral ischemic lesions related to generation of microemboli during dissection of carotid arteries in carotid endarterectomy (CEA). OBJECTIVE:The purpose of this prospectively controlled trial was to determine whether increased mean blood flow velocity in the MCA by intentional hypertension during carotid dissection in CEA prevented postoperative development of new cerebral ischemic lesions caused by intraoperative microemboli. METHODS:Patients with ipsilateral internal carotid artery stenosis (>70%) underwent CEA under transcranial Doppler monitoring of mean blood flow velocity and microembolic signals in the ipsilateral MCA. Attempts were made to keep systolic blood pressure during carotid dissection between −10% and +10% of the preoperative value (controls, n = 65) or above a +10% increase (intentional hypertension group, n = 65). RESULTS:Incidence of new ischemic lesions on postoperative diffusion-weighted magnetic resonance imaging was significantly lower in the intentional hypertension group both for all patients (controls, 15.4%; intentional hypertension group, 3.1%; P = .03) and in a subgroup of 37 patients showing microembolic signals during carotid dissection (controls, 52.6%; intentional hypertension group, 11.1%; P = .013). Logistic regression analysis demonstrated the absence of intentional hyperperfusion (95% confidence interval: 1.77-100.00; P = .012) and high number of microembolic signals (95% confidence interval: 1.00-1.62; P = .05) during carotid dissection were significant independent predictors of the postoperative development of new ischemic lesions on diffusion-weighted magnetic resonance imaging. CONCLUSION:Increased MCA mean blood flow velocity by intentional hypertension during dissection of the carotid artery in CEA prevents the postoperative development of new cerebral ischemic lesions caused by intraoperative microemboli.

Accuracy of central benzodiazepine receptor binding potential/cerebral blood flow SPECT imaging for detecting misery perfusion in patients with unilateral major cerebral artery occlusive diseases: comparison with cerebrovascular reactivity to acetazolamide and cerebral blood flow SPECT imaging.

Purpose: The aim of the present study was to determine whether central benzodiazepine receptor binding potential (BRBP)/cerebral blood flow (CBF) or a combination of CBF and cerebrovascular reactivity (CVR) to acetazolamide on single-photon emission computed tomography (SPECT) more accurately detects misery perfusion, indicating elevation of absolute value of oxygen extraction fraction (OEF) on positron emission tomography (PET), in patients with unilateral major cerebral artery occlusive diseases. Methods: In 84 patients, OEF, CBF, CVR to acetazolamide, and BRBP were assessed using 15O-PET and N-isopropyl-p-[123I]-iodoamphetamine and [123I]-iomazenil SPECT, respectively. A region of interest was automatically placed in the middle cerebral artery territory using a 3-dimensional stereotactic region of interest template. Results: Sensitivity, specificity, and positive and negative predictive values for the affected side-to-contralateral side asymmetry on SPECT-BRBP/CBF to detect the abnormally elevated PET-OEF in the affected hemisphere were 100%, 86.4%, 66.7%, and 100%, respectively. Area under the receiver operating characteristic curve in detecting the abnormally elevated PET-OEF in the affected hemisphere did not differ between analysis of the combination of SPECT-CBF and SPECT-CVR in the affected hemisphere (0.89; 95% confidence interval, 0.80–0.94) and that of the affected side-to-contralateral side asymmetry on SPECT-BRBP/CBF (0.93; 95% confidence interval, 0.86–0.97). The combination of the 3 detected abnormally elevated PET-OEF with 97.0% specificity and 90.0% positive predictive value. Conclusions: The accuracy of central BRBP/CBF asymmetry on SPECT is equivalent to that of the combination of CBF and CVR to acetazolamide on SPECT for detecting misery perfusion in patients with unilateral major cerebral artery occlusive disease.

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.

Standardized uptake value in high uptake area on positron emission tomography with 18F-FRP170 as a hypoxic cell tracer correlates with intratumoral oxygen pressure in glioblastoma.

PurposeThe aim of this study was to clarify the reliability of positron emission tomography (PET) using a new hypoxic cell tracer, 1-(2-[18F]fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole (18F-FRP170).ProceduresTwelve patients with glioblastoma underwent 18F-FRP170 PET before tumor resection. Mean standardized uptake value (SUV) and normalized SUV were calculated at regions within a tumor showing high (high-uptake area) and relatively low (low-uptake area) accumulations of 18F-FRP170. In these areas, intratumoral oxygen pressure (tpO2) was measured using microelectrodes during tumor resection.ResultsMean tpO2 was significantly lower in the high-uptake area than in the low-uptake area. A significant negative correlation was evident between normalized SUV and tpO2 in the high-uptake area.ConclusionThe present findings suggest that high accumulation on 18F-FRP170 PET represents viable hypoxic tissues in glioblastoma.

Preoperative Central Benzodiazepine Receptor Binding Potential and Cerebral Blood Flow Images on SPECT Predict Development of New Cerebral Ischemic Events and Cerebral Hyperperfusion After Carotid Endarterectomy

Risk factors for cerebrovascular complications developing during or after carotid endarterectomy (CEA) include preoperative impairments in cerebral hemodynamics, as detected by the demonstration of decreased cerebrovascular reactivity (CVR) to acetazolamide on brain perfusion SPECT. Central benzodiazepine receptor binding potential (CBRBP) and cerebral blood flow (CBF) images on SPECT provide high sensitivity and high specificity for detecting misery perfusion in patients with chronic unilateral major cerebral artery occlusive disease. The aim of the present study was to determine whether preoperative CBRBP/CBF images on SPECT could identify patients at risk for new cerebral ischemic events, including neurologic deficits and cerebral ischemic lesions on diffusion-weighted MRI, or cerebral hyperperfusion after CEA and to compare the predictive accuracy of CBRBP/CBF with that of CVR to acetazolamide on SPECT. Methods: CBF, CVR, and CBRBP were assessed using N-isopropyl-p-123I-iodoamphetamine (123I-IMP) and 123I-iomazenil SPECT before CEA in 112 patients with unilateral internal carotid artery stenosis (≥70%). CBF measurement using 123I-IMP SPECT was also performed immediately and 3 d after CEA. A region of interest was automatically placed in the middle cerebral artery territory in both cerebral hemispheres using a 3-dimensional stereotactic region-of-interest template. Diffusion-weighted MRI was performed within 3 d before and 24 h after surgery. Results: A preoperative increase in the affected side–to–contralateral side asymmetry on CBRBP/CBF value was the only significant independent predictor of postoperative new cerebral ischemic events (95% confidence intervals [CI], 1.145–1.608; P = 0.0004) or post-CEA hyperperfusion (95% CI, 1.244–2.252; P = 0.0007). There was no difference in the ability to predict post-CEA hyperperfusion when comparing the area under the receiver-operating-characteristic curve of the affected side–to–contralateral side asymmetry on CBRBP/CBF and that of the CVR in the affected hemisphere. However, the former value (0.924; 95% CI, 0.854–0.972) was significantly greater than the latter value (0.782; 95% CI, 0.697–0.852) for the prediction of new postoperative cerebral ischemic events (P < 0.05). Conclusion: Preoperative CBRBP/CBF images on SPECT can more accurately identify patients at risk for cerebrovascular complications occurring during or after CEA when compared with preoperative CVR to acetazolamide.