Effect of Temporal Sampling Rate on Estimates of the Perfusion Parameters for Patients with Moyamoya Disease Assessed with Simultaneous Multislice Dynamic Susceptibility Contrast-enhanced MR Imaging.

PURPOSE: The effect of temporal sampling rate (TSR) on perfusion parameters has not been fully investigated in Moyamoya disease (MMD); therefore, this study evaluated the influence of different TSRs on perfusion parameters quantitatively and qualitatively by applying simultaneous multi-slice (SMS) dynamic susceptibility contrast-enhanced MR imaging (DSC-MRI). METHODS: DSC-MRI datasets were acquired from 28 patients with MMD with a TSR of 0.5 s. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and time to maximum tissue residue function (Tmax) were calculated for eight TSRs ranging from 0.5 to 4.0 s in 0.5-s increments that were subsampled from a TSR of 0.5 s datasets. Perfusion measurements and volume for chronic ischemic (Tmax ≥ 2 s) and non-ischemic (Tmax < 2 s) areas for each TSR were compared to measurements with a TSR of 0.5 s, as was visual perfusion map analysis. RESULTS: CBF, CBV, and Tmax values tended to be underestimated, whereas MTT and TTP values were less influenced, with a longer TSR. Although Tmax values were overestimated in the TSR of 1.0 s in non-ischemic areas, differences in perfusion measurements between the TSRs of 0.5 and 1.0 s were generally minimal. The volumes of the chronic ischemic areas with a TSR ≥ 3.0 s were significantly underestimated. In CBF and CBV maps, no significant deterioration was noted in image quality up to 3.0 and 2.5 s, respectively. The image quality of MTT, TTP, and Tmax maps for the TSR of 1.0 s was similar to that for the TSR of 0.5 s but was significantly deteriorated for the TSRs of ≥ 1.5 s. CONCLUSION: In the assessment of MMD by SMS DSC-MRI, application of TSRs of ≥ 1.5 s may lead to deterioration of the perfusion measurements; however, that was less influenced in TSRs of ≤ 1.0 s.

A rare case of focal multiple medullary venous malformations with ipsilateral cerebral surface varix.

We report here a rare case of focal multiple venous malformations (VMs) in the white matter, via a draining vein arising from each VM, connecting with an ipsilateral cerebral surface venous varix. The male teen was asymptomatic neurologically. A diagnostic process using of MRI/MRDSA in this extremely rare entity is important as the more incidental discovery is expected with increasing opportunities of performing brain CT/MRI for various indications.

Associations among q-space MRI, diffusion-weighted MRI and histopathological parameters in meningiomas.

OBJECTIVES: The purposes of this MR-based study were to calculate q-space imaging (QSI)-derived mean displacement (MDP) in meningiomas, to evaluate the correlation of MDP values with apparent diffusion coefficient (ADC) and to investigate the relationships among these diffusion parameters, tumour cell count (TCC) and MIB-1 labelling index (LI). METHODS: MRI, including QSI and conventional diffusion-weighted imaging (DWI), was performed in 44 meningioma patients (52 lesions). ADC and MDP maps were acquired from post-processing of the data. Quantitative analyses of these maps were performed by applying regions of interest. Pearson correlation coefficients were calculated for ADC and MDP in all lesions and for ADC and TCC, MDP and TCC, ADC and MIB-1 LI, and MDP and MIB-1 LI in 17 patients who underwent subsequent surgery. RESULTS: ADC and MDP values were found to have a strong correlation: r = 0.78 (P = <0.0001). Both ADC and MDP values had a significant negative association with TCC: r = -0.53 (p = 0.02) and -0.48 (P = 0.04), respectively. MIB-1 LI was not, however, found to have a significant association with these diffusion parameters. CONCLUSION: In meningiomas, both ADC and MDP may be representative of cell density. KEY POINTS: • Diffusion-weighted MRI offers possibilities to assess the aggressiveness of meningiomas. • The q-space imaging-derived mean displacement correlates strongly with apparent diffusion coefficients. • Both diffusion parameters showed a strong negative association with tumour cell counts. • Derived mean displacement may help assess the aggressiveness of meningiomas preoperatively.

Age-related white matter changes in high b-value q-space diffusion-weighted imaging.

INTRODUCTION: To assess and compare age-related diffusion changes in the white matter in different cerebral lobes, as quantified by diffusion-weighted imaging (DWI) and high b-value q-space imaging (QSI). METHODS: Seventy-three cases without neurological symptoms or imaging abnormalities were grouped by age as young (<30 years, n = 20), middle-aged (30-49 years, n = 19), old (50-69 years, n = 18), and very old (> 70 years, n = 16) and imaged by a 1.5-T MR scanner for DWI and QSI. Apparent diffusion coefficient (ADC) and mean displacement (MDP) values were calculated in the white matter of frontal, parietal, and temporal lobes and compared using Dunnett's test, with the young group as a control. RESULTS: MDP values in frontal and parietal lobes were significantly higher in old and very old age groups than in the young, while those in the temporal lobes were significantly higher only in the very old group. ADC values were significantly higher in all three lobes in the very old group. CONCLUSION: QSI is more sensitive than DWI to age-related myelin loss in white matter.

Diffusion-weighted imaging in optic neuritis.

PURPOSE: To evaluate imaging characteristics of optic nerves by using magnetic resonance imaging, especially diffusion-weighted imaging (DWI) with apparent diffusion coefficient measurements in acute and chronic phases of optic neuritis (ON). MATERIALS AND METHODS: A retrospective study was conducted by using records of 14 patients with clinically suspected acute ON (15 nerves), 5 chronic ON (7 nerves), and 11 normal volunteers with no eye symptoms were used as controls. Magnetic resonance imaging was performed by a 1.5T scanner. Affected nerves were evaluated for sizes, signal characteristics on DWI and T2-weighted imaging (T2WI), contrast enhancement, and apparent diffusion coefficient values. Visually assessed characteristics were compared between the acute and chronic, whereas apparent diffusion coefficient values were assessed among acute ON, chronic ON, and the control groups by using the Fisher exact test and Mann-Whitney U test. RESULTS: There were significant differences in the diameter of the optic nerves, hyperintensity on DWI, and enhancement characteristics on post-enhanced images in acute and chronic phases of ON (P = .0001, P < .0001, and P = .0022, respectively), apparent diffusion coefficient values of the optic nerves in acute ON, chronic ON, and control groups also differed significantly from each other. CONCLUSION: In conclusion, DWI can add valuable information in assessment of damage to nerve and neuronal barriers and thus in predicting recovery in cases of ON.

Basi-parallel anatomical scanning (BPAS)-MRI can improve discrimination of vertebral artery dissection from atherosclerosis and hypoplasia.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the effectiveness of combining basi-parallel anatomic scanning (BPAS)-magnetic resonance (MR) imaging findings with those of time-of-flight (TOF)-MR angiography (MRA) for differentiating vertebral artery dissection (VAD) from other causes of true artery narrowing such as atherosclerosis or an anatomical variation such as vertebral artery hypoplasia. MATERIALS AND METHODS: Fifteen cases of VAD, 15 of atherosclerotic narrowing, and 8 of hypoplastic vertebral arteries were retrospectively selected for this study. Conventional MR sequences (T1WI, T2WI, and T2*WI, fluid attenuation inversion recovery, TOF-MRA) and BPAS images were analyzed by two readers blinded to the patients' clinical data and history. Receiver operating characteristic analyses were performed to compare the diagnostic capability of conventional MR sequences with and without BPAS imaging in suspected VAD cases. RESULTS: The area under the curve increased significantly by combining BPAS imaging findings with those of conventional MRI (0.72 vs. 0.96 and 0.81 vs. 0.99; P = .0022 and P = .0068, respectively, for readers 1 and 2). In addition, the sensitivity was 100% (15/15) for both readers and significantly greater than that of conventional MRI (53.3% [8/15] for both readers, P = .0156); however, specificities were not significantly different (82.6% [19/23] vs. 82.6% [19/23] and 91.33% [21/23] vs. 95.7% [22/23]). The interobserver agreement also improved by adding BPAS imaging. CONCLUSIONS: Adding BPAS imaging to conventional MRI and MRA sequences can improve diagnostic capability and sensitivity in suspected VAD cases and be helpful in differentiating it from other causes of vertebral artery narrowing such as atherosclerosis or hypoplasia.

High b-value q-space analyzed diffusion-weighted MRI using 1.5 tesla clinical scanner; determination of displacement parameters in the brains of normal versus multiple sclerosis and low-grade glioma subjects.

PURPOSE: We aimed to determine the displacement parameters in the brains of normal individuals relative to brain parenchymal abnormalities, such as multiple sclerosis (MS) and low-grade glioma, by q-space imaging (QSI) using 1.5-T magnetic resonance (MR) scanner. MATERIALS AND METHODS: Thirty-five normal, three pathologically proven low-grade glioma, and five MS subjects were imaged by a 1.5-T MR unit for QSI (b-values, 0-12,000 s/mm(2)). Mean displacement (MD) values in white matter (WM), gray matter (GM), and lateral ventricle (cerebrospinal fluid [CSF]) of normal subjects, plaques, and normal appearing WM (NAWM) of MS subjects and glioma lesions were calculated. Mann-Whitney U test was used for comparison. RESULTS: In normal subjects, MD values were 6.6 ± 0.2, 8.44 ± 0.41, and 17.08 ± 0.80 µm for WM, GM, and CSF, respectively, while those for NAWM and WM plaques in MS, and glioma lesions were significantly higher at 7.0 ± 0.17, 9.3 ± 2.3, and 9.6 ± 0.40 µm, respectively, compared to WM in normal subjects. CONCLUSION: We propose that the relative values of MD obtained by QSI in control and diseased tissues can be useful for diagnosing various WM abnormalities.

Mean displacement map of spine and spinal cord disorders using high b-value q-space imaging-feasibility study.

BACKGROUND: Q-space analysis is a new metric that uses multiple, high b-value, diffusion-weighted magnetic resonance (MR) data. This technique shows promising results as a tool to provide information complementary to that of other imaging techniques used on biological tissue in vivo. PURPOSE: To investigate the use of a mean displacement (MDP) map of high b-value, q-space imaging (QSI) to characterize spinal and spinal cord lesions in vivo. MATERIAL AND METHODS: Eight patients with spine or spinal cord disorders (two neurinomas, one myeloma, three cases of syringohydromyelia, and two cases of cervical spondylosis) were included. The MR imaging protocol consisted of conventional MR sequences, conventional diffusion-weighted imaging (DWI; b = 1000), and high b-value QSI with a maximum q value of 836.9 cm(-1). Apparent diffusion coefficient (ADC) maps of conventional DWI and MDP maps of QSI data were obtained and region-of-interest analyses for the lesions were performed. RESULTS: MDP values of normal spinal cord, cerebrospinal fluid (CSF), and tumor parenchyma were 6.57 ± 0.52, 17.6 ± 2.75, and 8.49 ± 2.09, respectively (µm, mean ± standard deviation). In general, MDP maps were not well correlated with the corresponding ADC maps at the pathologic lesions. Spondylotic lesions tended to have higher MDP values than normal spinal cord, whereas syringohydromyelia produced MDP values slightly lower than those of CSF. CONCLUSION: The heterogeneous MDP values were probably due to differences in tissues and pathologic structures. This technique has potential to provide additional clinical information to that obtained with conventional MR imaging.

A comparison of mean displacement values using high b-value Q-space diffusion-weighted MRI with conventional apparent diffusion coefficients in patients with stroke.

RATIONALE AND OBJECTIVES: Q-space analysis using high b-value diffusion-weighted magnetic resonance (MR) data provides information on tissue microstructure in contrast to conventional MR imaging (MRI) based on low b-value diffusion-weighted imaging (DWI). The purpose of this study was to evaluate the use of mean displacement (MDP) map in stroke patients using q-space diffusion-weighted MRI (QSI). MATERIALS AND METHODS: Twenty-one patients presenting with a total of 22 acute or subacute cerebral infarctions were included. MR protocol consisted of conventional MR sequences, DWI (b-value; 1000 s/mm(2)) and QSI (b-value; maximum 12,000 s/mm(2)). Apparent diffusion coefficient (ADC) maps of conventional DWI and MDP maps of QSI data were obtained and compared in the ischemic lesions and corresponding normal tissues. RESULTS: Decreased ADC values were present in all lesions. There was no correlation between ADC and MDP values in the lesions (r = 0.21). MDP values of the lesions were 8.60 ± 1.26 µm (mean ± SD). Most of the lesions (16/22) had higher MDP values than normal brain tissue. Three lesions showed lower MDP values and three showed mixed MDP values. CONCLUSIONS: The MDP maps using QSI data provides additional information for stroke patients compared to conventional DWI.

Precontrast and postcontrast susceptibility-weighted imaging in the assessment of intracranial brain neoplasms at 1.5 T.

PURPOSE: The goal of this study was to estimate pre- and post-gadolinium-enhanced high-spatial resolution susceptibility-weighted imaging (SWI) in patients with brain neoplasms. MATERIALS AND METHODS: A total of 17 patients (8 women, 9 men) with brain neoplasms participated in this study. In addition to conventional magnetic resonance imaging, pre- and post-gadolinium-enhanced SWI was performed. The contrast-to-noise ratio (CNR) and major diameters of the brain tumor were measured for quantitative analyses, and intratumoral susceptibility signal intensity (ITSS) was graded for semiquantitative analysis. RESULTS: Both bright and dark enhancement were observed at the pathological lesion on postcontrast SWI. Some postcontrast SWI results suggested leakage of contrast material due to breakdown of the blood-brain barrier. There were no statistical differences (Student's t-test) between postcontrast SWI and three-dimensional (3D) T1-weighted images regarding the major diameters of the brain tumors. CNR of postcontrast 3D T1-weighted images was statistically superior to that of postcontrast SW images (P < 0.01, Wilcoxon signed-rank test). Malignant tumors tended to have a higher ITSS score. CONCLUSION: SWI clearly visualized the architecture of brain neoplasms. This imaging technique may be useful for evaluating tumor characterization in clinical use.

Time-resolved contrast-enhanced magnetic resonance digital subtraction angiography (MRDSA) in an infant with congenital pial arteriovenous fistula in the brain: a case report.

INTRODUCTION: Evaluation of the congenital vascular lesions of the brain requires multiple conventional intra-arterial digital subtraction angiographic examinations which have many associated risks including exposure to ionizing radiations. Magnetic resonance digital subtraction angiography is a non-invasive procedure with no related risks of radiation exposure. This technique can be of greater clinical significance in diagnosis and treatment planning of neurovascular abnormalities among children who are at far greater risk of invasive procedures like intra-arterial digital subtraction angiography. CASE REPORT: We report a congenital pial arteriovenous fistula in an infant which is a rare vascular lesion and has recently been identified as different from other vascular malformations. Magnetic resonance digital subtraction angiography provided hemodynamic information in absolute agreement with intra-arterial digital subtraction angiography indicating its significance in evaluating vascular lesions. DISCUSSION: Magnetic resonance digital subtraction angiography can be used in children in conjunction with intra-arterial digital subtraction angiography to minimize the cumulative radiation dose and multiple anesthesias.

Can balloon-occluded retrograde transvenous obliteration be performed for gastric varices without gastrorenal shunts?

PURPOSE: To evaluate the feasibility for balloon-occluded retrograde transvenous obliteration (BRTO) for gastric varices without gastrorenal shunts. MATERIALS AND METHODS: Of 76 patients with gastric varices who were referred for treatment by BRTO, 11 did not have gastrorenal shunts. Contrast medium-enhanced computed tomography (CT) was performed in all patients; seven patients also underwent CT during splenic arteriography. BRTO was performed to insert a balloon catheter into the main draining vein and inject 5% ethanolamine oleate into gastric varices under the temporary balloon occlusion. RESULTS: The main draining veins were the subphrenic transverse part of the inferior phrenic vein to the inferior vena cava in five patients, the pericardial vein to the left brachiocephalic vein in two, and the paraesophageal vein to the azygos vein in two. In two patients, the main draining vein was unknown. The overall success rate of BRTO in the nine cases with main draining veins was 67%; BRTO was successful in four of the patients in whom the inferior phrenic vein was the main draining vein, one of the patients in whom the pericardial vein was the main draining vein, and one of the patients in whom the paraesophageal vein was the main draining vein. In the other cases in which the inferior phrenic vein or pericardial vein was the main draining vein, BRTO could not be performed because of extravasation. In another patient in whom the paraesophageal vein was the main draining vein, the main draining pathway could not be identified at angiography because of a complicated azygos venous network. CONCLUSIONS: It is feasible to use BRTO to treat cases of gastric varices in which the inferior phrenic vein is the main draining vein. Cases in which the main draining pathway is the pericardial vein are less feasibile for BRTO. The use of BRTO in cases in which the paraesophageal vein is the main draining vein is possible but may be difficult because of a complicated venous network.

[Dilation of subarachnoid space around the optic nerve in a patient with subdural effusion: a case report].

A fifty-year-old man who had a history of minor head injury a month previously presented with headache, visual disturbance and papilloedema. Brain MR imaging showed bilateral subdural effusion and fat saturated orbital MR imaging demonstrated dilated subarachnoid space around the optic nerve. The diameter of the subarachnoid space behind the globe was 7.0 mm and that of the optic nerve was 3.5 mm. Bilateral simple drainage was performed to prevent deterioration of the visual disturbance. Light bloody fluid with a subdural pressure of 10.5 cmH2O was drained from the burr hole at the left side, and colorless fluid was drained from the right. Orbital MR imaging during continuous drainage revealed shrinkage of the subarachnoid space around the optic nerve. However, follow-up MR imaging 5 months after drainage showed disappearance of the subdural effusion and the reappearance of the subarachnoid space around the optic nerve, even though the size was smaller than before surgery. These findings suggest that the diameter of the optic subarachnoid space co-relates with the intracranial pressure, and may be an indication for increased intracranial pressure.

Effect of intracranial pressure on the diameter of the optic nerve sheath.

OBJECT: The subarachnoid space around the optic nerve in the orbit can be visualized using T2-weighted MR imaging with the fat-saturation pulse sequence. The optic nerve sheath (ONS) diameter can be estimated by measuring the outer diameter of the subarachnoid space. Dilated ONS is associated with idiopathic intracranial hypertension and hydrocephalus, and is believed to reflect increased intracranial pressure (ICP). The relationship between dilated ONS and ICP is unclear because of the difficulty in obtaining noninvasive measurements of ICP. The authors investigated the relationship between subdural pressure measured at the time of surgery and ONS diameter measured on MR images in patients with chronic subdural fluid collection. METHODS: Twelve patients underwent bur-hole craniostomy with continuous drainage for chronic subdural hematoma or hygroma in 2006. Orbital thin-slice fat-saturated MR images were obtained before and after surgery, and the ONS diameters were measured just behind the optic globe. Subdural pressure was measured using a manometer before opening of the dura mater. RESULTS: A significant correlation was found between the ONS diameter and the subdural pressure (correlation coefficient 0.879, p = 0.0036). The ONS diameter before surgery (6.1 +/- 0.7 mm) was significantly reduced after surgery (4.8 +/- 0.9 mm, p = 0.003; measurements are expressed as the mean +/- standard deviation). CONCLUSIONS: Increased ONS diameter measured on coronal orbital thin-slice fat-saturated T2-weighted MR images is a strong indicator of increased ICP, and helps to differentiate between passive subdural fluid collection due to brain atrophy and subdural hygroma with increased ICP.

Diffusion tensor tractography predicts motor functional outcome in patients with spontaneous intracerebral hemorrhage.

OBJECTIVE: We prospectively investigated the predictive value of diffusion tensor tractography for motor functional outcome in a case series of patients with intracerebral hemorrhage. METHODS: Diffusion tensor tractography was performed in 17 patients with intracerebral hemorrhage (putamen, nine patients; thalamus, seven patients; combined, one patient) within 5 days after onset. Mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values along the corticospinal tracts at the level of the hematoma were measured bilaterally, and the ratios of values (hematoma side/contralateral side) were determined as FA and ADC ratios, respectively. Patients were evaluated for motor function on admission and at 3 months after onset using the manual muscle test score and then divided into good (manual muscle test, 4-5) and poor (manual muscle test, 0-3) motor function groups. RESULTS: FA ratio measured shortly after the onset of intracerebral hemorrhage correlated well with motor functional outcome at 3 months (P < 0.05) but not with motor function on admission. FA ratios in the group with good motor functional outcome were significantly higher than those in the group with poor motor functional outcome (P < 0.01). The ADC ratio did not correlate with motor function either on admission or at 3 months. All patients with an FA ratio greater than 0.8 had a good motor functional outcome. In three patients, however, motor functional outcomes were favorable even though FA ratios were not high; in these patients, ADC ratios tended to be elevated. CONCLUSION: Motor functional outcome in patients with intracerebral hemorrhage can be predicted by measuring FA values using diffusion tensor tractography.

Mean diffusivity, fractional anisotropy maps, and three-dimensional white-matter tractography by diffusion tensor imaging. Comparison between single-shot fast spin-echo and single-shot echo-planar sequences at 1.5 Tesla.

Single-shot fast spin-echo (SSFSE)-based magnetic resonance imaging (MRI) has been introduced as a technique with less distortion and fewer artifacts for diffusion tensor imaging (DTI). The purpose of this study was to compare mean diffusivity maps, fractional anisotropy (FA) maps, and three-dimensional white-matter tractography using data obtained with SSFSE diffusion-tensor MRI technique and the much more common DTI method, echo-planar imaging (EPI), in the brain using a 1.5-Tesla clinical MR imager. Thirty patients with neurological disorders were scanned with both SSFSE-DTI and EPI-DTI using comparable scan times. Mean diffusivity and FA maps were calculated from the SSFSE-DTI and EPI-DTI data and qualitatively compared using two criteria. Three-dimensional fiber tracking was also performed on each data set. SSFSE-DTI produced image artifacts less frequently than EPI-DTI. However, demonstration of three-dimensional fiber-tracking of white matter on SSFSE-DTI was inferior to that on EPI-DTI. In conclusion, SSFSE-DTI is a promising alternative to conventional EPI-DTI imaging, producing fewer image artifacts and geometric distortions. However, for 3D streamline fiber-tracking, EPI data produced more consistent and reliable results.

Cerebral vascular mean transit time in healthy humans: a comparative study with PET and dynamic susceptibility contrast-enhanced MRI.

Cerebral vascular mean transit time (MTT), defined as the ratio of cerebral blood volume to cerebral blood flow (CBV/CBF), is a valuable indicator of the cerebral circulation. Positron emission tomography (PET) and dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) are useful for the quantitative determination of MTT in the clinical setting. The aim of this study was to establish a normal value set of MTT as determined by PET and by DSC-MRI and to identify differences between these methods. Seven healthy volunteers were studied with (15)O-PET (H(2)(15)O and C(15)O) and gradient-echo echo-planar DSC-MRI at 1.5 T. In the DSC-MRI study with bolus injection of contrast agent, deconvolution analysis was performed. Comparison of gray-to-white matter ratios showed fairly good agreement between PET and DSC-MRI for all parameters (relative CBV, relative CBF, and relative MTT), confirming the validity of relative measurements with DSC-MRI. However, quantitative MTT measured by DSC-MRI was significantly shorter than that measured by PET in cerebral cortical regions (2.8 to 3.0 secs for DSC-MRI versus 3.9 to 4.3 secs for PET) and the centrum semiovale (3.5 secs for DSC-MRI versus 4.8 secs for PET). These discrepancies may be because of the differences in the intrinsic sensitivity of each imaging modality to vascular components; whereas PET measurement of CBV is equally sensitive to all vascular components, measurement with DSC-MRI originates from the microvasculature in the vicinity of the brain parenchyma. This underlying difference may influence interpretation of MTT determined by PET or by DSC-MRI for patients with cerebrovascular disease.