Gradient-recalled Echo Sequence Research Articles

Combined magnetic resonance imaging of deep venous thrombosis and pulmonary arteries after a single injection of a blood pool contrast agent

Agreement rate between magnetic resonance imaging (MRI) and Doppler ultrasound (DUS) for the detection of deep vein thrombosis (DVT) in the lower extremities was attempted by using the intravascular MRI contrast agent gadofosveset trisodium. The potential of this method to detect pulmonary embolism (PE) was also evaluated. Forty-three consecutive inpatients with ultrasound-confirmed DVT but no clinical signs of PE were prospectively enrolled in this feasibility study. MRI was performed after a single injection of gadofosveset trisodium. The pulmonary arteries were imaged using a 3D Fast Low Angle Shot (FLASH) gradient recalled echo sequence. Additionally, pulmonary arteries, abdominal veins, pelvic and leg veins were imaged using a fat-suppressed 3D gradient echo Volume Interpolated Breath-hold Examination (VIBE FS). Gadofosveset trisodium-enhanced MRI detected more thrombi in the pelvic region, upper leg and lower leg than the initial DUS. In addition, PE was detected in 16 of the 43 DVT patients (37%). This study shows the feasibility of a combined protocol for the MRI diagnosis of DVT and PE using gadofosveset trisodium. This procedure is not only more sensitive in detecting DVT compared to standard DUS, but is also able to detect PE in asymptomatic patients.

MRI Markers of Small Vessel Disease in Lobar and Deep Hemispheric Intracerebral Hemorrhage

MRI evidence of small vessel disease is common in intracerebral hemorrhage (ICH). We hypothesized that ICH caused by cerebral amyloid angiopathy (CAA) or hypertensive vasculopathy would have different distributions of MRI T2 white matter hyperintensity (WMH) and microbleeds. Data were analyzed from 133 consecutive patients with primary supratentorial ICH and adequate MRI sequences. CAA was diagnosed using the Boston criteria. WMH segmentation was performed using a validated semiautomated method. WMH and microbleeds were compared according to site of symptomatic hematoma origin (lobar versus deep) or by pattern of hemorrhages, including both hematomas and microbleeds, on MRI gradient recalled echo sequence (grouped as lobar only-probable CAA, lobar only-possible CAA, deep hemispheric only, or mixed lobar and deep hemorrhages). Patients with lobar and deep hemispheric hematoma had similar median normalized WMH volumes (19.5 cm versus 19.9 cm(3), P=0.74) and prevalence of >or=1 microbleed (54% versus 52%, P=0.99). The supratentorial WMH distribution was similar according to hemorrhage location category; however, the prevalence of brain stem T2 hyperintensity was lower in lobar hematoma versus deep hematoma (54% versus 70%, P=0.004). Mixed ICH was common (23%). Patients with mixed ICH had large normalized WMH volumes and a posterior distribution of cortical hemorrhages similar to that seen in CAA. WMH distribution is largely similar between CAA-related and non-CAA-related ICH. Mixed lobar and deep hemorrhages are seen on MRI gradient recalled echo sequence in up to one fourth of patients; in these patients, both hypertension and CAA may be contributing to the burden of WMH.

Changes in the Frontotemporal Cortex and Cognitive Correlates in First-Episode Psychosis

BackgroundLoss of cortical volume in frontotemporal regions has been reported in patients with schizophrenia and their relatives. Cortical area and thickness are determined by different genetic processes, and measuring these parameters separately may clarify disturbances in corticogenesis relevant to schizophrenia. Our study also explored clinical and cognitive correlates of these parameters.MethodsThirty-seven patients with first-episode psychosis (34 schizophrenia, 3 schizoaffective disorder) and 38 healthy control subjects matched for age and sex took part in the study. Imaging was performed on an magnetic resonance imaging 1.5-T scanner. Area and thickness of the frontotemporal cortex were measured using a surface-based morphometry method (Freesurfer). All subjects underwent neuropsychologic testing that included measures of premorbid and current IQ, working and verbal memory, and executive function.ResultsReductions in cortical area, more marked in the temporal cortex, were present in patients. Overall frontotemporal cortical thickness did not differ between groups, although regional thinning of the right superior temporal region was observed in patients. There was a significant association of both premorbid IQ and IQ at disease onset with area, but not thickness, of the frontotemporal cortex, and working memory span was associated with area of the frontal cortex. These associations remained significant when only patients with schizophrenia were considered.ConclusionsOur results suggest an early disruption of corticogenesis in schizophrenia, although the effect of subsequent environmental factors cannot be excluded. In addition, cortical abnormalities are subject to regional variations and differ from those present in neurodegenerative diseases.

High-Resolution Double Arterial Phase Hepatic MRI Using Adaptive 2D Centric View Ordering: Initial Clinical Experience

The objective of our study was to evaluate a new 3D fast spoiled gradient-recalled echo (FSPGR) sequence referred to as modified liver acceleration volume acquisition (LAVA) for high-resolution gadolinium-enhanced dual arterial phase liver MRI and to determine the effect of this technique on the timing of the contrast bolus and lesion detection. Gadolinium-enhanced dual arterial phase liver MRI was performed in 109 patients using a modified LAVA sequence that supports adaptive 2D centric view ordering, efficient 2D autocalibrated acceleration, and partial-Fourier to achieve faster scan times while maintaining the same slice thickness, resolution, and coverage as single-phase imaging. After a fixed 20-second scan delay, a modified LAVA acquisition required a single 24- to 26-second breath-hold for two arterial phases with 56-60 slices per pass. Images were reviewed for timing relative to liver enhancement, lesion conspicuity, and lesion detection. Liver lesion depiction was evaluated qualitatively and quantitatively. A control group of 109 patients underwent imaging using a single arterial phase 3D FSPGR sequence, which was also performed with a fixed 20-second scan delay. The single arterial phase images produced optimal timing in the middle or late arterial phase in 79 (72%) of the 109 control group patients compared with 99 (91%) of the 109 study group patients who underwent imaging using a dynamic modified LAVA dual arterial phase sequence. For the modified LAVA sequence, the first-pass images were obtained during the mid arterial phase in 34 patients (31%). The second-pass images were obtained during the mid arterial phase in 51 patients (47%) and late arterial phase in 26 patients (24%). Sixty-two patients had liver lesions showing greater conspicuity--on the first phase in 17 patients (27%) and second phase in 45 patients (73%). Hypovascular lesions were more conspicuous on second-phase images in 24 (86%) of 28 patients. Hypervascular lesions were more conspicuous on first-phase images in 13 patients (38%) and on second-phase images in 21 (62%) of 34 patients. The first-phase images detected 165 and 155 liver lesions, respectively, for two observers compared with 233 and 224 lesions on the second-phase images, whereas the combined dual arterial phase images detected 256 and 248 hepatic lesions. High-resolution dual arterial phase 3D FSPGR MRI improves the timing of the arterial phase of liver enhancement and provides additional information for liver lesion detection.

Coronary MR Imaging: Effect of Timing and Dose of Isosorbide Dinitrate Administration

To quantify the effect of sublingual isosorbide dinitrate (ISDN) administration on coronary magnetic resonance (MR) imaging. Written informed consent was obtained from all participants, and the HIPAA-compliant protocol was approved by the Institutional Review Board. Coronary MR imaging was performed at 1.5 T before and after administration of ISDN (2.5 or 5 mg) in 25 healthy adult volunteers (mean age, 23 years +/- 4; nine men, 16 women) with three-dimensional targeted (n = 20, randomized into four groups) or whole-heart (n = 5) acquisitions with gradient-recalled echo (GRE) or balanced steady-state free precession (SSFP) sequences. Image quality was assessed by two cardiologists on a four-point scale. Signal-to-noise ratio (SNR), vessel diameter, and vessel sharpness were characterized. A linear mixed-effects model was used for data analysis. A P value of less than .05 was considered to indicate a significant difference. The maximum SNR enhancement with 5 mg of ISDN (GRE: 22.0% +/- 10.7%; SSFP: 20.1% +/- 6.0%) was similar (P > .05) to that with 2.5 mg (GRE: 21.9% +/- 5.4%; SSFP: 19.1% +/- 3.0%). However, the time to maximum SNR enhancement for the 5-mg dose (15.5 minutes +/- 6.0) was earlier (P < .01) than that for 2.5 mg (23.5 minutes +/- 6.7). The increase in vessel diameter with 5 mg of ISDN was greater than that with 2.5 mg (P < .05 for both GRE and SSFP sequences). The coronary images were sharper after ISDN administration (P < .03). Subjective image quality score significantly improved after ISDN administration for GRE images (P < .05 for both doses) but was similar for SSFP images (P = .24 for 2.5 mg; P = .27 for 5 mg). Whole-heart coronary SNR was improved about 10% after ISDN administration (P < .05). Sublingual ISDN improves coronary MR imaging SNR. Practitioners need to consider the dose and temporal effects of ISDN when performing coronary MR imaging.

DISTAL INTERPHALANGEAL ARTICULAR CARTILAGE ASSESSMENT USING LOW-FIELD MAGNETIC RESONANCE IMAGING

The suitability of low-field magnetic resonance (MR) imaging for assessment of articular cartilage has been questioned, based on insufficient image quality. The purposes of this study were to describe the MR anatomy of the normal distal interphalangeal (DIP) cartilage, and to evaluate the sensitivity and accuracy of low-field MR imaging for identification of cartilage erosions that were created ex vivo. Imaging sequences included sagittal and dorsal multiple-oblique T1-weighted gradient-recalled echo (GRE) and sagittal dual echo sequences. In the thickest regions, normal cartilage appeared as a trilaminar structure on high-resolution T1-weighted GRE sequences. All 8 mm large full-thickness erosions were correctly identified (100% sensitivity and accuracy) using T1-weighted GRE sequences. Sensitivity and accuracy ranged from 80% to 100% and 10% to 80%, respectively, for detecting focal full-thickness erosions and from 35% to 80% and 35% to 60%, respectively, for detecting partial thickness erosions, using T1-weighted GRE sequences. Superficial irregularities were not diagnosed using any sequence. Overall, fewer cartilage alterations were detected with sagittal dual echo sequences than with sagittal T1-weighted GRE sequences. The dorsal multiple-oblique plane was useful to detect linear dorsopalmar erosions. A combination of T1-weighted GRE sequences in two planes has potential for identification of severe DIP cartilage erosion in anesthetized horses using low-field MR imaging.

Non‐contrast‐enhanced pulmonary vein MRI with a spatially selective slab inversion preparation sequence

We propose a non-contrast-enhanced, three-dimensional, free-breathing, electrocardiogram-gated, gradient recalled echo sequence with a slab-selective inversion for pulmonary vein (PV) MRI. A sagittal inversion slab was applied prior to data acquisition to suppress structures adjacent to the left atrium (LA) and PVs, thereby improving the conspicuity of the PV and LA. Compared with other MR angiography methods using an inversion pulse, the proposed method does not require signal subtraction and the inversion slab is not parallel to the imaging slab. The feasibility of the proposed method was demonstrated in healthy subjects. The inversion slab thickness and inversion time were optimized to be 60 mm and 500 ms, respectively. Compared to conventional gradient recalled echo imaging without inversion, the proposed technique significantly increased the contrast-to-noise ratios between the LA and the right atrium by 20-fold (P < 0.01), increased the contrast-to-noise ratios between the PVs and right atrium by 10-fold (P < 0.03), and increased the contrast-to-noise ratios between the PVs, LA and pulmonary artery by 4-fold (P < 0.01 for both). The signal-to-noise ratios of the PVs and the LA were similar with and without the inversion slab (P > 0.3). The proposed technique greatly enhances the conspicuity of the PVs and LA without significant loss of signal-to-noise ratio.

Non-contrast enhanced pulmonary vein MRI with a spatially selective slab inversion preparation sequence

We propose a non-contrast-enhanced, three-dimensional, free-breathing, electrocardiogram-gated, gradient recalled echo sequence with a slab-selective inversion for pulmonary vein (PV) MRI. A sagittal inversion slab was applied prior to data acquisition to suppress structures adjacent to the left atrium (LA) and PVs, thereby improving the conspicuity of the PV and LA. Compared with other MR angiography methods using an inversion pulse, the proposed method does not require signal subtraction and the inversion slab is not parallel to the imaging slab. The feasibility of the proposed method was demonstrated in healthy subjects. The inversion slab thickness and inversion time were optimized to be 60 mm and 500 ms, respectively. Compared to conventional gradient recalled echo imaging without inversion, the proposed technique significantly increased the contrast-to-noise ratios between the LA and the right atrium by 20-fold (P 0.3). The proposed technique greatly enhances the conspicuity of the PVs and LA without significant loss of signal-to-noise ratio.

Improved Delineation of Ventricular Shunt Catheters Using Fast Steady-State Gradient Recalled-Echo Sequences in a Rapid Brain MR Imaging Protocol in Nonsedated Pediatric Patients

Rapid brain MR imaging is often substituted for head CT in multiply imaged patients with shunted hydrocephalus. Fast TSE-T2 sequences are commonly used in these protocols. One limitation of TSE-T2 sequences is the decreased catheter delineation compared with CT. The aim of this study was to compare fast TSE-T2 with rapid SS-GRE sequences in the evaluation of intracranial shunt catheter delineation as part of a rapid nonsedated pediatric brain MR imaging protocol. We evaluated the findings from 179 consecutive patients who underwent routine clinical imaging according to the rapid nonsedated pediatric brain MR imaging protocol. Comparison of the quality of intracranial shunt catheter localization on SS-GRE versus TSE-T2 was performed. Of the total of 179 rapid nonsedated pediatric brain MR images that were reviewed, 62 (35%) had an intracranial shunt catheter. The shunt catheter tip was better localized on the SS-GRE than on the TSE-T2 images in 49/62 (79%) of these patients. Of the remaining 13/62 (21%), the TSE-T2 was either better or equivalent in localizing the shunt catheter tip. Our study shows that rapid SS-GRE sequences can provide better delineation of standard intracranial shunt catheters than standard rapid MR imaging protocols containing only fast TSE-T2 sequences.

MR angiography of midaortic syndrome

A 12-year-old boy presented with hypertension and intermittent lower extremity claudication. Breath-hold high spatial resolution MRA at 3.0 T (gradient recalled echo sequence; 10 ml of Magnevist) revealed abdominal aortic coarctation (Fig. 1, thin long arrow), severely narrowed right renal artery and atrophy of the ipsilateral kidney (Fig. 1b, arrowhead), and hypertrophied inferior mesenteric artery (Fig. 1a, thick short arrow) feeding the superior mesenteric artery (Fig. 1a, thin short arrow) through the arc of Riolan (Fig. 1a, arrowhead). The child had previously undergone placement of an aorto-aortic graft (Fig. 1, thick long arrow). Fig. 1 3-D volume-rendered MR angiograms (Vitrea 3.6; Vital Images, Minneapolis, MN) Midaortic syndrome (MAS) is a rare disease caused by segmental narrowing of the abdominal or distal descending thoracic aorta associated with concomitant stenoses involving the renal (63%) and visceral (33%) arteries [1]. MAS can be congenital or acquired caused by giant cell or Takayasu arteritis, retroperitoneal fibrosis, Williams syndrome, fibromuscular dysplasia, neurofibromatosis, and mucopolysaccharidosis [1, 2]. Noninvasive diagnosis is made by MRA or CT angiography [2]. Surgical bypass grafting is the optimal method of treatment [1].

Contrast-enhanced MR angiography with frequency-dependent mask subtraction

One of the main challenges for high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) is the limited signal-to-noise ratio (SNR). In conventional CE-MRA, spoiled gradient-recalled echo sequence is typically used to acquire raw data before and after contrast material injection, followed by mask subtraction to improve vessel contrast at the cost of increased image noise. We reported here on a frequency-dependent mask subtraction technique where only low spatial frequency data were subject to mask subtraction to improve image contrast and reduce motion artifact while high spatial frequency data were not subtracted to preserve image noise level. The feasibility of this technique was demonstrated through phantom, animal, and human volunteer studies. The lowest half, quarter, 1/8 and 1/16 of all spatial frequencies were subject to mask subtraction, respectively. These partial subtraction techniques were compared with conventional mask subtraction in terms of SNR and artifact power. An SNR gain up to 37% was achieved without significant artifact power increase for quarter-subtraction where only the central one quarter k-space data were subject to mask subtraction.

Assessment of Myocardial Viability with 3D MRI at 3 T

The aim of our study was to show that spatial resolution can be improved without loss of diagnostic accuracy if a 3D inversion recovery gradient-recalled echo (GRE) sequence is used instead of a segmented inversion recovery GRE at 3 T for the assessment of myocardial infarction. Fifteen patients with myocardial infarction were examined on a 3-T MR system. A segmented breath-hold 3D inversion recovery GRE technique with a voxel size of 6.3 mm(3) was compared with a breath-hold standard 2D inversion recovery GRE technique with a voxel size of 21.3 mm(3) for the detection of delayed enhancement. Contrast-to-noise ratios (CNRs) were calculated and infarct volumes were measured. Detection and transmural extent of infarctions were evaluated using kappa statistics. Total acquisition times were measured for both sequences. The CNR in the 3D technique did not show any significant difference compared with the 2D technique. The correlation coefficients of the infarct volumes determined with the 3D and 2D inversion recovery GRE studies at 3 T were r = 0.99 (p < 0.001). The assessment of the presence of hyperenhanced myocardium in all segments and the evaluation of transmurality resulted in very good agreement (kappa = 0.98 and kappa = 0.90). Total acquisition time was significantly shorter with the 3D technique (2.4 +/- 0.9 minutes) than with the 2D technique (4.9 +/- 1.5 minutes) (p < 0.001). The use of a 3D inversion recovery GRE sequence at 3 T allows accurate assessment of myocardial infarction without loss of CNR compared with the standard 2D technique. Furthermore, data acquisition time can be significantly reduced.

Quantitative MR imaging evaluation of the cartilage thickness and subchondral bone area in patients with ACL-reconstructions 7 years after surgery

To evaluate the cartilage thickness (ThC) and subchondral bone area (tAB) of the operated and contra-lateral non-operated (healthy) knees in patients with anterior cruciate ligament (ACL)-reconstruction 7 years after surgery using a quantitative and regional cartilage MR imaging (qMRI) technique. Charts of 410 patients with ACL-reconstructions were retrospectively reviewed. Fifty-two patients (male/female, 28/24; mean age, 33.3 years) were included. Patients underwent KT-1000 testing and qMRI of both knees using coronal fat-saturated 3D spoiled gradient-recalled echo (SPGR) sequences (TR/TE, 44/4 ms) at 1.5 T. Quantitative analyses of ThC and tAB in the femoro-tibial cartilage plates were performed using a subregional approach. In addition, qualitative and quantitative assessment of femoral condyle shapes was performed. t tests with Bonferroni corrections were used for statistical analysis of side-to-side differences between the operated and non-operated knees. KT-1000 testing was abnormal in 3/52 patients (6%). Lateral femoral tAB was significantly lower (-9.2%), and medial tibial tAB was significantly larger (+2%) in the operated vs non-operated knee (P<0.001). Regional and subregional ThC side-to-side differences were less than 0.1mm and, except for the external lateral femoral subregion, they were not statistically significant. Flattened and broader shapes of medial femoral condyles (P<0.001) were found in operated knees. No significant association of presence of cartilage or meniscus lesions at surgery with ThC 7 years post-operatively was found (P=0.06-0.98). There is evidence for changes in the tAB and femoral shape 7 years post-ACL-reconstruction, but no side-to-side differences in subregional ThC were found between the operated and contra-lateral non-operated knees.

Hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide-enhanced magnetic resonance imaging in cirrhosis or chronic hepatitis: comparison of four magnetic resonance sequences for lesion conspicuity

The aim of this study was to determine the adequate MR sequence for the lesion conspicuity of hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide (SPIO)-enhanced MRI. SPIO-enhanced MRI was performed using a 1.5-T system. Among 25 patients with hypovascular hepatocellular nodules on contrast-enhanced dynamic CT (no early enhancement at arterial phase and hypoattenuation at equilibrium phase), 39 lesions with increased iron uptake on SPIO-enhanced MRI were evaluated. SPIO-enhanced MRI included (1) T1-weighted in-phase gradient recalled echo (GRE) images, (2) T2-weighted fast spin echo (FSE) images, (3) T2*-weighted GRE with moderate TE (7 ms) and (4) long TE (12 ms). The lesion-to-liver contrast-to-noise ratios of the hepatocellular nodule and the signal-to-noise ratio (SNR) of the hepatic parenchyma were calculated by one radiologist for a quantitative assessment. MR images were reviewed retrospectively by two independent radiologists to compare the subjective lesion conspicuity in each image set based on a four-point rating scale. The mean lesion-to-liver contrast-to-noise ratios with T2*-weighted GRE with moderate TE (7 ms) was highest (5.79+/-3.71) and was significantly higher than those with T1-weighted, in-phase images (3.79+/-3.23, P<.01), T2-weighted images (2.72+/-1.52, P<.001) and T2*-weighted GRE with long TE (12 ms) (3.93+/-2.69, P<.05). The subjective rating of lesion conspicuity was best on the T2*-weighted GRE with moderate TE (7 ms), followed by that on the T2*-weighted GRE with moderate TE (7 ms; P<.05). T2*-weighted GRE sequence with moderate TE (7 ms) showed high lesion-to-liver contrast-to-noise ratios in hepatocellular lesions with increased iron uptake on SPIO-enhanced MRI, indicating better lesion conspicuity of hypointense hepatocellular nodules in cirrhosis or chronic hepatitis.

Four-dimensional transcatheter intraarterial perfusion (TRIP)-MRI for monitoring liver tumor embolization in VX2 rabbits

Transcatheter intraarterial perfusion (TRIP)-MRI is an intraprocedural technique to iteratively monitor liver tumor perfusion changes during transcatheter arterial embolization (TAE) and chemoembolization (TACE). However, previous TRIP-MRI approaches using two-dimensional (2D) T(1)-weighted saturation-recovery gradient-recalled echo (GRE) sequences provided only limited spatial coverage and limited capacity for accurate perfusion quantification. In this preclinical study, a quantitative 4D TRIP-MRI technique (serial iterative 3D volumetric perfusion imaging) with rigorous radiofrequency (RF) B(1) field calibration and dynamic tissue longitudinal relaxation rate R(1) measurement is presented for monitoring intraprocedural liver tumor perfusion during TAE. 4D TRIP-MRI and TAE were performed in five rabbits with eight VX2 liver tumors (N = 8). After B(1) calibrated baseline and dynamic R(1) quantification, subsequent tissue contrast agent concentration time curves were derived. A single-input flow-limited pharmacokinetic model and peak gradient method were applied for perfusion analysis. The perfusion Frho reduced significantly from pre-TAE 0.477 (95% confidence interval [CI]: 0.384-0.570) to post-TAE 0.131 (95% CI: 0.080-0.183 ml/min/ml, P < 0.001).

Magnetic resonance imaging of the cervical spine: comparison of 2D T2-weighted turbo spin echo, 2D T2*weighted gradient-recalled echo and 3D T2-weighted variable flip-angle turbo spin echo sequences

To compare an isotropic three-dimensional (3D) high-resolution T2-weighted (w) MR sequence and its reformations with conventional sequences for imaging of the cervical spine. Fifteen volunteers were examined at 1.5 T using sagittal and axial 3D T2-w, sagittal and axial 2D T2w, and axial 2D T2*w MR sequences. Axial reformations of the sagittal 3D dataset were generated (3D MPR T2w). Signal-to-noise and image homogeneity were evaluated in a phantom and in vivo. Visibility of ten anatomical structures of the cervical spine was evaluated. Artifacts were assessed. For statistical analysis, Cohen's kappa, Wilcoxon matched pairs, and t-testing were utilized. There were no significant differences in homogeneity between the sequences. Sagittal 3D T2w enabled better delineation of nerve roots, neural foramina, and intraforaminal structures compared to sagittal 2D T2w. Axial 3D T2w and axial 3D MPR T2w resulted in superior visibility of most anatomical structures compared to axial 2D T2w and comparable results to 2D T2*w concerning the spinal cord, nerve roots, intraforaminal structures, and fat. Artifacts were most pronounced in axial 2D T2w and axial 3D T2w. Acquisition of a 3D T2w data set is feasible in the cervical spine with superior delineation of anatomical structures compared to 2D sequences.

Microbleed Topography, Leukoaraiosis, and Cognition in Probable Alzheimer Disease From the Sunnybrook Dementia Study

Microbleeds are hemosiderin deposits around small vessels and are well visualized with T2*-weighted gradient-recalled echo (GRE) imaging. To determine frequency and topography of microbleeds in Alzheimer disease (AD) and to assess their association with leukoaraiosis and cognition. Case-control cross-sectional analysis. Microbleeds were counted using GRE imaging. Leukoaraiosis was rated on T2-weighted and proton density-weighted scans using the Age-Related White Matter Changes Rating Scale (ARWMC). Neuropsychological tests indexed cognition. The Cognitive Neurology Clinic, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. Individuals with probable AD (n = 80) and healthy controls (n = 25) from a longitudinal cohort with GRE sequences as part of standard imaging protocol (2002-2006). Microbleeds occurred in 29% of patients with AD and 12% of controls and were multiple (> 1) in 48% of patients with AD and 33% of controls. There was lobar (vs centrencephalic) predominance in 92% of AD patients, with occipital lobes accounting for 57% of these microbleeds. The ARWMC scores (P < .005) were significantly higher in AD patients with microbleeds than in those without, and microbleeds correlated with total (r = 0.39, P = .01) and parietooccipital (r = 0.28, P < .01) ARWMC scores. We were unable to demonstrate an association between microbleeds (or leukoaraiosis) and cognitive performance. Occipital predominance of microbleeds with corresponding parietooccipital leukoaraiosis has not been well described in prior imaging studies of AD. Microbleeds were frequent, often multiple, and predicted greater leukoaraiosis. These findings illustrate the complexity of AD vasculopathy and the need for additional studies in dementia and stroke populations.

Response to Letter by Vernooij et al

HomeStrokeVol. 39, No. 7Response to Letter by Vernooij et al Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBResponse to Letter by Vernooij et al Jens Fiehler, MD, PhD and Jens FiehlerJens Fiehler Department of Neuroradiology, University Medical Center Hamburg, Hamburg, Germany Search for more papers by this author and Department of Neuroradiology, University Medical Center Hamburg, Hamburg, Germany Search for more papers by this author and on behalf of the BRASIL investigators Originally published22 May 2008https://doi.org/10.1161/STROKEAHA.107.522235Stroke. 2008;39:e116Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: May 22, 2008: Previous Version 1 Response:We thank Vernooij et al for their interest in the BRASIL study1 and for giving us the opportunity to explain our interpretation of the data. Vernooij et al conclude that BRASIL is compatible with a “substantial increased risk” of hemorrhage associated with thrombolysis therapy in patients with cerebral microbleeds (CMBs). We agree. It is stated explicitly in the article that the data are compatible with an increase in hemorrhage risk. However, it is essential that any such risk is set against the benefit of thrombolysis. What Vernooij et al mean by “substantial” is unclear in this respect.Clinicians need to make treatment decisions based on the absolute likelihood of benefit for individual patients and trial results should be expressed as absolute risk reductions.2 Based on a large pooled analysis of randomized trials of thrombolysis in acute ischemic stroke3 the absolute reduction in the rate of a poor outcome with thrombolysis was estimated to be 13% (95% CI: 4% to 22%) in CT-selected patients, and the benefit might be even higher if selection is based on MRI.4 The results of BRASIL suggest that the presumed CMB related excess absolute risk of hemorrhage is unlikely to exceed this absolute benefit of thrombolytic treatment.The BRASIL data were collected by 13 experienced high-volume stroke centers with a overall detection rate of CMBs typical for MRI in acute stroke.5 Although this approach results in a high external validity for acute stroke imaging, there is certainly room for improvement of MRI techniques. We agree that a large prospective study with standardized MRI parameters would allow a more precise estimation of the CMB related risk. It is well established that even small differences in imaging techniques influence size and number of CMBs.6 The higher CMB rate in the general population of ischemic stroke patients might be explained by higher image quality in epidemiological studies where MRI is less time critical. Differentiating amyloid angiopathy from hypertensive angiopathy based on a CMB pattern is not very promising in the BRASIL dataset as the number of CMBs in the individual patients is low.For the time being, we need to make decisions for or against the thrombolytic therapy which has been proven highly effective by several independent trials. Withholding this therapy needs a strong rationale. Such a rationale is not given by BRASIL.DisclosuresNone.1 Fiehler J, Albers GW, Boulanger JM, Derex L, Gass A, Hjort N, Kim JS, Liebeskind DS, Neumann-Haefelin T, Pedraza S, Rother J, Rothwell P, Rovira A, Schellinger PD, Trenkler J. Bleeding risk analysis in stroke imaging before thromboLysis (BRASIL): pooled analysis of T2*-weighted magnetic resonance imaging data from 570 patients. Stroke. 2007; 38: 2738–2744.LinkGoogle Scholar2 Rothwell PM, Mehta Z, Howard SC, Gutnikov SA, Warlow CP. Treating individuals 3: from subgroups to individuals: general principles and the example of carotid endarterectomy. Lancet. 2005; 365: 256–265.CrossrefMedlineGoogle Scholar3 Hacke W, Donnan G, Fieschi C, Kaste M, von Kummer R, Brott T, Frankel M, Grotta J, Haley EJ, Kwiatkowski T, Levine S, Lewandowski C, Lu M, Lyden P, Marler J, Patel S, Tilley B, Albers G, Bluhmki E, Wilhelm M, Hamilton RL, for the ATLANTIS E, and NINDS rt-PA Study Group Investigators. Association of outcome with early stroke treatment: pooled analysis of ATLANTIS, ECASS, and NINDS rt-PA stroke trials. Lancet. 2004; 363: 768–774.CrossrefMedlineGoogle Scholar4 Schellinger PD, Thomalla G, Fiehler J, Kohrmann M, Molina CA, Neumann-Haefelin T, Ribo M, Singer OC, Zaro-Weber O, Sobesky J. MRI-based and CT-based thrombolytic therapy in acute stroke within and beyond established time windows: an analysis of 1210 patients. Stroke. 2007; 38: 2640–2645.LinkGoogle Scholar5 Kidwell CS, Saver JL, Villablanca JP, Duckwiler G, Fredieu A, Gough K, Leary MC, Starkman S, Gobin YP, Jahan R, Vespa P, Liebeskind DS, Alger JR, Vinuela F. Magnetic resonance imaging detection of microbleeds before thrombolysis: an emerging application. Stroke. 2002; 33: 95–98.CrossrefMedlineGoogle Scholar6 Tatsumi S, Ayaki T, Shinohara M, Yamamoto T. Type of gradient recalled-echo sequence results in size and number change of cerebral microbleeds. AJNR Am J Neuroradiol. 2008; 29: e13.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails July 2008Vol 39, Issue 7 Advertisement Article InformationMetrics https://doi.org/10.1161/STROKEAHA.107.522235 Originally publishedMay 22, 2008 PDF download Advertisement

Comparison of two different measurement techniques of hippocampal resection length in temporal lobe epilepsy: results of a prospective study

Magnetic resonance imaging (MRI) volumetry has evolved to a highly sensitive method for presurgical detection of hippocampal sclerosis in temporal lobe epilepsy (TLE). Seizure resolution and neuropsychological sequelae are believed to correlate with extent of resection. Therefore an easy volumetric method to determine extent of resection is desirable. The purpose of this work is to evaluate and compare two different measurement techniques for hippocampal resection length. Sixty-one patients with a mean seizure history of 25.1 years and medically intractable TLE were included. They underwent MRI with sagittal acquired 3D T1-weighted spoiled gradient recalled echo sequence in 1 mm(3) isotropic voxel. Hippocampal resection length was calculated with two different methods. In the slice counting method (SCM) the number of consecutive 1-mm-thick slices containing resected hippocampus formation was counted. In the vector method (VM) the sum of the oblique and thus longer distances between the centre points of segmented hippocampal areas on each MRI slice were calculated. Since the hippocampus is a curved body, the resection lengths measured with VM were always larger than measured with SCM. The comparison of resection length expressed in "percent of total length" showed good agreement between the two methods, because unlike the absolute values of resection length, the percentage values are unaffected by the three-dimensional shape of the hippocampus. The easier and quicker method of "slice counting" may be used to determine resection length expressed in "percent of total length", giving reliable values for resection length but causing less volumetric work.

Brain Parenchymal Signal Abnormalities Associated with Developmental Venous Anomalies: Detailed MR Imaging Assessment

The occurrence of brain parenchymal signal-intensity changes within the drainage territory of developmental venous anomalies (DVAs) in the absence of cavernous malformations (CMs) has been incompletely assessed. This study was performed to evaluate the prevalence of brain parenchymal signal-intensity abnormalities subjacent to DVA, correlating with DVA morphology and location. One hundred sixty-four patients with brain MR imaging with contrast studies performed from July 2005 through June 2006 formed the study group. The examinations were reviewed and data were collected regarding the following: location, depth, size of draining vein, associated increased signal intensity on fluid-attenuated inversion recovery and T2-weighted images, associated CMs, and associated signal intensity on gradient recalled-echo sequences. Of the 175 DVAs identified, 28 had associated signal-intensity abnormalities in the drainage territory. Seven of 28 DVAs with signal-intensity abnormalities were excluded because of significant adjacent white matter signal-intensity changes related to other pathology overlapping the drainage territory. Of the remaining DVAs imaged in this study, 21/168 (12.5%) had subjacent signal-intensity abnormalities. An adjusted prevalence rate of 9/115 (7.8%) was obtained by excluding patients with white matter disease more than minimal in degree. Periventricular location and older age were associated with DVA signal-intensity abnormality. Signal-intensity abnormalities detectable by standard clinical MR images were identified in association with 12.5% of consecutively identified DVAs. Excluding patients with significant underlying white matter disease, we adjusted the prevalence to 7.8%. The etiology of the signal-intensity changes is unclear but may be related to edema, gliosis, or leukoaraiosis secondary to altered hemodynamics in the drainage area.