Weighted Gradient Echo Magnetic Resonance Research Articles

Abstract TP186: The Presence of Low Signal on T2*-Weighted Gradient Echo Magnetic Resonance Imaging Before MT Should Be Not Associated With Hemorrhagic Complications

Background: In patients with acute ischemic stroke with the large vessel occlusion (LVO), the presence of low signal including microbleeds on T2*-weighted gradient echo magnetic resonance imaging (T2*-positive) which suggestive of an old cerebral hemorrhage before mechanical thrombectomy (MT) may be associated with hemorrhagic change after MT, but the significance of this finding is unclear. Methods: Patients with acute stroke with LVO underwent T2* before MT. Patients were classified into two groups as T2*-positive and T2*-negative. We compared hemorrhagic change after MT, outcome at discharge and clinical characteristics between two groups. The occurrence of hemorrhagic change was assessed on CT after MT. Patients outcomes were classified into two group; good outcome as modified Rankin Scale (mRS) 0-2 and poor outcome as mRS 5-6, respectively. Clinical characteristics and imaging factors associated with any ICH after MT were evaluated by multivariate regression analysis. Results: 348 patients (median age, 78 years; men, 60.1%; median NIHSS score, 16) were enrolled. The site of occlusion was the ICA (n=92, 26.4%), M1 (n=168, 48.3%), M2 (n=49, 14.1%) and BA(n=29, 8.3%). T2*-positive and T2*-negative were found in 73 (21.0%) and 275 (79.0%), respectively. There were no differences in age, history of hypertension, diabetes, atrial fibrillation and stroke, TOAST type, DWI-ASPECTS, NIHSS, use of tPA, or TICI≧2B rate between the two groups. Any ICH after MT was 28 (38.4%) in T2*-positive and 96 (34.9%) in T2*-negative (P=0.585). PH and SAH were 7 (9.6%) and 2 (2.7%) in T2*-positive and 40 (14.9%) and 25 (9.1%) in T2*-negative (P=0.337, and P=0.085), respectively. Poor outcome was 27 (37.0%) in T2*-positive and 65 (23.6%) in T2*-negative (P=0.025), respectively. Multivariate regression analysis demonstrated that T2*-positive was not associated with any ICH (odds ratio, 0.884; confidence interval, 0.473-1.654; P=0.700). Conclusions: In patients with acute ischemic stroke with LVO, low signal on T2* before MT should not be associated with hemorrhagic change after MT.

Abstract TP248: Distribution and Number of Cerebral Microhemorrhages Differ According to Ischemic Stroke Subtype

Introduction: Cerebral microhemorrhages/microbleeds (CMBs) are foci of hemosiderin deposition that appear as well-circumscribed hypointensities on T2*-weighted gradient echo magnetic resonance imaging(1). They are a bio marker of small vessel disease but may also be seen as a consequence of thromboembolism to the brain and are commonly seen in the wake of acute ischemic stroke(2). We sought to understand the relationship between CMB burden and distribution and ischemic stroke subtype. Methods: We undertook a retrospective observational study of patients admitted for management of acute ischemic stroke via clinical data archived as part of an institutional quality improvement project. Patient information was gathered including demographics, past medical history, treatment and ischemic stroke subtype. T2*/GRE imaging was inspected and the presence or absence, number and distribution of definite CMBs (according to Microbleed Anatomic Rating Scale (MARS) criteria(3) was documented for each patient. Results: 695 patients with acute ischemic stroke confirmed on imaging had T2*/GRE imaging of adequate quality. The mean age in our population was 71.14 (+-15.28). 22.3% of the population had CMBs and the average number of CMBs per person was 0.66. The mean number of CMBs was higher in patients with stroke of small vessel etiology (mean of 1.97) compared with the group as a whole and this difference persisted after adjusting for age and hypertension (p=0.024). Patients with stroke of cardioembolic etiology had a higher proportion of lobar microhemorrhages (11.83%) compared with those with stroke of small vessel etiology (6.90%) though this difference did not persist after adjusting for age. Discussion: Distribution and number of CMBs differ based on stroke pathophysiology. CMB pattern may aid in distinguishing strokes of small vessel etiology from other ischemic stroke subtypes.

Susceptibility Vessel Sign on T2*-Weighted Gradient Echo Imaging in Lacunar Infarction.

In stroke due to large vessel occlusion, thrombotic material can be demonstrated by the susceptibility vessel sign (SVS), a hypointense signal on T2*-weighted gradient echo magnetic resonance (GRE) images. In the present study, we evaluated the value of GRE for the detection of perforating artery occlusion in hyperacute lacunar infarction (LI). The presence of SVS on GRE in 58 patients with LI who underwent magnetic resonance imaging within 24 hours after symptom onset was analyzed. On diffusion-weighted images (DWI), LI was found in the basal ganglia in 17.2%, internal capsule in 25.9%, corona radiata in 19.0%, thalamus in 32.8%, and brainstem in 5.2%. On GRE a subtle circumscribed hypointense signal at the lower edge of the LI consistent with SVS was detected in 11/58 (19%) patients. Patients with SVS had larger ischemic lesions on DWI (p=0.045). SVS on GRE may be useful for detection of perforating artery occlusion in a subset of patients with hyperacute LI.

Risk Factors of Cerebral Microbleeds in Strictly Deep or Lobar Brain Regions Differed

T2*-weighted gradient echo magnetic resonance imaging is sensitive in detecting cerebral microbleeds (MBs), but there are few reports on the risk factors of MBs in different brain regions. Therefore, we aimed to investigate whether the risk factors associated with the presence of MBs in strictly deep or lobar brain regions were different. This study consisted of 696 consecutive acute ischemic stroke patients from 6 hospitals in the Chinese IntraCranial AtheroSclerosis Study. We evaluated the number and location of MBs, severity of lacune and leukoaraiosis (LA), and etiologic subtype of ischemic stroke. Multivariable logistic regression was used to analyze risk factors of MBs in different brain regions. Among 696 acute ischemic stroke patients, 162 patients (23.3%) had MBs. Of them, 62 patients had strictly deep brain MBs, 49 patients had strictly lobar MBs. There was a significant correlation between the number of MBs, the number of lacune, and the severity of LA (P < .0001). In multivariable logistic regression analysis, both strictly deep and strictly lobar brain, MBs were significantly associated with history of cerebral hemorrhage (P = .037 and P = .026, respectively), presence of lacune (P = .004 and P = .032, respectively), and severe LA (P = .002 and P = .008, respectively). However, MBs in strictly deep regions were significantly associated with higher mean arterial pressure (P = .030), and those in strictly lobar brain regions were significantly associated with older age (P = .023). The risk factors of MBs in strictly deep or lobar regions differ modestly, which may be related to heterogeneous vascular pathologic changes.

Assessment of Hepatic and Pancreatic Iron Overload in Pediatric Beta-Thalassemic Major Patients by Weighted Gradient Echo Magnetic Resonance Imaging

Background. MRI has emerged for the noninvasive assessment of iron overload in various tissues. The aim of this paper is to evaluate hepatic and pancreatic iron overload by T2∗ weighted gradient echo MRI in young beta-thalassemia major patients and to correlate it with glucose disturbance and postsplenectomy status. Subjects and Methods. 50 thalassemic patients, in addition to 15 healthy controls. All patients underwent clinical assessment and laboratory investigations. Out of 50 thalassemic patients, 37 patients were splenectomized. MRI was performed for all subjects. Results. All patients showed significant reduction in the signal intensity of the liver and the pancreas on T2∗GRD compared to controls, thalassemic patients who had abnormal glucose tolerance; diabetic and impaired glucose tolerance patients displayed a higher degree of pancreatic and hepatic siderosis and more T2∗ drop in their signal intensity than those with normal blood sugar level. Splenectomized thalassemic patients had significantly lower signal intensity of the liver and pancreas compared to nonsplenectomized patients. Conclusion. T2∗ gradient echo MRI is noninvasive highly sensitive method in assessing hepatic and pancreatic iron overload in thalassemic patients, more evident in patients with abnormal glucose tolerance, and is accelerated in thalassemic splenectomized patients.

Stroke patients with cerebral microbleeds on MRI scans have arteriolosclerosis as well as systemic atherosclerosis

Cerebral microbleeds (CMBs) are recognized as a manifestation of arteriolosclerosis in cerebral small vessels. However, little is known regarding whether stroke patients with CMBs often have systemic atherosclerosis. The aim of the present study was to elucidate this issue using the cardio-ankle vascular index (CAVI), a new index of systemic atherosclerosis, in acute ischemic stroke patients. We prospectively studied 105 patients (71 males, median age=70.0 years) with acute ischemic stroke. All of the patients were examined using T2*-weighted gradient echo magnetic resonance imaging (MRI) to look for and assess the CMBs and using fluid-attenuated inversion recovery to evaluate white matter hyperintensity (WMH). We assigned the patients into CMB and non-CMB groups and compared the clinical characteristics of these groups. The factors associated with CMBs were investigated using multivariate logistic regression analysis. T2*-weighted gradient echo MRI revealed CMBs in 47 patients (44.8%) and no CMBs in 58 patients (55.2%). The CAVI was significantly higher in the CMBs group (10.5 vs. 8.6, P<0.001). In the multivariate logistic regression analysis, CAVI per one point increase (odds ratio (OR), 1.50; 95% confidence interval (CI), 1.12-2.00; P=0.006), advanced WMH (OR, 4.78; 95% CI, 1.55-14.74; P=0.006) and impaired kidney function (OR, 3.31; 95% CI, 1.16-9.81; P=0.031) were independent factors associated with the presence of CMBs. A high CAVI was independently associated with CMBs in patients with acute ischemic stroke. Our results indicated that ischemic stroke patients with CMBs may have cerebral arteriolosclerosis as well as systemic atherosclerosis.

Comparative Magnetic Resonance Imaging at 1.5 and 3 Tesla for the Evaluation of Traumatic Microbleeds

Traumatic microbleeds (TMBs) can be regarded as a radiological marker of diffuse axonal injury (DAI). We sought to investigate the impact of the field strengths on the depiction of TMBs by T2*-weighted gradient echo magnetic resonance imaging (MRI). By the use of comparative MRI of 14 patients (age range, 22-62 years) on 1.5- and a 3 T (Tesla) systems at a median time interval of 61 months after traumatic brain injury (TBI), we found 239 (range 0.5-48.5, median 7.5) TMBs at 1.5 T, and 470 (range 2-118, median 18.5) TMBs at 3 T, respectively (p=0.001). However, in all but one patients MRI at 1.5 T also clearly showed TMBs. A significant negative correlation between the number of TMBs and the time interval TBI-MRI was observed, which was weaker for the imaging at 3 T (r(s)=-0.798; p=0.001; and r(s)=-0.649; p=0.012, respectively). In conclusion, T2*-weighted gradient-echo MRI at 3 T is superior as compared to MRI at 1.5 T for the detection of TMBs. Nevertheless, in clinical practice, MRI at 1.5 T seems to be sufficient for this purpose. MRI at 3 T may be appropriate if there is a strong clinical suspicion of DAI, despite unremarkable routine MRI, and possibly also if evidence of DAI is sought after a long interval from trauma.

High Incidence of Microbleeds in Hemodialysis Patients Detected by T2*-Weighted Gradient-Echo Magnetic Resonance Imaging

The incidence and characteristics of microbleeds in hemodialysis (HD) patients were investigated to elucidate the clinical significance with T(2)(*)-weighted gradient-echo magnetic resonance (MR) imaging. The 57 patients with chronic renal failure maintained by HD had no previous history of stroke. The control group consisted of 53 patients without previous history of stroke or chronic renal failure. The incidence and the number of microbleeds were assessed in the HD and control groups. The findings of microbleeds with T(2)(*)-weighted gradient-echo MR imaging were compared with those of T(1)- and T(2)-weighted MR imaging in HD patients. The incidence of microbleeds was significantly greater in the HD patients compared with the control patients. T(2)(*)-weighted gradient-echo imaging revealed a total of 44 microbleeds in 11 HD patients. T(2)-weighted imaging demonstrated 13 of 44 microbleeds as hyperintensity, whereas T(1)-weighted imaging demonstrated 12 lesions as hypointensity. T(2)- and T(1)-weighted imagings did not demonstrate any findings in 31 and 32 lesions, respectively. T(2)(*)-weighted gradient-echo MR imaging is effective to detect microbleeds which may be a predictor of intracerebral hemorrhage in HD patients and should be included in the protocol for the study of cerebrovascular disease, because T(2)- and T(1)-weighted MR imaging recognizes microbleeds as lacunar infarction.

Relationship between stroke and asymptomatic minute hemorrhages in hypertensive patients.

Asymptomatic small hemorrhages were identified in hypertensive patients by T2*-weighted gradient echo magnetic resonance (MR) imaging to investigate the relationship between hypertensive intracerebral hemorrhage and asymptomatic minute hemorrhages. Forty-eight patients with hypertensive intracerebral hemorrhage or cerebral infarction with hypertension (these diseases were defined as stroke) were treated in National Defense Medical College from April 1998 to February 2000. All patients had no past history of stroke or head injury, underwent MR imaging within 6 months of the stroke attack, were aged from 40 to 80 years, and had no diagnosis of aneurysm, angioma, or moyamoya disease. Patients were divided into the infarction group and hemorrhage group. All foci over 2 mm in size appearing as hypointense on T2*-weighted MR imaging and unrelated to stroke areas were defined as minute hemorrhages. There were no significant differences between the two groups with respect to sex, age, and history of diabetes mellitus. The incidence of minute hemorrhages in the hemorrhage group (21/26) was greater than in the infarction group (9/22, p < 0.01). The incidence of minute hemorrhages in the basal ganglia (18/26) was greater in the hemorrhage group than in the infarction group (4/22, p < 0.001). Symptomatic intracerebral hemorrhage may be preceded by asymptomatic minute hemorrhage.