Detection of clinically silent intracranial emboli ipsilateral to internal carotid occlusions during cerebral angiography

OBJECTIVE: Embolic ischemic events have long been suspected to occur in the cerebral arteries distal to an ipsilateral occluded internal carotid artery (ICA). Documentation of microemboli by transcranial Doppler sonography during catheter angiography in patients with ICA occlusions provides objective evidence of such distal emboli. SUBJECTS AND METHODS: Seven patients undergoing carotid angiography were evaluated with transcranial Doppler sonography. Patients were also screened for ICA occlusions using carotid duplex sonography. In the seven patients, we saw five right ICA occlusions and two left ICA occlusions. Real-time visual and auditory confirmations of emboli were obtained by recognizing their specific spectral signatures and harmonic qualities. Routes of collateral flow were determined from angiography. Specific phases of the examination were correlated with embolic occurrences. RESULTS: Overall, emboli were seen during all phases of arteriography. In the individual patients, emboli were identified in one to four of the eight angiographic phases we defined. Most emboli occurred during catheter flushing and contrast injection rather than during wire and catheter manipulation. The emboli were detected in the middle cerebral artery distribution ipsilateral to the occluded ICA in all seven patients. Collateral flow patterns included, in four patients, external carotid artery-to-ICA collateral flow; in all seven patients, patent anterior communicating arteries; and in three patients, patent posterior communicating arteries. CONCLUSION: Emboli seen in middle cerebral arteries ipsilateral to occluded ICAs during cerebral angiography strongly indicate that emboli can occur distal to an occlusion. Our findings support the thought that emboli arising from sources proximal to an occluded ICA may reach the hemisphere distal to the occlusion, resulting in parenchymal ischemia or infarction.     

明胶海绵栓塞建立实验动物急性脑梗死模型

目的 探讨明胶海绵栓塞猴颈内动脉复制急性脑梗死模型的可行性。方法选用成年猴6只，经股动脉穿刺插管，明胶海绵栓塞颈内动脉，然后行数字减影血管造影（DSA）显示血管闭塞情况，栓塞后3h，4h，6h，8h，12h，24hCT平扫，观察脑梗死CT表现。结果6只猴栓塞后DSA显示颈内动脉闭塞，大脑前、中动脉未显影。栓塞后6hCT平扫可见栓塞侧大脑半球片状低密度坏死区。结论用明胶海绵栓塞颈内动脉复制急性脑梗死模型可行。     

Carotid artery stenosis: intraindividual correlations of 3D time-of-flight MR angiography, contrast-enhanced MR angiography, conventional DSA, and rotational angiography for detection and grading

PURPOSE: To compare three-dimensional (3D) time-of-flight (TOF) MR angiography, contrast-enhanced MR angiography, digital subtraction angiography (DSA), and rotational angiography for depiction of stenosis. MATERIALS AND METHODS: The study had Ethics Committee approval, and each patient gave written informed consent. Forty-nine patients (18 women, mean age, 67.2 years +/- 9.1 [+/- standard deviation], and 31 men, mean age, 63.1 years +/- 8.0) with symptomatic stenosis of internal carotid artery (ICA) diagnosed at duplex ultrasonography underwent transverse 3D TOF MR angiography with sliding interleaved kY acquisition and coronal contrast-enhanced MR angiography, followed by DSA and rotational angiography within 48 hours. MR angiography was performed at 1.5-T with a cervical coil. Contrast-enhanced MR angiograms were obtained after a bolus injection of 20 mL of gadobenate dimeglumine. Maximum ICA stenosis on maximum intensity projection and source images was quantified according to NASCET criteria. Correlations for 3D TOF MR angiography, contrast-enhanced MR angiography, DSA, and rotational angiography were determined by means of cross tabulation, and accuracy for detection and grading of stenoses were calculated. Data were evaluated with analysis of variance, Wilcoxon signed rank test, and McNemar test, all at significance of P < .05. RESULTS: Ninety-eight ICAs were evaluated at contrast-enhanced MR angiography, DSA, and rotational angiography, and 97 were evaluated at 3D TOF MR angiography. Correlations for contrast-enhanced MR angiography, 3D TOF MR angiography, and DSA relative to rotational angiography were r2 = 0.9332, r2 = 0.9048, and r2 = 0.9255, respectively. Lower correlation (r2 = 0.8593) was noted for contrast-enhanced MR angiography and DSA. Respective sensitivity and specificity for detection of hemodynamically relevant stenosis relative to rotational angiography were 100% and 90% for contrast-enhanced MR angiography, 95.5% and 87.2% for 3D TOF MR angiography, and 88.6% and 100% for DSA. Four of 31 severe stenoses were underestimated at DSA, and three were underestimated at contrast-enhanced MR angiography. Three severe stenoses were underestimated at 3D TOF MR angiography, and one was misclassified as occluded. Of 13 moderate (50%-69%) stenoses, one was overestimated at contrast-enhanced MR angiography, two were underestimated and three overestimated at 3D TOF MR angiography, and two were underestimated at DSA. CONCLUSION: DSA results in an underestimation of ICA stenosis compared with rotational angiography. Contrast-enhanced MR angiography correlates best with rotational angiography.     

Vasospasm after subarachnoid hemorrhage: diagnosis with MR angiography

BACKGROUND AND PURPOSE: The possibility of treating intracranial vasospasm has increased the significance of its diagnosis and follow-up; however, so far, no ideal method is available. The goal of this study was to assess the accuracy of MR angiography versus intraarterial angiography (IA-DSA) in detecting vasospasm. METHODS: The study included 42 patients with acute spontaneous subarachnoid hemorrhage (SAH). Serial MR angiograms (minimum, two per patient within 10 days after the event; total, 149) were obtained prospectively using a 3D time-of-flight technique covering the circle of Willis at 0.5 T. Forty-seven MR angiograms could be compared with intraarterial angiograms obtained within 24 hours of MR angiography. Vascular narrowing on both studies was rated consensually by two pairs of neuroradiologists using a scale from 0 (no narrowing) to 3 (severe narrowing). Categories 0 and 1 were considered an absence of vasospasm and categories 2 and 3 a presence of vasospasm. RESULTS: Agreement between MR angiography and IA-DSA (assessed with weighted kappa statistics) was substantial for the middle and anterior cerebral arteries (MCA and ACA) but moderate for the internal carotid artery (ICA). The sensitivity, specificity, accuracy, and positive and negative predictive values of MR angiography for detecting patients with vasospasm were 92%, 98%, 96%, 92%, and 98%, respectively. Considering each vessel separately, specificity was high for all locations (95-99%) and sensitivity was excellent for the ACA (100%) but poorer for the ICA (25%) and MCA (56%). CONCLUSION: MR angiography at 0.5 T is capable of identifying vasospasm after acute SAH but is less sensitive than IA-DSA for depicting vasospasm in the ICA and MCA.     

High-spatial-resolution 3D balanced turbo field-echo technique for MR angiography of the renal arteries: initial experience

PURPOSE: To compare a multislab balanced turbo field-echo magnetic resonance (MR) angiographic technique, without the use of a contrast agent, with digital subtraction angiography (DSA) for imaging of the renal arteries. MATERIALS AND METHODS: Twenty-five randomly selected patients (eight women and 17 men; age range, 27-88 years; mean age, 72 years) suspected of having renal artery stenosis underwent both DSA and balanced turbo field-echo MR angiography. A consensus result was obtained among three radiologists in evaluation of main renal arteries on balanced turbo field-echo images and DSA images. Sensitivity, specificity, and negative and positive predictive values of the balanced turbo field-echo technique were calculated, and receiver operating characteristic analysis was performed for depiction of hemodynamically significant stenosis. Cohen kappa analysis was used to assess agreement between the two imaging methods in grading of stenoses and depiction of significant stenosis. Accessory renal arteries also were evaluated. RESULTS: Fifty main renal arteries and 11 accessory arteries were fully depicted with DSA. DSA depicted 11 stenotic lesions in the main renal arteries. In comparison, balanced turbo field-echo MR angiography enabled visualization of 46 of 50 main renal arteries to their first branching points and depicted 10 of 11 accessory arteries. Sensitivity, specificity, negative predictive value, and positive predictive value of this technique for depiction of significant stenosis were 100% (four of four), 98% (41 of 42), 100% (41 of 41), and 80% (four of five), respectively. The area under the receiver operating characteristic curve was 0.988. kappa was 0.782 for grading of stenoses and 0.877 for depiction of significant stenosis. CONCLUSION: Multislab balanced turbo field-echo imaging has potential as an MR angiography technique for depiction of normal and diseased renal arteries.     

Contrast-enhanced moving-table MR angiography: prospective comparison to catheter arteriography for treatment planning in peripheral arterial occlusive disease

PURPOSE: Prospective comparison of contrast-enhanced moving-table magnetic resonance (MR) angiography to catheter arteriography in endovascular and surgical treatment planning in patients with peripheral arterial occlusive disease. MATERIALS AND METHODS: Thirteen patients scheduled for catheter arteriography for lower extremity arterial occlusive disease underwent contrast-enhanced moving-table MR angiography immediately prior to arteriography. A treatment plan was determined by the vascular surgeon, based on MR angiography, who was blinded to the catheter arteriogram. The treatment plan determined by the MR angiogram was compared to the final treatment plan, which was based on the catheter arteriogram and intraluminal pressure measurements. RESULTS: Treatment plans based on MR angiography and catheter arteriography were identical in 10 of 13 patients (71%). For identifying lesions resulting in intervention, MR angiography had sensitivity of 100% and a positive predictive value of 92%. MR angiography had a treatment specific predictive value of 88% for each lesion identified, and 95% for lesions identified in patients evaluated for claudication. If treatment plans were based on MR angiography only, 46% of patients would have avoided catheter arteriography. CONCLUSION: Contrast-enhanced moving-table MR angiography may be an effective alternative to catheter arteriography in endovascular and surgical treatment planning in selected patients with peripheral arterial occlusive disease, but larger studies are necessary to confirm this.     

Incidence of postangiographic abnormalities revealed by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Occasionally we have observed anecdotal cases of asymptomatic hyperintensities on diffusion-weighted MR (DW-MR) examinations of the brain of patients who previously underwent routine cerebral angiography. These observations, as well as MR imaging and transcranial Doppler data in the literature suggesting a high rate of procedure-associated emboli, raise concern regarding the underdiagnosis of asymptomatic focal infarction associated with cerebral angiography. In order to determine whether asymptomatic diffusion abnormalities are frequently associated with procedures, we prospectively obtained DW-MR images before and after routine cerebral angiography. METHODS: Twenty consecutive patients, who met protocol criteria and received a routine three- or four-vessel diagnostic cerebral angiogram at our institution, were evaluated. Using a Bayesian estimate to establish an upper bound for the incidence of an event with zero occurrences in a study sample, the study group size was selected to exclude a 10% incidence of abnormalities revealed by DW-MR imaging of patients who underwent previous cerebral angiography. Two neuroradiologists evaluated imaging studies. RESULTS: Neither clinical signs nor abnormalities on DW-MR images were found, which suggested no infarction after angiography in our patient sample. Based on this data, an upper bound of 9% (95% confidence) is predicted for the appearance of abnormalities revealed by DW-MR imaging after cerebral angiography. CONCLUSION: Cerebral angiography is associated with an incidence of asymptomatic cerebral infarction of no more than 9%. It well may be substantially lower than this estimate; a more accurate evaluation of the true incidence would require a significantly larger study population. This test provides a convenient noninvasive means of assessing procedure-related cerebral infarction, such as that which occurs after carotid endarterectomy or vascular angioplasty and stenting.     

Imaging of the internal carotid artery: the dilemma of total versus near total occlusion.

PURPOSE: To evaluate ultrasonography (US) and magnetic resonance (MR) angiography in the differentiation between occlusion and near occlusion of internal carotid artery (ICA). MATERIALS AND METHODS: Consecutive patients with occlusion or near occlusion of ICA at catheter angiography and who underwent MR angiography and US were included. MR angiography and US were compared with catheter angiography, the standard, for the ability to help distinguish occlusion from near occlusion. Noninvasive examinations were evaluated for the ability to classify near occlusions as having severe focal stenosis with distal luminal collapse versus diffuse nonfocal disease. The 95% CIs were calculated. RESULTS: In 55 of 274 patients with 548 ICAs, catheter angiography depicted 37 total occlusions and 21 near occlusions. US depicted all total occlusions; MR angiography depicted 34 (92%) (95% CI: 0.78, 0.98). US depicted 18 (86%) of 21 (95% CI: 0.64, 0.97) near occlusions; MR angiography depicted all (100%). Of 18 vessels that were determined to be patent at US, 17 (94%) (95% CI: 0.73, 0.99) were classified as having focal stenosis or diffuse disease. Because flow gaps were identified in vessels with focal and diffuse disease, MR angiography was not effective in helping to differentiate these lesions. CONCLUSION: Assuming US is the initial imaging examination, when occlusion is diagnosed, MR angiography can depict it. If occlusion is confirmed, no further imaging is necessary. US performed well in helping to differentiate vessels with focal severe stenosis from those with diffuse disease. MR angiography added little in this group. Catheter angiography remains beneficial for vessels with diffuse nonfocal narrowing.     

Combined arterial and venous whole-body MR angiography with cardiac MR imaging in patients with thromboembolic disease—initial experience

The objective was to assess the feasibility of a combined arterial and venous whole-body three-dimensional magnetic resonance (MR) angiography, together with a cardiac MR examination, in patients with arterial thromboembolism. Ten patients with arterial thromboembolism underwent a contrast-enhanced whole-body MR examination of the arterial and venous vessels, followed by a cardiac MR examination on a separate occasion within 24 h. All examinations were performed on a 1.5-T MR scanner. For both arterial and venous MR angiography only one injection of contrast agent was necessary. The cardiac imaging protocol included dark-blood-prepared half-Fourier acquisition single-shot turbo-spin-echo sequences, fast steady-state free precession cine sequences, T2-weighted turbo-spin-echo sequences and inversion recovery gradient-echo fast low-angle-shot sequences after injection of contrast agent. MR imaging revealed additional clinically unknown arterial thromboembolisms in four patients. The thoracic aorta was depicted as embolic source in four patients, while deep vein thrombosis (DVT) was found in one patient as the underlying disease. Unsuspected infarction of parenchymal organs was detected by MRI in two patients. An unknown additional DVT was found in one patient. Four patients were considered to have arterial emboli of cardiac origin. In conclusion, acquisition of arterial and venous MR angiograms of the entire vascular system combined with cardiac MR imaging is a most comprehensive and valuable strategy in patients with arterial thromboembolism.     

Pulmonary embolism: comparison of gadolinium-enhanced MR angiography with contrast-enhanced spiral CT in a porcine model

RATIONALE AND OBJECTIVES: The purpose of this study was to compare gadolinium-enhanced magnetic resonance (MR) angiography with contrast material-enhanced computed tomography (CT) for the detection of small (4-5-mm) pulmonary emboli (PE), with a methacrylate cast of the porcine pulmonary vasculature used as the diagnostic standard. MATERIALS AND METHODS: In 15 anesthetized juvenile pigs, colored methacrylate beads (5.2 and 3.8 mm diameter-the size of segmental and subsegmental emboli in humans) were injected via the left external jugular vein. After embolization, MR angiographic and CT images were obtained. The pigs were killed, and the pulmonary arterial tree was cast in clear methacrylate, allowing direct visualization of emboli. Three readers reviewed CT and MR angiographic images independently and in random order. RESULTS: Forty-nine separate embolic sites were included in the statistical analysis. The mean sensitivity (and 95% confidence intervals) for CT and MR angiography, respectively, were 76% (68%-82%) and 82% (75%-88%) (P > .05); the mean positive predictive values, 92% (85%-96%) and 94% (88%-97%) (P > .05). In this porcine model, PE were usually seen as parenchymal perfusion defects (98%) with MR angiography and as occlusive emboli (100%) with CT. CONCLUSION: MR angiography is as sensitive as CT for the detection of small PE in a porcine model.     

Arterial hyperintensity on fast fluid-attenuated inversion recovery images: a subtle finding for hyperacute stroke undetected by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging is generally acknowledged to be more sensitive in detecting acute stroke than is conventional MR imaging. Our purpose in the present study was to evaluate the utility of fast fluid-attenuated inversion recovery (FLAIR) MR imaging compared with that of diffusion-weighted MR imaging for the diagnosis of hyperacute stroke. METHODS: We reviewed patient records and cerebral MR images from all patients in a 13-month period from whom diffusion-weighted and fast-FLAIR imaging were obtained within 6 hours after symptom onset (n = 11). Special attention was paid to the presence or absence of arterial hyperintensity on FLAIR images and abnormally high-signal regions on diffusion-weighted images in the affected vascular territories. RESULTS: Arterial hyperintensity was found in eight of 11 patients, all of whom had embolic or thrombotic infarctions with middle cerebral arterial (MCA) distribution. Arterial hyperintensity was negative in the remaining three patients; the vascular territories were the posterior circulation region in two of these patients and the MCA region in one, and the types of infarction in these same patients were lacunar in two and embolic in one. Regions with high-signal diffusion abnormalities relevant to the patients' symptoms were found in 10 of 11 patients. One patient showed no diffusion abnormalities but the presence of arterial hyperintensity in the affected MCA territory on the initial MR examination, and manifested embolic infarction along with arterial hyperintensity on the initial FLAIR image. CONCLUSION: Although diffusion-weighted MR imaging is highly sensitive to stroke, diffusion-weighted MR imaging alone may not rule out a possible infarction. Arterial hyperintensity on FLAIR images can precede diffusion abnormalities and may provide a clue to the early detection of impending infarction.     

Preliminary experience with dynamic MR projection angiography in the evaluation of cervicocranial steno-occlusive disease

The application of a contrast-enhanced, two-dimensional MR technique, which provides dynamic projection angiograms at a subsecond temporal frame rate for depiction of the cervical and intracranial arteries, was evaluated in three healthy volunteers and seven patients with various cervicocranial steno-occlusive diseases. Intra-arterial digital subtraction angiography (DSA) served as standard of reference for findings in the patients. Magnetic resonance projection angiography (MRPA) was performed on a standard 1.5-T clinical MR imaging system at intravenous injection of a single dose of contrast agent (0.1 mmol/kg GdDTPA-BMA). Sixty consecutive images of the cerebral circulation were acquired at a temporal frame rate of 900 ms per image in the coronal plane. The collateral flow and the perfusion of the compromised vessel territory were readily assessed by MPRA in patients with occlusion of the internal cerebral artery (ICA) or middle cerebral artery (MCA). The leptomeningeal collateralisation of these patients was displayed in a dynamic fashion. Furthermore, quantitative perfusion measurement provided a difference between both MCA territories in the time to peak (ΔDTTP) of the contrast bolus of 1.12 ± 0.28 s in five patients with severe stenosis or occlusion of the ICA (healthy volunteers 0.19 ± 0.05 s). However, important pathological findings, such as the evaluation of carotid artery stenoses and the intracranial collateral flow pattern in patients with severe carotid stenoses, were not sufficiently assessable as compared with DSA. We conclude that the possibility of obtaining simultaneously information about morphology and perfusion dynamics of the cervicocranial vessels is unique in MPRA as compared with other MR techniques. However, in the applied form, the technique is not a reliable tool for the complete evaluation of the cervicocranial vessels in patients with steno-occlusive disease. Received: 27 January 2000/Revised: 11 July 2000/Accepted: 13 July 2000     

Noninfarcted myocardium: correlation between dynamic first-pass contrast-enhanced myocardial MR imaging and quantitative coronary angiography

PURPOSE: To determine the accuracy of first-pass contrast material-enhanced stress myocardial magnetic resonance (MR) imaging for depiction of myocardial ischemia in patients without myocardial infarction. MATERIALS AND METHODS: First-pass contrast-enhanced MR images of the entire left ventricle were acquired in 104 patients at rest and during dipyridamole-induced stress by using an interleaved notched saturation technique. Coronary angiography was performed in all patients, and stress perfusion single photon emission computed tomography (SPECT) was performed in 69 patients. Receiver operating characteristic curve analysis was performed to compare the diagnostic accuracies of first-pass contrast-enhanced stress MR imaging and stress SPECT, with coronary angiography as the reference standard. RESULTS: The overall sensitivity of MR imaging for depicting at least one coronary artery with significant stenosis was 90% (69 of 77 patients). The sensitivities of MR imaging for depiction of single-, double-, and triple-vessel stenoses were 85% (33 of 39 patients), 96% (22 of 23 patients), and 100% (15 of 15 patients), respectively. The specificity of MR imaging for identification of patients with significant coronary artery stenoses was 85% (23 of 27 patients). The areas under the receiver operating characteristic curve for detection of significant stenosis in individual coronary arteries were 0.888 (observer 1) and 0.911 (observer 2) for MR imaging and 0.707 (observer 1, P <.001) and 0.750 (observer 2, P <.001) for SPECT. CONCLUSION: In patients without myocardial infarction, stress enhancement at dynamic MR imaging correlates more closely with quantitative coronary angiography results than does stress enhancement at SPECT.     

Atherosclerotic disease: whole-body cardiovascular imaging with MR system with 32 receiver channels and total-body surface coil technology--initial clinical results

In this prospective study, the feasibility of a comprehensive cardiovascular imaging protocol with a dedicated whole-body 1.5-T magnetic resonance (MR) imager with 32 receiver channels in 34 patients with peripheral arterial occlusive disease was evaluated. Informed consent and institutional review board approval were obtained. Three-dimensional MR angiographic data sets were acquired with adapted injection protocol. Cardiac functional imaging and delayed-enhancement imaging were performed, as were fluid-attenuated inversion-recovery imaging of the brain and time-of-flight MR angiography of the intracranial blood vessels. Sensitivity and specificity for depiction of significant vascular stenosis (> 70%) were 96%, with conventional digital subtraction angiography as the standard. Substantial microangiopathic tissue alterations (n = 4) and/or cerebral infarction (n = 4) were diagnosed in seven patients. In seven patients, subendocardial or transmural delayed enhancement was detected in corresponding regions, indicating prior myocardial infarction. Previously unknown findings diagnosed with MR imaging required midterm follow-up or therapy in 24 patients, whereas change of therapy or immediate treatment was necessary in three. For patients suspected of having systemic atherosclerotic disease, comprehensive risk assessment is feasible within 30 minutes.     

小儿缺血性脑血管病的MRI及MRA诊断

目的 评价磁共振成像（MRI）及磁共振血管成像（MRA）对小儿缺血性脑血管病的诊断价值。方法 回顾性分析了42例小儿缺血性脑血管病患，年龄1.2-14岁，平均7.5岁，全部病例均以急性起病的运动，语言障碍为主要症状来诊，采用轴位T1，T2加权像，部分病例加做冠状位或矢状位成像，其中31例进行了时间飞跃（TOF）法MR血管成像。结果 本组共发现脑缺血8例，脑梗塞34例（其中腔隙梗塞22例，大面积梗塞12例），单支颅内动脉狭窄6例。多支动脉狭窄4例；单支动脉闭塞3例。多支动脉闭塞2例；MOYAMOYA病9例（其中3例可见脑底异常血管网）。4例图像上有运动伪影，但能达到诊断要求，全部病例中，MRI表现典型，能单独确诊36例，占85.7%，MRI与MRA相结合能确诊40例，达95.2%，其余2例仅用MRI及MRA不能明确诊断，需结合临床资料及经随访证实。结论 MRI结合MRA是小儿缺血性脑血管病的理想检查方法，可准确显示脑动脉的狭窄，闭塞性病变及其继发的脑缺血，梗塞病灶，对定性诊断具有重要价值。     

Acute pulmonary embolism: diagnosis with MR angiography

PURPOSE: To prospectively evaluate pulmonary magnetic (MR) angiography as a diagnostic examination for acute pulmonary embolism (PE). MATERIALS AND METHODS: Thirty-six consecutive patients (19 women, 17 men; age range, 28-84 years) underwent pulmonary digital subtraction angiography (DSA) and pulmonary MR angiography. MR angiograms were obtained during suspended respiration and the pulmonary arterial phase of gadolinium-based contrast medium injection. A steady-state gradient-recalled-echo sequence with free induction decay sampling was used. DSA studies were interpreted for the presence of acute PE by two independent radiologists; an adjudicator made the final decision on discordant interpretations. RESULTS: By using DSA, a total of 19 acute pulmonary emboli were depicted in 13 patients. Prospectively, 13 of these emboli were depicted by using MR angiography. MR angiography missed six emboli: Four required the DSA adjudicator to make the decision, and one was in a patient whose MR angiogram was acquired during breathing. Four of these six emboli were small subsegmental emboli, and two were segmental. CONCLUSION: Performed without pulmonary arterial catheterization, iodinated contrast media, or ionizing radiation, pulmonary MR angiography had a high accuracy for depicting lobar and segmental emboli, but was unable to depict four of five subsegmental emboli.     

Hyperacute ischemic stroke: middle cerebral artery susceptibility sign at echo-planar gradient-echo MR imaging

PURPOSE: To evaluate the accuracy of echo-planar T2*-weighted magnetic resonance (MR) sequences in detection of acute middle cerebral artery (MCA) or internal carotid artery (ICA) thrombotic occlusion. MATERIALS AND METHODS: Forty-two consecutive patients with stroke involving the MCA territory underwent MR imaging within 6 hours after clinical onset. MR examination included echo-planar T2*-weighted, diffusion-weighted (DW), and perfusion-weighted (PW) imaging and MR angiography. Presence or absence of the susceptibility sign on echo-planar T2*-weighted images, which is indicative of acute thrombotic occlusion involving MCA or ICA, was assessed in consensus by two observers blinded to clinical information and other MR imaging data. Differences in lesion volume on DW and PW images between patients with and those without the susceptibility sign were evaluated with the Mann-Whitney test. P <.05 was considered to indicate a significant difference. RESULTS: Thirty patients (71%) had a positive susceptibility sign that correlated with MCA or ICA occlusion at MR angiography in all cases (sensitivity, 83%; specificity, 100%). Mean lesion volume on PW images was higher in patients with a positive susceptibility sign (P =.01), but no significant differences were found in mean lesion volume on DW images. Cases in which the susceptibility sign was identified proximal to MCA divisional bifurcation (27 patients) showed a mean perfusion deficit of 83.9% of the total MCA territory (range, 50%-100%). CONCLUSION: Presence of the susceptibility sign proximal to MCA bifurcation provides fast and accurate detection of acute proximal MCA or ICA thrombotic occlusion.     

MR angiography in children with cerebral neurovascular diseases: findings in 31 cases.

OBJECTIVE. We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease. SUBJECTS AND METHODS. Thirty-one children, 6 months to 14 years old, with intracranial lesions or clinically suspected vascular malformations were studied prospectively with conventional MR imaging and time-of-flight MR angiography. In nine cases, MR angiographic findings were verified with digital subtraction angiography or conventional angiography. All MR studies were performed on a 1.5-T MR system using a circularly polarized head coil. RESULTS. Arterial MR angiography, performed in 24 cases, revealed congenital abnormalities of the arterial vessels in 20 cases. Vessel stenosis was observed in nine patients, and displacement of intracranial arteries due to tumors could be seen in 10 patients. Seven children had no abnormal findings. Venous MR angiography was performed in seven children, with depiction of sinus thrombosis in six cases. The comparative analysis of MR angiography and digital subtraction angiography showed equivalent results in nine patients; in one patient the degree of stenosis was overestimated with MR angiography. CONCLUSION. MR angiography, when combined with MR imaging, reveals information about soft-tissue and vascular structures in a single setting. At this point, MR angiography can replace invasive conventional angiography or digital subtraction angiography only in selected cases because of software and hardware limitations. Arterial or venous MR angiography can be helpful as an additional scan in MR examinations of children with suspected cerebral neurovascular diseases, and its noninvasive nature makes it well suited for routine use in children.     

Right lobe living donor liver transplantation: preoperative evaluation of the donor with MR imaging

OBJECTIVE: The purpose of this study was to report our experience in preoperative evaluation of right hepatic lobe donors with a comprehensive MR examination and to compare abdominal MR images, MR cholangiograms, and MR angiograms with findings at surgery, intraoperative cholangiography, and digital subtraction angiography. MATERIALS AND METHODS: Twenty-eight right hepatic lobe donors underwent preoperative evaluation with MR imaging, MR cholangiography, and MR angiography. Two abdominal radiologists independently and randomly reviewed these studies. Points of assessment included focal and diffuse liver disease, calculation of right lobe volumes, depiction of the biliary tract and ductal anomalies, and depiction of the liver vasculature and vascular anomalies. Comparison was made with intraoperative cholangiograms (n = 20) and digital subtraction angiograms (n = 28). RESULTS: MR imaging revealed and characterized focal liver lesions in eight of 28 patients. Calculated right lobe volumes agreed with surgically determined volumes within 7% for reviewer 1 and within 15% for reviewer 2. Intrahepatic bile ducts were depicted completely with MR cholangiography in 25 of 28 patients and with intraoperative cholangiography in nine of 20 patients. MR cholangiography revealed ductal anomalies in six patients. MR imaging and MR angiography depicted the portal veins more completely than digital subtraction angiography. MR imaging and MR angiography correctly excluded portal venous anomalies in all patients and revealed surgically confirmed accessory hepatic veins in six of 28 patients. Angiographically confirmed arterial anomalies were correctly detected in three of 28 patients by at least one reviewer on MR imaging and MR angiography. CONCLUSION: MR imaging, MR cholangiography, and MR angiography provide a comprehensive, accurate means of evaluating donors for factors that may preclude or complicate right hepatic lobe donation.     

Various patterns of perfusion-weighted MR imaging and MR angiographic findings in hyperacute ischemic stroke.

BACKGROUND AND PURPOSE: Various clinical subtypes of patients presenting with sudden-onset ischemic stroke have been recognized, but classification of those types is not simple. We identified various patterns of perfusion-weighted MR imaging and MR angiographic findings in hyperacute ischemic stroke with relation to clinical outcomes. METHODS: Twelve patients with symptoms of acute ischemic stroke due to middle cerebral artery occlusion underwent perfusion-weighted MR imaging and MR angiography within 6 hours after the onset of symptoms. Perfusion-weighted imaging was performed with a conventional dynamic contrast-enhanced T2*-weighted sequence, and cerebral blood volume (CBV) maps were then created. CBV maps and MR angiographic findings were compared with 99mTc-HMPAO brain SPECT scans, short-term outcomes, and follow-up imaging findings. RESULTS: The combined CBV and MR angiographic findings were classified into three patterns: arterial occlusion and decreased CBV (n = 8), arterial occlusion and increased CBV (n = 2), and no arterial occlusion and normal CBV (n = 2). These three patterns were strongly related to SPECT findings, short-term outcomes, and follow-up imaging findings. Perfusion on SPECT decreased markedly in the affected regions in all patients with the first pattern, decreased slightly in the second pattern, and was normal in the third pattern. Symptoms were not significantly changed at 24 hours after onset in any of the patients with the first pattern, but resolved completely in all patients with the latter two patterns. Follow-up imaging showed large infarctions in all patients with the first pattern. Initially, no infarction was seen in the second pattern, but watershed infarction developed later in one of these patients. CONCLUSION: Hyperacute ischemic stroke may be differentiated into three imaging patterns with different clinical outcomes. The combined use of perfusion-weighted MR imaging and MR angiography may play a substantial role in guiding the choice of treatment of this disease.