Takayasu's arteritis: assessment of disease activity with contrast-enhanced MR imaging

OBJECTIVE: The purpose of this study was to evaluate the role of contrast-enhanced MR imaging in the determination of disease activity in patients with Takayasu's arteritis. SUBJECTS AND METHODS: High-resolution contrast-enhanced T1-weighted spinecho MR imaging using small fields of view (14-20 cm) and thin slices (4-5 mm) was performed in 26 patients with Takayasu's arteritis and 16 healthy subjects. The degree of aortic mural enhancement was assessed by measuring signal intensity and by visually estimating it in comparison with that of the myocardium. RESULTS: Contrast-enhanced MR imaging showed more enhancement of thickened aortic wall compared with myocardium, thus suggesting active Takayasu's arteritis on MR imaging in 16 patients. Determination of disease activity using contrast-enhanced MR imaging was concordant with clinical findings in 23 patients (88.5%). Contrast-enhanced MR findings were concordant with laboratory findings in most patients (erythrocyte sedimentation rate in 92.3% [24/26] and C-reactive protein in 84.6% [22/26]). The measured signal intensity of the aortic wall relative to that of myocardium during the early phase of contrast-enhanced MR imaging correlated well with the erythrocyte sedimentation rate (r = 0.78, p < 0.005) and with the C-reactive protein level (r = 0.63, p < 0.005). CONCLUSION: Contrast-enhanced MR imaging provides information about disease activity of Takayasu's arteritis, which may be useful in the diagnosis and treatment of Takayasu's arteritis.     

Contrast media for MR imaging of the heart

The role of contrast media for quantitative characterization of ischemic myocardial events with magnetic resonance (MR) imaging has advanced considerably in the past few years. Contrast material-enhanced MR imaging is useful for identifying and sizing myocardial infarcts and for distinguishing between occlusive and reperfused myocardial infarcts. Recent results suggest that contrast-enhanced MR imaging can also be used to identify areas of cell death in regions of reperfused myocardial infarction. With the aid of MR contrast media, fast MR imaging techniques may be useful in estimating regional myocardial perfusion. Although no simple relationship between signal intensity and concentration exists, contrast-enhanced MR perfusion imaging can demonstrate the presence and relative severity of hypoperfused myocardium. Combining myocardial perfusion imaging with the anatomic and functional information provided by other MR imaging techniques could make MR imaging a comprehensive noninvasive means of evaluating ischemic cardiac disease.     

Occlusive myocardial infarction: investigation of bis-gadolinium mesoporphyrins-enhanced T1-weighted MR imaging in a cat model

PURPOSE: To test whether bis-gadolinium mesoporphyrins-enhanced magnetic resonance (MR) imaging can accurately depict irreversibly damaged myocardium in occlusive myocardial infarction. MATERIALS AND METHODS: Ten cats were subjected to 90 minutes of occlusion of the left anterior descending coronary artery. Bis-gadolinium mesoporphyrins-enhanced T1-weighted MR imaging was performed in the cats for 6 hours. Histopathologic examinations with 2'3'5-triphenyl tetrazolium chloride (TTC) staining and electron microscopy were performed on the resected specimens. The time course and pattern of signal intensity enhancement were evaluated. The size of the infarcted myocardium was estimated on the MR images by measuring the size of the signal intensity-enhanced area. RESULTS: In eight of 10 cats, it was impossible to distinguish infarcted myocardium from normal myocardium at visual inspection of T1-weighted MR images. The contrast ratio between infarcted and normal myocardium did not increase significantly over time. In one of the two remaining cats, a doughnut pattern of signal intensity enhancement was noted. The other cat showed intensely homogeneous enhancement of infarcted myocardium at MR imaging. The size of the area of signal intensity enhancement at MR imaging in these two cats was accurately mapped to that of the infarction on the TTC-stained specimens. CONCLUSION: Occlusive myocardial infarction cannot be accurately detected at bis-gadolinium mesoporphyrins-enhanced MR imaging.     

Differences in null points between the left and right ventricles in contrast-enhanced inversion recovery MR imaging in patients with cardiac diseases.

Delayed contrast-enhanced inversion recovery (IR) gradient-echo MR imaging has been applied to several cardiac diseases, including myocarditis, sarcoidosis, hypertrophic cardiomyopathy, and myocardial damages induced by medical procedures. Although a preliminary study has indicated the usefulness of this imaging for the detection of right ventricular (RV) myocardial damage associated with arrhythmogenic right ventricular cardiomyopathy, the null points of the RV myocardium have not been assessed on contrast-enhanced IR MR imaging. In this study, the null points of the RV and left ventricular (LV) myocardia were evaluated using an IR fast multi-shot echo-planar imaging (Look-Locker sequence) in 26 patients with various cardiac diseases. In nine of the 26 patients, the null points of the RV myocardium were shorter than those of the LV myocardium in the Look-Locker sequence. The RV myocardial signals were significantly higher than the LV myocardial signals in delayed contrast-enhanced MR images. Thus, more attention should be paid to evaluation of the late enhancement of the RV myocardium, and delayed contrast-enhanced MR imaging with a shorter inversion time may be required in some cases.     

Dynamic multi-section CT imaging in acute myocardial infarction: preliminary animal experience

To evaluate the feasibility of myocardial first-pass perfusion imaging with multidetector CT (MDCT). In five pigs, myocardial infaction was induced by permanent balloon occlusion of the left anterior descending coronary artery. Dynamic contrast-enhanced MDCT (12×1.5 mm, 120 kV, 30 mAs, 64 acquisitions, 40 ml iopromide 370@4ml/s) and contrast-enhanced first-pass perfusion magnetic resonance (MR) imaging (TR 7.7 ms/TE 2.6 ms, 64 acquisitions, 0.05 mmol/kg Gd-DTPA) were performed. Finally, the animals were sacrificed, and the heart was excised and stained with triphenyltetrazolin-chloride (TTC). Maximum signal intensity (SI_max), contrast material arrival time (CAT), wash-in time (T_max) and slope were calculated from time-density/signal-intensity curves. The area of myocardial hypoperfusion was measured as the percentage of the left-ventricular area (%LV). Parameters were compared using Bland-Altman plots and Student's t-tests. The hypoperfused area on MDCT was 19.3±4.5%LV (MR imaging 17.2±4.0%LV). The mean size of infarction was 18.7±5.7%LV with TTC. Semiquantitative analysis of MR imaging and MDCT for SI_max, T_max and slope showed significant differences between normal and infarcted myocardium (P<0.05). No significant differences were found for CAT. MDCT and MR imaging both allowed for the differentiation of hypoperfused and normal myocardium. Results given in absolute values differed significantly between both imaging modalities (P<0.05). MDCT has the potential for visual and semiquantitative assessment of first-pass myocardial perfusion.     

Spatially resolved imaging of myocardial function with strain-encoded MR: comparison with delayed contrast-enhanced MR imaging after myocardial infarction

Strain-encoded magnetic resonance (MR) imaging was prospectively evaluated for direct imaging of systolic myocardial strain and compared with cross-registered delayed contrast material-enhanced MR imaging in five healthy volunteers and nine patients with infarction. Local contractile performance was decreased in infarcted myocardium versus that in remote and adjacent myocardium (P < .01) and in adjacent versus remote myocardium (P < .05). The extent of dysfunctional myocardium, as assessed with strain-encoded MR imaging, was greater than that of hyperenhancement, as assessed with delayed contrast-enhanced MR imaging (P < .05). Strain values obtained with strain-encoded MR imaging were strongly correlated with those obtained with three-dimensional tagged MR imaging (r = 0.75, P < .001). Strain-encoded MR imaging provides spatially resolved (1.5 x 2.5-mm) imaging and measurement of myocardial strain in humans without the need for postprocessing, which may improve routine comprehensive evaluation of myocardial viability.     

颅内原发恶性淋巴瘤的MRI诊断(附12例报告)

目的　探讨颅内原发恶性淋巴瘤CT及MR的表现特征 ,以提高诊断准确率。方法　对 12例经手术病理证实的颅内原发恶性淋巴瘤的CT及MR表现进行回顾分析。结果　共检出 3 2个病灶 ,其中单发 9例 ,分别位于额、颞、顶叶深部脑白质 8例 ,位于颞叶表面 1例 ;多发 3例 ,病灶多位于深部脑白质。CT多表现为圆形或类圆形稍高密度灶 ,MRI表现为T1WI低或等信号 ,T2 WI为稍低信号。多数病灶周围有轻 -中度高信号水肿带 ,病灶边界尚清楚。增强扫描见所有病灶均有强化 ,2 3个 ( 72 .0 % )病灶呈均匀强化 ,18个 ( 5 6.2 5 % )病灶强化后出现缺口或凹陷改变。病理结果 :11例为非何杰金氏淋巴瘤 ,1例为浆细胞淋巴瘤。结论　尽管颅内原发恶性淋巴瘤的影像表现与其它颅内肿瘤如脑膜瘤、胶质瘤及转移瘤等有许多相似之处 ,但通过认真分析其影像特征 ,术前的正确诊断是有可能的     

Enhancement pattern of normal extraocular muscles in dynamic contrast-enhanced MR imaging with fat suppression

Purpose: To evaluate the internal structure of normal extraocular muscles on fat-suppressed dynamic contrast-enhanced MR imaging.Material and Methods: Ten subjects were examined using fat-suppressed dynamic contrast-enhanced MR imaging. We evaluated the enhancement pattern (C-shaped or ring-like) of extraocular muscles and quantified the maximum ratios of enhancement (R_max) and maximum ratios of signal increase (V_max). We also quantified R_max and V_max in the central and peripheral portions of medial rectus muscles.Results: In the early phase of dynamic contrast-enhanced MR imaging, a C-shaped or ring-like pattern was observed in 100% of inferior rectus, 95% of medial rectus, 55% of superior rectus, 20% of lateral rectus, and 15% of superior oblique muscles. Overall mean R_max and V_max values showed statistically significant differences to the temporal muscles. For the peripheral portion of medial rectus muscles, mean R_max and V_max values were greater than for the central portion.Conclusion: Using fat-suppressed dynamic contrast-enhanced MR imaging, the C-shape or ring-like internal structure of the extraocular muscles could be visualized, and were considered to reflect their structure of orbital and global layers. Potential usefulness of the fat-suppressed dynamic contrast-enhanced MR imaging for detecting pathological status is suggested.     

Optimal use of contrast medium in contrast enhanced MR imaging of the heart

With the recent development of fast MR imaging techniques, the diagnostic value of contrast enhanced MR imaging of the heart has been substantially improved. Since no tissue-specific contrast medium is available for clinical cardiac MR imaging at this point, both the early and late dynamics of extracellular MR contrast medium should be carefully evaluated for assessing the multiple aspects of cardiac function, including myocardial blood flow, myocardial, viability, and left ventricular function. Myocardial blood flow can be assessed by monitoring the first-pass passage of MR contrast medium. Quantitative assessments of arterial input function and output function in the regional myocardium can provide more accurate detection of altered myocardial blood flow in patients with coronary artery disease. Excellent contrast between infarcted myocardium and normal tissue can be obtained with delayed contrast enhanced MR imaging. Myocardial infarction, including small subendocardial infarction and chronic scar, is demonstrated as an area of "hyperenhancement" on delayed enhanced MR images, while the signal from normal myocardium is nearly null. This review paper describes the optimal dose and injection rate of MR contrast material for functional cardiac MR imaging studies. In addition, practical suggestions for obtaining good cardiac MR images and interpreting contrast enhanced MR images are given and are explained in detail.     

Benefit of T1 reduction for magnetic resonance coronary angiography: a numerical simulation and phantom study

Contrast agents have dramatically improved magnetic resonance angiography (MRA) of the abdominal and peripheral arteries. The imaging technique for these applications is usually a steady-state acquisition, for which the relationship between T1 in blood and the MR signal is well known. However, in electrocardiography-triggered angiography with limited acquisition windows, this relationship is more complex. Therefore the purpose of this work is to define the relationship between the T1 in blood and the MR signal amplitude in three-dimensional magnetic resonance coronary angiography (3D-MRCA). Simulations were performed using equations describing the MR signal in both steady-state and triggered acquisition schemes. Triggered acquisition schemes use flip-angle sweeps to maintain a constant signal during the acquisition. In this study, the effect of the flip angle sweep was calculated as a function of T1. The results show that the effect of T1 shortening in contrast-enhanced 3D-MRCA differs substantially from that in conventional contrast-enhanced MRA. The triggered acquisition allows unsaturated blood to enter the volume between the acquisitions and thereby gives a much higher signal at long T1s than does steady-state acquisition. Therefore, to gain a benefit in signal amplitude with contrast agents for 3D-MRCA using gradient-echo sequences, the T1 in blood may have to be as low as 50 msec. In addition, when using a prepulse to null myocardium, the results indicate the need for a large difference in T1 between blood and myocardium to avoid signal loss in blood.     

Gd—DTPA增强MRI诊断心肌梗塞

15例心脏作Gd-DTPA增强前后MRI检查,增强后为连续动态观察。其中7例为正常对照;7例为心肌梗塞(包括5例亚急性和2例慢性心肌梗塞);1例为陈旧性心肌梗塞。结果显示:增强前正常心肌信号率与梗塞心肌信号率无差别。增强后梗塞心肌信号率既高于增强前也明显高于其周围的正常心肌。无论肉眼观察还是信号测量均发现Gd-DTPA增强MRI能诊断心肌梗塞,改善心肌梗塞的显示。作者对增强后心肌信号率的系列变化作了描述。     

乳腺MR灌注时间-信号强度曲线表现及价值研究

目的探讨乳腺MRT2*WI首次通过灌注时间-信号强度曲线(TIC)表现及其在乳腺病变鉴别诊断中的价值。资料与方法对40例乳腺肿瘤患者行乳腺动态增强成像扫描,绘制T2*WI首次通过灌注TIC及T1WI动态增强TIC。采用Fisher’s确切概率法检验,判定良、恶性病灶T1WI动态增强及灌注TIC的差异。结果良、恶性病灶灌注TIC之间差异具有显著性统计学意义(P<0.05=0.000);良、恶性病灶T1WI动态增强TIC之间差异有显著性统计学意义(P<0.05=0.011),但在平台型曲线类型中良恶性病灶有较大重叠。结论乳腺MR灌注TIC在良、恶性病灶具有显著差别,恶性病灶灌注TIC主要表现为信号快速下降后缓慢回升(A型)与快速下降后不回升(B型);良性病灶灌注TIC主要表现为平直型(C型)及缓慢上升后平台型(D型)。灌注TIC与病灶形态学结合可大大提高乳腺疾病诊断的准确性。     

MR imaging evaluation of regional, remote, and global effects of percutaneous transluminal septal myocardial ablation in hypertrophic obstructive cardiomyopathy

OBJECTIVE: To evaluate regional, remote, and global effects of percutaneous transluminal septal myocardial ablation (PTSMA) in hypertrophic obstructive cardiomyopathy (HOCM) using magnetic resonance (MR) imaging. METHODS: Twenty-one patients with HOCM underwent cine and delayed contrast-enhanced MR imaging. The regional effects of ablated myocardium as well as remote and global effects of PTSMA were assessed. RESULTS: The ablated interventricular septal myocardium was hyperenhanced and thinned after successful PTSMA. Decreases in posterior wall thickness and myocardial mass were observed more than 12 weeks after PTSMA. Decreases in posterior wall thickness, myocardial mass, and left atrial diameter were observed in patients without myocardial hyperenhancement before PTSMA. Neither reduction nor increase in hyperenhancing myocardium, except for the ablated myocardium, was observed after PTSMA. CONCLUSIONS: Cardiac MR imaging showed regional, remote, and global effects of PTSMA on the myocardium in HOCM and might indicate patients with a good global response to PTSMA.     

Magnetic resonance findings of primary uterine malignant lymphoma.

To clarify the magnetic resonance (MR) characteristics of primary uterine malignant lymphoma, we identified 4 patients with primary uterine lymphoma in the MR database of our institute from 1994 to 2005 and evaluated their clinical and MR findings for tumor extension, size, shape, and signal intensity, multinodular growth pattern, preservation of normal endometrium, and lymphadenopathy. In all 4 patients, tumors extended to the uterus and vagina or parametrium, and uterine tumors showed relatively homogeneous intensity on both T(1)- and T(2)-weighted MR imaging. Two patients showed multinodular tumor growth; three revealed pelvic lymphadenopathy; and none had intact endometrium or normal uterine zonal structure. Thus, large tumors with relatively homogeneous signal intensity seemed to be a specific MR finding of uterine lymphoma, and findings of multinodular growth were considered a possible characteristic suggesting the uterine involvement of malignant lymphoma.     

Importance of perfusion in myocardial viability studies using delayed contrast-enhanced magnetic resonance imaging

PURPOSE: To investigate whether an extracellular gadolinium-(Gd)-based contrast agent (CA) enters nonperfused myocardium during acute coronary occlusion, and whether nonperfused myocardium presents as hyperintense in delayed contrast-enhanced (DE) MR images in the absence of CA in that region. MATERIALS AND METHODS: The left anterior descending coronary artery (LAD) was occluded for 200 minutes in six pigs. The longitudinal relaxation rate (R(1)) in blood, perfused myocardium, and nonperfused myocardium was repeatedly measured using a Look-Locker sequence before and during the first hour after administration of Gd-DTPA-BMA. RESULTS: While blood and perfused myocardium showed a major increase in R(1) after CA administration, nonperfused myocardium did not. R(1) in nonperfused myocardium was significantly lower than in blood and perfused myocardium during the first hour after CA administration. When the signal from perfused myocardium was nulled, demarcation of the hyperintense nonperfused myocardium was achieved in all of the study animals. CONCLUSION: Gd-DTPA-BMA does not enter ischemic myocardium within one hour after administration during acute coronary occlusion. The ischemic region with complete absence of CA still appears bright when the signal from perfused myocardium is nulled using inversion-recovery DE-MRI. This finding is important for understanding the basic pathophysiology of inversion-recovery viability imaging, as well as for imaging of acute coronary syndromes.     

Acute myocardial infarction: myocardial viability assessment in patients early thereafter comparison of contrast-enhanced MR imaging with resting (201)Tl SPECT. Single photon emission computed tomography

PURPOSE: To compare contrast material-enhanced magnetic resonance (MR) imaging with resting thallium 201 ((201)Tl) single photon emission computed tomography (SPECT) for predicting myocardial viability in patients early after acute myocardial infarction. MATERIALS AND METHODS: Inversion-recovery contrast-enhanced MR images and resting (201)Tl SPECT images were obtained in 22 patients after acute myocardial infarction. The (201)Tl SPECT images were obtained 4.3 days +/- 0.2 (standard error) after the onset of myocardial infarction. Contrast-enhanced MR imaging was performed 7.9 days +/- 1.6 after (201)Tl SPECT. Transmural extent of hyperenhancement on contrast-enhanced MR images and regional (201)Tl activity were quantitatively analyzed with a 12-segment model. Regional wall thickening on follow-up cine MR images obtained 67 days +/- 17 after contrast-enhanced MR imaging was used as an index for myocardial viability. Statistical analyses were performed with the chi(2) and two-tailed Student t tests. RESULTS: Both contrast-enhanced MR and resting (201)Tl SPECT images showed significant correlations with regional wall thickening on follow-up cine MR images. The sensitivity, specificity, and accuracy of contrast-enhanced MR imaging in the prediction of viable myocardium were significantly higher than those of resting (201)Tl SPECT (98.0% vs 90.3%, P <.01; 75.0% vs 54.4%, P <.05; and 92.0% vs 81.1%, P <.001, respectively). CONCLUSION: Delayed contrast-enhanced MR imaging can help predict myocardial viability as seen on follow-up cine MR images after acute myocardial infarction, with significantly improved sensitivity, specificity, and accuracy in comparison with those of resting (201)Tl SPECT.     

Three-dimensional contrast-enhanced MR angiography of endovascular covered stents in patients with peripheral arterial occlusive disease

OBJECTIVE: Three-dimensional contrast-enhanced MR angiography was performed to study MR characteristics of Hemobahn devices. MATERIALS AND METHODS: Changes in endoluminal signal intensities and the precision of the endoluminal diameter measurement were investigated in phantom studies for different concentrations of gadopentetate dimeglumine. Before and after the Hemobahn devices had been implanted, 10 patients with peripheral arterial occlusive disease were examined on MR imaging and three-dimensional contrast-enhanced MR angiography. RESULTS: Phantom experiments using three-dimensional MR angiography showed stent-related signal void as a dark ring in the axial image orientation, providing a precise delineation of the stent--vessel border (mean endoluminal diameter, 8.2 mm; SD, 0.6 mm). Changes in endoluminal signal intensity were evaluated quantitatively. Stent-related artifacts did not compromise diagnostic imaging quality. All Hemobahn devices were found to be patent without migration of an implanted graft. In one patient, an extensive perigraft reaction (edema and contrast-enhanced perivascular tissue) was postinterventionally detected on MR imaging and corresponded to clinically evident postimplantation symptoms. CONCLUSION: Three-dimensional contrast-enhanced MR angiography is a suitable tool to follow up the implantation of Hemobahn devices and to detect intra- and extraluminal abnormalities.     

Acute myocardial infarction: tissue characterization with T1rho-weighted MR imaging--initial experience

Acute myocardial injury was evaluated in 21 patients by using a contrast material-enhanced T1rho-weighted cine turbo field-echo magnetic resonance (MR) imaging sequence and a delayed-enhancement sequence. In 12 of 21 patients, conventional T1-weighted contrast-enhanced cine turbo field-echo MR images were also collected for direct comparison with T1rho-weighted images. Delayed-enhancement technique distinctly characterized irreversible injury (percentage enhancement, 588% +/- 344). With T1rho weighting, percentage enhancement of irreversibly injured myocardium was 68% +/- 41, compared with 23% +/- 24 without T1rho weighting (P <.006). The addition of T1rho weighting to contrast-enhanced cine turbo field-echo MR sequences may offer a new contrast enhancement mechanism for characterization of acutely infarcted myocardium.     

Kikuchi disease: CT and MR findings.

Two cases of Kikuchi disease showed variable nodal enhancing features, including homogeneous enhancement and focal or extensive nodal necrosis on contrast-enhanced CT scans. At MR imaging, the area of central necrosis was isointense or hypointense on T1-weighted images and had a lower signal than nonnecrotic areas on T2-weighted images. The CT appearance of Kikuchi disease can be variable and can mimic not only lymphoma but various nodal diseases with nodal necrosis, including metastasis and tuberculosis.     

An improved MR imaging technique for the visualization of myocardial infarction

PURPOSE: To design a segmented inversion-recovery turbo fast low-angle shot (turboFLASH) magnetic resonance (MR) imaging pulse sequence for the visualization of myocardial infarction, compare this technique with other MR imaging approaches in a canine model of ischemic injury, and evaluate its utility in patients with coronary artery disease. MATERIALS AND METHODS: Six dogs and 18 patients were examined. In dogs, infarction was produced and images were acquired by using 10 different pulse sequences. In patients, the segmented turboFLASH technique was used to acquire contrast material-enhanced images 19 days +/- 7 (SD) after myocardial infarction. RESULTS: Myocardial regions of increased signal intensity were observed in all animals and patients at imaging. With the postcontrast segmented turboFLASH sequence, the signal intensity of the infarcted myocardium was 1,080% +/- 214 higher than that of the normal myocardium in dogs-nearly twice that of the next best sequence tested and approximately 10-fold greater than that in previous reports. All 18 patients with myocardial infarction demonstrated high signal intensity at imaging. On average, the signal intensity of the high-signal-intensity regions in patients was 485% +/- 43 higher than that of the normal myocardium. CONCLUSION: The segmented inversion-recovery turboFLASH sequence produced the greatest differences in regional myocardial signal intensity in animals. Application of this technique in patients with infarction substantially improved differentiation between injured and normal regions.