Internal derangement of the wrist: indirect MR arthrography versus unenhanced MR imaging

PURPOSE: To compare indirect magnetic resonance (MR) arthrography with unenhanced MR imaging of the wrist for evaluation of the central disk of the triangular fibrocartilage complex (TFCC) and the scapholunate and lunotriquetral interosseous ligaments. MATERIALS AND METHODS: Eighty-six wrists were evaluated at MR imaging (41 indirect MR arthrography and 45 unenhanced MR imaging examinations). Three musculoskeletal radiologists independently evaluated the central disk of the TFCC and scapholunate and lunotriquetral ligaments and compared the results with those of wrist arthroscopy. Sensitivity and specificity were calculated for each of the readers, and the means were obtained. Sensitivities and specificities were compared with the Student t test. RESULTS: Thirty-three tears of the central disk of the TFCC and 13 scapholunate and 18 lunotriquetral ligament tears were identified at arthroscopy. Sensitivities and specificities were 54%-73% and 83%-91%, respectively, in the evaluation of the central disk of the TFCC, with no significant difference between indirect MR arthrography (P =.666) and unenhanced MR imaging (P =.559). Sensitivities and specificities in the evaluation of the scapholunate ligament were 38%-69% and 75%-99%, respectively, with a significant improvement in sensitivity at indirect MR arthrography (P =.017) and no significant difference in specificity (P =.876). Sensitivities in the evaluation of the lunotriquetral ligament were poor, 0%-22%, though the specificities were 88%-99%, with no significant difference between indirect MR arthrography and unenhanced MR imaging (P =.592 and P =.354, respectively, for sensitivity and specificity. CONCLUSION: Indirect MR arthrography significantly improves sensitivity in the evaluation of the scapholunate ligament when compared with unenhanced MR imaging of the wrist but does not significantly improve the ability to evaluate the central disk of the TFCC or the lunotriquetral ligament.     

High-spatial-resolution multistation MR imaging of lower-extremity peripheral vasculature with segmented volume acquisition: feasibility study

A method of three-station three-dimensional magnetic resonance (MR) angiography of the lower extremities with segmented volume acquisition is presented. Three-dimensional MR angiographic data were acquired in two passes, with the central k-space views acquired during the arterial phase for the more proximal stations. This allowed a faster bolus injection rate and potentially improved visualization of the tibioperoneal arteries.     

Three-dimensional MR imaging of the pulmonary vasculature: preliminary experience.

The design and implementation of a rapid three-dimensional, gradient-echo magnetic resonance (MR) imaging technique that uses short echo and repetition times are described. This technique was used to evaluate patients with pulmonary vascular disease. The technique has demonstrated the potential of acquiring high-resolution pulmonary vascular information with good image quality and little image degradation from moving blood and respiratory motion. Nearly isotropic data collection allows multiplanar and maximum-intensity projection reconstructions to depict local regions in the lungs. In the present study, 15 volunteers and 10 patients were examined. High-quality images were obtained in all 15 volunteers and in six patients. The technique presented demonstrates that MR imaging is capable of generating good to excellent pulmonary vascular images in approximately 10-13 minutes in the thoracic region, showing that this approach may prove useful for a wide variety of applications.     

Detection of hepatic metastases: comparison of contrast-enhanced CT, unenhanced MR imaging, and iron oxide-enhanced MR imaging

Diagnostic accuracy of contrast-enhanced CT, unenhanced MR imaging, and MR images enhanced with superparamagnetic iron oxide was evaluated in 10 patients with histologically proved hepatic metastases. First, diagnostic performance of the imaging technique with respect to the ability of radiologists to recognize the presence or absence of a metastasis was measured by using receiver-operating-characteristic (ROC) analysis of single images. Second, the total number of lesions (N = 108) detected by "complete" CT and MR examinations was counted. Finally, lesion-liver contrast-to-noise ratios (CNR) were measured in all MR sequences. The area under the ROC curve was .67 +/- .03 for contrast-enhanced CT, .81 +/- .07 for the unenhanced SE 260/14 sequence, and .92 +/- .01 for the iron oxide-enhanced SE 1500/40 sequence. The enhanced SE 1500/40 sequence yielded significantly (p less than .005) greater accuracy than did contrast-enhanced CT. The same sequence detected significantly (p less than .05) more lesions than all other imaging techniques (19% more than the best unenhanced MR sequence and 36% more than contrast-enhanced CT). The enhanced SE 1500/40 sequence also yielded the highest CNR value (19.5 +/- 10.2) of all MR sequences. These results indicate that iron oxide-enhanced MR imaging is a superior imaging technique for the detection of hepatic lesions.     

Recent myocardial infarction: assessment with unenhanced T1-weighted MR imaging

The purpose of the study was to prospectively evaluate a T1-weighted technique for detection of myocardial edema resulting from recent myocardial infarction (MI) or intervention. This study was HIPAA compliant and institutional review board approved. Fifteen men and one woman (mean age, 57.8 years+/-11.5 [standard deviation]) were examined with T1-weighted magnetic resonance (MR) imaging and inversion-recovery cine pulse sequence in two groups, recent MI and chronic MI, and gave informed consent. T1 relaxation times of MI and adjacent myocardium were compared (Student t test and correlation analysis). In patients with recent MI, areas of myocardial edema were well depicted with T1-weighted MR imaging. T1 relaxation times of recent infarcts were longer than those of older MIs (925 msec+/-169 vs 551 msec+/-107, P<.001). From local edema, T1 relaxation time of infarcted myocardium is increased, may remain elevated for 2 months, and enables imaging with T1-weighted techniques.     

MR imaging of pelvic masses in women: contrast-enhanced vs unenhanced images.

OBJECTIVE. We compared the value of contrast-enhanced MR images with that of T2-weighted MR images in the diagnosis and staging of pelvic masses in women. MATERIALS AND METHODS. The findings on preoperative MR studies of 97 patients with a total of 124 surgically proved lesions were retrospectively analyzed. Unenhanced T1- and T2-weighted spin-echo images were compared with contrast-enhanced T1-weighted images. The final diagnosis included benign (36 patients), borderline (six patients), and malignant (15 patients) ovarian masses, fallopian tube masses (15 patients), endometrial tumors (seven patients), cervical carcinomas (32 patients), subserous leiomyomas (11 patients), and two masses of extragenital origin. RESULTS. In the depiction of pelvic lesions, the sensitivity of contrast-enhanced MR imaging (96%) was equal to that of unenhanced T2-weighted imaging (97%). Contrast-enhanced images were useful in the definition of intratumoral architecture and tumor borders of 72 adnexal masses, resulting in better determination of malignancy (accuracy, 95%) than on T2-weighted images (85%). Size of viable tumor, differentiation of tumor from retained fluid, and depth of myometrial invasion of six endometrial carcinomas were most reliably shown on contrast-enhanced images. In the evaluation of cervical carcinoma, overall staging accuracy of contrast-enhanced imaging (80%) was slightly inferior to that of T2-weighted imaging (83%). However, contrast-enhanced images improved assessment of parametrial and organ invasion in seven cases in which findings on T2-weighted MR images were equivocal. Administration of contrast material was not helpful in the evaluation of subserous leiomyomas or masses of extragenital origin. CONCLUSIONS. The findings suggest that when results of unenhanced T1- and T2-weighted MR imaging of pelvic masses are equivocal, contrast-enhanced MR images should be used as supportive and complementary pulse sequences to (1) improve definition of intratumoral architecture and prediction of malignancy in adnexal tumors, (2) stage endometrial carcinoma, and (3) determine tumor extension in cervical carcinoma.     

Extracardiac vasculature in candidates for Fontan surgery: MR imaging

Magnetic resonance (MR) imaging was performed in 53 patients considered to be candidates for a modified Fontan operation to repair cardiac or extracardiac vascular anomalies. The MR studies were reviewed retrospectively, and the findings with regard to the extracardiac vascular anatomy were compared with the findings from angiography or surgery. The accuracy of MR for the correct identification of the systemic veins was 98%; for pulmonary arteries, 97%; and for pulmonary veins, 95%. For identification of pulmonary veins, MR imaging had a sensitivity of 90% and a specificity of 100%. MR provides excellent demonstration of the extracardiac vascular structures, which are of particular importance in patients being considered for a Fontan procedure.     

Pulmonary vasculature: single breath-hold MR imaging with phased-array coils.

The authors obtained magnetic resonance images of the pulmonary vasculature with reduced artifacts caused by cardiac and respiratory motion by acquiring a series of moderately thin sections in a single breath-hold with an ultrafast gradient-echo pulse sequence. The series of two-dimensional images was postprocessed with a maximum-intensity projection algorithm. Time-of-flight inflow enhancement increased the signal intensity of arteries and veins while radiofrequency phase spoiling produced limited stationary spin suppression of the chest wall. Moderately thin (8-mm) section thicknesses were used to attain the resolution necessary to visualize smaller pulmonary vascular segments up to the chest wall while the number of acquired sections was minimized. Because the body coil did not provide an adequate signal-to-noise ratio (S/N) for a single excitation and thin-section acquisitions, phased-array coils covering either the right or left lung were used to single breath-holds prevented the misregistration and blurring that occurred in examinations performed with multiple breath-holds.     

Cardiac and vascular imaging with an MR snapshot technique

Real-time vascular and cardiac magnetic resonance (MR) imaging has been reported only with echo-planar imaging. In this study, the fast low-angle shot (FLASH) MR imaging sequence was reduced to repetition times of 3 msec and echo times of less than 1.3 msec with use of an improved MR imaging system. The resulting 200-msec MR images (64 X 128 pixels) are called snapshot FLASH images. They allow measurements from dynamic series of MR images depicting processes such as relaxation behavior and the cardiac cycle in the absence of motion and flow artifacts. In animal studies (at 4.7 T) and in studies of human volunteers (at 2.0 T), vascular and cardiac snapshot FLASH images were obtained as a single shot, as reconstructed motion, and as real-time movies. The arbitrary and fast T1 contrast of these images and the reduction of motion artifacts result in favorable applications for the depiction of myocardial and great-vessel anatomy. These clinical applications can be performed on conventional MR imagers with minor technical modifications.     

周围型肝内胆管细胞癌的磁共振诊断

目的 :评价磁共振 (MRI)平扫及联合动态增强MRI对周围型肝内胆管细胞癌 (PCC)的诊断价值。方法 :回顾性分析 15例经手术病理证实的周围型肝内胆管细胞癌的MRI平扫及动态增强表现。结果 :全部病灶显示满意。参考平扫胆管扩张情况定性诊断符合率为 3 3 .3 % ,联合动态增强定性符合率提高至 86.7%。结论 :MRI平扫能较好显示病灶和胆管扩张情况 ,平扫联合动态增强检查可提高对PCC的定性符合率。     

Mucocutaneous and peripheral soft-tissue hemangiomas: MR imaging

Hemangiomas are common congenital lesions that may have devastating sequelae. The extent and location of a lesion determines the therapeutic approach. We describe 11 patients with mucocutaneous or peripheral soft-tissue hemangiomas to illustrate the ability of magnetic resonance (MR) imaging to define clearly and noninvasively the extent and anatomic relationships of hemangiomas. The major advantage of MR imaging over computed tomography or angiography is the exquisite difference in contrast between hemangiomas and the surrounding structures on T2-weighted MR images, in which hemangiomas have a relatively intense signal. Hemangiomas demonstrated relatively low signal intensity (similar to muscle) on T1-weighted images, which were markedly inferior to T2-weighted images in defining the extent of the lesions. Phleboliths and feeding or draining vessels were rarely visible. The information obtained with MR imaging may be valuable clinically in planning surgical resection or laser therapy of aggressive lesions, in evaluating effectiveness of medical or embolic therapy, and in defining recurrence.