Spiral MR angiography of the popliteal trifurcation

Gadolinium-enhanced MDCT angiography of the abdomen: feasibility and limitations

OBJECTIVE

The purpose of this study was to evaluate a protocol for gadolinium-enhanced MDCT angiography of the abdomen and to identify technical parameters that optimize image quality.

CONCLUSION

The degree of enhancement and image quality achieved using this gadolinium-enhanced MDCT angiography appear adequate for angiographic evaluation of the abdominal aorta and its major branches.

Technical note: postgadolinium two-dimensional time-of-flight MR angiography of the foot

OBJECTIVE

The purpose of this study was to determine the ability of postgadolinium time-of-flight (TOF) MR angiography to image the foot of patients compared to conventional TOF MR angiography.

SUBJECTS AND METHODS

Six feet in five patients were included in this prospective study. Standard two-dimensional axial TOF sequences of the lower extremities, followed by three-dimensional (3D) contrast-enhanced moving-table images of the aorta to the foot during the intravenous bolus administration of gadolinium, were obtained in all patients. Two-dimensional axial respiratory-compensated TOF sequences were then obtained over the foot. Axial images and maximum intensity projections (MIP) reconstructions were evaluated by two blinded radiologists and images rated with respect to overall image quality, large-vessel and small-vessel visualization, degree of venous overlap, and extent of vessel stenosis.

RESULTS

The 2D postgadolinium TOF technique resulted in an improvement in all areas of image quality compared with the noncontrast acquisition method, with very good interobserver agreement (kappa 0.67). Postcontrast images provided superior vessel visualization ( p=0.024, Wilcoxon signed rank test), with minimal artifact (84% with none, kappa 1.0), and excellent agreement on grading of dorsalis pedis stenosis (kappa 0.78). Vessel-to-background signal intensity ratio was doubled compared to the standard technique (mean 19.5, SD 6.5 versus 8.8, SD 4.5; p=0.016).

CONCLUSION

Postgadolinium TOF MR angiography of the foot demonstrates significantly improved image quality over noncontrast techniques.

Prediction rule for diagnosis of arrhythmogenic right ventricular dysplasia based on wall thickness measured on MR imaging

MRI is seeing an increasing role in the evaluation of suspected arrhythmogenic right ventricular dysplasia (ARVD). Our aims were to establish wall thickness criteria for diagnosis of ARVD based on MR imaging measurements. A cross-sectional case-control retrospective study of 21 cardiac MR exams over a 3 year period identified five patients (two men, three women) of average age 43 years (range 36-48) who were diagnosed with ARVD and 16 patients (nine men, seven women) of average age 52 years (range 25-78) who were diagnosed with normal right ventricular wall motion. Patient demographic characteristics (age, sex) and right ventricular free wall thickness (RVFWT) were evaluated for predictive ability. Calculated RVFWT was (mean+/-SD, in mm); (4.4+/-1.4) for ARVD, and (7.8+/-2.9), controls with P<0.001. Logistic regression analysis indicated that sex and age were not significant independent predictors (P>0.05). RVFWT allowed for a prediction rule with Area under the receiver operator curve of 0.94 to be generated. In our study, measurement of the thickness of the right ventricular free wall using cardiac-gated MRI proved to be a statistically significant predictor of ARVD.

MR imaging of renal masses interpreted on CT to be suspicious

OBJECTIVE

Prior studies have shown that renal MR contrast enhancement improves the efficacy of mass and proximal vascular evaluation. This study assessed the usefulness of different sequences for characterization of masses that appeared suspicious on CT and for prediction of their potential for malignancy.

SUBJECTS AND METHODS

In a prospective manner 32 patients (age range, 26-78 years: average age, 54 years), each with at least one suspicious mass on CT, were examined with MR imaging. The following sequences were performed: conventional spin-echo with and without fat saturation, fast spin-echo, and dynamic gadopentetate dimeglumine-enhanced infusion using a 1.5-T superconducting magnet. Results were analyzed and compared with pathologic results after resection.

RESULTS

A total of 65 renal masses of average size 2.6 cm (range, 1-10 cm) were detected with dynamic MR imaging. Seventeen of the 65 masses were malignant. Of the 17 malignant masses, three did not enhance on dynamic MR imaging (because of hemorrhage). Sixteen of the 17 malignant masses were heterogeneous on T2-weighted images. Three enhancing masses contained fat and all were angiomyolipomas. Thirty-five of the 65 masses (four with hemorrhage) did not show enhancement, all of which were homogeneous on T2-weighted images and were proven to be cysts. Five masses resulted from infections and had heterogeneous T2 appearance. The remaining masses were three hematomas with hemorrhage, one column of Bertin, and one aneurysm.

CONCLUSION

Renal masses that are interpreted as suspicious on CT may lack MR enhancement because of hemorrhage effects; heterogeneity of their T2 appearance is thus critical in differentiating malignancy from benign disease. Odds-ratio calculations give an adjusted estimate of a 3.36-fold increase (95% confidence interval, 1.8-6.27) in the likelihood of malignancy when masses are heterogeneous on T2-weighted images and a 29-fold increase (95% confidence interval, 3.67-241.8) for predicting malignancy when enhancement is present.