Image quality and diagnostic accuracy of unenhanced SSFP MR angiography compared with conventional contrast-enhanced MR angiography for the assessment of thoracic aortic diseases.

OBJECTIVES: The purpose of this study was to determine the image quality and diagnostic accuracy of three-dimensional (3D) unenhanced steady state free precession (SSFP) magnetic resonance angiography (MRA) for the evaluation of thoracic aortic diseases. METHODS: Fifty consecutive patients with known or suspected thoracic aortic disease underwent free-breathing ECG-gated unenhanced SSFP MRA with non-selective radiofrequency excitation and contrast-enhanced (CE) MRA of the thorax at 1.5 T. Two readers independently evaluated the two datasets for image quality in the aortic root, ascending aorta, aortic arch, descending aorta, and origins of supra-aortic arteries, and for abnormal findings. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined for both datasets. Sensitivity, specificity, and diagnostic accuracy of unenhanced SSFP MRA for the diagnosis of aortic abnormalities were determined. RESULTS: Abnormal aortic findings, including aneurysm (n = 47), coarctation (n = 14), dissection (n = 12), aortic graft (n = 6), intramural hematoma (n = 11), mural thrombus in the aortic arch (n = 1), and penetrating aortic ulcer (n = 9), were confidently detected on both datasets. Sensitivity, specificity, and diagnostic accuracy of SSFP MRA for the detection of aortic disease were 100% with CE-MRA serving as a reference standard. Image quality of the aortic root was significantly higher on SSFP MRA (P < 0.001) with no significant difference for other aortic segments (P > 0.05). SNR and CNR values were higher for all segments on SSFP MRA (P < 0.01). CONCLUSION: Our results suggest that free-breathing navigator-gated 3D SSFP MRA with non-selective radiofrequency excitation is a promising technique that provides high image quality and diagnostic accuracy for the assessment of thoracic aortic disease without the need for intravenous contrast material.

Adult Tetralogy of Fallot: quantitative assessment of pulmonary perfusion with time-resolved three dimensional magnetic resonance angiography.

PURPOSE: To determine the potential role of dynamic temporally resolved three dimensional (3D) contrast-enhanced magnetic resonance angiography (MRA) for quantitative evaluation of pulmonary perfusion in adult patients with surgically treated Tetralogy of Fallot (ToF). MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained for this Health Insurance Portability and Accountability Act-compliant study. Thirty consecutive patients with surgically repaired ToF and 30 age-matched controls underwent breath-hold 3D time-resolved MRA (TR-MRA) and single-phase high-resolution 3D MRA of the thorax at 1.5 T. Two readers evaluated both datasets for image quality and findings. On TR-MRA datasets, regions-of-interest were placed over main pulmonary artery and lung fields obtaining signal intensity time curves. Using analytic software, time-to-peak (TTP), mean transit time (MTT), maximal signal intensity (MSI), maximum upslope of the curve (MUS), pulmonary blood volume (PBV), and pulmonary blood flow (PBF) were calculated. Pulmonary radionuclide scintigraphy was available for a subgroup of patients with ToF (n = 12). RESULTS: For ToF patients with unilateral pulmonary artery (PA) stenosis, TTP, and MTT were significantly longer, and MSI, MUS, PBV, and PBF were significantly lower in the ipsilateral lung compared with control subjects (P < 0.001 for all). There was no significant difference in TTP, MTT, MSI, MUS, PBV, and PBF between ToF patients without postsurgical stenotic residua and control subjects (P > 0.05 for all), nor between the mentioned perfusion indices for the contralateral lung in ToF patients with unilateral PA stenosis and control subjects (P > 0.05 for all). In ToF, patient with unilateral PA stenosis, analysis of contralateral-to-ipsilateral lung perfusion ratios on radionuclide scintigraphy and TR-MRA revealed significant correlation (r = 0.96). Bland-Altman plot showed a mean difference of 2.2% between the measured ratios (limits of agreement; -7.6%-12.0%). CONCLUSION: Time-resolved 3D contrast-enhanced MRA has potential for noninvasive and quantitative assessment of altered patterns of pulmonary perfusion in adult ToF, and may be a reliable technique for evaluation of postsurgical residua in these patients.