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

Abstract

ObjectivesThe 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.MethodsFifty 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.ResultsAbnormal 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).ConclusionOur 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.

Noninvasive aortic imaging

“…In patients who cannot perform breath holds, 3D SSFP can acquire images during free breathing utilizing a diaphragm navigator sequence. In some studies, 3D SSFP MRA has actually been demonstrated to provide better measured SNR and CNR compared to CE MRA, with higher image quality of the aortic root (57). One of the drawbacks to 3D SSFP, particularly at 3T, are off resonance artifacts which can manifest as dark bands traversing the images and possibly mimic aortic dissection.…”

“…2D SSFP was first developed but often has problematic out-ofslice contributions, with suboptimal voxel resolution (57). The development of 3D SSFP greatly minimized these shortcomings to become a valuable NC MRA technique ( Figure 6).…”

Surgical Management of the Aortic Root

“…It has demonstrated a higher sensitivity and specificity than other forms of MR imaging and echocardiography. [85] Emergency use of MR is limited. Steady state free procession MR is a newer technology that allows for better visualization of structures by decreasing surrounding interference without the use of contrast.…”

Magnetic Resonance Imaging of the Thoracic Aorta: A Review of Technical and Clinical Aspects, Including Its Use in the Evaluation of Aneurysms and Acute Vascular Conditions

“…A rapid morphologic assessment can be achieved in urgent situations, such as demonstrating aortic abnormalities in unstable patients, for example intimal flaps and false lumens in aortic dissection (Pereles, 2002;Gebker, 2007). Free-breathing cardiac and respiratory-gated 3D SSFP MRA has also been shown valuable in the evaluation of thoracic vessels (Fuchs, 2003;Krishnam, , 2010, and represents an alternative for free-breathing SSFP MRA. SSFP sequences can also be acquired in a cine mode, and have become the foundation for cine imaging.…”