Abstract
ObjectivesTo compare Dixon water-fat suppression with spectral pre-saturation with inversion recovery (SPIR) at 3T for coronary magnetic resonance angiography (MRA) and to demonstrate the feasibility of fat suppressed coronary MRA at 3T without administration of a contrast agent.Materials and methodsCoronary MRA with Dixon water-fat separation or with SPIR fat suppression was compared on a 3T scanner equipped with a 32-channel cardiac receiver coil. Eight healthy volunteers were examined. Contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), right coronary artery (RCA), and left anterior descending (LAD) coronary artery sharpness and length were measured and statistically compared. Two experienced cardiologists graded the visual image quality of reformatted Dixon and SPIR images (1: poor quality to 5: excellent quality).ResultsCoronary MRA images in healthy volunteers showed improved contrast with the Dixon technique compared to SPIR (CNR blood-fat: Dixon = 14.9 ± 2.9 and SPIR = 13.9 ± 2.1; p = 0.08, CNR blood-myocardium: Dixon = 10.2 ± 2.7 and SPIR = 9.11 ± 2.6; p = 0.1). The Dixon method led to similar fat suppression (fat SNR with Dixon: 2.1 ± 0.5 vs. SPIR: 2.4 ± 1.2, p = 0.3), but resulted in significantly increased SNR of blood (blood SNR with Dixon: 19.9 ± 4.5 vs. SPIR: 15.5 ± 3.1, p < 0.05). This means the residual fat signal is slightly lower with the Dixon compared to the SIPR technique (although not significant), while the SNR of blood is significantly higher with the Dixon technique. Vessel sharpness of the RCA was similar for Dixon and SPIR (57 ± 7 % vs. 56 ± 9 %, p = 0.2), while the RCA visualized vessel length was increased compared to SPIR fat suppression (107 ± 21 vs. 101 ± 21 mm, p < 0.001). For the LAD, vessel sharpness (50 ± 13 % vs. 50 ± 7 %, p = 0.4) and vessel length (92 ± 46 vs. 90 ± 47 mm, p = 0.4) were similar with both techniques. Consequently, the Dixon technique resulted in an improved visual score of the coronary arteries in the water fat separated images of healthy subjects (RCA: 4.6 ± 0.5 vs. 4.1 ± 0.7, p = 0.01, LAD: 4.1 ± 0.7 vs. 3.5 ± 0.8, p = 0.007).ConclusionsDixon water-fat separation can significantly improve coronary artery image quality without the use of a contrast agent at 3T.
Highlights
Coronary artery magnetic resonance angiography (CMRA) requires effective fat suppression as coronary arteries are embedded in epicardial fat
Every subject received two different scans: (1) conventional whole heart CMRA with spectral presaturation with inversion recovery (SPIR) fat suppression and (2) whole heart CMRA with two-point Dixon water fat separation in the same imaging session
Fat suppression and vessel delineation with Dixon was visually superior to the SPIR technique (Fig. 2)
Summary
Coronary artery magnetic resonance angiography (CMRA) requires effective fat suppression as coronary arteries are embedded in epicardial fat. Various fat suppression techniques have been proposed for CMRA such as short tau inversion recovery (STIR) and spectral presaturation with inversion recovery (SPIR) [2]. These methods are based on the relaxation time (T1) as well as chemical shift differences between fat and water. SPIR images have higher SNR compared to STIR images because the STIR prepulse inverts both the water and fat magnetization For these reasons the SPIR technique has become the preferable fat suppression method for coronary artery imaging
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