Pitfalls in Coronary Magnetic Resonance Angiography
Right Coronary Artery Occlusion
A 72-year-old man was referred to University Hospital in Münster for recurrent chest pain. Standard navigator-gated free-breathing cardiac-triggered coronary magnetic resonance angiography (MRA) was performed with 4 different acquisition techniques:
A T2-prepared 3D turbo field-echo (TFE) sequence (TE 2.4 ms, TR 7.2 ms) with Cartesian k-space sampling (resolution 0.7×1.0 mm) (Figure 1A).
A black-blood coronary 2D fast spin-echo (FSE) sequence (TE 25 ms, Turbo Factor 23, TR 2 cardiac cycles) with a dual-inversion prepulse and an initial 90° RF excitation followed by repetitive 160° refocusing pulses (spatial resolution 0.7×0.9 mm) (Figure 1B).
A segmented 3D balanced fast field-echo (BFFE) sequence (TR 4 ms, TE 2 ms) with a centric-ordered k-space acquisition scheme and 14 RF excitations with a 75° constant excitation angle during each R-R interval (in-plane resolution of 1.2×1.2 mm) (Figure 1C).
A 3D spiral coronary TFE MRA sequence (TE 1.5 ms, TR 26 ms) with 42 interleaves that used ramped RF excitation angles of 45° and 90° per R-R interval (in-plane spatial resolution of 0.7×0.7 mm) (Figure 1D).
The right coronary artery (RCA) was successfully visualized by all 4 techniques and was considered to be normal despite some signal inhomogeneities visible on the bright-blood images (Figure 1A, B, D). Catheter-based x-ray coronary angiography showed proximal occlusion of the RCA (Figure 2A), with retrograde filling of the vessel through large collaterals originating from the left anterior descending coronary artery (Figure 2B).
The diagnosis of coronary artery occlusion may be missed on contemporary coronary MRA images if the vessel distal to the occlusion is filled by collaterals.