Abstract
Objective: Myocardial first-pass perfusion imaging with MRI is well-established clinically. However, it is potentially weakened by limited myocardial coverage compared to nuclear medicine. Clinical evaluations of whole-heart MRI perfusion by 3D methods, while promising, have to date had the limit of breathhold requirements at stress. This work aims to develop a new free-breathing 3D myocardial perfusion method, and to test its performance in a small patient population.Methods: This work required tolerance to respiratory motion for stress investigations, and therefore employed a “stack-of-stars” hybrid Cartesian-radial MRI acquisition method. The MRI sequence was highly optimised for rapid acquisition and combined with a compressed sensing reconstruction. Stress and rest datasets were acquired in four healthy volunteers, and in six patients with coronary artery disease (CAD), which were compared against clinical reference information.Results: This free-breathing method produced datasets that appeared consistent with clinical reference data in detecting moderate-to-strong induced perfusion abnormalities. However, the majority of the mild defects identified clinically were not detected by the method, potentially due to the presence of transient myocardial artefacts present in the images.Discussion: The feasibility of detecting CAD using this 3D first-pass perfusion sequence during free-breathing is demonstrated. Good agreement on typical moderate-to-strong CAD cases is promising, however, questions still remain on the sensitivity of the technique to milder cases.
Highlights
Impaired myocardial perfusion under stress is a consequence of several diseases, most prominently coronary artery disease where such impairment occurs early in the ischaemic cascade.[1]
The artefacts remain for 2–3 frames before dissipating as the myocardial intensity increases and the LV bloodpool becomes less bright, as with the well-known dark-rim artefact (DRA) in 2D-first-pass perfusion (FPP).[33]
While the images of Patient 4 were degraded by the mistriggering which probably impeded detection of the small expected defect, Patients 3, 5 and 6 showed high image quality by 3D-SOS-FPP but the stress images appeared to miss some perfusion defects identified by MPS or 2D-FPP, raising potential questions
Summary
Impaired myocardial perfusion under stress is a consequence of several diseases, most prominently coronary artery disease where such impairment occurs early in the ischaemic cascade.[1]. In clinical CMR perfusion, myocardial T1-weighted images are acquired rapidly within each cardiac cycle tracing the arrival of contrast agent causing intensification of the myocardial image pixels, exposing perfusion abnormalities as regions of myocardium that brighten more slowly than normally perfused remote myocardium. This real-time bolus-tracking application demands ‘‘instant’’ imaging of multiple slices during each R-R interval, potentially with tachycardia during stress testing, which prevents MRI acquisition of fine image resolution throughout the entire myocardium during each cardiac cycle. This extension of FPP is known as ‘‘3D FPP’’ because it is inherently a wholevolume acquisition, rather than multiple seperately acquired ‘‘2D’’ slices that have timing and cardiac phase differences
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