Abstract
PurposeTo develop a framework for efficient and simultaneous acquisition of motion‐compensated whole‐heart coronary MR angiography (CMRA) and left ventricular function by MR and myocardial integrity by PET on a 3T PET‐MR system.MethodsAn acquisition scheme based on a dual‐phase CMRA sequence acquired simultaneously with cardiac PET data has been developed. The framework is integrated with a motion‐corrected image reconstruction approach, so that non‐rigid respiratory and cardiac deformation fields estimated from MR images are used to correct both the CMRA (respiratory motion correction for each cardiac phase) and the PET data (respiratory and cardiac motion correction). The proposed approach was tested in a cohort of 8 healthy subjects and 6 patients with coronary artery disease. Left ventricular (LV) function estimated from motion‐corrected dual‐phase CMRA was compared to the gold standard estimated from a stack of 2D CINE images for the healthy subjects. Relative increase of signal in motion‐corrected PET images compared to uncorrected images was computed for standard 17‐segment polar maps for each patient.ResultsMotion‐corrected dual‐phase CMRA images allow for visualization of the coronary arteries in both systole and diastole for all healthy subjects and cardiac patients. LV functional indices from healthy subjects result in good agreement with the reference method, underestimating stroke volume by 3.07 ± 3.26 mL and ejection fraction by 0.30 ± 1.01%. Motion correction improved delineation of the myocardium in PET images, resulting in an increased 18F‐FDG signal of up to 28% in basal segments of the myocardial wall compared to uncorrected images.ConclusionThe proposed motion‐corrected dual‐phase CMRA and cardiac PET produces co‐registered good quality images in both modalities in a single efficient examination of ~13 min.
Highlights
For the second healthy subject, the tortuous anatomy of the left anterior descending (LAD) in systole prevented an appropriate reformatting in the coronal plane, as shown in Figure 4B
For the second coronary artery disease (CAD) patient (Figure 5B), residual cardiac motion was observed in the motion correction (MC) systolic coronary MR angiography (CMRA), affecting the sharpness of the mid and distal right coronary artery (RCA)
Our results suggest that quantification of left ventricular function from dual‐phase CMRA data is in agreement with the reference method, with an average underestimation in stroke volume of 3.07 ± 3.26 mL and a 0.30 ± 1.01% underestimation of ejection fraction
Summary
Since the development of simultaneous PET‐MR scanners, cardiovascular imaging has been proposed as one of the clinical applications that could greatly benefit from this new technology.[1,2,3,4,5,6] The high spatial and temporal resolution offered by MR and its superior soft‐tissue contrast, combined with the absolute quantification provided by PET has shown potential for improved diagnosis of different cardiac conditions, including coronary artery disease (CAD),[7] cardiac sarcoidosis,[8,9,10] and myocarditis.[11,12] some early reports[2,13] suggested that by simultaneously acquiring complementary information with both modalities, the cardiac PET‐MR clinical protocol could be optimized to reduce total scan time. A shorter MR acquisition can be performed at the beginning of the scan so that deformation fields are used to create a motion model that can be applied to longer PET acquisitions. This approach has been recently demonstrated in oncology patients, resulting in an increased uptake in liver, lung, and pancreatic lesions.[14,15]
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