Abstract
PurposeCardiovascular magnetic resonance first-pass perfusion for the pixel-wise detection of coronary artery disease is rapidly becoming the clinical standard, yet no widely available method exists for its assessment and validation. This study introduces a novel phantom capable of generating spatially dependent flow values to enable assessment of new perfusion imaging methods at the pixel level.MethodsA synthetic multicapillary myocardial phantom mimicking transmural myocardial perfusion gradients was designed and manufactured with high-precision 3D printing. The phantom was used in a stationary flow setup providing reference myocardial perfusion rates and was scanned on a 3T system. Repeated first-pass perfusion MRI for physiological perfusion rates between 1 and 4 mL/g/min was performed using a clinical dual-sequence technique. Fermi function-constrained deconvolution was used to estimate pixel-wise perfusion rate maps. Phase contrast (PC)-MRI was used to obtain velocity measurements that were converted to perfusion rates for validation of reference values and cross-method comparison. The accuracy of pixel-wise maps was assessed against simulated reference maps.ResultsPC-MRI indicated excellent reproducibility in perfusion rate (coefficient of variation [CoV] 2.4-3.5%) and correlation with reference values (R2 = 0.985) across the full physiological range. Similar results were found for first-pass perfusion MRI (CoV 3.7-6.2%, R2 = 0.987). Pixel-wise maps indicated a transmural perfusion difference of 28.8-33.7% for PC-MRI and 23.8-37.7% for first-pass perfusion, matching the reference values (30.2-31.4%).ConclusionThe unique transmural perfusion pattern in the phantom allows effective pixel-wise assessment of first-pass perfusion acquisition protocols and quantification algorithms before their introduction into routine clinical use.
Highlights
Recent advances in cardiovascular magnetic resonance (CMR) for first-pass myocardial perfusion have led to its recommendation for use in patients with intermediate pretest probability of significant coronary artery disease (CAD) by European guidelines.[1]
Perfusion images demonstrate the spatial dependence in myocardium flow, with capillaries at Figure 6 shows example perfusion rate maps and corresponding root mean square error (RMSE) and coefficient of variation (CoV) maps for phase contrast (PC)-MRI and dynamic contrast-enhanced (DCE)-MRI
Mean perfusion rate was accurately estimated by both methods
Summary
Recent advances in cardiovascular magnetic resonance (CMR) for first-pass myocardial perfusion have led to its recommendation for use in patients with intermediate pretest probability of significant coronary artery disease (CAD) by European guidelines.[1] One of the most promising techniques is quantitative analysis of perfusion data for the production of pixel-wise perfusion maps,[2,3,4,5] with emerging studies suggesting an accuracy for the detection of CAD comparable or superior to visual assessment by expert operators.[6,7,8] In particular, pixel-wise quantification would allow the assessment of regional and local perfusion variations It is known since the early 1970s that myocardial blood flow is characterized by a transmural (radial) variation, when Downey and colleagues measured the uptake of radioactive tracers in different transmural layers of the dog’s myocardium and observed a 30% decrease in the uptake from the subendocardium to the subepicardium during diastole.[9,10] Such observations were recently confirmed with CMR first-pass perfusion.[11,12,13]. True cross-validation requires hybrid PET-MR machines for simultaneous imaging of patients under the same physiological and hemodynamic conditions.[17,18,19]
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