May 22, 2020

Pixel-Wise Assessment of Cardiovascular Magnetic Resonance First-Pass Perfusion Using a Cardiac Phantom Mimicking Transmural Myocardial Perfusion Gradients

Xenios Milidonis, Muhummad Sohaib Nazir, Torben Schneider, Myles Capstick, Sita Drost, Gertjan Kok, Nikola Pelevic, Christian Poelma, Tobias Schaeffter, and Amedeo Chiribiri, Magnetic Resonance in Medicine 2020, Volume 84, Issue 5, online 19 May 2020; doi: 10.1002/mrm.28296

Cardiovascular magnetic resonance (CMR) 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. A 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 magnetic resonance imaging (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. PC-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%). The 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.

The scientific and technical impact of the study can be summarized as:

  • A novel 3D printed synthetic myocardial phantom simulating transmural myocardial perfusion gradients has been developed
  • The phantom generates realistic enhancement curves across the full physiological range of perfusion rate and is found to be accurate and repeatable using PC-MRI and clinical dynamic contrast enhanced (DCE)-MRI
  • The phantom can be used for effective pixel-wise assessment and validation of CMR first-pass perfusion methods and can become an essential tool for quality assurance in the clinic
  • This can ultimately help reduce the number of animals and patients that are essential for current validation methods