Abstract
BackgroundPrevious studies have linked cardiac dysfunction to loss of metabolites in the creatine kinase system. Chemical exchange saturation transfer (CEST) is a promising metabolic cardiovascular magnetic resonance (CMR) imaging technique and has been applied in the heart for creatine mapping. However, current limitations include: (a) long scan time, (b) residual cardiac and respiratory motion, and (c) B0 field variations induced by respiratory motion. An improved CEST CMR technique was developed to address these problems.MethodsAnimals with chronic myocardial infarction (N = 15) were scanned using the proposed CEST CMR technique and a late gadolinium enhancement (LGE) sequence as reference. The major improvements of the CEST CMR technique are: (a) Images were acquired by single-shot FLASH, significantly increasing the scan efficiency. (b) All images were registered to reduce the residual motion. (c) The acquired Z-spectrum was analyzed using 3-pool-model Lorentzian-line fitting to generate CEST signal, reducing the impact of B0 field shifting due to respiratory motion. Feasibility of the technique was tested in a porcine model with chronic myocardial infarction. CEST signal was measured in the scar, border zone and remote myocardium. Initial studies were performed in one patient.ResultsIn all animals, healthy remote myocardial CEST signal was elevated (0.16 ± 0.02) compared to infarct CEST signal (0.09 ± 0.02, P < 0.001) and the border zone (0.12 ± 0.02, P < 0.001). For both animal and patient studies, the hypointense regions in the CEST contrast maps closely match the bright areas in the LGE images.ConclusionsThe proposed CEST CMR technique was developed to address long scan times, respiratory and cardiac motion, and B0 field variations. Lower CEST signal in bright region of the LGE image is consistent with the fact that myocardial infarction has reduced metabolic activity.
Highlights
Previous studies have linked cardiac dysfunction to loss of metabolites in the creatine kinase system
We developed a clinically translatable Chemical exchange saturation transfer (CEST) cardiovascular magnetic resonance (CMR) technique with significantly reduced scan time (~5 min), improved motion registration and CEST signal analysis to address the aforementioned challenges
Animal study In total, the CEST CMR scans were performed in 15 animals
Summary
Previous studies have linked cardiac dysfunction to loss of metabolites in the creatine kinase system. Chemical exchange saturation transfer (CEST) is a promising metabolic cardiovascular magnetic resonance (CMR) imaging technique and has been applied in the heart for creatine mapping. The creatine kinase (CK) system plays a vital role in the synthesis of myocardial ATP. Previous studies have linked cardiac dysfunction to the Chemical exchange saturation transfer (CEST) is an emerging MRI technique for metabolic imaging [10]. It has been shown that CEST can be used to map Cr distribution because of chemical transfer between its amine protons (−NH2) and water protons. CEST can detect Cr separately from other CK metabolites because Cr protons alone have an intermediate transfer rate with water protons [12,13,14]
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