Fast in vivo assay of creatine kinase in human brain by 31P magnetic resonance fingerprinting

Abstract

A new and efficient magnetisation transfer 31P magnetic resonance fingerprinting (MT-31P-MRF) approach is introduced to measure the creatine kinase metabolic rate kCK between phosphocreatine (PCr) and adenosine triphosphate (ATP) in human brain. The MRF framework is extended to overcome challenges in conventional 31P measurement methods in the human brain in vivo by reducing specific absorption rate deposition, incorporating system imperfection into a model, and testing a range of values for each parameter to arrive at their estimation. To compute complex high-dimensional datasets, we propose a nested iteration interpolation method (NIIM). As the number of parameters to estimate increases, the size of the dictionary grows exponentially. NIIM can reduce the computational load by breaking dictionary matching into subsolutions of linear computational order. The MT-31P-MRF combined with the NIIM provides T1PCr , T 1ATP , and kCK estimates in good agreement with those obtained by the exchange kinetics by band inversion transfer (EBIT) method and literature values. Furthermore, the test-retest reproducibility results showed that the MT-31P-MRF achieves less than 10% of the coefficient of variation for T1PCr , T 1ATP , and kCK measurements in 4 min 15 s, which is more than four times faster than the EBIT method. We conclude that MT-31P-MRF in combination with the NIIM is a fast, accurate and reproducible approach for in vivo kCK assays in the human brain, which enables the potential for investigating energy metabolism in a clinical setting.