Two repetition time saturation transfer (TwiST) with spill-over correction to measure creatine kinase reaction rates in human hearts

Michael Schar, Refaat E. Gabr, Abdel Monem M El-Sharkawy, Angela Steinberg, Paul A Bottomley, Robert George Weiss

Research output: Contribution to journalArticle

Abstract

Background: Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-repetition time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation time of PCr while γ-ATP is saturated, T1', is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short repetition time of one of the acquisitions. Here, a two-repetition time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short repetition time is dropped. Instead of measuring T1', an intrinsic relaxation time T1 for PCr, T1 intrinsic, is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF). Methods: Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 intrinsic and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients. Results: Simulations showed that both kf measured by TwiST and T1 intrinsic require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 intrinsic∈=∈8.4∈±∈1.4 s (mean∈±∈SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33∈±∈0.08 s-1 vs. 0.20∈±∈0.06 s-1 in healthy vs HF hearts, respectively (p∈f in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

Original languageEnglish (US)
Article number70
JournalJournal of Cardiovascular Magnetic Resonance
Volume17
Issue number1
DOIs
StatePublished - Aug 8 2015

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Keywords

  • 3 Tesla
  • Creatine-kinase
  • Heart failure
  • High-energy phosphate
  • Human heart
  • Metabolism
  • Reaction rate
  • Saturation transfer
  • TwiST

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology
  • Family Practice

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