147 31 P Cardiac spectroscopy at 3 T: T1 quantification
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147 31P Cardiac spectroscopy at 3 T: T1 quantification AbdEl-Monem M El-Sharkawy*1, Michael Schär2, Ronald Ouwerkerk3, Robert G Weiss4 and Paul A Bottomley3 Address: 1Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, USA, 2Johns Hopkins University and Philips Medical Systems, Baltimore, USA, 3Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, USA and 4Cardiology Division, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, USA * Corresponding author
from 11th Annual SCMR Scientific Sessions Los Angeles, CA, USA. 1–3 February 2008 Published: 22 October 2008 Journal of Cardiovascular Magnetic Resonance 2008, 10(Suppl 1):A48
doi:10.1186/1532-429X-10-S1-A48
Abstracts of the 11th Annual SCMR Scientific Sessions - 2008
Meeting abstracts – A single PDF containing all abstracts in this Supplement is available here. http://www.biomedcentral.com/content/pdf/1532-429X-10-S1-info.pdfThis abstract is available from: http://jcmr-online.com/content/10/S1/A48 © 2008 El-Sharkawy et al; licensee BioMed Central Ltd.
Introduction Phosphorus (31P) MRS provides measures of the high energy metabolites, phosphocreatine (PCr) and adenosine triphosphate (ATP), in the heart. It permits the evaluation of ischemic changes during myocardial stress [1], and ATP turnover through the creatine-kinase reaction in the normal and failing human heart[2,3]. Recent cardiac 31P MRS studies suggest higher signal-to-noise atio (SNR) at 3 T compared to 1.5 T in healthy subjects[4]. For accurate metabolite quantification, the longitudinal relaxation times (T1) are needed, and measuring these at 3 T is confounded by the combined effects of: (i) RF field uniformity with surface coil use; (ii) the available RF pulse power and its decrease with depth; and (iii) RF power deposition limits. While prior studies at 1.5 T used low-angle adiabatic (BIR4) pulses [2,3], at 3 T these are limited by low bandwidth and high power requirements. We show, using a Bloch equation analysis that such effects can significantly reduce the accuracy of T1 measurements at long adiabatic pulse lengths (≥ 10 ms) for 31P MRS, but that the problems are ameliorated by use of adiabatic half passage 90° (AHP) pulses. The first aim of this work was to construct a high-SNR surface coil set for 3 T cardiac 31P MRS that provides adequate adiabatic pulse power at the depth of the myocardium, while avoiding local power deposition problems. The second aim was to determine the T1 of PCr and γ-ATP in the human heart using a new, efficient dual repetition time (2TR) approach that minimizes T1 estimation errors at 3
T. The method is validated against the conventional saturation-recovery (SR) method.
Methods A dual 31P coil with 17-cm transmitter and 8-cm receiver set was designed and built to optimize the transmit RF field at a 10 cm depth with 4 kW transmit power. Coils were interfaced to a 3 T Achieva (
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