Ronald Ouwerkerk1, Robert G Weiss, Paul A Bottomley. 1. Division of MR Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-0845, USA. rouwerke@mri.jhu.edu
Abstract
PURPOSE: To measure tissue sodium concentrations in the human heart with (23)Na MRI using a surface coil, thereby eliminating the effects of inhomogeneous excitation by surface coils and minimizing T(1) and T(2) relaxation. MATERIALS AND METHODS: We combined fully relaxed, very short-echo, (23)Na twisted projection imaging (TPI) with adiabatic half passage (AHP) excitation and external referencing on subjects and comparing with a concentration reference phantom scan to quantify TSC with surface coils. (23)Na signal losses during hard (square), composite, and tanh/tan amplitude/frequency-modulated AHP excitation pulses were analyzed over a wide range of RF field strengths and T(2short) values. RESULTS: AHP excitation yielded a homogeneous excitation flip angle and negligible losses compared to a 90 degrees hard pulse wherever the B1 field exceeded the adiabatic threshold, rendering this sequence suitable for applications that use surface coil excitation. An AHP (23)Na TPI sequence was used with a surface coil at 1.5 T to noninvasively quantify myocardial TSC in 10 normal volunteers. The mean TSC was 43 +/- 4, 53 +/- 12, and 17 +/- 4 micromol/g in the left ventricular (LV) free wall, septum, and adipose tissue, respectively, consistent with prior invasive measurements on biopsy and autopsy specimens. CONCLUSION: It is now possible to noninvasively quantify TSC in the human heart with surface coil (23)Na MRI.
PURPOSE: To measure tissue sodium concentrations in the human heart with (23)Na MRI using a surface coil, thereby eliminating the effects of inhomogeneous excitation by surface coils and minimizing T(1) and T(2) relaxation. MATERIALS AND METHODS: We combined fully relaxed, very short-echo, (23)Na twisted projection imaging (TPI) with adiabatic half passage (AHP) excitation and external referencing on subjects and comparing with a concentration reference phantom scan to quantify TSC with surface coils. (23)Na signal losses during hard (square), composite, and tanh/tan amplitude/frequency-modulated AHP excitation pulses were analyzed over a wide range of RF field strengths and T(2short) values. RESULTS: AHP excitation yielded a homogeneous excitation flip angle and negligible losses compared to a 90 degrees hard pulse wherever the B1 field exceeded the adiabatic threshold, rendering this sequence suitable for applications that use surface coil excitation. An AHP (23)Na TPI sequence was used with a surface coil at 1.5 T to noninvasively quantify myocardial TSC in 10 normal volunteers. The mean TSC was 43 +/- 4, 53 +/- 12, and 17 +/- 4 micromol/g in the left ventricular (LV) free wall, septum, and adipose tissue, respectively, consistent with prior invasive measurements on biopsy and autopsy specimens. CONCLUSION: It is now possible to noninvasively quantify TSC in the human heart with surface coil (23)Na MRI.
Authors: Ping Wang; Muge Serpil Deger; Hakmook Kang; T Alp Ikizler; Jens Titze; John C Gore Journal: Magn Reson Imaging Date: 2016-10-27 Impact factor: 2.546
Authors: Michael A Jacobs; Vered Stearns; Antonio C Wolff; Katarzyna Macura; Pedram Argani; Nagi Khouri; Theodore Tsangaris; Peter B Barker; Nancy E Davidson; Zaver M Bhujwalla; David A Bluemke; Ronald Ouwerkerk Journal: Acad Radiol Date: 2010-09-21 Impact factor: 3.173
Authors: Ronald Ouwerkerk; Paul A Bottomley; Meiyappan Solaiyappan; Amy E Spooner; Gordon F Tomaselli; Katherine C Wu; Robert G Weiss Journal: Radiology Date: 2008-07 Impact factor: 11.105