Minimum acquisition methods for simultaneously imaging T1, T2, and proton density with B1 correction and no spin-echoes

Guan Wang, Abdel Monem M El-Sharkawy, Paul A Bottomley

Research output: Contribution to journalArticle

Abstract

The spin lattice (T1) and spin-spin (T2) relaxation times, along with the proton density (PD) contain almost all of the information that 1H MRI routinely uses in clinical diagnosis and research, but are seldom imaged directly. Here, three methods for directly imaging T 1, T2, and PD with the least possible number of acquisitions - three, are presented. All methods utilize long 0° self-refocusing adiabatic pre-pulses instead of spin-echoes to encode the T 2 information prior to a conventional gradient-echo MRI sequence. T1 information is encoded by varying the flip-angle (FA) in the 'Dual-τ Dual-FA' and 'Four-FA' methods, or the sequence repetition period, TR, in the 'Dual-τ Dual-TR' method. Inhomogeneity in the FA distribution and slice-selection profile are recognized as the main error sources for T 1 measurements. The former is remedied by integrating an extra FA-dependent acquisition into the 'Four-FA' method to provide self-corrected T1, T2, PD, and FA in just four acquisitions - again, the minimum possible. Slice profile errors - which manifest as differences between 2D and 3D T1 measurements, can be addressed by Bloch equation analysis and experimental calibration. All three methods are validated in phantom studies, and the 'Dual-τ Dual-FA' and 'Four-FA' methods are validated in human brain studies using standard partial saturation and spin-echo methods for reference. The new methods offer a minimum-acquisition option for imaging single-component T1, T2, and PD. 'Four-FA' performs best overall in accuracy, with high efficiency per unit accuracy vs. existing methods when B1-inhomogeneity is appropriately addressed.

Original languageEnglish (US)
Pages (from-to)243-255
Number of pages13
JournalJournal of Magnetic Resonance
Volume242
DOIs
StatePublished - 2014

Fingerprint

Protons
acquisition
echoes
Imaging techniques
Magnetic resonance imaging
Relaxation time
Brain
Calibration
inhomogeneity
profiles
brain
repetition
Research Design
relaxation time
saturation
gradients
pulses
Research

Keywords

  • Measurement
  • MRI
  • Proton density
  • Spin-latice relaxation
  • Spin-spin relaxation

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Biochemistry
  • Biophysics
  • Condensed Matter Physics
  • Medicine(all)

Cite this

Minimum acquisition methods for simultaneously imaging T1, T2, and proton density with B1 correction and no spin-echoes. / Wang, Guan; El-Sharkawy, Abdel Monem M; Bottomley, Paul A.

In: Journal of Magnetic Resonance, Vol. 242, 2014, p. 243-255.

Research output: Contribution to journalArticle

@article{73f77841f6904b409bf12b998fa13ced,
title = "Minimum acquisition methods for simultaneously imaging T1, T2, and proton density with B1 correction and no spin-echoes",
abstract = "The spin lattice (T1) and spin-spin (T2) relaxation times, along with the proton density (PD) contain almost all of the information that 1H MRI routinely uses in clinical diagnosis and research, but are seldom imaged directly. Here, three methods for directly imaging T 1, T2, and PD with the least possible number of acquisitions - three, are presented. All methods utilize long 0° self-refocusing adiabatic pre-pulses instead of spin-echoes to encode the T 2 information prior to a conventional gradient-echo MRI sequence. T1 information is encoded by varying the flip-angle (FA) in the 'Dual-τ Dual-FA' and 'Four-FA' methods, or the sequence repetition period, TR, in the 'Dual-τ Dual-TR' method. Inhomogeneity in the FA distribution and slice-selection profile are recognized as the main error sources for T 1 measurements. The former is remedied by integrating an extra FA-dependent acquisition into the 'Four-FA' method to provide self-corrected T1, T2, PD, and FA in just four acquisitions - again, the minimum possible. Slice profile errors - which manifest as differences between 2D and 3D T1 measurements, can be addressed by Bloch equation analysis and experimental calibration. All three methods are validated in phantom studies, and the 'Dual-τ Dual-FA' and 'Four-FA' methods are validated in human brain studies using standard partial saturation and spin-echo methods for reference. The new methods offer a minimum-acquisition option for imaging single-component T1, T2, and PD. 'Four-FA' performs best overall in accuracy, with high efficiency per unit accuracy vs. existing methods when B1-inhomogeneity is appropriately addressed.",
keywords = "Measurement, MRI, Proton density, Spin-latice relaxation, Spin-spin relaxation",
author = "Guan Wang and El-Sharkawy, {Abdel Monem M} and Bottomley, {Paul A}",
year = "2014",
doi = "10.1016/j.jmr.2014.02.010",
language = "English (US)",
volume = "242",
pages = "243--255",
journal = "Journal of Magnetic Resonance",
issn = "1090-7807",
publisher = "Academic Press Inc.",

}

TY - JOUR

T1 - Minimum acquisition methods for simultaneously imaging T1, T2, and proton density with B1 correction and no spin-echoes

AU - Wang, Guan

AU - El-Sharkawy, Abdel Monem M

AU - Bottomley, Paul A

PY - 2014

Y1 - 2014

N2 - The spin lattice (T1) and spin-spin (T2) relaxation times, along with the proton density (PD) contain almost all of the information that 1H MRI routinely uses in clinical diagnosis and research, but are seldom imaged directly. Here, three methods for directly imaging T 1, T2, and PD with the least possible number of acquisitions - three, are presented. All methods utilize long 0° self-refocusing adiabatic pre-pulses instead of spin-echoes to encode the T 2 information prior to a conventional gradient-echo MRI sequence. T1 information is encoded by varying the flip-angle (FA) in the 'Dual-τ Dual-FA' and 'Four-FA' methods, or the sequence repetition period, TR, in the 'Dual-τ Dual-TR' method. Inhomogeneity in the FA distribution and slice-selection profile are recognized as the main error sources for T 1 measurements. The former is remedied by integrating an extra FA-dependent acquisition into the 'Four-FA' method to provide self-corrected T1, T2, PD, and FA in just four acquisitions - again, the minimum possible. Slice profile errors - which manifest as differences between 2D and 3D T1 measurements, can be addressed by Bloch equation analysis and experimental calibration. All three methods are validated in phantom studies, and the 'Dual-τ Dual-FA' and 'Four-FA' methods are validated in human brain studies using standard partial saturation and spin-echo methods for reference. The new methods offer a minimum-acquisition option for imaging single-component T1, T2, and PD. 'Four-FA' performs best overall in accuracy, with high efficiency per unit accuracy vs. existing methods when B1-inhomogeneity is appropriately addressed.

AB - The spin lattice (T1) and spin-spin (T2) relaxation times, along with the proton density (PD) contain almost all of the information that 1H MRI routinely uses in clinical diagnosis and research, but are seldom imaged directly. Here, three methods for directly imaging T 1, T2, and PD with the least possible number of acquisitions - three, are presented. All methods utilize long 0° self-refocusing adiabatic pre-pulses instead of spin-echoes to encode the T 2 information prior to a conventional gradient-echo MRI sequence. T1 information is encoded by varying the flip-angle (FA) in the 'Dual-τ Dual-FA' and 'Four-FA' methods, or the sequence repetition period, TR, in the 'Dual-τ Dual-TR' method. Inhomogeneity in the FA distribution and slice-selection profile are recognized as the main error sources for T 1 measurements. The former is remedied by integrating an extra FA-dependent acquisition into the 'Four-FA' method to provide self-corrected T1, T2, PD, and FA in just four acquisitions - again, the minimum possible. Slice profile errors - which manifest as differences between 2D and 3D T1 measurements, can be addressed by Bloch equation analysis and experimental calibration. All three methods are validated in phantom studies, and the 'Dual-τ Dual-FA' and 'Four-FA' methods are validated in human brain studies using standard partial saturation and spin-echo methods for reference. The new methods offer a minimum-acquisition option for imaging single-component T1, T2, and PD. 'Four-FA' performs best overall in accuracy, with high efficiency per unit accuracy vs. existing methods when B1-inhomogeneity is appropriately addressed.

KW - Measurement

KW - MRI

KW - Proton density

KW - Spin-latice relaxation

KW - Spin-spin relaxation

UR - http://www.scopus.com/inward/record.url?scp=84899838998&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84899838998&partnerID=8YFLogxK

U2 - 10.1016/j.jmr.2014.02.010

DO - 10.1016/j.jmr.2014.02.010

M3 - Article

C2 - 24705365

AN - SCOPUS:84899838998

VL - 242

SP - 243

EP - 255

JO - Journal of Magnetic Resonance

JF - Journal of Magnetic Resonance

SN - 1090-7807

ER -