Time Saving in Measurement of NMR and EPR Relaxation Times

Look, David C.; Locker, Donald R.

doi:10.1063/1.1684482

Cited by 748 publications

(678 citation statements)

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“…The spoiling of transverse magnetization in FLASH generally leads to T 1 saturation since longitudinal magnetization is permanently used up during signal detection. T 1 quantification based on FLASH thus requires correction procedures as proposed by Look and Locker (18). As demonstrated, TrueFISP provides excellent results if T 2 is greater than several TRs.…”

Section: Discussionmentioning

confidence: 99%

“…Most T 1 quantification techniques are based on measuring the longitudinal magnetization at different time intervals TI after an inversion or saturation pulse (1)(2)(3)(4)(5). The magnitude of the longitudinal magnetization as a function of TI is then fitted to a monoexponential recovery function [M 0 (1 Ϫ e TI/T1 ) for saturation, and M 0 (1 Ϫ 2e TI/T1 ) for inversion recovery] to give T 1 and proton density M 0 values.…”

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confidence: 99%

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T₁ quantification with inversion recovery TrueFISP

Scheffler

Hennig

2001

Magnetic Resonance in Med

176

186

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A snapshot FLASH sequence can be used to acquire the time course of longitudinal magnetization during its recovery after a single inversion pulse. However, excitation pulses disturb the exponential recovery of longitudinal magnetization and may produce systematic errors in T 1 estimations. In this context the possibility of using the TrueFISP sequence to detect the recovery of longitudinal magnetization for quantitative T 1 measurements was examined. Experiments were performed on different Gd-doped water phantoms and on humans. Most T 1 quantification techniques are based on measuring the longitudinal magnetization at different time intervals TI after an inversion or saturation pulse (1-5). The magnitude of the longitudinal magnetization as a function of TI is then fitted to a monoexponential recovery function [M 0 (1 Ϫ e TI/T1 ) for saturation, and M 0 (1 Ϫ 2e TI/T1 ) for inversion recovery] to give T 1 and proton density M 0 values. Conventionally, one data set with a given TI is acquired after each inversion pulse and the experiment is repeated after a sufficient long recovery period (Ͼ 5T 1 ) with different TIs (single-point method (1)). As an alternative to this time-consuming technique, inversion recovery snapshot fast low-angle shot (FLASH) can be used (5). Here, the magnitude of the longitudinal magnetization is acquired continuously during its recovery using a FLASH sequence with low excitation flip angles of 5°to 10°. An intrinsic drawback of this method is the influence of the excitation pulses on the recovery of longitudinal magnetization even for small flip angles.Inversion recovery-prepared true Fast Imaging with Steady Precession (TrueFISP) was first proposed by Deimling and Heid (6) to modify the mainly T 2 -weighted image contrast of TrueFISP. In this work, we examined the possibility of replacing the intrinsically T 1 -weighted FLASH readout module by a TrueFISP readout module to continuously acquire the recovery of longitudinal magnetization. Quantitative T 1 measurements on phantoms and humans based on FLASH and TrueFISP were compared to the gold standard of separately acquired TI measurements. THEORYThe FISP sequence as proposed by Oppelt et al. (7) (now called TrueFISP (Siemens) or fully refocused SSFP (8)) consists of consecutive ␣ excitation pulses with alternating polarity. The gradient areas between these Ϯ␣ pulses are zero for all three gradient axes. Figure 1 shows one repetition cycle of TrueFISP, starting at the center of the ϩ␣ pulse and ending at the center of the Ϫ␣ pulse. At the beginning of one TR cycle the steady-state magnetization is aligned in the z direction and is then flipped into transverse magnetization by the ϩ␣/2 pulse. The echo is Fourier encoded by a symmetric readout gradient GR consisting of a dephasing period, a readout period, and a final rephasing step to refocus transverse magnetization. This pure transverse magnetization is finally flipped back to the z axis by the Ϫ␣/2 pulse. Except for T 2 and T* 2 effects, no transverse magnetization is lost between ␣ pu...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

T₁ quantification with inversion recovery TrueFISP

Scheffler

Hennig

2001

Magnetic Resonance in Med

176

186

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“…Measurements were performed on a 1.5 T clinical scanner (Achieva, Philips Healthcare). For T 1 mapping, inversion recovery data were acquired with a Look-Locker sequence including a correction for apparent T 1 values (17). The following parameters were used for the measurement: 40 inversion time increments, ∆T i = 72 msec, inversion repetition time (TR) 3 sec, FOV 250 × 250 mm, 7-mm slice thickness, 224 × 224 matrix.…”

Section: Measurementsmentioning

confidence: 99%

Compressed sensing reconstruction for magnetic resonance parameter mapping

Doneva

Börnert

Eggers

et al. 2010

Magnetic Resonance in Med

312

392

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Compressed sensing (CS) holds considerable promise to accelerate the data acquisition in magnetic resonance imaging by exploiting signal sparsity. Prior knowledge about the signal can be exploited in some applications to choose an appropriate sparsifying transform. This work presents a CS reconstruction for magnetic resonance (MR) parameter mapping, which applies an overcomplete dictionary, learned from the data model to sparsify the signal. The approach is presented and evaluated in simulations and in in vivo T 1 and T 2 mapping experiments in the brain. Accurate A major concern in MR parameter mapping is the often long scan time. This has led to an estimation of T 1 and T 2 relaxation times from three or even only two data points, which entails poor accuracy and does not give any indication of multicompartmental signal behavior. Higher numbers of measurements are necessary to cover a large dynamic range of tissue parameters relevant in clinical applications (4) and also to improve the accuracy of the fit and SNR. Multiexponential fits can be applied to decrease partial volume effects and to characterize multicompartmental relaxation curves (5). Several works consider measurements of T 2 distributions in tissue acquiring several thousand echoes (6,7).This article presents a technique for reducing the acquisition time in multipoint MR parameter mapping experiments, which is inspired by the theory of compressed

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“…Following a 2D cine imaging study, a gadolinium-based contrast agent (gadodiamide dimeglumine, Omniscan, GE Healthcare, Milwaukee, WI) at 0.15 mmol/kg was injected manually. Ten minutes after the injection, a cardiac-gated inversion-recovery 2D gradient-echo T1 scout imaging (ie, Look-Locker imaging) with an approximately 20 -30-second breath-hold was performed to determine the null point of the normal myocardium (14). Thereafter, breath-hold 2D inversion-recovery gradient-echo viability MRI was performed in the short-and long-axis views with the following imaging parameters: TR 10 msec; echo time (TE) 2.9 msec; flip angle 15°; acquisition of 30 k-space lines per heart beat; RBW 241 Hz/pixel; field of view (FOV) 36 ϫ 36 cm; imaging matrix 203 ϫ 304 (spatial resolution 1.77 ϫ 1.18 mm); slice thickness 10 mm; and two signal excitations.…”

Section: Mrimentioning

confidence: 99%

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

Amano

Matsumura

Kumita

2008

Magnetic Resonance Imaging

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Purpose:To assess the feasibility of free-breathing highspatial-resolution delayed contrast-enhanced three-dimensional (3D) viability magnetic resonance imaging (MRI) at 3.0T for the detection of myocardial damages. Materials and Methods:Twenty-five patients with myocardial diseases, including myocardial infarction and cardiomyopathies, were enrolled after informed consent was given. Free-breathing 3D viability MRI with high spatial resolution (1.5 ϫ 1.25 ϫ 2.5 mm) at 3.0T, for which cardiac and navigator gating techniques were employed, was compared with breath-hold two-dimensional (2D) viability imaging (1.77 ϫ 1.18 ϫ 10 mm) for assessment of contrastto-noise ratio (CNR) and myocardial damage.Results: Free-breathing 3D viability imaging was achieved successfully in 21 of the 25 patients. This imaging technique depicted 84.6% of hyperenhancing myocardium with a higher CNR between hyperenhancing myocardium and blood and with excellent agreement for the transmural extension of myocardial damage (k ϭ 0.91). In particular, the 3D viability images delineated the myocardial infarction and linear hyperenhancing myocardium, comparable to the 2D viability images. Conclusion:Free-breathing high-spatial-resolution delayed contrast-enhanced 3D viability MRI using 3.0T was feasible for the evaluation of hyperenhancing myocardium, as seen with myocardial infarction and cardiomyopathies.

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Time Saving in Measurement of NMR and EPR Relaxation Times

Cited by 748 publications

References 5 publications

T₁ quantification with inversion recovery TrueFISP

T₁ quantification with inversion recovery TrueFISP

Compressed sensing reconstruction for magnetic resonance parameter mapping

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

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Time Saving in Measurement of NMR and EPR Relaxation Times

Cited by 748 publications

References 5 publications

T1 quantification with inversion recovery TrueFISP

T1 quantification with inversion recovery TrueFISP

Compressed sensing reconstruction for magnetic resonance parameter mapping

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

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T₁ quantification with inversion recovery TrueFISP

T₁ quantification with inversion recovery TrueFISP