Fast B1 + mapping using three consecutive RF pulses and balanced gradients for improved bSSFP imaging

Min Oh Kim, Taehwa Hong, Donghyun Kim

Research output: Contribution to journalArticle

Abstract

Purpose To develop a B1 + mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1 + inhomogeneity compensation. Methods Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1 +) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1 + was estimated using the two magnitude images and bSSFP data was sequentially acquired. B1 + estimation error due to the assumptions and other factors such as FA and off-resonance were assessed using Bloch simulation. Phantom and in vivo experiments were performed with α-2α-3α scheme. Results The simulation results indicated that the proposed method was less sensitive to T1 relaxation and B1 + mapping FA (α) of approximately 60° produced minimum estimation error. The B1 +-induced intensity variation was reduced with the proposed method in the phantom experiment. For both the phantom and in vivo experiments, the estimated B1 + map showed comparable to the conventional B1 + map using spin-echo DAM. Conclusion B1 + map was estimated during the transient phase of bSSFP and subsequently compensated bSSFP images. There was no scan time increment and hence the technique can be used in a prescan manner for B1 + mapping or shimming.

Original languageEnglish
Pages (from-to)40-46
Number of pages7
JournalMagnetic Resonance Imaging
Volume46
DOIs
Publication statusPublished - 2018 Feb 1

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Imaging techniques
Error analysis
Experiments
Compensation and Redress

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biomedical Engineering
  • Radiology Nuclear Medicine and imaging

Cite this

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abstract = "Purpose To develop a B1 + mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1 + inhomogeneity compensation. Methods Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1 +) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1 + was estimated using the two magnitude images and bSSFP data was sequentially acquired. B1 + estimation error due to the assumptions and other factors such as FA and off-resonance were assessed using Bloch simulation. Phantom and in vivo experiments were performed with α-2α-3α scheme. Results The simulation results indicated that the proposed method was less sensitive to T1 relaxation and B1 + mapping FA (α) of approximately 60° produced minimum estimation error. The B1 +-induced intensity variation was reduced with the proposed method in the phantom experiment. For both the phantom and in vivo experiments, the estimated B1 + map showed comparable to the conventional B1 + map using spin-echo DAM. Conclusion B1 + map was estimated during the transient phase of bSSFP and subsequently compensated bSSFP images. There was no scan time increment and hence the technique can be used in a prescan manner for B1 + mapping or shimming.",
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Fast B1 + mapping using three consecutive RF pulses and balanced gradients for improved bSSFP imaging. / Kim, Min Oh; Hong, Taehwa; Kim, Donghyun.

In: Magnetic Resonance Imaging, Vol. 46, 01.02.2018, p. 40-46.

Research output: Contribution to journalArticle

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N2 - Purpose To develop a B1 + mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1 + inhomogeneity compensation. Methods Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1 +) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1 + was estimated using the two magnitude images and bSSFP data was sequentially acquired. B1 + estimation error due to the assumptions and other factors such as FA and off-resonance were assessed using Bloch simulation. Phantom and in vivo experiments were performed with α-2α-3α scheme. Results The simulation results indicated that the proposed method was less sensitive to T1 relaxation and B1 + mapping FA (α) of approximately 60° produced minimum estimation error. The B1 +-induced intensity variation was reduced with the proposed method in the phantom experiment. For both the phantom and in vivo experiments, the estimated B1 + map showed comparable to the conventional B1 + map using spin-echo DAM. Conclusion B1 + map was estimated during the transient phase of bSSFP and subsequently compensated bSSFP images. There was no scan time increment and hence the technique can be used in a prescan manner for B1 + mapping or shimming.

AB - Purpose To develop a B1 + mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1 + inhomogeneity compensation. Methods Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1 +) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1 + was estimated using the two magnitude images and bSSFP data was sequentially acquired. B1 + estimation error due to the assumptions and other factors such as FA and off-resonance were assessed using Bloch simulation. Phantom and in vivo experiments were performed with α-2α-3α scheme. Results The simulation results indicated that the proposed method was less sensitive to T1 relaxation and B1 + mapping FA (α) of approximately 60° produced minimum estimation error. The B1 +-induced intensity variation was reduced with the proposed method in the phantom experiment. For both the phantom and in vivo experiments, the estimated B1 + map showed comparable to the conventional B1 + map using spin-echo DAM. Conclusion B1 + map was estimated during the transient phase of bSSFP and subsequently compensated bSSFP images. There was no scan time increment and hence the technique can be used in a prescan manner for B1 + mapping or shimming.

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