Feedback Control of the Nuclear Magnetization State: Experimental Results

J. L. Schiano, A. G. Webb, R. L. Magin

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Conventional MRI is an open-loop process in the sense that measurements of the magnetization state are not utilized until after the completion of a pulse sequence. Optimization of pulse parameters occurs before the pulse sequence is transmitted. In a previous paper, we investigated feedback control of the nuclear magnetization state [1]. This strategy facilitates the optimization of the pulse parameters during the imaging sequence. A systematic method for modeling and controlling the nuclear magnetization state was presented. The method was illustrated by a theoretical example in which the angle between the bulk magnetization and the axis of an applied static magnetic field is controlled using feedback. In this paper, results from a series of experiments used to test the theoretical predictions are presented. Two groups of experiments are performed using a commercial imager and a small sample of distilled water. In the first group of experiments the control objective is to regulate the magnetization orientation to a constant reference angle. These experiments are used to compare the performance of open and closed-loop systems. The experimental results show that a closed-loop system produces the desired orientation. In contrast, an open-loop input results in an appreciable error between the desired and measured orientation. A second group of experiments shows that a closed-loop system can force the magnetization orientation to track a desired trajectory. In both groups, the closed-loop experimental and simulation results are in excellent agreement. The application of feedback control to MRI and spectroscopy is discussed.

Original languageEnglish (US)
Pages (from-to)203-214
Number of pages12
JournalIEEE transactions on medical imaging
Volume11
Issue number2
DOIs
StatePublished - Jun 1992

Fingerprint

Feedback control
Magnetization
Closed loop systems
Magnetic Fields
Experiments
Magnetic resonance imaging
Spectrum Analysis
Control Groups
Water
Image sensors
Trajectories
Spectroscopy
Magnetic fields
Feedback
Imaging techniques

All Science Journal Classification (ASJC) codes

  • Software
  • Radiological and Ultrasound Technology
  • Computer Science Applications
  • Electrical and Electronic Engineering

Cite this

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Feedback Control of the Nuclear Magnetization State : Experimental Results. / Schiano, J. L.; Webb, A. G.; Magin, R. L.

In: IEEE transactions on medical imaging, Vol. 11, No. 2, 06.1992, p. 203-214.

Research output: Contribution to journalArticle

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