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High Resolution Minimal Scan Technique for Localized Magnetic Resonance Proton Chemical Shift Imaging Using the Back-Projection Algorithm

IP.com Disclosure Number: IPCOM000037030D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

Feig, E: AUTHOR

Abstract

A method for providing a chemical shift image of a windowed chemical slice using high resolution magnetic resonance is provided. The reconstructed image is localized by windowing in the polar coordinate radial dimension (desired amplitude for all angles), and the method for accomplishing the same generally comprises (with a coherent detector tuned so that the proton peak for fat is set to zero):

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High Resolution Minimal Scan Technique for Localized Magnetic Resonance Proton Chemical Shift Imaging Using the Back-Projection Algorithm

A method for providing a chemical shift image of a windowed chemical slice using high resolution magnetic resonance is provided. The reconstructed image is localized by windowing in the polar coordinate radial dimension (desired amplitude for all angles), and the method for accomplishing the same generally comprises (with a coherent detector tuned so that the proton peak for fat is set to zero):

(a) selectively exciting a body along a desired plane;

(b) measuring the induced free induction decay in the presence of a time varying gradient which is a superposition of a fixed linear gradient and a cosinusoidal gradient with a first predetermined amplitude and phase;

(c) tuning the coherent detector so that tk l2 = f, where l2 is the proton peak for water, and tk is a waiting period between the excitation of the body and the measurement, and repeating steps (a) and (b) with a waiting period for tk inserted between steps (a) and (b); and, then

(d) processing the measured free induction decays by multiplying the obtained measurements by eim'at for various m' which are chosen in accordance with linear combinations that provide the desired window, low-pass filtering the acquired product, Fourier transforming the filtered measurements with respect to time, taking the sum and difference of the results processed for the detector tuned for fat and water to get individual components, and back projecting each component according to back-projection techniques. The provided method gives a very high resolution reconstruction of the chemical shift of a slice of the body which is windowed in the polar coordinate radial dimension.

In a body having a line L passing through the origin, where r denotes the angle L makes with the x axis, and p denotes the position along that line, P(r,p) is said to equal the line integral of the density function taken along the line perpendicular to L which intersects it at the point (r,p). The excitation, encoding, and induced free induction decay measurement of a body having a line integral of its density function P(r, p) is indicated in the figure. It is recognized that the chemical shift spectrum of protons has two distinct peaks, l1 and l2, corresponding to fat and water. As shown by pulse 10, a desired plane of the body i...