High‐precision t1 imaging method for magnetic resonance imaging

Abstract

AbstractIt is expected in magnetic resonance imaging (MRI) that the measurement of the longitudinal relaxation time (T1) will be useful in the diagnosis of cancer and in the tissue characterization. The present problem in this regard is the deterioration of the accuracy due to the various factors such as the rotation angle error of 180 deg pulse and the finite repetition time for imaging.From such a viewpcint, this paper derived an expression for the signal intensity for the inversion recovery image (IR image) considering those factors, and it is shown that a highly accurate T1 image with small error can be constructed by the proposed method from at least three images with different inversion times. Then a simplified method is proposed which can derive analytically the T1 image from three IR images obtained without using the iterative calculation, by controlling the inversion times so that they form an arithmetic progression. It was verified by a computer simulation that the error in the T1 image due to the forementioned factors can be kept below 1 percent by the proposed method. Using the MRI system, the T1 image as well as the proton density (rH) image are obtained from a copper‐sulfate phantom. The error between the object and the reconstructed image, which has been as large as 7 to 15 percent, is now suppressed to approximately 1 percent by the proposed method. Thus, the accuracy improvement in T1 and rH images is verified.