Cooperative T₁ and T₂ effects on contrast using a new driven inversion spin‐echo (DISE) MRI pulse sequence

Abstract

A pulse sequence is presented for obtaining a single image with combined T1/T2 weighting. T2 relaxation is made to increase intensity, in cooperation with the effect of T1 relaxation, by providing T2 weighting with a 90 degrees-180 degrees-90 degrees driven inversion pulse triplet in an inversion recovery method. Unlike the inversion spin-echo method having a short inversion time (TI), signals in the new driven inversion spin-echo (DISE) method need not be negative and the most T1-sensitive region of the recovery curve can be used. Selecting sensitivity to one relaxation time does not degrade the sensitivity to the other relaxation time. T1 sensitivity is thus extended to longer echo times (TE intervals). T2 sensitivity is extended to longer TI intervals, and the combined T1/T2-weighted technique with intermediate TE and TI has highly cooperative and near-maximal T1 and T2 effects on contrast. Intensity is not multiplicatively degraded by T1 and T2 weighting so that the signal-to-noise of the combined T1/T2-weighted method is high. High intensity and T1 and T2 cooperatively occur for a much wider range of relaxation times, and especially for images heavily weighted to the pathologic intermediate and long T1 and T2 regime.

Signal‐to‐noise in phase angle reconstruction: Dynamic range extension using phase reference offsets

“…Similarly, magnetic susceptibility ( 9, l o ) , static field inhomogeneity (11)(12)(13), radiofrequency (RF) field inhomogeneity (14, 1 5 ) , chemical shift (16)(17)(18), and perfusion (19,20) can all be encoded using either the signal magnitude or phase angle. Inversion recovery (21)(22)(23) and other pulse sequences producing negative intensities (24)(25)(26) can be used with phase reconstruction of the real component of the NMR signal. To choose the best technique for informational encoding and reconstruction, it is thus necessary to investigate the theoretical and experimental signalto-noise ratio ( S I N ) of phase-reconstructed data compared to magnitude data.…”

Application of a Mixed Imaging Sequence for MR Imaging Characterization of Human Breast Disease

“…Imaging sequences which are designed to differentiate between tissues, taking into account the influences of both Tl and T2 in a single image acquisition, are the subject of current research (2).…”

Abstracts-part III (Continue in Part IV)

“…Each shot, 2-32 echoes are acquired at a sampling bandwidth of f32 kHz about the refocussed point TE. Implementation included a sliding data acquisition window [9] to insure smooth magnitude and phase modulations in k-space and tuning of the data acquisition window to minimize errors in echo centering.…”

“…PreDaration phase: In both simulations and imaging, the contrast preparation type was Inversion Recovery (IR) for T1 weighting [7], Driven Equilibrium Fourier Transform (DEFT) for T2 weighting [8], or Driven Equilibrium Spin Echo (DISE) for cooperative T1-T2 weighting [9]. In simulations, nonselective pulses were assumed.…”