Density-Matrix Calculations of the 1.5 T Citrate Signal Acquired with Volume-Localized STEAM Sequences
✍ Scribed by R.V. Mulkern; J.L. Bowers; S. Peled; D.S. Williamson
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 290 KB
- Volume
- 110
- Category
- Article
- ISSN
- 1064-1866
No coin nor oath required. For personal study only.
✦ Synopsis
Citrate detection and quantitation with proton spectroscopic the coherences which contribute to the AB STEAM methods are of current interest as potential tools in the diagnosis signal. and staging of prostate cancer. The stimulated echo acquisition Wilman and Allen (8) have recently addressed the citratemode (STEAM) sequence is a commonly used volume-localization STEAM-signal problem with an AB product-operator formethod for detecting citrate signal. Since the 1 H citrate resonance mulation (9). Specifically, they calculated the AB STEAM at clinically available field strengths arises from a strongly coupled signal for a 90Њ x -t 1 -90Њ x -t 2 -90Њ x -t 1 -acquire setwo-spin system, the 90Њ RF pulses and localizing gradients used quence in which full dephasing gradients are applied during in STEAM sequences result in a complicated dependence of signal the ''mixing time'' t 2 and during the two t 1 periods of this intensity on timing intervals and gradient amplitudes. The densitysequence. Although the solution is useful for studying cimatrix formalism has been applied to arrive at a general solution trate-STEAM-signal properties under these conditions, it is to this problem. Citrate-signal properties at 1.5 T for different gradient localization schemes are examined with the solution. Op-not general enough to study the effects of alternate gradienttimal interpulse delays, deleterious gradient balances, zero-quandisposition schemes which may prove useful for enhancing tum oscillations with mixing time, and a low-frequency, largecitrate signal.
amplitude oscillation with echo time are identified for signals ac-
In this work, a density-matrix approach is applied to genquired with the standard disposition of gradients in STEAM. The erate the general solution to the AB-STEAM-signal problem. generality of the solution also allows for an examination of non-Specifically, the AB signal from 90Њ y -t 1 -90Њ {ystandard gradient disposition schemes for enhancing citrate signal t 2 -90Њ y -t 1 -acquire sequences is derived for arbitrary and for quantifying the sensitivity of such approaches to both field