title: Fundamental Study of Three-dimensional Fast Spin-echo Imaging with Spoiled Equilibrium Pulse.
abstract: Three-dimensional fast spin-echo (3D FSE) imaging with variable refocusing flip angle has been recently applied to pre- or post-enhanced T1-weighted imaging. To reduce the acquisition time, this sequence requires higher echo train length (ETL), which potentially causes decreased T1contrast. Spoiled equilibrium (SpE) pulse consists of a resonant +90° radiofrequency (RF) pulse and is applied at the end of the echo train. This +90° RF pulse brings residual transverse magnetization to the negative longitudinal axis, which makes it possible to increase T1contrast. The purpose of our present study was to examine factors that influence the effect of spoiled equilibrium pulse and the relationship between T1contrast improvement and imaging parameters and to understand the characteristics of spoiled equilibrium pulse. Phantom studies were conducted using an magnetic resonance imaging (MRI) phantom made of polyvinyl alcohol gel. To evaluate the effect of spoiled equilibrium pulse with changes in repetition time (TR), ETL, and refocusing flip angle, we measured the signal-to-noise ratio and contrast-to-noise ratio (CNR). The effect of spoiled equilibrium pulse was evaluated by calculating the enhancement rate of CNR. The factors that influence the effect of spoiled equilibrium pulse are TR, ETL, and relaxation time of tissues. Spoiled equilibrium pulse is effective with increasing TR and decreasing ETL. The shorter the T1value, the better the spoiled equilibrium pulse functions. However, for tissues in which the T1value is long (>600 ms), at a TR of 600 ms, improvement in T1contrast by applying spoiled equilibrium pulse cannot be expected.
authors.affiliation: Department of Radiology, Nippon Medical School Hospital.
authors.forename: Masashi
authors.initials: M
authors.lastname: Ogawa
authors.forename: Naoto
authors.initials: N
authors.lastname: Kaji
authors.forename: Toshio
authors.initials: T
authors.lastname: Tsuchihashi
mesh_terms: D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D013679:Technology, Radiologic / Q000295:instrumentation / Q000379:methods*