COSESS and INSESS: Coherent and incoherent spin echoes in the steady state

Abstract

A new fast sequence type, called COSESS/INSESS, is described. The steady state for COSESS is coherent but incoherent for INSESS. COSESS/INSESS combine the contrast behavior of fast imaging with steady-state free precession (FISP) and fast low angle shot (FLASH), respectively, to the robustness of spin-echo (SE) sequences with regard to susceptibility and field inhomogeneities. In contrast to other fast sequences such as rapid spin-echo excitation (RASEE), fast low angle spin echo with short echo time (FATE) or the missing pulse sequence, which also uses a spin echo, COSESS/ INSESS can additionally handle time-dependent disturbances arising from eddy currents, hysteresis or B(zero) instability. The acquisition time is 2 to 3 times longer than with gradient-based steady-state sequences. The principle of echo generation is evaluated and shows a superposition of several subechoes in the spin echo. Different solutions were elaborated to attain a coherent superposition of sub-echo signals for COSESS. Signal and contrast behavior were investigated both by simulations and experiments and demonstrate the performance of COSESS/INSESS.

Development and validation of 3D MP‐SSFP to enable MRI in inhomogeneous magnetic fields

“…The RF pulse interval τ in MP‐SSFP is adjustable. A previous study used a different RF pulse interval or an extra gradient pulse between data acquisition and the following RF pulse to split primary and secondary echo pathways 42 . Splitting primary and secondary echoes was demonstrated to reduce aliasing artifacts from eddy currents and B 0 instability.…”

“…A previous study used a different RF pulse interval or an extra gradient pulse between data acquisition and the following RF pulse to split primary and secondary echo pathways. 42 Splitting primary and secondary echoes was demonstrated to reduce aliasing artifacts from eddy currents and B 0 instability. Although such artifacts were not clearly seen in our experiments at 4T, this type of modification might improve image quality when commissioning MP-SSFP as part of an inhomogeneous MRI system in the future.…”

Advanced Algorithmic Approaches to Medical Image Segmentation

“…Other fast imaging methods include: dynamic contrast-enhanced breast MRI done using twoand three-dimensional variable flip angle fast low-angle shot Tl measurement (see Brookes et al [35]); dynamic-breathing MRI (see Suga et al [36]) ; ultrafast MRI (see Outwater [37]); hepatic lesion fat suppressed T2-weighted MR imaging pulse sequence (see Kanematsu et al [38]); coronary MR angiography (see Duerinckx [39]); fast-FLAIR MTC pulse sequence (see Filippi [40]); Single Shot Fast Spin Echo (SSFSE) pulse sequence (see Kadoya et al [41]); Fast Spin Echo Diffusion Coefficient Mapping MRI (see Brockstedt et al [42]); adiabatic multiple Spin Echo pulse sequence (see Zweckstetter et al [43]); half-Fourier TUrbo Spin Echo MRI (HASTE12) (see Coates et al [44]) ; 3-D Time of Flight MR angiography by Ultrafast MP-RAGE sequence (see Yamashita et al [45]); Coherent and Incoherent steady-state spin-echo (COSESS 13 and INSESS 14 ) sequences (see Werthner et al [46]) ; phase-modulated binominal RF pulses for spectrally selective imaging (see Thomasson et al [47]) ; Dual Echo Steady-State Free Precession (DESS-FP) pulse sequence (see Hardy et al [48]); optimized ultra-Fast Imaging Sequence (OUFIS) (see Zha et al [49]) ; fast three -dimensional Inversion-Recovery GRE pulse sequence (see Foo et al [50]); diffusion-weighted EPI pulse sequences for glioma (see Tien et al [51]) ; Time of Flight carotid vascular contrast MRA pulse sequences (see Tkach et al [52]); incremental Flip Angle Snapshot FLASH MRI pulse sequence (see Urhahn et al [53]); Steady-State Free Precession Rapid 2-DFT MRI: FAST and CE-FAST sequences (see Gyngell [54]). …”

Impact of structured product definition on market success

“…compact, intermediate, limousine) and the gradients and RF system are equivalent to the horsepower of the engine. For further reading on MR see Hahn (1959), Werthner et al (1996), Hoult (1977) and Hoult and Lauterbur (1979).…”