eTHRIVE SEQUENCE
Introduction
Magnetic resonance imaging (MRI) is a
clinical mainstay in the detection and characterization of both focal liver
lesions and diffuse liver disease [1–4]. In particular, contrast-enhanced
T1-weighted sequences (CE- T1w) provide crucial information for the
differential diagnosis of focal liver lesions (FLL) [5]. State-of-the-art MR
protocols of the liver comprise 3D T1-w fat-saturated fast-fieldecho sequences
(T1w-FS-FFE) acquired dynamically before and after the administration of intravenous
extracellular or hepatocyte-specific contrast agents. These T1w-FS-FFE
sequences with Cartesian k-space sampling have different vendor-specific names,
such as eTHRIVE (“enhanced T1 high-resolution isotropic volume excitation”;
Philips), VIBE (“volumetric interpolated breath-hold
examination”;Siemens)orLAVA(“Liver Acquisition with Volume Acceleration“; GE)
[6, 7]. Dynamic contrast-enhanced (DCE) imaging with consecutive breath-holds
allows for the acquisition of pre-contrast, arterial-phase, portal-venous
phase, equilibrium, and delayed-phase images using bolus triggering or fixed
timepoint methods [8]. However, the diagnostic imaging quality could be
dramatically hampered by breathing artifacts in conventional breath-hold
techniques with necessary consecutive breath-holds of about 15–20 seconds
depending on coverage and resolution. Especially in the case of patients with
compromised respiratory function, elderly patients, and children who may not be
able to adequately hold their breath, impairment of image quality and
subsequent diagnostic inaccuracy can be a severe clinical issue [9]. Different
MR approaches using respiratory triggering and gating utilizing data from
specific motion states have been developed to reduce respiratory-induced motion
artifacts [10–12]. Moreover, k-space undersampling techniques and parallel
imaging have led to a significant acceleration of 3D T1w-FS sequences with
acquisition times of <10 seconds per dynamic scan [13, 14]. On the other
hand, novel radial k-space sampling techniques acquired during free breathing
have been shown to be robust against respiratory motion-induced artifacts
[15–17]. The purpose of this retrospective study was to evaluate the subjective
and objective clinical image quality of a novel 3D T1wFS FFE sequence based on
“pseudo golden angle” radial k-space sampling (Radial-eTHRIVE). Therefore
free-breathing RadialeTHRIVE images of the delayed post-contrast phase were
compared to the standard breath-hold 3D T1w-FS FFE with Cartesian k-space
sampling (Cartesian-eTHRIVE).
