Multiband diffusion‐weighted MRI of the eye and orbit free of geometric distortions using a RARE‐EPI hybrid

Abstract

Diffusion-weighted imaging (DWI) provides information on tissue microstructure. Single-shot echo planar imaging (EPI) is the most common technique for DWI applications in the brain, but is prone to geometric distortions and signal voids. Rapid acquisition with relaxation enhancement [RARE, also known as fast spin echo (FSE)] imaging presents a valuable alternative to DWI with high anatomical accuracy. This work proposes a multi-shot diffusion-weighted RARE-EPI hybrid pulse sequence, combining the anatomical integrity of RARE with the imaging speed and radiofrequency (RF) power deposition advantage of EPI. The anatomical integrity of RARE-EPI was demonstrated and quantified by center of gravity analysis for both morphological images and diffusion-weighted acquisitions in phantom and in vivo experiments at 3.0 T and 7.0 T. The results indicate that half of the RARE echoes in the echo train can be replaced by EPI echoes whilst maintaining anatomical accuracy. The reduced RF power deposition of RARE-EPI enabled multiband RF pulses facilitating simultaneous multi-slice imaging. This study shows that diffusion-weighted RARE-EPI has the capability to acquire high fidelity, distortion-free images of the eye and the orbit. It is shown that RARE-EPI maintains the immunity to B inhomogeneities reported for RARE imaging. This benefit can be exploited for the assessment of ocular masses and pathological changes of the eye and the orbit.

Standard Diffusion-weighted MRI for the Diagnosis of Central Retinal Artery Occlusion

“…RE-SOLVE technique, Siemens, Erlangen, Germany) as well as the use of additional orbital surface coils. These techniques have already been introduced into clinical practice K and should be implementable with well-manageable efforts [33][34][35][36][37].…”

Controlled Release of Therapeutics from Thermoresponsive Nanogels: A Thermal Magnetic Resonance Feasibility Study

“…For this purpose, a fast spin-echo MRI variant [ 43 ], which simultaneously supports T 2 relaxation-based and PRF-based temperature mapping in a single acquisition (two-in-one) provides a speed gain and advancement over traditional gradient-echo-based PRF approaches. For multislice acceleration and enhanced anatomic coverage of the fast spin-echo MRI variant, a low RF power multiband approach can be incorporated [ 44 ]. For further speed gain and reduction of RF power deposition, an echo-planar read-out can be amended to the fast spin-echo read-out train [ 44 ].…”

“…For multislice acceleration and enhanced anatomic coverage of the fast spin-echo MRI variant, a low RF power multiband approach can be incorporated [ 44 ]. For further speed gain and reduction of RF power deposition, an echo-planar read-out can be amended to the fast spin-echo read-out train [ 44 ].…”

Cartesian MR fingerprinting in the eye at 7T using compressed sensing and matrix completion‐based reconstructions

“…One of the main challenges in ocular imaging is in‐plane and through‐plane eye motion, often associated with eye blinking . The motion results in corrupted k‐space data that introduces artifacts and blurring throughout the entire image.…”

“…One of the main challenges in ocular imaging is in-plane and through-plane eye motion, often associated with eye blinking. [11][12][13] The motion results in corrupted k-space data that introduces artifacts and blurring throughout the entire image. Shortening the scans would reduce motion-related artifacts, but standard acceleration techniques are not optimal for the current eye application due to the following 3 reasons.…”