Rapid Volumetric MRI Using Parallel Imaging With Order-of-Magnitude Accelerations and a 32-Element RF Coil Array

Abstract

Rationale and Objectives-Many clinical applications of Magnetic Resonance Imaging are constrained by basic limits on imaging speed. Parallel MRI relaxes these limits by using the sensitivity patterns of arrays of radiofrequency receiver coils to encode spatial information in a manner complementary to traditional encoding with magnetic field gradients. Until now, parallel MRI has been used to achieve modest improvements in imaging speed; order-of-magnitude improvements have been elusive given fundamental losses in signal-to-noise ratio. The goal of this work was to demonstrate that, with appropriate hardware and careful SNR management, rapid volumetric imaging at high accelerations is in fact feasible.Materials and Methods-Contrast-enhanced MRI with an axial 3D spoiled gradient echo imaging sequence was performed in healthy adult subjects using a 32-element RF coil array and a prototype 32-channel MR imaging system. Large imaging volumes were prescribed, in place of traditional limited slabs targeted only to suspect regions.Results-As much as 16-fold net accelerations of imaging were achieved repeatably using this approach. The use of large 3D volumes allowed comprehensive anatomical coverage at clinically useful spatial and/or temporal resolution. The need for careful, time-consuming, and subject-specific scan prescription was also eliminated. Conclusion-The highly parallel imaging approach presented here allows previously inaccessible volumetric coverage for time-sensitive MRI examinations such as contrast-enhanced MRA, and simultaneously provides a substantially simplified imaging paradigm. The resulting capability for rapid volumetric imaging promises to combine the strengths of MRI with some of the advantages of alternative imaging modalities such as multidetector CT.

Compressed sensing MRI: a review of the clinical literature

“…This excess degradation is characterized by a geometry factor, also known as the g-factor. 43 It is possible that a similar SNR-degrading factor also exists in CS MRI, a topic that warrants attention. However, SNR comparisons are only Figure 9.…”

Comparison of the high relaxivity Gd chelates P1152 and Gd‐BOPTA for contrast‐enhanced MR angiography in rabbits at 1.5 Tesla and 3.0 Tesla

“…Although image quality was rated equally high for the two contrast agents at both field strengths, the evidently increased CNR caused by P1152 may offer potential to improve the diagnostic performance of CE-MRA. Advanced imaging applications which take advantage of high-acceleration parallel acquisition techniques (10,11) are associated with a considerable decrease of the signal intensity (12). This drawback might be partially counterbalanced by the use of contrast agents with higher relaxivities.…”

Toward single breath‐hold whole‐heart coverage coronary MRA using highly accelerated parallel imaging with a 32‐channel MR system

“…A 32-channel acquisition system was constructed using four sets of GE EXCITE II system electronics (GE Healthcare Technologies, Waukesha, WI, USA) in a master-slave arrangement (24,25). Each set consisted of eight channels that included analog-to-digital converters, a digital data pipeline, and a scanner console.…”

“…Third, a sufficient number of receivers allows the use of multidimensional RF coil array arrangements that are capable of multidimensional accelerations, which will serve to reduce the noise amplification that is inherent to parallel imaging and hence preserve SNR as compared to 1D accelerations (22,23). Furthermore, recent studies have shown that large 3D volumetric acquisitions that can benefit the most from multidimensional acceleration also serve to recover SNR via noise averaging (24,25).…”