A cryogenic 14-channel C receiver array for 3T human head imaging.

Purpose: This article presents a novel 14-channel receive-only array for C human head imaging at 3 T that explores the SNR gain by operating at cryogenic temperature cooled by liquid nitrogen.

Methods: Cryostats are developed to evaluate single-coil bench SNR performance and cool the 14-channel array with liquid nitrogen while having enough thermal insulation between the coils and the sample. The temperature distribution for the coil array is measured.

Trade-off between preamplifier noise figure and decoupling in MRI detectors.

Purpose: There is a limit to the maximum achievable preamplifier decoupling. In many cases, this level is not enough. To overcome this limit, the preamplifier noise figure can be compromised for further decoupling increase.

Multi-site benchmarking of clinical C RF coils at 3T.

A quality assurance protocol for RF coils is proposed, which can be used for volume (Tx/Rx) and surface (Rx) coils. Following this protocol, a benchmarking of seven coils (from three different MR sites) dedicated to C MRI at 3T is reported. Coil performance is particularly important for 3T MRI at the C frequency, since the coil-to-sample noise ratio is typically high.

Three-element matching networks for receive-only MRI coil decoupling.

Purpose: Preamplifier decoupling is useful for minimizing interaction between MRI array elements. The purpose of this work is to propose a general approach to designing networks for preamplifier decoupling while keeping the number of elements to a minimum. The approach is applicable to arbitrary impedance preamplifiers and arbitrary coil impedances.

Three-dimensional accelerated acquisition for hyperpolarized C MR with blipped stack-of-spirals and conjugate-gradient SENSE.

Purpose: To test a new parallel imaging strategy for acceleration of hyperpolarized C MR acquisitions based on a 3D blipped stack-of-spirals trajectory and conjugate-gradient SENSE reconstruction with precalibrated sensitivities.

Methods: The blipped stack-of-spirals trajectory was developed for an acceleration factor of 4, based on an undersampled stack-of-spirals with gradient blips during spiral readout. The trajectory was developed with volumetric coverage of a large FOV and with high spatial resolution.

Autonomous cryogenic RF receive coil for C imaging of rodents at 3 T.

Purpose: To develop an autonomous, in-bore, MR-compatible cryostat cooled with liquid nitrogen that provides full-day operation, and to demonstrate that the theoretical signal-to-noise benefit can be achieved for C imaging at 3 T (32.13 MHz).

Methods: The cryogenic setup uses a vacuum-insulated fiberglass cryostat, which indirectly cools a cold finger where the RF coil is attached.

Coil profile estimation strategies for parallel imaging with hyperpolarized C MRI.

Purpose: To investigate auto- and pre-calibration coil profile estimation for parallel imaging reconstruction of hyperpolarized C MRI volumetric data.

Methods: Parallel imaging reconstruction was studied with 3 different approaches for coil profile estimation: auto-calibration, phantom calibration, and theoretic calibration. Acquisition was performed with a 3D stack-of-spirals sequence with spectral-spatial excitation and Cartesian undersampling.

Low-Noise Active Decoupling Circuit and its Application to C Cryogenic RF Coils at 3 T.

We analyze the loss contributions in a small, 50-mm-diameter receive-only coil for carbon-13 (C) magnetic resonance imaging at 3 T for 3 different circuits, which, including active decoupling, are compared in terms of their Q-factors and signal-to-noise ratio (SNR). The results show that a circuit using unsegmented tuning and split matching capacitors can provide >20% SNR enhancement at room temperature compared with that using more traditional designs. The performance of the proposed circuit was also measured when cryogenically cooled to 105 K, and an additional 1.