Simple partial volume transceive coils for in vivo ¹H MR studies at high magnetic fields

Abstract

The development of simple radiofrequency (RF) coils for magnetic resonance (MR) of the human brain is still of high interest in the engineering of systems for which phased arrays are not yet available. Particularly, high-field MR studies will benefit from configurations with simple coils that are easy to build and require only a few RF parts for operation (e.g., quadrature hybrids). In this article we describe selected simple transmit/receive (transceive) partial volume coil assemblies for human brain studies at high magnetic fields of 3, 4, and 7 T (130, 170, and 300 MHz). To characterize coil performance, the experimental results of MRI of phantoms, anatomical MRI, and singlevoxel MRS of healthy human volunteers are presented.

Longitudinal changes of cerebral glutathione (GSH) levels associated with the clinical course of disease progression in patients with secondary progressive multiple sclerosis

“…All MR scan protocols and setups for this longitudinal study were identical to our initial study 6 performed on a 3-T MR system (Allegra; Siemens, Erlangen, Germany) using a custom-built partial volume transmit/receive coil, a quadrature radiofrequency (RF) helmet coil. 18 The participants lay supine in the MR scanner, and a series of MR scans were performed identical to their initial MR scans at Time 1: (1) three-plane scout MR images to locate the volume of interest (VOI), a 3-cm axial slab positioned above the corpus callosum including the frontal to parietal regions; (2) localized automated shimming to optimize static magnetic field homogeneity in the CSI volume by adjusting all first- and second-order shim currents based on measured field maps; (3) conventional CSI for creatine measurement (slice thickness = 2 cm, matrix size = 16 × 16, field of view (FOV) = 20 × 20 cm 2 , VOI = 10 × 12 cm 2 , time to echo (TE)/repetition time (TR) = 30/2000 ms, and number of averages = 2); and 4) the selective multiple quantum CSI of GSH acquired from the selected CSI slice (slice thickness = 3 cm, matrix size = 8 × 8, FOV = 20 × 20 cm 2 , TE/TR = 115/1500 ms, spectral width = 2 kHz, and number of averages = 12). The CSI of GSH is based on a two-echo scheme, allowing simultaneous acquisition of the creatine signal, which serves as an internal concentration reference.…”

Doubly selective multiple quantum chemical shift imaging and T1 relaxation time measurement of glutathione (GSH) in the human brain in vivo

“…The system was equipped with an actively shielded gradient coil (38‐cm inner diameter, Magnex Scientific, Abingdon, UK) capable of switching to 40 mT/m with a rise time of 400 µs. An in‐house built circularly polarized 1 H radiofrequency (RF) helmet coil (diameter ~ 21 cm) was used that conformed to the human head and provided a high filling factor and coil sensitivity . Automated localized and slice shimming techniques were used to adjust DC currents in all first‐ and second‐order shim coils.…”

“…Thirteen healthy subjects were studied (28 ± 9 yrs old, mean ± SD) according to consent approved by the Institutional Review Board of the Nathan Kline Institute. All subjects were positioned supine with the head inside the helmet coil . Transverse T 1 ‐weighted images of the brain were acquired using an inversion‐prepared 3D gradient echo sequence, magnetization‐prepared rapid gradient‐echo (MPRAGE), with the following parameters: FOV = 20 × 20 cm; matrix = 256 × 160 × 120; slab thickness = 15 cm; TR = 2 s; RAGE TR = 11.8 ms; TE = 5.4 ms; and effective TI = 1.1 s .…”

Lower levels of glutathione in the brains of secondary progressive multiple sclerosis patients measured by 1H magnetic resonance chemical shift imaging at 3 T

“…A custom-built quadrature radiofrequency (RF) helmet coil, a partial volume transmit/receive coil, was used to provide a relatively homogeneous RF field and high sensitivity with volume coverage above the eyes. 24 After positioning the participant supine in the magnet, three-plane scout MR images were acquired using a gradient echo sequence to locate the volume of interest (VOI). The VOI, a 3-cm axial slab for the chemical shift imaging (CSI) of GSH, was positioned to cover the area above the corpus callosum including the frontal to parietal regions, and also located in the iso-center of the magnet (Fig.…”