Photograph of the first-generation digital receiver module prototype with each dedicated Rx core containing a single Rx channel.
Photograph of the proposed digital receiver module with multiple Rx channels implemented inside a single FPGA-based Rx core.
Block diagram of the proposed receiver hardware incorporated in a self-built digital transceiver.
Block diagram of the console that integrates the proposed DRMs. Up to 12 DRMs are available under control of a single master controller. The number of the controllers can be further increased using distributed Ethernet network.
Flow chart of the phase synchronization method for both the receiver and exciter.
Plot of the phase variation acquired by the repeated loop-back test procedures. The dots represent the phase values of the Sinc pulse's peak captured every one second.
Plot of the phase variation acquired using repeated standard SE sequences. A total of 247 echoes were captured at the center line of the k-space. The dots represent initial phase values of the each echo. The phase variation mainly results from the magnetic field stability.
Multi-slice T2-weighted 2D FSE images of a standard phantom (J5298, J. M. Specialty Parts, San Diego, CA) with a localizer image shown in the upper left. Imaging parameters: TR/TE/FA = 3000 ms/115 ms/90°; image matrix (MAT) = 256 × 256; field of view (FOV) = 250 × 250 mm; thickness (THK) = 5 mm; number of excitation (NEX) = 4; RF frequency (SF) = 21.4 MHz.
Axial cross section of a square water phantom selected from the LSDWI images (TR/TE/FA = 150 ms/128 ms/90°, MAT = 128 × 82, FOV = 199 × 250 mm, THK = 7 mm, NEX = 2, SF = 21.4 MHz). Left-hand images were acquired using an AD6620 receiver and a dc artifact is induced from the intrinsic truncation effects of the chipset; right-hand images were acquired using the DRM where the dc bias is eliminated with minimized quantization error. Both images were displayed at the same window and level.
(a) Two spin echo images of a standard phantom (J5298) acquired with a commercial receiver of a DRX2 console (left-hand image), and with the proposed receiver module (right-hand image). Imaging parameters: TR/TE/FA = 460 ms/16 ms/90°; MAT = 256 × 192; FOV = 250 × 250 mm; THK = 5 mm; NEX = 2; SF = 63.89 MHz. (b) Axial cross section of a normal volunteer's brain selected from T1-weighted images (TR/TE/FA = 560 ms/13 ms/90°, MAT = 320 × 202, FOV = 220 × 220 mm, THK = 5 mm, NEX = 2, SF = 63.89 MHz), acquired with the DRX2 (lower images), and with the proposed DRM (upper images). Right-hand images = enlarged view (×4). All images were displayed at the same window and level.
The MR vascular image acquired from 3D TOF sequence with MIP post-processing. Imaging parameters: TR/TE/FA = 35 ms/10.6 ms/30°; MAT = 256 × 192; FOV = 200 × 200 mm; THK = 1 mm; NEX = 1; SF = 63.89 MHz.
The specifications of the anti-aliasing filters used in 0.5 T and 1.5 T MRI experiments.
Article metrics loading...
Full text loading...