gr-MRI: A software package for magnetic resonance imaging using software defined radios

Abstract

The goal of this work is to develop software that enables the rapid implementation of custom MRI spectrometers using commercially-available software defined radios (SDRs). The developed gr-MRI software package comprises a set of Python scripts, flowgraphs, and signal generation and recording blocks for GNU Radio, an open-source SDR software package that is widely used in communications research. gr-MRI implements basic event sequencing functionality, and tools for system calibrations, multi-radio synchronization, and MR signal processing and image reconstruction. It includes four pulse sequences: a single-pulse sequence to record free induction signals, a gradient-recalled echo imaging sequence, a spin echo imaging sequence, and an inversion recovery spin echo imaging sequence. The sequences were used to perform phantom imaging scans with a 0.5 Tesla tabletop MRI scanner and two commercially-available SDRs. One SDR was used for RF excitation and reception, and the other for gradient pulse generation. The total SDR hardware cost was approximately $2000. The frequency of radio desynchronization events and the frequency with which the software recovered from those events was also measured, and the SDR’s ability to generate frequency-swept RF waveforms was validated and compared to the scanner’s commercial spectrometer. The spin echo images geometrically matched those acquired using the commercial spectrometer, with no unexpected distortions. Desynchronization events were more likely to occur at the very beginning of an imaging scan, but were nearly eliminated if the user invoked the sequence for a short period before beginning data recording. The SDR produced a 500 kHz bandwidth frequency-swept pulse with high fidelity, while the commercial spectrometer produced a waveform with large frequency spike errors. In conclusion, the developed gr-MRI software can be used to develop high-fidelity, low-cost custom MRI spectrometers using commercially-available SDRs.

The MR Cap: A single‐sided MRI system designed for potential point‐of‐care limited field‐of‐view brain imaging

“…For example, it could potentially be replaced by a previously published low‐cost laterally diffused metal oxide semiconductor amplifier capable of achieving 1.4 kW at a cost of $1500 USD . Likewise, there has been recent effort toward compact, low‐cost MRI consoles that could be a great cost savings, such as the $500 field programmable gate array‐based open‐source system . A total bill of materials cost using these two low‐cost options is provided in Supporting Information Table , detailing a potential total system parts cost of $3350 USD.…”

On the Economic Value of Open Source Hardware – Case Study of an Open Source Magnetic Resonance Imaging Scanner

“…Two software defined radios (SDR) are used to generate RF and gradient pulses (Blücher, 2017). The SDRs are compatible with an open source software framework to enable hardware independent development of MRI techniques (Hasselwander, Cao and Grissom, 2016 are musculoskeletal imaging of extremities such as knee, foot, wrist or elbow. The system is low-cost, smaller and lighter (total weight: ~1 00 kg) than commercially available extremity MR devices which makes it also interesting for mobile applications.…”

A low‐cost multi‐channel software‐defined radio‐based NMR spectrometer and ultra‐affordable digital pulse programmer

“…6, where the detection of and recovery from "de-synchronization events" are described. This issue has not been commonly addressed in publications of previous SDR-based NMR systems, and where it has, it appears to have been a serious problem, for example in Ref.…”

“…This issue has not been commonly addressed in publications of previous SDR-based NMR systems, and where it has, it appears to have been a serious problem, for example in Ref. 6, where the detection of and recovery from "de-synchronization events" are described. A great deal of effort has gone into ensuring accurate and consistent timing of the outputs of the various devices used here.…”

“…In recent years, several publications have described the development of low-cost NMR systems (eg, [1][2][3][4][5], NMR systems built upon SDR devices, [6][7][8][9] and custom integrated circuits for NMR. [10][11][12][13] Many of these systems are limited to low-field use, and the vast majority have been single-frequency instruments.…”