Purpose: To develop software that enables the rapid implementation of custom MRI spectrometers using commercially-available software defined radios (SDRs).
Methods: The 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 a spin echo inversion recovery imaging sequence.
The gr-MRI 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 SDRâs ability to generate frequency-swept RF waveforms was validated and compared to the scannerâs spectrometer.
Results: Gradient echo and spin echo images geometrically matched those acquired using the scannerâs spectrometer, with no unexpected distortions. Inversion recovery images exhibited expected behavior as a function of inversion time. Desynchronization events were more likely to occur at the very beginning of an imaging scan, but were nearly eliminated if the user invokes the sequence for a short period before beginning data recording. The SDR was able to produce a 500 kHz bandwidth frequency-swept pulse with high fidelity, while the scannerâs spectrometer produced a waveform with large frequency spike errors.
Conclusion: The developed gr-MRI software can be used to develop high-fidelity, low-cost custom MRI spectrometers using commercially-available SDRs.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-04082016-131931 |
| Date | 08 April 2016 |
| Creators | Hasselwander, Christopher Jordan |
| Contributors | Brett C. Byram, Ph.D., Mark Does, Ph.D., William A. Grissom, Ph.D. |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-04082016-131931/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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