Conventional Magnetic Resonance Imaging (MRI) consoles are expensive, closed systems. Proprietary spectrometer architectures, locked pulse-sequence compilers, and restrictive software interfaces make it difficult for students and researchers to inspect signal paths, modify low-level control loops, or build accessible scanners for education and low-field research.
In 2018, researchers at the Athinoula A. Martinos Center for Biomedical Imaging (Massachusetts General Hospital / MIT) addressed this barrier by developing OCRA (Open-source Console for Real-time Acquisition). Proving that an open console could be built from commercially available hardware, the team demonstrated imaging on a ~0.4 T educational tabletop MRI scanner using less than $500 in essential console electronics.
Key Takeaways
Rather than treating the console as a proprietary black box, OCRA transferred its critical control functions onto accessible, commercial components:
The core technical strength of OCRA was leveraging the Zynq SoC's heterogeneous architecture, pairing hardware determinism with flexible software control:
This architecture allowed RF pulses, gradient waveforms, and sequence timing to be updated just microseconds before execution, avoiding the constraints of static, precompiled experiments.
Image 2: OCRA to MaRGE timeline. Source: Red Pitaya.
OCRA's low-cost and open architecture also made it well suited to education. OCRA was developed for the MGH/MIT tabletop MRI scanners, which are used in MIT classes to teach students about MRI. Its Python-based GUI was explicitly intended as an educational tool, giving students a way to interact with and learn from the underlying MRI system.
That combination of accessible hardware and hands-on experimentation continued at Otto von Guericke University (OVGU) Magdeburg and the STIMULATE research center. Between 2019 and the early 2020s, OCRA became part of hands-on MR system engineering education, where students could work with the hardware rather than simply operate a finished imaging system.
To make that work more accessible at the benchtop, the Magdeburg team developed the OCRA1 peripheral shield, mounting directly onto the Red Pitaya extension headers:
Integrated into OVGU’s MR System Engineering course, the shield turned the open console into a teaching platform: students could assemble hardware, characterize its behavior, program the control system, and see how their changes affected an actual MRI experiment. Instead of treating the scanner as a finished instrument, they could study and modify the individual building blocks that made the system work.
That educational use also illustrates an important part of OCRA’s evolution. Its open hardware and software made the underlying instrumentation accessible enough to be incorporated into hands-on engineering education.
Image 3: Red Pitaya, OCRA1 and a power-supply/distributor in a 19” case. Credit: Marcus Prier
As researchers began demanding longer and more complex experiments, limitations in OCRA's sequence length, timing flexibility, and assembly-style programming interface became apparent.
An international collaboration then took the OCRA approach further with MaRCoS (MAgnetic Resonance COntrol System), a ground-up re-engineering of the MRI control stack. While moving the main control platform to the Red Pitaya SDRlab 122-16, MaRCoS retained compatibility with the OCRA1 four-channel gradient hardware alongside newer gradient interfaces:
Want a deeper look at the MaRCoS hardware architecture?
Read the companion technical feature: MaRCoS: An Open-Source MRI Control System Built with Red Pitaya SDRlab 122-16.
In 2024, the consortium published MaRGE (MaRCoS Graphical Environment), providing a user-oriented interface tailored for clinical-style workflows—including protocol management, DICOM export, and integrated reconstruction tools.
The MaRCoS/MaRGE platform has been demonstrated across diverse experimental systems, including:
Image 4: MaRGE: A graphical environment for MaRCoS. Credit: https://www.sciencedirect.com/science/article/pii/S1090780724000466
OCRA and OCRA1 use external 18-bit DACs (AD5780/AD5781B) for gradient generation, while the Red Pitaya’s high-speed onboard converters handle the RF transmit and receive paths. The external DACs provide the precision and analog output characteristics needed by the gradient-control chain, while the onboard high-speed converters are used for RF signal processing.
MaRCoS represents a ground-up re-engineering rather than a simple software update: it changes how MRI sequences are represented, transferred, and executed. Its streaming architecture and Pulseq compatibility support sequences of arbitrary length while reducing the memory and assembly-level programming constraints of the original OCRA design.
The MaRCoS project is primarily designed around the SDRlab 122-16, but community documentation notes that it could be ported to the STEMlab 125-14 with reduced receive FIFO depth. The SDRlab remains the primary hardware target because of its larger FPGA resource capacity and 16-bit ADC resolution.