From Aluminum to Plastic: Designing a MRI-Compatible LBNP Chamber
In the winter of 2023, a researcher came to us with a request; one that would allow the investigation of an entirely novel set of research questions. The request was: "can you engineer a LBNP chamber that is MRI-compatible?" Given our traction in the field of pressure chamber engineering, we decided this was a terrific opportunity for us to expand our knowledge and experience into the area of MRI-compatible devices. So, we set out on our learning journey...
Design #1 – Gantry-style and external to the MRI bore.
After an initial meeting with the researcher to gather required specifications and discuss a few ideas, we got to work on an initial design. It consisted of a gantry-style framework, built from non-ferromagnetic metals (mostly aluminum) that we believed were MRI-compatible. The idea was that the chamber would slide and hover over the MRI subject bed while remaining mostly outside the MRI scanner. The plumbing and electronics would be separated into a stand-alone pump box, and pressure would be controlled remotely from the MRI control room using our automated pressure control software. We thought it was an elegant solution…
New engineering considerations are revealed for MRI-compatibility.
We had the opportunity to meet with an MRI physicist that had spent decades of his career working with MRI scanners. We quickly realized there were significant problems with our proposed initial design. It turns out MRIs have dynamic magnetic fields in addition to static fields, which means that they induce electric currents in conductive materials, even if they are non-ferromagnetic. This meant our proposed aluminum framing would get quite hot if it came close to the MRI bore. Back to the drawing board…
Design #2 – Modify the chamber to fit within the MRI scanner.
So, our stand-alone pump box was still a go, but we needed a new solution for a chamber design. After some internal discussion, the new chamber design was composed entirely of plastic components and was engineered to slide within the MRI scanner. However, this required addressing one remaining significant problem: the limited space and the resulting restrictive mobility imposed on research participants by the MRI bed.
With these space constraints, research participants would not be able to climb into the chamber once it was placed on the MRI bed. The Technavance elegant solution to this limitation was for the chamber to be assembled around the participant once they were already lying on the MRI bed.
In order to accomplish this, the chamber was split into four main sections: a baseplate, a front entry sealing panel, a seat platform, and a half-cylinder.
The research participants would lie on the baseplate, already positioned on the MRI bed, and the remaining three chamber pieces would be assembled around them.
To bring the entire design together, long, flexible tubing would connect the chamber, after being slid inside the MRI scanner, to the pump box in the control room.
Design #2 was it!
As with any first-of-its-kind instrument, our learning continued. There were minor changes over the next year or so once the instrument was in use and weaknesses in the design revealed themselves. Fast forward almost three years later, and we have installed numerous MRI-compatible LBNP chambers across North America and Europe, fitting within MRI scanners of various shapes and sizes.
Stay tuned for an exciting new capability for our MRI-compatible LBNP chambers, coming soon… One that will open even more doors to investigate innovative research questions!
