ThermoSlide: an MR-compatible thermode positioning device

Purpose

The ThermoSlide presented here allows the thermode Medoc PATHWAY CHEPS (https://www.medoc-web.com/pathway-model-cheps) to be placed and repositioned on the forearm of a participant in an MRI scanner remotely, without having to move the participant or the scanner table, and with easier access compared to reaching into the scanner bore.

Construction

Two coaxial PVC tubes (rigid conduit EN16 and EN20) and a 3D-printed holder are used for this purpose. The holder consists of four parts that are screwed together (4 pcs. M4 x 12 countersunk flat head, 4 pcs. M3 x 12 slotted cheese head). The inner fixed tube (length: 136cm) is firmly attached to Part_2 of the holder using two M3 x 25 screws and nuts. The movable outer tube (length: 121cm) has a bobbin at the end, and an elastic band that can be tightened or loosened by rotating it. Both flanges of the bobbin have cut-outs on the end faces into which an M3 screw will fit. This is used to lock the bobbin in place by shifting the outer tube longitudinally when the elastic strap is tightened sufficiently.

During assembly, the elastic band (size: 3.5cm x 50cm) must first be threaded through the two slits in the bobbin and then sewn into a loop. The bobbin can then be plugged onto the movable tube and secured with two M2 x 8 brass screws. To reduce the friction with the elastic band, an accordingly punched out PTFE foil (approx. 90mm x 40mm x 0.3mm) can be wrapped around the center bar of Part_1 and then fixed from below with four M3 x 4 screws.

Optionally, the ThermoSlide can be equipped with a simple torque gauge (as done here), allowing one to apply approximately the same pressure when repositioning the thermode to another part of the forearm. The main component is a special 3D printed torsion spring. The end with the angle indicators is attached to the moving tube with three M4 x 12 screws. At the other end, three 120 spaced pointers and a short handle tube (EN25 rigid conduit) are screwed on.

The torsion spring was fabricated from KEYENCE AR-M2 at a local service provider. All other components were printed on a Stratasys Eden260VS 3D printer. The material used was MED610. Nylon screws are used unless otherwise noted.

Usage, citation and contact

We have used this device in various fMRI studies at 3T and 7T (e.g. https://www.biorxiv.org/content/10.1101/2023.12.22.572825v1) and would be happy to provide help in case you are interest in using such a device as well. In case you use this device, please cite it as shown under 'Cite this repository' on the right. If you have any questions, please feel free to reach out to rmueller@cbs.mpg.de.

License

This work is licensed under a Creative Commons Attribution 4.0 International License.