Magnetic field exposimeter for MRI staff
A wearable headset that measures exposure to magnetic fields for people working near MRI scanners.
- 1Two 3-axis Hall sensors (SENM3DX), one on each temple, measuring fields up to 4 T.
- 2Controller behind the head: nRF52840 on Zephyr, external flash for logging, status LED, piezo buzzer at the start and end of a measurement, 100 mAh battery and a USB connector underneath.
- 3Button on top: the wearer adds a timestamp to the recording when they feel a physiological effect, such as vertigo.
- 4Automatic logging: the device sleeps until a threshold interrupt from a TMAG5273 magnetic sensor detects the strong field of the MRI room, then wakes up and starts recording on its own.
- 5Desktop application: downloads the logs over USB.
- 6Phone application: retrieves the data over BLE (developed by an intern I supervised).
- Category
- Medtech & research
- Organization
- FHNW
- Period
- 2023 – 2026
- Technologies
- nRF52840, Zephyr, SENM3DX, TMAG5273, BLE, USB, External flash, Altium
Context
People working around MRI scanners are regularly exposed to strong static magnetic fields, and their exposure is rarely measured. The device is worn like a bone-conduction headset, with a field sensor on each temple. It wakes up on its own when the wearer enters the MRI room and records the field throughout their work, without any action on their part.
My role
Designed the compact PCB and developed the low-power firmware on Zephyr: sleep with wake-up on a magnetic threshold interrupt, continuous logging to external flash, status LED, buzzer and timestamp button, and USB and BLE data transfer. Developed the desktop application that retrieves the logs over USB, and supervised an intern who developed the phone application. Wrote the technical documentation and the user manual.