A standalone and cost-effective MR-compatible computer numerical control machine for simultaneous, multi-parameter mapping

Abstract

Measuring parameters like magnetic field strength and temperature inside a magnet bore is of interest to characterize the system and use that information for downstream image quality improvement or to determine safety thresholds. Multiple commercial measurement systems are available to achieve this goal. However, these systems are often expensive, utilizing proprietary hardware and software, and making adjustments for specific applications is challenging, if not prohibitive. In this work, we design, build, and test a simple, MR-compatible 3D movement robot with a sensor holder as a standalone system using a Raspberry Pi and a 16-channel ADC hat. This design costs less than $1200 and is assembled from widely available components with a working volume of 397 × 398 × 310 mm3. We demonstrate the 3D field mapping of a 47 mT scanner and six-inch wide disc magnets as examples of the robot’s use over multiple trials and geometries. We simultaneously mapped data from one magnetic flux density sensor and three temperature probes. We found the measurements highly repeatable, with the maximum value of the average coefficient of variation across space and time measurements from multiple experiments less than 3.5%. We characterized our robot’s spatial accuracy, acoustic noise, and vibrations and found them to be capable of 0.5 mm spatial resolution, less than 75 dB, and less than 1 m s−2 during periods of probe movement.