Needle Tracking with Single Smartphone Magnetometer and Compliant Mechanism Needle Holder

Advances in medical imaging modalities (e.g. ultrasound, computed tomography, and MRI) have led to improvements in image-guided needle interventions, such as biopsy and radiation ablation. Traditionally, radiologists would perform interventional procedures freehand under the guidance of an imaging system (i.e. to track the position of the needle during alignment and insertion). Such procedures require high motor-visual coordination from the radiologist and are time-consuming, with positional accuracy highly dependent on experience. [1]. A compliant mechanism-based device combined with a smartphone has been designed to address the shortcomings of current image-guided needle targeting systems. Smartphones are ubiquitous, with sufficient processing power for real-time data analysis, and do not require an external power supply during operation. The compliant mechanism is disposable, 3D-printed, cost- effective, and designed in such a way that it minimises tissue damage during positioning.[2] The compliant mechanism holds the needle such that there is a remote centre of motion (RCM) on the surface of the patient's skin. An RCM allows for a fixed point of entry around which the needle can be rotationally positioned, minimising possible tissue tearing that would otherwise occur due to unintended needle translation. The compliant mechanism benefits from a simple design that is compact and has great flexibility [3]. The integrated magnetometer of the smartphone is used to track the needle orientation, with real-time targeting information shown on the phone's display. This abstract presents the operating principles of the compliant mechanism-based needle targeting system with preliminary open-air test results given.