113 - Novel Acousto-Optic Sensor Stylet for Needle Tip Tracking, Needle Tip Imaging, and Tissue Characterization Compared to Capabilities of Electromagnetic Tracking

Purpose: To assess the accuracy of a novel acousto-optic sensor for needle tip 3D

localization within ultrasound (US) imaging compared to electromagnetic (EM) tracking in phantoms. The ability to localize tumor and reconstruct US view from the needle tip was also evaluated.

Materials and Methods: An acousto-optic 50µm sensor was prototyped and

integrated into a 20G stylet inside an 18G needle. The sensor was interfaced with US and a visualization software (DeepSight Technology). It provided 3D location of the needle tip relative to US plane and an internal US view from the needle tip. A phantom with target tumors (Sun Nuclear) was punctured using the acousto-optic sensor and using a commercial EM tracking system (PercuNav, Philips). Because of inherent high echogenicity, the needle tip was not visible under conventional ultrasound within the target tumors. The EM tracking system was composed of a US transducer sensor, a needle holder sensor (the offset to the tip was corrected by the system according to needle length), a patient tracker sensor placed on the phantom and an EM field generator placed above the phantom. Needle insertions were completed when the tracking system indicated the needle tip was located at the center of the target tumor. Accuracy of needle placement was defined as the distance from the needle tip to the target center on CT imaging (iQon, Philips). Paired t-test was used to compare accuracy (tip-to-target center distance) (Rstudio v2024).

Results: Target tumors of various diameters (5-10mm) and various depths (5-13cm) were targeted using the acousto-optic tracking system (N=10) and then the EM tracking system (N=10). The mean tip-to-center accuracy was 2.85mm (SD 1.32mm) for the acousto-optic tracking system and 3.57mm (SD 1.18mm; P=0.19) for the EM tracking system. Using the acousto-optic system, US imaging from needle tip was feasible for each insertion, with sufficient resolution to allow characterization of target-specific echogenicity around the needle tip. The EM tracking system did not allow internal imaging or tissue characterization capabilities but enables fusion with an additional imaging modality like CT or MRI.

Conclusion: This novel acousto-optic sensor could successfully localize the needle tip in 3 dimensions with accuracy similar to EM tracking in phantom, while enabling internal US imaging from the needle tip. This dual tracking and imaging technology could augment current US guided interventions and facilitate new applications.