SMART tracking: Simultaneous anatomical imaging and real-time passive device tracking for MR-guided interventions

TL;DR

This paper introduces SMART tracking, a method combining anatomical imaging and real-time passive device tracking in MRI, enabling accurate, high-speed localization of surgical tools without specialized hardware.

Contribution

The study presents a novel MRI technique that simultaneously captures anatomical images and tracks devices passively in real-time, improving intervention guidance.

Findings

Average tracking error of ~0.3 mm compared to CT

Stable tracking during needle insertion and retraction

High frame rate with automatic slice positioning

Abstract

Purpose: This study demonstrates a proof of concept of a method for simultaneous anatomical imaging and real-time (SMART) passive device tracking for MR-guided interventions. Methods: Phase Correlation template matching was combined with a fast undersampled radial multi-echo acquisition using the white marker phenomenon after the first echo. In this way, the first echo provides anatomical contrast, whereas the other echoes provide white marker contrast to allow accurate device localization using fast simulations and template matching. This approach was tested on tracking of five 0.5 mm steel markers in an agarose phantom and on insertion of an MRI-compatible 20 Gauge titanium needle in ex vivo porcine tissue. The locations of the steel markers were quantitatively compared to the marker locations as found on a CT scan of the same phantom. Results: The average pairwise error between the MRI and CT locations was 0.30 mm for tracking of stationary steel spheres and 0.29 mm during motion. Qualitative evaluation of the tracking of needle insertions showed that tracked positions were stable throughout needle insertion and retraction. Conclusions: The proposed SMART tracking method provided accurate passive tracking of devices at high framerates, inclusion of real-time anatomical scanning, and the capability of automatic slice positioning. Furthermore, the method does not require specialized hardware and could therefore be applied to track any rigid metal device that causes appreciable magnetic field distortions.