Feasability of A-mode Ultrasound Based Registration to Track Scapula Motion : A Simulation Study

6 pages•Published: September 25, 2020

Abstract

We describe an A-mode ultrasound-based scapula tracker for pre-operative diagnosis and planning. One paper investigated this technology but did not assess its rotational accuracy, which is the critical variable. Therefore, we ran simulations and optimizations to investigate whether this technology’s rotational accuracy was adequate to make this a viable tool.
Simulations were created by converting a CT-derived scapula into an even density point cloud and positioning it in a neutral pose (our ground truth). This was reposed to a known mid-range motion, and its points were randomly sampled to mimic the data yielded by an array of single- element A-mode ultrasound transducers. This sampled dataset was registered to the ground truth using ICP, and to determine the resultant error, the resulting transformation was compared to the known transformation applied to the ground truth. The Monte Carlo method was applied to this simulation to yield varying samplings; as well, the samples were subjected to varying levels of random noise (replicating ultrasound error) to assess robustness. The effects of the number of sample points and their location were also investigated.
For 10 simulated sensors in an optimized pattern across the scapula, corrupted by random error, registration rotational errors for a sagittal plane 70◦ shoulder flexion were 0.82◦ ± 0.63◦ for posterior tilting, 0.68◦ ± 0.6◦ for upward rotation and 0.54◦ ± 0.54◦ for internal rotation.
We have successfully demonstrate that, in this simulation study, a clinically viable number of ultrasound sensors (∼ 10) could yield adequate accuracy to be diagnostically useful, if they are properly distributed across the scapula.

Keyphrases: a mode ultrasound, biomechanics, kinematics, motion capture, numerical simulation, scapula

In: Ferdinando Rodriguez Y Baena and Fabio Tatti (editors). CAOS 2020. The 20th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery, vol 4, pages 97-102.

Links:	https://easychair.org/publications/paper/gvs1
	https://doi.org/10.29007/345z