Verification of needle guidance accuracy in pelvic phantom using registered ultrasound and MRI images for intracavitary/interstitial gynecologic brachytherapy

Zhiyong Yang; Ziqi Liu; Shan Jiang; Jing Zeng; Yuanjing Hu; Guobin Zhang

doi:10.5114/jcb.2020.94583

Verification of needle guidance accuracy in pelvic phantom using registered ultrasound and MRI images for intracavitary/interstitial gynecologic brachytherapy

J Contemp Brachytherapy. 2020 Apr;12(2):147-159. doi: 10.5114/jcb.2020.94583. Epub 2020 Apr 30.

Authors

Zhiyong Yang¹, Ziqi Liu¹, Shan Jiang¹, Jing Zeng², Yuanjing Hu², Guobin Zhang¹

Affiliations

¹ School of Mechanical Engineering, Tianjin University, Tianjin, China.
² Department of Gynecology, Tianjin Central Hospital of Genecology and Obstetrics & Affiliated Hospital of Nankai University, Tianjin, China.

Abstract

Purpose: In combined intracavitary/interstitial (IC/IS) gynecologic brachytherapy, trackers attached to interstitial needles of localize real-time needle trajectories, and intraoperative ultrasound (US) images provide updated anatomy information during needle insertions. To achieve an effective visualization and image guidance, real-time needle trajectories and US images can be unified in preoperative magnetic resonance imaging (MRI) image space together. This study evaluates the rigid registration accuracy between US images and MRI images as well as the registration accuracy between US images and real-time needle trajectories in a pelvic phantom.

Material and methods: A method for US probe calibration and accomplished rigid registration between MRI images and US images was proposed. An IC/IS applicator was designed. Micro electromagnetic sensor to track and localize real-time needle trajectories in 3D MRI image space was used. Marker validation to test the accuracy of US probe calibration and pelvic phantom validation to test the registration accuracy between US images and MRI images was conducted as well as and pelvic phantom study to verify the registration accuracy between real-time needle trajectories and needle trajectories in registered US images.

Results: US probe calibration accuracy was 0.80 ±0.23 mm (n = 60). Registration accuracy between US images and MRI images were 1.01 ±0.22 mm in the axial plane (n = 60) and 1.14 ±0.20 mm in the sagittal plane (n = 24). Registration accuracy between real-time needle trajectories and needle trajectories in registered US images were 1.25 ±0.31 mm (n = 40) and 1.61 ±0.28 degrees (n = 5), respectively.

Conclusions: In this study, we showed that under ideal conditions, rigid registration between MRI images and US images obtained high accuracy for real-time image guidance. Additionally, registered US images provided accurate image guidance during visual needle insertion in IC/IS gynecologic brachytherapy to achieve a combination of effective visualization and image guidance.

Keywords: image-guidance; intracavitary/interstitial brachytherapy; needle trajectory visualization; ultrasound image registration.