High-dose-rate prostate brachytherapy imaging optimization: A motorized sagittal three-dimensional ultrasound acquisition system.

Background

High-dose-rate prostate brachytherapy (HDR-BT) relies on precise three-dimensional (3D) ultrasound imaging for treatment planning. Sagittally reconstructed 3D (SR3D) ultrasound images have been shown to reduce dosimetric uncertainty compared to axial approaches but are not broadly implemented due in part to image quality degradation and variability caused by non-uniform manual probe rotation during acquisition.

Purpose

We aimed to develop a system enabling motorized SR3D ultrasound acquisitions with the CIVCO EX3 stepper and evaluate improvements in image quality and scan variability.

Methods

The system was developed, allowing for automated rotation of a housed transrectal ultrasound probe in the CIVCO EX3 stepper. Image quality was assessed by comparing motorized and manual SR3D acquisitions of a wire phantom against an ideal clinical reference (slow manual scan) using peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and multi-scale SSIM (MS-SSIM) using a variety of scan speeds (2-27.5°/s). Additionally, quantitative metrics such as axial and elevational resolution and distance errors, as well as volume errors were compared between the two acquisition methods across two operators.

Results

Motorized scans were of greater similarity to an ideal reference when compared to manual acquisition regardless of acquisition speed. Manual scans showed significantly higher variability for elevational distance errors and volume errors. Additionally, manual scans had significant inter-operator variability which was not present in the motorized acquisitions.

Conclusions

The motorized attachment for SR3D acquisition reduced image variability and improved image quality. Through these improvements, this system may encourage broader use of sagittal reconstruction in HDR-BT, potentially improving patient outcomes.