Author: Kevin Barker, David Jeffrey Contella, Chandima Edirisinghe, Aaron Fenster, Douglas A Hoover, Elizabeth Huynh 👨🔬
Affiliation: Robarts Research Institute, University of Western Ontario, London Health Sciences Center, Department of Radiation Oncology, London Health Sciences Centre 🌍
Purpose: We aim to develop a system that integrates micro-ultrasound into focal prostate cancer radiotherapy. This requires developing a mechatronic stepper capable of performing motorized rotation of the micro-ultrasound probe coupled with custom software to generate accurate 3D images for treatment planning.
Methods: The mechatronic stepper and 3D reconstruction software were successfully developed. To ensure reconstructed 3D images are spatially accurate, multiple geometric validation tests were performed. First, we imaged a grid phantom suspending wires spaced by known physical distances. Measurements in each Cartesian direction on the reconstructed 3D image were acquired using our software and compared to the known spacing between wires. We then validated volumetric measurements by imaging a prostate-mimicking phantom using our 3D micro-ultrasound system and MRI. The largest artificial tumor inside the phantom was segmented on the MRI and three separate micro-ultrasound images and the measured volumes were compared.
Results: The system was capable of generating 3D micro-ultrasound images. Results from the grid phantom tests revealed that linear measurements performed on the reconstructed images were accurate, with the l average error in any Cartesian direction being 0.2±0.1mm. Similarly, results from volumetric testing further validated the system’s accuracy, as the average measured volume of the segmented tumor differed by 0.07±0.02cm3 between the MRI (1.06cm3) and 3D micro-ultrasound images (0.99cm3±0.02cm3).
Conclusion: This work marks the first steps toward implementing 3D micro-ultrasound for focal prostate cancer radiotherapy. The results highlight that our system is capable of reconstructing 3D micro-ultrasound images suitable for radiotherapy treatment planning. This has the potential to be a more accessible and low-cost alternative for imaging DILs for focal prostate treatments within both external beam radiotherapy and brachytherapy. In addition, it can replace standard transrectal ultrasound imaging used within the intra-operative brachytherapy workflow, obviating the need for multi-modality image fusion and its associated complexities and uncertainties.