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Updated: Aug 4, 2025

Use of MRI-ultrasound Fusion to Achieve Targeted Prostate Biopsy
Published on: April 9, 2019
Reid Vassallo1, Tajwar Abrar Aleef2, Qi Zeng3
1School of Biomedical Engineering, The University of British Columbia, 251-2222 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada. reidvass@student.ubc.ca.
This article introduces a new robotic system designed to improve how doctors perform prostate biopsies. By automating the movement of a high-resolution micro-ultrasound probe, the device creates precise 3D images of the prostate. This technology matches the accuracy of traditional MRI scans, potentially offering a more reliable and accessible way to detect cancer.
Area of Science:
Background:
Current prostate imaging techniques often fail to provide the necessary precision for accurate biopsy guidance. Clinicians frequently encounter significant difficulties with existing diagnostic tools regarding their reliability and overall complexity. High-frequency micro-ultrasound has emerged as a promising alternative for visualizing prostate tissue with superior spatial resolution. This modality achieves detection rates comparable to standard magnetic resonance imaging protocols. However, the specific physical shape of common micro-ultrasound probes complicates the collection of consistent three-dimensional data volumes. No prior work had resolved the challenge of achieving repeatable volumetric acquisition with these specialized devices. This gap motivated the development of a dedicated mechanical solution to stabilize and control the imaging process. Researchers sought to overcome these limitations by integrating automated hardware to enhance diagnostic consistency.
Purpose Of The Study:
The researchers aimed to design and validate a robotic system for acquiring three-dimensional micro-ultrasound images of the prostate. Current diagnostic solutions for biopsy guidance suffer from significant reliability issues and high operational complexity. The unique geometry of high-frequency probes makes manual acquisition of consistent volumetric data extremely difficult for clinicians. That uncertainty drove the need for an automated, computer-controlled approach to stabilize the imaging process. The team sought to create a platform that allows for the accurate use of high-resolution devices during prostate examinations. They intended to demonstrate that robotic control could produce images comparable to those obtained via magnetic resonance imaging. This project addresses the critical need for more reliable and repeatable imaging tools in urological cancer detection. The study focuses on the engineering and validation of this novel acquisition system to improve clinical outcomes.
Main Methods:
The team designed and fabricated a custom robotic interface to automate the imaging probe movement. They utilized a computer-controlled brachytherapy stepper to rotate the transducer during the data collection phase. This approach ensures the device follows a strictly defined path for every scan. The investigators performed geometric validation using a phantom with precisely known physical dimensions. They assessed the spatial accuracy by comparing the reconstructed volumes against the actual object geometry. The researchers also conducted a comparative analysis using a commercial quality assurance anthropomorphic prostate phantom. This setup allowed them to benchmark the system against standard magnetic resonance imaging outputs. The study focused on establishing the reliability of the robotic acquisition process through these controlled experimental trials.
Main Results:
The robotic system achieves spatial accuracy of one millimeter or less in all three measured directions. Images captured from the anthropomorphic phantom show high qualitative similarity to those produced by magnetic resonance imaging. Quantitative analysis confirms good agreement between the robotic micro-ultrasound data and the reference magnetic resonance imaging scans. This represents the first successful demonstration of acquiring robotically controlled three-dimensional images using the specified high-frequency device. The reconstructed volumes demonstrate sufficient precision for clinical and specimen-based diagnostic tasks. These findings validate the effectiveness of the motorized stepper in overcoming previous geometric limitations. The system successfully produces consistent data that matches the performance of established diagnostic modalities. The results highlight the potential for automated hardware to improve the reliability of high-resolution prostate imaging.
Conclusions:
The authors demonstrate the first successful implementation of a robotic system for volumetric micro-ultrasound imaging. This platform enables the acquisition of precise three-dimensional data using the specified high-frequency probe. Geometric validation confirms that the system maintains spatial accuracy within one millimeter across all measured axes. Quantitative comparisons against magnetic resonance imaging standards reveal strong agreement between the two modalities. These results suggest that the automated approach effectively mitigates previous challenges related to manual probe manipulation. The team anticipates that this technology will facilitate future applications in both specimen analysis and clinical patient imaging. This work provides a foundation for more reliable prostate cancer detection through improved image guidance. The findings support the integration of robotic control to enhance the utility of high-resolution ultrasound in urological practice.
The researchers propose a motorized, computer-controlled brachytherapy stepper. This device rotates the high-frequency transducer about its central axis to capture consistent volumetric data, overcoming the geometric constraints that previously hindered manual acquisition of three-dimensional images.
The system utilizes the ExactVu transrectal micro-ultrasound probe. This specific hardware is selected for its high-frequency imaging capabilities, which provide the spatial resolution required to match the diagnostic performance of multiparametric magnetic resonance imaging.
A brachytherapy stepper is necessary because the unique physical geometry of the probe makes manual rotation inconsistent. The robotic control ensures the transducer moves along a precise, repeatable path, which is required to reconstruct accurate volumetric representations of the prostate.
The researchers employ a phantom with known dimensions to perform geometric validation. This controlled environment allows them to measure the spatial accuracy of the reconstructed volumes, ensuring the system meets the required one-millimeter tolerance in all directions.
The team measures the spatial accuracy of the system, confirming errors remain at or below one millimeter. Furthermore, they compare the quality of the reconstructed ultrasound images against those obtained from standard magnetic resonance imaging scans.
The authors propose that this technology will enable future applications in prostate specimen imaging and in vivo clinical diagnostics. They suggest that the increased accuracy provided by the robotic system will improve the reliability of biopsy guidance.