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Updated: May 16, 2026
Use of MRI-ultrasound Fusion to Achieve Targeted Prostate Biopsy
Published on: April 9, 2019
Automated needle reconstruction for HDR prostate brachytherapy using a commercially compatible 3D-printed transrectal
Catherine Holly Frank1, Andrew Moyo2, Dalton Griner1
1Department of Radiation Oncology, Mayo Clinic, Rochester, MN.
Purpose:
Electromagnetic (EM) tracking can enhance the quality and efficiency of ultrasound-based HDR prostate brachytherapy by enabling automated digital needle reconstruction during treatment planning. This work integrates EM tracking sensors within a biocompatible, 3D-printed transrectal ultrasound (TRUS) sleeve engineered for compatibility with a commercially available probe and stepper to support clinical translation.
Methods And Materials:
A clinical TRUS probe was digitally scanned, and a conformal sleeve was designed in CAD and 3D-printed using sterilizable materials. The sleeve incorporated channels for EM sensors and snap-on mounting features to ensure reproducible positioning relative to the probe. Sensors were placed at the probe apex within the TRUS axial imaging plane to minimize uncertainties from mounting or EM field distortions. Multiple sleeves were fabricated to evaluate consistency and performance. EM tracking-based reconstruction accuracy was assessed in a water-tank phantom containing seven needles placed to approximate the peripheral needle positions of a typical HDR prostate implant.
Results:
EM-tracked needle reconstruction showed close agreement with manual, image-based reconstruction, yielding median (interquartile range) errors of 0.60 (0.28-0.78) mm for needle depths and 0.64 (0.40-0.93) mm for needle shafts. Sleeve mounting reproducibility had 90% confidence intervals whose absolute bounds were below 0.17 mm (3D offset), 0.09° (pitch), 0.06° (yaw), and 0.51° (roll). A patient-specific calibration procedure was developed to correct potential variability in 3D printing and sensor placement. The potential net reduction in procedure time using EM-based reconstruction versus manual reconstruction was approximately 28 minutes.
Conclusions:
Integrating EM sensors into a 3D-printed TRUS sleeve provided automated needle reconstruction with sub-millimeter accuracy for HDR prostate brachytherapy. Future clinical implementation is supported by the use of sterilizable, patient-safe materials and compatibility with standard TRUS systems.
