Augmented reality assisted MRI/US fusion for non-rectal fully trans-perineal prostate biopsy

Abstract

Augmented reality (AR) technologies enable the superimposition of imaging upon a patient in real time with three dimensional instrument tracking during procedures. We sought to demonstrate the feasibility of using an AR system (XR90, MediView XR Inc., Cleveland, OH) to fuse a pelvic multi-parametric magnetic resonance image segmentation with ultrasound to perform a non-rectal, fully trans-perineal (FTP), AR-assisted prostate biopsy. AR-assisted biopsy results were congruent with standard fusion biopsy results, showing benign prostate tissue. No adverse events occurred. Limitations include the current workflow and reliance on a non-specialized ultrasound probe.

1. Introduction

The trans-perineal (TP) approach for prostate biopsy has gained traction due to its potential lower risk of infection compared to the traditional transrectal route. However, recent randomized clinical trials have failed to show a significant reduction in infectious complications over the transrectal approach.^1,2 Conventional TP biopsy methods still require the insertion of the ultrasound probe into the rectum, creating a potential nidus for the introduction of pathogenic bacteria, though targeted antibiotic prophylaxis is effective. Our institution has previously reported fully trans-perineal (FTP) multi-parametric magnetic resonance imaging (mpMRI)/ultrasound (US) fusion biopsy, which showed an agreement rate of 79 % for grade group ≥2 prostate cancer in comparison to conventional TP biopsy.³ Additionally, the conventional TP biopsy relies on template grids or freehand US guidance, which may limit flexibility in needle placement. Despite advances in prostate cancer diagnosis with mpMRI-US fusion targeting, approximately 14 % of patients will still have upgrading on final pathology at radical prostatectomy.⁴ Augmented reality (AR) is being recognized as an emerging tool with broad applications in healthcare, providing real-time 3D visualization to enhance procedural accuracy. Recent advancements in AR head-mounted displays enabled the hands-free integration of imaging data, allowing intuitive needle navigation, with similar error in preliminary studies as the free-hand approach.^5,6 We present a case in which we performed an FTP AR-assisted mpMRI/US fusion targeted prostate biopsy.

1.1. Case presentation

A 78-year-old male with an extensive family history of breast cancer was initially referred with a history of elevated prostate-specific antigen (PSA) level of 7.8 ng/mL and a prior negative systematic prostate biopsy. He underwent an mpMRI of the pelvis, revealing a 0.5 cm Prostate Imaging Reporting and Data System (PIRADS) 2 lesion in the peripheral zone at the midline. Given his elevated PSA and significant family history, he was appropriately counseled and elected to undergo a repeat biopsy with 12-core systematic and mpMRI/US targeting, in addition to an FTP AR-assisted mpMRI/US fusion targeted prostate biopsy. The patient had no prior history of urinary tract infections or urinary retention.

A fiducial grid was used to place pen marks at fixed distances in the suprapubic region, where MRI-compatible fiducial markers (MR-Spot® Skin Markers, Beekley Corporation, Bristol, CT) were placed before the patient underwent a pre-biopsy mpMRI. Anatomic segmentation of the fiducial markers, target lesion, prostate, bladder, rectum, pelvic vasculature, and pelvic/lower extremity bones was performed using third-party software (Axial 3D, Belfast, UK). An electromagnetic (EM) field generator was integrated onto the operating table (Aurora, Northern Digital Inc, Waterloo, Canada). The operator wore a commercially available headset (Microsoft HoloLens 2, Redmond, WA), and a standard US with abdominal probe was used (Fig. 1A). Optically tracked registration markers were placed at the three fiducial marker locations and used to register the patient-specific segmentation using the EM generator to the tracked instruments (Fig. 1B and C), which include the US probe (Vivid iq, GE HealthCare, Chicago, IL) and trocar (E-Trax, Civco, Coralville, IA). The FDA-cleared AR headset-based system was used to perform a targeted biopsy after performing our standard combined mpMRI/US fusion-guided and systematic prostate biopsy (UroNav, Koninklijke Philips N.V., Amsterdam, Netherlands).

Fig. 1.

Augmented reality (AR)-assisted, fully trans-perineal prostate biopsy using electromagnetic tracking and smart goggle visualization. A. The operator wears a head-mounted Microsoft HoloLens 2 goggle displaying real-time fusion of ultrasound and mpMRI segmentations while an electromagnetic field generator tracks instrument position. B. Patient in dorsal lithotomy position with registration markers placed over the location of fiducials. C. Close-up AR headset view showing fused ultrasound and segmented mpMRI, pelvic anatomy including bladder (green), pelvic vasculature (red/blue), and pelvis (white). D. Electromagnetic tracked needle trocar to target the region of interest using freehand needle insertion through a non-rectal, fully trans-perineal approach.

The biopsy was conducted using an 18-gauge core biopsy needle inserted through a freehand, non-rectal, FTP approach, using the US projection ("flashlight") to adjust targeting (Fig. 1D). A total of 12 systematic cores, two targeted cores from the MRI-visible lesion, and two AR-assisted cores were obtained. The procedure was completed with minimal patient discomfort. No complications, including urinary retention or infection, were observed postoperatively. Histopathology was consistent between the mpMRI/US fusion-targeted and AR-assisted cores.

2. Discussion

This case highlights the potential of AR assistance in performing an FTP prostate biopsy. Unlike conventional TP biopsy techniques, which rely on rigid templates or operator-dependent freehand US, AR guidance provides a real-time, intuitive interface for needle navigation. The use of a head-mounted display offers an ergonomically beneficial alternative to handheld devices, potentially reducing the need for external monitors and improving workflow efficiency.⁷ Additional ergonomic benefit with the AR system lies in its potential to reduce operator neck strain due to monitor positioning.⁸ Prior studies in humans have demonstrated a 70 % concordance comparing AR-guided prostate biopsies and standard approaches, although they utilized a trans-rectal US, and real-time needle visualization was not performed.⁹ Additionally, Sparwasser and colleagues showed improved prostate cancer detection with the use of AR assistance over standard systematic transrectal prostate biopsy, also using transrectal US.¹⁰

Compared to traditional FTP biopsy, AR guidance enhances spatial awareness, enabling precise targeting of lesions while maintaining an entirely extra-rectal approach. This may be particularly advantageous in patients with contraindications to transrectal US, such as those with a history of or active anorectal pathology or prior radiation therapy. Additionally, the discomfort of the rectal probe may contribute to poor compliance with clinician recommendations to undergo repeat prostate biopsy.¹¹ Offering an alternative approach may increase biopsy compliance, particularly among patients with contraindications to rectal access or heightened discomfort.

Limitations include the need for pre-procedural imaging with fiducial markers in place, image segmentation and system registration with the patient in dorsal lithotomy (while the mpMRI is performed supine), and reliance on a non-specialized ultrasound probe. Future research should further evaluate the safety, procedural time, patient-reported outcomes, and learning curve associated with AR-assisted prostate biopsy, and compare its diagnostic yield with that of conventional techniques.

3. Conclusion

AR-guided FTP prostate biopsy using a head-mounted display represents a promising advancement in image-guided prostate biopsy. This proof-of-concept case underscores AR-assisted biopsy as a viable and ergonomic method for performing targeted transperineal prostate biopsy, particularly in patients with contraindications to transrectal access. Further studies are needed to validate its clinical utility.

CRediT authorship contribution statement

Braden Millan: Conceptualization, Data curation, Formal analysis, Writing – original draft, Writing – review & editing. Nikhil Pramod: Data curation, Methodology, Writing – original draft, Writing – review & editing. Jaskirat Saini: Writing – review & editing. Ruben Blachman-Braun: Writing – review & editing. Baris Turkbey: Conceptualization, Investigation, Resources, Software, Writing – review & editing. Sheng Xu: Project administration, Resources, Software. Ming Li: Conceptualization, Methodology, Resources, Software, Writing – review & editing. Michael Evans: Project administration, Software, Writing – review & editing. Gabreille Stefy: Project administration, Software, Writing – review & editing. Sandeep Gurram: Supervision, Writing – review & editing. Bradford Wood: Conceptualization, Data curation, Supervision, Writing – review & editing. Peter A. Pinto: Conceptualization, Funding acquisition, Investigation, Supervision, Writing – review & editing.

Ethics declaration

The patient presented in this study is enrolled into the NCI/NIH through the IRB-approved protocol (No. NCI-16-C-0010) and provided informed consent to be part of this protocol.

Source of Funding

This research was supported in part by the Intramural Research Program of the National Institutes of Health (NIH). The contributions of the NIH authors were made as part of their official duties as NIH federal employees, are in compliance with agency policy requirements, and are considered Works of the United States Government. However, the findings and conclusions presented in this paper are those of the authors and do not necessarily reflect the views of the NIH or the U.S. Department of Health and Human Services. Devices were supplied by MediView XR, Inc. (Cleveland, OH).

Declaration of conflict of interest

BW is Principal Investigator on the following CRADA's = Cooperative Research & Development Agreements, between NIH and industry: Philips (CRADA). Philips/In Vivo Inc pays royalties to NIH for a licensing agreement, and NIH then pays royalties to PP and BW. MediView supported this work via technical support and loan of equipment. NIH owns intellectual property in this space.