Feasibility and preliminary clinical tolerability of low-field MRI-guided prostate biopsy.

OBJECTIVE: We evaluate the clinical feasibility of a portable, low-field magnetic resonance imaging (MRI) system for prostate cancer (PCa) biopsy. METHODS: A retrospective analysis of men who underwent a 12-core systematic transrectal ultrasound-guided prostate biopsy (SB) and a low-field MRI guided transperineal targeted biopsy (MRI-TB). Comparison of the detection of clinically significant PCa (csPCa) (Gleason Grade [GG] ≥ 2) by SB and low field MRI-TB, stratified by Prostate Imaging Reporting & Data System (PI-RADS) score, prostate volume, and prostate serum antigen (PSA) was performed. RESULTS: A total of 39 men underwent both the MRI-TB and SB biopsy. Median (interquartile range [IQR]) age was 69.0 (61.5-73) years, body mass index (BMI) was 28.9 kg/m2 (25.3-34.3), prostate volume was 46.5 cc (32-72.7), and PSA was 9.5 ng/ml (5.5-13.2). The majority (64.4%) of patients had PI-RADS ≥ 4 lesions and 25% of lesions were anterior on pre-biopsy MRII. Cancer detection rate (CDR) was greatest when combining SB and MRI-TB (64.1%). MRI-TB detected 74.3% (29/39) cancers. Of which, 53.8% (21/39) were csPCa while SB detected 42.5% (17/39) csPCa (p = 0.21). In 32.5% (13/39) of cases, MRI-TB upstaged the final diagnosis, compared to 15% (6/39) of cases in which SB upstaged the final diagnosis (p = 0.11). CONCLUSION: Low-field MRI-TB is clinically feasible. Although future studies on the accuracy of MRI-TB system are needed, the initial CDR is comparable to those seen with fusion-based prostate biopsies. A transperineal and targeted approach may be beneficial in patients with higher BMI and anterior lesions.

Office-Based, Single-Sided, Low-Field MRI-Guided Prostate Biopsy.

This paper describes the workflow of transperineal prostate biopsy (TBx) using the single-sided, low-field Promaxo MRI system (Promaxo Inc., Oakland, California, United States) operating at a field strength ranging between 58 and 74 millitesla (mT). Prostate cancer (PCa) is the leading cause of cancer-related death and the second most frequently diagnosed cancer in men. Systematic biopsy (SBx) with 12-14 cores is the preferred standard of care procedure. The blinded approach of SBx, however, results in several shortcomings, including high rates of false negatives and increased infection rates due to the transrectal approach. The evolution of clinical use and scientific research using different prostate biopsy modalities is discussed, including the potential for the Promaxo MRI system to mitigate logistical constraints often associated with standard magnetic resonance (MR)-guided biopsy through the utilization of an office-based, low-field MRI.

Initial phantom studies for an office-based low-field MR system for prostate biopsy.

PURPOSE: Prostate cancer is the second most prevalent cancer in US men, with about 192,000 new cases and 33,000 deaths predicted for 2020. With only a 31% 5-year survival rate for patients with an initial diagnosis of stage-four prostate cancer, the necessity for early screening and diagnosis is clear. In this paper, we present navigation accuracy results for Promaxo's MR system intended to be used in a physician's office for image-guided transperineal prostate biopsy. METHODS: The office-based low-field MR system was used to acquire images of prostate phantoms with needles inserted through a transperineal template. Coordinates of the estimated sample core locations in the office-based MR system were compared to ground truth needle coordinates identified in a 1.5T external reference scan. The error was measured as the distance between the planned target and the ground truth core center and as the shortest perpendicular distance between the planned target and the ground truth trajectory of the whole core. RESULTS: The average error between the planned target and the ground truth core center was 2.57 ± 1.02 mm, [1.93-3.21] 95% CI. The average error between the planned target to the actual core segment was 2.05 ± 1.24 mm, [1.53-2.56] 95% CI. CONCLUSION: The average navigation errors were below the clinically significant threshold of 5 mm. The initial phantom results demonstrate the feasibility of the office-based system for prostate biopsy.