Transperineal Prostate Biopsy Using a Cone-shaped Double-hole Method with Dual-plane Probe Guidance

Summary

This study presents an enhanced transperineal prostate biopsy technique using a cone-shaped double-hole method and dual-plane probe guidance. These modifications reduce trauma, enhance patient recovery, and improve biopsy accuracy, making the procedure a reliable and minimally invasive approach for prostate cancer diagnosis.

Abstract

Prostate cancer, the second most common malignancy in men, frequently necessitates biopsy for accurate diagnosis. This study presents a transperineal cone-shaped double-hole prostate biopsy method guided by micro-ultrasound, performed under local anesthesia. This innovative technique offers a minimally invasive approach that maintains high diagnostic accuracy while enhancing patient comfort and reducing adverse events. The cone-shaped double-hole method is designed to minimize tissue trauma and reduce recovery times. The dual-plane ultrasound probe facilitates precise, real-time needle navigation and improves lesion-targeting accuracy.

Our retrospective analysis of 526 cases demonstrated that the improved method significantly reduced the procedure time for lesion localization from 30 min to 10 min using dual-plane probe guidance. Furthermore, statistical comparisons revealed a marked reduction in pain scores, and notably, the infection rate has remained at zero to date. Compared to previous techniques that required general or spinal anesthesia, this method minimizes trauma and expedites recovery, with only two small needle punctures visible on the skin post-procedure. The findings underline the efficacy and safety of this simple, minimally invasive prostate biopsy technique under micro-ultrasound guidance, offering an alternative that improves patient outcomes without compromising diagnostic accuracy.

Introduction

Prostate cancer is a major global health concern, representing the second most frequently diagnosed cancer and a leading cause of cancer-related death among men worldwide¹. According to recent epidemiological data, its incidence continues to rise, partly due to aging populations and improved diagnostic capabilities. Early and accurate detection of prostate cancer is critical, as it significantly impacts treatment decisions and long-term prognosis². For patients with elevated prostate-specific antigen (PSA) levels or abnormal findings on digital rectal examination, biopsy is the definitive diagnostic procedure, serving as the cornerstone for histopathological confirmation and risk stratification.

Traditionally, the transrectal ultrasound-guided biopsy (TRUS-Bx) method has been used to perform prostate biopsies by the insertion of a biopsy needle through the rectal mucosa into the prostate gland. Despite its widespread adoption over the past several decades, the transrectal approach presents several significant limitations. One of the most pressing concerns is the high rate of infectious complications, including urinary tract infections, prostatitis, and sepsis, due to the direct penetration of the rectal wall and exposure to fecal flora. Studies estimate that the risk of postbiopsy sepsis can range from 2% to 7%, even with prophylactic antibiotic administration, posing a substantial burden on both patients and healthcare systems^3,4. Furthermore, the transrectal route often provides limited access to the peripheral zone of the prostate, where approximately 70% of prostate cancers originate, leading to potential undersampling and underdiagnosis of clinically significant lesions.

In response to these challenges, the transperineal biopsy approach has gained increasing attention as a safer and more accurate alternative. Unlike the transrectal method, the transperineal route bypasses the rectal mucosa, thereby eliminating the risk of contamination from rectal bacteria and substantially reducing the incidence of post-procedure infections⁵. In addition to its safety advantages, the transperineal approach provides superior access to the entire prostate gland, including both the anterior and peripheral zones, ensuring a more comprehensive sampling strategy. The integration of advanced imaging techniques, such as multiparametric MRI and ultrasound fusion guidance, has further improved the diagnostic yield of transperineal biopsies by enabling precise targeting of suspicious lesions identified on pre-biopsy imaging⁶.

Despite these advancements, standard transperineal biopsy techniques are not without challenges. Patients often experience discomfort due to prolonged procedure times, and the complexity of needle guidance in this approach can necessitate greater technical expertise. Recognizing these limitations, our hospital has developed a novel modification to the transperineal biopsy technique to enhance procedural efficiency, accuracy, and patient comfort. Specifically, we have introduced a cone-shaped double-hole method, designed to minimize tissue trauma and reduce recovery times. This technique is further supported by the use of a dual-plane ultrasound probe, which facilitates precise, real-time needle navigation and improves lesion-targeting accuracy.

This study aims to provide a detailed description of this refined transperineal biopsy method and evaluate its clinical outcomes. By systematically analyzing the safety, diagnostic accuracy, and procedural efficiency of the cone-shaped double-hole method with dual-plane probe guidance, we aim to demonstrate its potential to address the limitations of existing biopsy techniques and establish a new standard of care for prostate cancer diagnosis. The findings from this research hold significant implications for improving patient outcomes and advancing clinical practice in the field of urologic oncology.

Protocol

This study was approved by the Ethics Committee of Jiangnan University Medical Center (No. 2023-Y-038). Informed consent was obtained from all patients for the use of their biopsy specimens in this study. Patient confidentiality was strictly maintained throughout the research.

1. Preparation of ultrasound probe

1. Disinfect the dual-plane ultrasound probe 2x with 75% ethanol.
2. Apply acoustic gel to both interfaces of the probe. Cover the probe with a sterile transducer sheath, ensuring all air bubbles are removed, and use a sterile protective cover to maintain sterility of the handle and wires.
3. Set the ultrasound machine to preset prostate biopsy conditions, adjusting the depth based on the patient's imaging data, ensuring at least 1 cm beyond the prostate's largest dimension is visible (Figure 1A).
   1. Set the transducer specifications. Set the central frequency of the transducer to 6 MHz to balance image resolution and tissue penetration. Adjust the frame rate to a maximum of 22 Hz, allowing for smooth and real-time imaging during the biopsy procedure.
   2. Maintain the thermal index (TIS) below 1.0 throughout the procedure to minimize the risk of tissue heating and ensure patient safety.
   3. Set the mechanical index (MI) between 0.6 and 1.0, depending on the patient's anatomy and tissue characteristics, to reduce the mechanical impact on soft tissues.
   4. Initially set the gain between 50% and 70%, then fine-tune during the procedure to enhance the contrast and visibility of prostate tissues while minimizing background noise.
      NOTE: See Figure 1B for the setup used in this study.

2. Patient preparation and anesthesia

NOTE: Before the operation, operators should wear masks, hats, and gloves and disinfect their hands.

1. Ask the patient to assume the lithotomy position, with the anus at the edge of the bed and the scrotum taped upward to expose the perineum. Support the head and place a drape over the genitals for comfort and privacy. Adjust the bed height to place the anus at the level of the surgeon's elbow.
2. Apply 5 mL of sterile paraffin oil to the rectum.
   NOTE: Ensure patient comfort and prepare all necessary materials during this time.
3. Disinfect the perineal skin with iodine from the scrotum to the anus.
4. Administer 10 mL of 2% lidocaine using a 0.07 x 3.2 cm needle at 10 o'clock and 2 o'clock positions, 2 cm from the anus, injecting approximately 1 mL of lidocaine at each point⁷.
5. Insert the dual-plane probe into the rectum, then switch to a 0.7 x 80 mm needle for deeper anesthesia under ultrasound guidance. Inject lidocaine into the perineal tissues and prostate capsule (targeting the prostatic apex) (Figure 1C).
   NOTE: To ensure efficiency and accuracy, this step should be carried out under ultrasound guidance, because patient anatomy differs with pelvic shape, gluteal musculature, and obesity.

3. Biopsy procedure

1. Begin by conducting a preliminary scan of the prostate using both longitudinal and transverse ultrasound planes to locate regions of interest (ROIs), such as nodules or abnormal echo patterns. First, perform a systematic biopsy, with biopsies spaced evenly across the prostate's non-ROI areas to minimize the risk of iatrogenic tumor seeding.
2. Insert an 18 G biopsy needle through the anesthetized perineal region under ultrasound guidance (Figure 1D). Initially, perform a systematic biopsy, ensuring that the needle enters the prostate in the transverse plane (cross-sectional imaging) (Figure 2). Maintain the probe in a fixed position to stabilize the imaging and guide the needle in a manner that ensures it does not deviate from the pre-designated path. For non-targeted biopsies, advance the needle at a perpendicular angle relative to the ultrasound beam, minimizing any angle of entry into normal prostate tissue.
3. If the needle is not visualized clearly, adjust the ultrasound probe to reorient it slightly, and rotate the probe by small increments to achieve the best view of the needle path. If the needle deviates, gently retract the needle and adjust the entry angle, ensuring that the tip remains within the designated target area. Use the dual-plane ultrasound system to monitor needle trajectory from both longitudinal and transverse views, making gradual adjustments to ensure alignment. Perform the adjustment delicately, using the visual feedback to fine-tune the needle path as necessary.
4. Once the biopsy needle is correctly positioned, fire the biopsy gun to collect tissue samples from the peripheral and transition zones. In areas of suspicious lesions, perform 2-3 biopsy passes per region to ensure maximum detection accuracy (Figure 3). Maintain proper tissue pressure on the biopsy site to ensure minimal bleeding.
   NOTE: In cases where a single pass can sample multiple regions (i.e., in small prostates), the systematic biopsy can be skipped or minimized. This includes instances where systematic core samples would overlap with an ROI already sampled, or where a single pass can achieve sampling from both the prostate apex and base.
5. Throughout the procedure, continuously monitor the placement of the needle under ultrasound guidance, ensuring accurate entry into the prostate tissue. If deviation occurs, retract and reinsert the needle, keeping it in alignment with the pre-determined trajectory.

4. Post procedure care

1. Apply compression to the biopsy sites using sterile gauze until bleeding stops.
2. Instruct the patient about potential side effects, such as hematuria and hematospermia.
3. Monitor patients for urinary retention and consider catheterization if necessary.

Results

A retrospective analysis was conducted on 526 patients who underwent transperineal prostate biopsy using the improved cone-shaped double-hole method with dual-plane probe guidance between September 2023 and August 2024. Pain scores were recorded using a 1-10 Likert scale and evaluated at various stages of the procedure. The results demonstrated a significant reduction in pain scores when compared to the previous biopsy method. Patients who underwent the improved method reported a pain score range of 0-1, which represents a marked improvement over the 1-2 pain score range observed in patients who received the previous biopsy technique (Table 1). This section summarizes the number of patients in each pain score category (from 0 to 3+ points) under each method. In both methods, patients' scores are categorized to capture the spread of perceived pain levels. The results of the non-parametric Mann-Whitney U test show a highly significant difference in pain scores between the two methods (p < 0.05).

The low p-value indicated a statistically significant difference in pain scores between the two methods, suggesting that the modified method offers a notable improvement in pain management during the biopsy procedure.

This reduction in pain can be attributed to the high precision of lesion targeting and the minimally invasive nature of the modified method. Furthermore, no significant post-procedural complications were observed in either group. Patients who underwent the modified biopsy method reported faster recovery times and minimal discomfort. Notably, no cases of sepsis, prostatitis, or other infections were observed in the study cohort.

Regarding detection rates, the improved method demonstrated a clinically significant prostate cancer (PCa) detection rate of 71.29% (Table 2). This highlights the enhanced sensitivity of the cone-shaped double-hole technique with dual-plane probe guidance. The method proved particularly effective in detecting PCa in patients with elevated PSA levels or suspicious imaging findings. The transperineal approach offered several advantages over the traditional transrectal method, including a reduced risk of infection, particularly in patients with a history of rectal interventions or chronic prostatitis. Additionally, the transperineal approach provided superior access to the posterior prostate, which is critical for accurate sampling, particularly in patients with elevated PSA levels or suspected cancer in the posterior region.

Figure 1: Micro-ultrasound setup, biopsy tray, needle placement, and double-hole position. (A) The procedure room setup with the ultrasound machine placed on the surgeon's left. (B) Biopsy table including (a) 4 cm x 4 cm gauze pads, (b) sterile sheet, (c) betadine-soaked 4 cm x 4 cm gauze pads, (d) 18 G biopsy needle, (e) 2% lidocaine in 10 mL syringes with a 0.07 x 3.2 cm needle, (f) needle, (g) Isolation transparent film. (C) The needle or dual-plane probe position: needle at 10 o'clock (not shown) and 2 o'clock positions, 2 cm from the anus. (D) The biopsy needle or dual-plane probe position: biopsy needle at 10 o'clock (not shown) and 2 o'clock positions, 2 cm from the anus. (E) Position of two puncture needle holes: 10 o'clock and 2 o'clock positions. Please click here to view a larger version of this figure.

Figure 2: Systematic biopsy template for the proposed technique. (A) The cone-shaped puncture angle from the sagittal plane. (B) The location of the pinhole from the coronal plane. (C) The puncture route from the cross-section and only two holes in the skin. Please click here to view a larger version of this figure.

Figure 3: Demonstration of the prostate anatomy and biopsy. (A) Systematic biopsy showing the entire tissue located in the peripheral zone. (B) Clear visualization of the urethra, avoiding damage to the urethra by the biopsy needle. (C) Dual-plane confirmation of the biopsy needle hitting the target lesion. Please click here to view a larger version of this figure.

Method	Number of patients	Pain Score Distribution	U Statistic	P-value
Modified	526	0 points (351)	49,541.5	2.33 x 10-77
Method		1 point (173)
		2 points (2)
		3+ points (0)
Traditional	501	0 points (90)
method		1 point (201)
		2 points (208)
		3+ points (2)

Table 1: Statistical analysis of pain scores of two methods. The table presents a statistical summary comparing two pain assessment methods: the Modified Method and the Traditional Method.

		Time (min)	Detection results		Total samples (N)	Detection rate
			(+)	(-)
Method	Modified Method	10.13(±0.93)*	375	151	526	71.3%**
	Traditional Method	30.24(±2.98)	175	326	501	34.9%

Table 2: Comparison of procedural time and detection rates between modified and traditional methods. This table compares the procedural time and detection rates between the modified method and the traditional method of prostate biopsy. The modified method demonstrated a significantly shorter procedural time (10.13 min ± 0.93 min) compared to the traditional method (30.24 min ± 2.98 min, P < 0.0001). Additionally, the modified method showed a higher detection rate of 71.3%, with 375 positive results out of 526 total samples, whereas the traditional method had a detection rate of only 34.9% with 175 positive results out of 501 samples (P < 0.0001). These findings indicate that the modified method offers both improved efficiency and a higher detection rate. *The duration time was statistically analyzed using the t-test (P < 0.0001). **The detection rates of the two methods were compared using the Chi-square test (P < 0.0001).

Discussion

The cone-shaped double-hole method combined with dual-plane probe guidance provides substantial clinical advancements in the transperineal prostate biopsy process. This discussion will delve into the specific benefits and broader implications of these innovations, contextualizing their contributions within current clinical practices and comparing them to established methods.

Enhanced lesion localization and efficiency
The introduction of the dual-plane probe for lesion targeting significantly optimizes the biopsy procedure. Traditionally, lesion targeting could be time-consuming, often extending up to 30 min due to the need for multiple adjustments and real-time image reorientation. With the dual-plane probe, our study demonstrated a remarkable reduction in targeting time, cutting it down to just 10 min. This enhancement in procedural efficiency is pivotal, not only streamlining the workflow for clinical teams but also minimizing the duration a patient must remain in a potentially uncomfortable position. Shorter biopsy times correlate with reduced patient stress and lower risk of procedural fatigue, which can impact both patient compliance and the precision of tissue sampling.

The probe's dual-plane capability allows simultaneous longitudinal and transverse visualization, enabling a more comprehensive view of the needle trajectory relative to the prostate anatomy. This multidimensional approach enhances the operator's ability to navigate complex cases where lesions are located in less accessible areas, such as the peripheral zone. The ability to precisely adjust the needle path without repositioning the probe reduces the chances of needle deviation and missed targets, thus contributing to higher diagnostic accuracy. This is particularly significant given that accurate sampling is critical for proper disease grading and subsequent treatment planning.

Reduction of patient trauma and postprocedural recovery
A major advantage of the cone-shaped double-hole method lies in its minimally invasive nature. Unlike traditional multi-puncture techniques, which involve multiple needle insertions across various sites on the skin, this method confines the entry points to just two small punctures (Figure 1E). This not only decreases immediate trauma to the perineal tissue but also facilitates a faster and less painful recovery. Our observations showed that patients subjected to this method reported less postprocedural pain and resumed their daily activities more swiftly compared to those who underwent traditional biopsies.

The minimized trauma contributes to a decreased risk of complications such as bleeding and infection, common concerns with transperineal procedures⁸. This aligns with findings from other studies, which have underscored the safety profile of the transperineal approach, particularly in its ability to limit infection risks as compared to transrectal biopsies. In our cohort, the reduced incidence of complications was evident, supporting the broader adoption of this method as a safer alternative for prostate sampling.

Comparative efficacy and safety
When examining the dual-plane probe method alongside established techniques, it is important to highlight the significant reduction in both infection rates and patient discomfort. Transrectal biopsies, for instance, while historically popular, carry an inherent risk of introducing rectal flora into the prostate or bloodstream, leading to infections. Studies have shown that transperineal approaches offer a safer alternative with lower rates of postprocedural infections due to the reduced risk of fecal contamination^5,9. Our findings corroborate this advantage, as no infections were reported in our patient cohort using the dual-plane probe and cone-shaped entry strategy.

Despite its clear advantages, the dual-plane probe technique does come with a learning curve. Operators must gain proficiency in handling the probe to maintain consistent visualization of both planes while adjusting the needle angle in real time. Initial training may require extended practice sessions, but the long-term benefits-improved accuracy, especially for challenging peripheral zone lesions, and better patient outcomes-justify the investment in training. The improved targeting accuracy is essential for comprehensive prostate sampling, as peripheral zone lesions are often implicated in clinically significant prostate cancer^10,11.

Implications for clinical practice and future research
The integration of these methods into routine clinical practice could redefine biopsy protocols, especially in facilities prioritizing high diagnostic accuracy and patient safety. Future research should aim to explore the scalability of this method across various clinical settings, including community hospitals with limited resources. Additionally, studies comparing patient-reported outcomes and long-term diagnostic efficacy between dual-plane-guided biopsies and other advanced methods (e.g., MRI-targeted biopsies) could further substantiate its clinical value. Moreover, advancements in probe technology and automation could help mitigate the learning curve associated with dual-plane visualization, making the technique more accessible to practitioners without extensive training. This potential for widespread adoption aligns with healthcare's overarching goal to improve diagnostic precision while minimizing patient risk.

The dual-plane probe-guided transperineal biopsy method, in conjunction with the cone-shaped double-hole approach, offers significant improvements in lesion localization, procedural efficiency, and patient safety. These benefits underscore the method's superiority over conventional practices by reducing both the time required for precise targeting and patient trauma. While a learning curve exists, the sustained improvements in diagnostic outcomes validate the method's integration into clinical protocols, promoting better patient experiences and potentially reshaping the landscape of prostate biopsy procedures.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Biplane ultrasonic probe	Brüel & Kjær	E14CL4b
ethanol	Anhui ante Food Co., Ltd	GB/T26373
Hypodermic needle	Shandong Weigao group medical polymer products Co., Ltd
Iodophor disinfectant	Hunan Kefu Medical Equipment Co., Ltd
Isolation transparent film	oumka
Lidocaine Hydrochloride InjECTion	Hebei Tiancheng Pharmaceutical Co., Ltd	H13022313
Magnetic resonance ultrasound image fusion targeted puncture system	Brüel & Kjær	BK2300
Medical sterile protective sleeve	Jiangxi 3L Medical Products Group Co., Ltd	WJ120x14R
Medical ultrasonic couplant	Beijing China Resources Kangtai high tech Development Institute
Statistical Product and Service Solutions 29.0.2.0	IBM
Tissue biopsy needle	Mairuitong medical devices (Beijing) Co., Ltd	12868360