Making MRI-Guided Prostate Procedures Safer and More Precise: A 9-Year Journey of Innovation

Table of Contents

• Background: Why MRI Guidance for Prostate Procedures?
• How the Study Was Conducted
• Key Findings: Seven Years of Technical Improvements
• Clinical Implications: What This Means for Patients
• Study Limitations
• Recommendations and Future Directions
• Source Information

Background: Why MRI Guidance for Prostate Procedures?

Prostate cancer is a significant health concern. The study notes that in 2017 alone, 161,360 men were diagnosed with prostate cancer in the USA, and 26,730 died from the disease. This highlights the ongoing challenge doctors face in both diagnosing and treating this condition effectively. For many men, especially those with less aggressive cancers, avoiding overtreatment is a key goal. Strategies like active surveillance (closely monitoring the cancer) or focal therapy (targeting only the tumor itself) are becoming important alternatives.

Magnetic Resonance Imaging (MRI) is widely recognized as the best imaging test for examining the prostate gland. It provides exceptionally clear pictures. When it comes to treatment, MRI-guided cryosurgery (a procedure that freezes and destroys cancer cells) offers several potential advantages over the more common ultrasound-guided methods. MRI allows doctors to see the freezing "ice ball" from multiple angles, guide needles with great accuracy using real-time MRI, and may offer better safety.

However, MRI-guided procedures are more complex, time-consuming, and expensive. There isn't yet definitive proof that they are superior to ultrasound. Despite this, the researchers behind this study believe that managing a prostate tumor—from initial diagnosis to treatment—should ideally be done entirely under MRI guidance for maximum precision. This article details their 9-year effort to improve these very techniques.

How the Study Was Conducted

This was a retrospective study, meaning the doctors looked back at data from patients treated in the past. From 2009 to 2018, a total of 62 patients underwent MRI-guided prostate procedures at their institution in Strasbourg, France. These patients were selected for MRI guidance for specific reasons.

Some patients could not have the standard transrectal ultrasound (TRUS)-guided procedure because of physical limitations like prior rectal surgery (rectal amputation) or a narrowed anal canal (anal stenosis). Others were chosen because there was a significant mismatch between what an earlier biopsy showed and what a new MRI scan revealed, particularly for tumors in the front (anterior) part of the prostate, which is harder to reach with standard methods. Importantly, all cryosurgery procedures performed during this period were done under MRI guidance.

The procedures were a collaboration between urologists (prostate surgeons) and interventional radiologists (doctors specializing in image-guided procedures). They worked in a dedicated hybrid operating room equipped with a special MRI machine. The team used a large-bore 1.5 Tesla MRI scanner (models Magnetom-Espree and Magnetom-Aera from Siemens) and an MRI-compatible freezing system called MR-Seednet from Galil Medical.

Throughout the 9 years, the team continuously refined their methods to protect two critical areas during cryosurgery: the rectum (the back passage) and the urethra (the tube that carries urine through the prostate and out of the body). Their goal was to enhance the accuracy and reproducibility—meaning the ability to perform the procedure consistently well—every single time.

Key Findings: Seven Years of Technical Improvements

The core of this research is the description of specific tools and techniques developed over nearly a decade to make MRI-guided prostate procedures safer and more reliable.

The Major Breakthrough: A Specialized Patient Stand and Template

The most significant improvement, introduced between 2012 and 2016, was the creation of an MRI-compatible patient stand called the Uni-Lift Prostate Intervention Device (made by NORAS GmbH). This device lifts and supports the patient's scrotum, providing urologists with clear access to the perineum (the skin between the scrotum and rectum) despite the confined space of the MRI machine.

Integrated into this stand is a crucial tool: an acrylic needle-guided template. This is a grid measuring 100 mm by 120 mm by 25 mm, filled with small holes. The holes are 1.3 mm in diameter and spaced 5 mm apart from each other. This grid, inspired by templates used in prostate brachytherapy (a radiation seed implant treatment), acts like a stencil or guide.

• Improved Accuracy: The template standardizes the entry point for needles, making every procedure more precise.
• Easier Navigation: It helps doctors navigate biopsy needles or cryoprobes (freezing needles) accurately through the perineum and into the exact spot in the prostate.
• Safety Spacing: During cryosurgery, it ensures freezing probes are placed at correct distances from each other to effectively treat the tumor while protecting healthy tissue.

Protecting the Rectum: The "Hemo-Dissection" Technique

To prevent the freezing ice ball from damaging the rectal wall during cryosurgery, the team developed an innovative protective technique. They create a cushion of the patient's own blood to push the prostate away from the rectum.

1. First, 50 to 80 milliliters of the patient's blood is drawn from a vein in the arm.
2. This blood is then injected into a thin layer of tissue called the Denonvillier’s fascia, which lies between the prostate and the rectum. This injection is done using ultrasound guidance for accuracy.
3. The injected blood forms a controlled hematoma (a collection of blood). A follow-up MRI scan confirms that this hematoma successfully creates a wider, safer space between the prostate and the rectum, acting as a protective barrier against the cold.

Protecting the Urethra: Continuous Temperature Monitoring

The urethra, which runs through the center of the prostate, is also at risk during freezing treatments. To protect it, the team uses a two-part strategy:

1. A catheter is placed in the bladder to continuously irrigate (wash) the urethra with warm saline solution.
2. Most importantly, a thermocouple probe (a tiny temperature sensor) is inserted through the guiding template and positioned directly into the urethral sphincter under MRI guidance. This allows for real-time temperature monitoring throughout the entire freezing procedure.

The procedure is automatically paused or adjusted if the temperature in the urethra drops below 15° Celsius (59° Fahrenheit), preventing thermal injury that could lead to incontinence or other complications.

Clinical Implications: What This Means for Patients

For patients facing a prostate cancer diagnosis or treatment, these technical improvements translate into several potential benefits:

• Greater Precision for Difficult Cases: Men who cannot have standard ultrasound-guided biopsies due to anatomy or who have confusing MRI findings now have a viable, highly accurate alternative. The study confirms MRI guidance is particularly valuable for targeting tumors in the anterior (front) part of the prostate.
• Safer Focal Therapy: The enhanced ability to protect the rectum and urethra makes MRI-guided cryotherapy a safer option for focal therapy. This means doctors can potentially freeze just the tumor itself, sparing the rest of the prostate gland and significantly reducing the risk of side effects like incontinence and impotence, which are more common with whole-gland treatments.
• A Collaborative Model of Care: The study highlights a successful partnership between urologists (experts in prostate anatomy and cancer) and interventional radiologists (experts in imaging and guided procedures). This teamwork in a hybrid operating room brings together the best skills for patient care.
• Pathway to New Treatments: By standardizing and simplifying these complex procedures, the research opens the door for more centers to offer MRI-guided management. This could accelerate the development and availability of precise focal therapies for appropriate patients.

Study Limitations

While the study reports on important innovations, it is essential to understand its constraints:

This was a retrospective study without a control group. The researchers observed and described their experience with 62 patients over time but did not directly compare their MRI-guided results to a group of patients treated with standard ultrasound guidance. Therefore, they cannot claim with statistical certainty that their method is "better" in terms of cancer control or long-term side effects.

The study involved a relatively small number of patients (62) over a long period (9 years). The techniques were also developed and used at a single, specialized institution with access to advanced hybrid operating rooms and specific equipment, which may not be available everywhere.

Finally, the authors clearly state that MRI-guided procedures are more labor-intensive and expensive. The cost-benefit analysis of these advanced techniques compared to established methods needs further economic study.

Recommendations and Future Directions

Based on their 9-year experience, the researchers point toward an exciting future for prostate cancer management:

They strongly believe that the future of precise prostate cancer care lies in continued collaboration between urologists and radiologists within the hybrid-room environment. They hope that simplifying the techniques, as they have done with the standardized stand and template, will motivate more urologists to adopt MRI-guided approaches.

The logical next step, which they mention, is the integration of robotic navigation systems. Software and robotics could further enhance needle placement accuracy for both biopsies and cryotherapy under MRI guidance.

For patients, this evolving field underscores the importance of seeking care at multidisciplinary centers that can offer a full range of diagnostic and treatment options. If you are considering a prostate biopsy or investigating focal therapy options, asking your doctor about the availability and appropriateness of MRI-guided procedures is a relevant and informed question.

Source Information

Original Article Title: “Prostate management” under MRI-guidance: 7 years of improvements
Authors: Thibault Tricard, Julien Garnon, Roberto Luigi Cazzato, Intisar Al Hashimi, Afshin Gangi, Hervé Lang
Publication: Translational Cancer Research, Vol 9, No 4, April 2020, pages 2280-2286.
DOI (Digital Object Identifier): 10.21037/tcr.2020.03.44

This patient-friendly article is based on peer-reviewed research. It is intended for educational purposes to help patients understand the findings and should not be used as a substitute for professional medical advice. Always consult with your healthcare provider for diagnosis and treatment options.