TRUS biopsy simulation to improve precision for prostate imaging and ablation
Since the 1980s, the standard prostate biopsy technique has been transrectal ultrasound-guided biopsy, or TRUS. Recommendations for biopsy are most commonly driven by elevated values of prostate-specific antigen. “This is essentially a random, non-targeted and non-specific biopsy technique,” said Thomas F. Stringer, M.D., an associate professor of urology in the UF College of Medicine. “A falsely negative biopsy misses existing cancer and may delay diagnosis and treatment as well as impact survival.”
The false-negative rate for TRUS-guided prostate biopsy is often quoted to be nearly 20% but has been reported as high as 47%. A principal challenge for accuracy for TRUS is that two-dimensional imaging requires mentally reconstructing in real time the complex 3D interactions between the handheld ultrasound device, the handheld biopsy probe and the prostate in order to accurately guide the biopsy probe to the intended location. Cancerous areas of the prostate may be undersampled and cancer-free areas may be oversampled.
At UF Health, an ultrasound visualization system is supervised by Samsun Lampotang, Ph.D., F.S.S.H., F.A.I.M.B.E., a professor of anesthesiology in the UF College of Medicine, and is being piloted with the urology department. This system uses magnetic sensors attached to the ultrasound probe, biopsy gun and embedded in the prostatic urethra via catheter that allows for real-time 3D feedback for improved biopsy accuracy. Biopsy templates can be immediately adjusted to accommodate larger prostates as well as to target often unbiopsied areas of the prostate that are more at risk for cancer in subpopulations of men, for example the anterior prostate zone in African Americans.
Additionally, the magnetic tracking system will allow for prostate and specific prostate lesion mapping for biopsy guidance, which will, in turn, facilitate application of focal prostate cancer treatment efforts.
“This system is especially important for patients with high-risk disease that is missed on the first biopsy,” Stringer said.
Stringer also notes that simulation is an increasingly important part of graduate medical education and resident training. Simulation addresses patient safety concerns as well as adds efficiency in a background of limited duty hours for the training of residents.
“Through a simulation model at UF Health, we’ve developed a freehand, pitch-neutral technique that lends itself to more intuitive and accurate utilization of the side-fire ultrasound probe. If you move your hand up, you’re moving the working part of the ultrasound down, so you want to be on a plane with the prostate. We stress to residents that they shouldn’t either drop or raise their hand — keep it on plane. Small movements of the probe really distort the visualization of the prostate and the placement of the biopsies,” Stringer explained.
It’s expected that the techniques being developed will eventually be applicable to many additional procedures, including ablation, lithotomy, anesthetic blocks, vascular access, drainage and brachytherapy in the prostate and other organs such as the bladder and kidney.