Published Wednesday, 15 October 14
Transrectal Ultrasonography of the Prostate or TRUS is a technique which uses a rectally inserted ultrasound probe to produce images of a patient’s prostate. When a needle is attached to this probe you have a technique which is currently the most widely practiced method for taking a biopsy of a patient’s prostate. It is typical for a procedure to last around 20 minutes and for the practitioner to take 6-12 samples in the initial procedure. A key issue with this technique is that prostate cancer is difficult or simply impossible to see on an ultrasound image. Due to the non-targeted approach adopted, it may happen that after the procedure is performed and the specimens have been imaged that the area of interest was missed and the procedure will need to be repeated until a successful biopsy is performed. To exacerbate this, a recent study found that TRUS guided biopsies can miss around 20 to 30 percent of clinically significant cancers.
Technological advances have lead to the development of more accurate and less invasive procedures for prostate biopsies. The use of MR imaging plays a pivotal role in these new techniques. There are two methods that are available which use MR to produce a better clinical outcome.
MRI Guided Biopsy
The gold standard in prostate biopsy procedures is an MRI only procedure which relies solely on MR imaging to position a transrectal biopsy probe. Once the probe is inserted an image is taken which, with the help of CAD software, clearly shows the area of interest and its position relative to the probe. A computer program can be used to calculate the required movements to position the probe at the precise location or the interventional radiologist can manually position the probe using information from the image before a single sample is taken. The benefits of this approach are obvious. Primarily, a single sample is excised opposed to 6-12 in a traditional TRUS procedure resulting in less pain and discomfort for the patient. And secondly, because cancer is more readily identifiable in an MR image, the need for repeat procedures is essentially eliminated.
DynaTRIM - Interventional Equipment
DynaTRIM is a first-of-its-kind fully MR compatible interventional device for Trans-Rectal Interventional MR biopsy of the prostate gland. It is a removable device that is designed to affix to an imaging table to an open design that allows for flexibility in coil choice and a cleanable foam pad for extra patient comfort. DynaTRIM can be used on any major scanner and must be used in conjunction with DynaCAD Prostate interventional software.
MRI/Ultrasound Fusion Biopsy
Another method which still relies on ultrasound is a multi-modality procedure. A radiologist takes an image using an MRI sometime before the procedure occurs. A urologist can then use software which fuses this MR image with realtime ultrasound images. This combines the diagnostic quality of an MR image with the realtime information provided by an ultrasound device and allows the urolgist to make a confident biopsy of a particular area of the prostate.
This procedure leads to the same benefits as MRI only. Only a single sample is required which leads to a better patient experience and the MR image provides enough information to ensure that the sample taken will be from the area of interest. Again, elminating repeat procedures.
UroNav - Fusion Biopsy System
The UroNav fusion biopsy system from Invivo enables easy clinical use of this powerful MR/US fusion technique. It combines electromagnetic tracking and navigation with an onboard computer and a real-time imaging interface in one easy-to-use, mobile workstation.Images ecnompassing a 3D map of the prostate and Regions of Interest (ROI) must be supplied from DynaCAD Prostate analysis software.
Pokorny MR, et al. Prospective Study of Diagnostic Accuracy Comparing Prostate Cancer Detection by Transrectal Ultrasound–Guided Biopsy Versus Magnetic Resonance (MR) Imaging with Subsequent MR-guided Biopsy in Men Without Previous Prostate Biopsies. Eur Urol (2014), http://dx.doi.org/10.1016/j.eururo.2014.03.002
Taira, A. V., Merrick, G. S., Galbreath, R. W., Andreini, H., Taubenslag, W., Curtis, R., et al. (2010). Performance of transperineal template-guided mapping biopsy in detecting prostate cancer in the initial and repeat biopsy setting. Prostate cancer and prostatic diseases, 13(1), 71–77. doi:10.1038/pcan.2009.42