What Are The Limitations of Transrectal Ultrasound (TRUS) For Detecting Prostate Cancer?

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Did you ever make a pinhole camera when you were young? Pinhole cameras are the most basic type of camera. All you need is a closed box with a black interior, a pinhole in one side, and some type of film opposite the side with the pinhole. They capture pretty good pictures, depending on the experience of the photographer. For the hobbyist, pinhole photography can be relaxing and fun. But for a wartime journalist recording dangerous situations, it would be essential to carry a very sensitive, responsive high-tech camera and several different lenses. The right tool is needed for capturing details in high resolution images in order to record accurate visual information. In fact, a single image can be a game-changer: a powerful 1972 photo of the “Napalm Girl” helped turn the tide of public opinion to end the Vietnam War.

When it comes to detecting prostate cancer, it’s important to think like a journalist in a combat zone.

If you don’t want to lose the battle against prostate cancer, you want to capture and transmit to decision-makers the most accurate visual information possible. You want images that can reveal suspicious areas, and precise scans that can be correlated with all other information such as biomarkers. You need those images to map out a strategy, determine if interventions such as a biopsy or treatment are needed, which “weapons” to use against a tumor, and where to direct them.

Before multiparametric MRI (mpMRI) became what it is today, the best prostate “camera” available was transrectal ultrasound, or TRUS. TRUS can do things that were previously impossible. Without having to physically open the abdomen or perineum, TRUS can depict the size and shape of the prostate, its location just below the bladder, and the biopsy needles as they are injected into the gland. This is what TRUS can do, and it’s better than the surgical procedures previously used to gain the same information.

However, TRUS has limitations. Rothwax et al (2014) succintly tell us what it cannot do “What TRUS fails to provide, however, is information that pertains to the composition of the prostate tissue itself, whether it is benign or malignant and, if malignant tissue is present, whether it has spread beyond the prostate capsule.” Multparametric MRI, on the other hand, is like a high-tech camera with different “lenses” or ways of capturing the same “scene” for different tissue effects. These are then correlated with each other to capture the total picture in 3D. Today’s mpMRI integrates three different scanning sequences: T2 weighted MRI, diffusion weighted MRI, and dynamic contrast enhanced MRI. Each sequence acts like a special lens to characterize certain features or composition of the tissue being scanned. At our Center, we have a state-of-the-art Tesla (3T) magnet that is so powerful we do not use an endorectal coil.

We follow the mpMRI protocol established by PI-RADS v2 that contains standards agreed upon by international experts for scanning, interpreting and reporting the results. We can determine which zones of the prostate contain healthy, normal tissue; which have benign conditions such as BPH, cysts or inflammation; and which contain cancer-suspicious lesions. We can rate the suspicious areas on the RI-RADS scale from 1 to 5, where 1 is very low likelihood that clinically significant cancer is present, and 5 shows very high likelihood that significant cancer is present.

Our prostate imaging at the Sperling Prostate Cancer is recognized as a game-changer, helping set the bar for excellence. We have made a powerful contribution toward turning the prostate imaging tide in favor of mpMRI. Compared with the limitations of transrectal ultrasound, mpMRI has become the prostate imaging of choice in the war against prostate cancer.

Copyright by Dan Sperling. MD. Reprint permission courtesy of Sperling Prostate Center (New York, Florida), the leading U.S. cneter for multiparametric detection, diagnosis and image-guided focal treatment of prostate cancer.

Read more in our Prostate Cancer Health Center.


Harris ME. Photographer who took iconic Vietnam photo looks back, 40 years after the war ended. Vanity Fair HIVE, 2015 Apr 3.

Rothwax J et al. Multiparametric MRI in biopsy guidance for prostate cancer: fusion-guided. Biomed Res Int 2014; 2014:439171

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