Information for Referring Physicians
(From left to right) Kathy Pitts, Leon Parris, Daryl Turlington, Dr. Mary Turner, Dr. Jinxing Yu, Dr. Charles Cockrell, Jean Snow, Michael Coleman, Dr. Robert Halvorsen and Brad Metcalf.
To Arrange an Appointment for an MR of the Prostate,
For an MR-guided Prostate Biopsy, call 804-628-7651.
At VCU Medical Center, magnetic resonance imaging (MRI), supplemented by MR spectroscopic imaging (MRSI), has been used in diagnosing and staging of prostate cancer for many years. Today, VCU Medical Center routinely uses multiple Advanced Prostate MR Imaging techniques, during a non-invasive 45-minute examination. These Advanced Prostate Imaging techniques include MR T2 weighted imaging, MR spectroscopic imaging, MR diffusion and dynamic contrast enhanced imaging. In combination of all these techniques, the accuracy in the diagnosis of prostate cancer is higher than 90% based on the published studies and our own experience.
T2 Weighted MR Imaging
MR T2 weighted imaging provides high sensitivity and excellent demonstration of zonal anatomy and pathological processes of the prostate (Figure 1).
The internal anatomy of the prostate demonstrates excellent differential soft tissue contrast on T2-weighted images. The signal intensity of the normal peripheral zone is very high on T2 owing to its higher water content. If the prostate cancer is in the peripheral zone, a low signal intensity focus is always present on T2-weighted image resulting in a high sensitivity of detection.
Unfortunately, the specificity of the low T2 signal foci in the peripheral zone is not great, about 70%, since these low signal foci may be seen in patients with focal infection, inflammation, bleed or post treatment changes.
MR Spectroscopic Imaging (MRSI)
Greater specificity and characterization of pathological processes is possible with MRSI (Figure 2).
MR spectroscopy (MRSI) is a MR technique that is capable of detecting and quantifying normal and cancer-related chemical compounds in the prostate gland. Normal prostate tissue contains a large amount of citrate and a small amount of choline. In contrast, prostatic adenocarcinoma contains a low level of citrate and a large quantity of choline. Therefore, MRSI provides information that helps differentiate the prostatic normal tissue or other diseases from adenocarcinoma, resulting in an improved specificity of about 82%.
More advanced MR techniques are now available and being used routinely at VCU Medical Center to stage and better detect prostate cancer. MR diffusion and dynamic contrast enhanced imaging (perfusion) are two of these advanced MR techniques currently used at VCU Medical Center to stage and to better detect prostate cancer in new patients as well as for patients status post radical prostatectomy or radiation therapy.
MR Diffusion Weighted Images (DWI) and ADC
Diffusion-weighted MR imaging (Figure 3) is sensitive to the structure of biologic tissue at the microscopic level. The cancer lesion often has a high cellularity that limits the movement of water molecules within the lesion. Therefore, in a patient with prostate cancer, the lesion usually appears dark on apparent diffusion coefficient (ADC) maps indicating diffusion restriction while normal tissue appears bright.
The specificity of DWI-ADC maps is about 86%.
MR Dynamic Contrast Enhanced Imaging (DCE-MRI)
Dynamic contrast-enhanced MRI (Figure 4) is a powerful tool in providing a map of blood flow of prostate gland, which is increased in prostate cancer. In recent studies, DCE-MRI of the prostate gland has been shown to provide excellent enhanced imaging that is useful for both the detection and the staging of prostate cancer. The specificity of DCE is about 85%
MR Guided Biopsy for Prostate Cancer
Currently, patients with PSA levels greater than 4 ng/mL, or with suspicious findings at digital rectal examination, are candidates for systematic biopsy guided with transrectal ultrasonography (US). However, results of the first prostate biopsy are negative in an estimated 66% of patients with PSA levels greater than 4 ng/mL. Thus, many patients require repeat biopsy even though the positive rate of repeat biopsy, is only 15 to 20%.
MR-guided prostate biopsy (Fig. 5) allows precise placement of the biopsy needle under direct vision and allows tissue sampling with fewer passes of the biopsy needle. MR guided biopsy of prostate cancer has been proven to be an accurate tool (positive yield up to 60%) in confirming the diagnosis of prostate cancer. It is particularly useful for patients with multiple prior negative transrectal US guided biopsies.
Figure 5: Dynamic contrast enhanced imaging (DCE) of prostate and MR guided prostate biopsy. a, DCE demonstrates enhancement with rapid wash-out (+) in the right transitional zone consistent with prostate cancer. b, MR guided prostate biopsy was performed and Gleason score 7 adenocarcinoma was found in the right transitional zone.
Under guidance of MR, the lesion in the prostate is well visualized. MR imaging monitors the advancement of the biopsy needle until the needle tip reaches the lesion. This guidance results in a higher positive biopsy rate.
Professor and Director of Prostatic Imaging, Dr. Jinxing Yu, and other specialized abdominal radiologists at VCU Medical Center, trained in MR imaging of the prostate gland, are using these new advanced techniques routinely to assess patients with suspected prostate cancer, and to evaluate patients who have been previously treated with surgery or radiation for recurrent disease. They work closely with the urologists and radiation oncologists to provide the latest, most advanced diagnostic tools for prostate imaging, resulting in more and more accurate detection of prostate cancers.