Information for Referring Physicians
Additional Clinical Information for Advanced Prostate Imaging at VCU Medical Center
MR T2 Weighted Imaging and MR Spectroscopy
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 since these low signal foci may be seen in patients with focal infection, inflammation, bleed or post treatment changes. 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 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 which helps to differentiate the prostatic normal tissue or other diseases from adenocarcinoma, resulting in an improved specificity.
New Advanced MR Techniques
MR diffusion and dynamic contrast enhanced imaging (perfusion) are currently used at VCU Medical Center routinely to stage and to better detect prostate cancer including for patients status post radical prostatectomy or radiation therapy. Diffusion-weighted MR imaging is a noninvasive technique that is sensitive to the structure of biologic tissue at the microscopic level. The cancer lesion often has a high cellularity so that it 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 and normal tissue appears bright. Dynamic contrast-enhanced MRI (DCE-MRI) 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 information of enhancement that is useful for both the detection and the staging of prostate cancer.
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 has been proven to be an accurate tool in confirming the diagnosis of prostate cancer, particularly useful for patients with prior failed transrectal US guided biopsy (positive yield up to 60%). Under guidance of MR, the lesion in the prostate is well visualized. Advancement of the biopsy needle is monitored by MR imaging until the needle tip reaches the lesion, so that a higher positive biopsy rate is achieved.
To set an appointment for an MR of the prostate, call 804-237-6645 or for an MR guided prostate biopsy, call 804-828-4467.