MRI of the Prostate

Authors: Dr Stefan Heinze*
                            Dr John Faulder *

What are the generally accepted indications for a prostate MRI?

Indications for prostate MRI:

• local staging of prostate cancer (specifically to determine whether disease has extended beyond the capsule of the prostate);
• in the setting of high and/or rising PSA, and one or more negative prostate biopsies;
• radiotherapy planning treatment for prostate cancer;
• detection of local recurrence.

MRI of the prostate is an evolving imaging process for detecting carcinoma of the prostate. Its most common use follows the diagnosis of prostate cancer (usually with transrectal ultrasound guided biopsies), where it is particularly useful for local staging and localisation of prostatic tumours. Prostate MRI can help distinguish between organ confined tumours (stage T1 or T2) and early advanced disease with local invasion (stage T3).

What are the prerequisites for having a prostate MRI done?

Patients are generally under the care of a urologist. Usually patients have an abnormal digital rectal examination, and an elevated or rising PSA and positive prostatic biopsies as an indication for the test.

What are the absolute contraindications for a prostate MRI?

• Any metalware in the body constitutes a potential risk in the setting of high magnetic fields. Radiology practices that offer MRI will have a comprehensive list of metallic foreign bodies (such as welding or metalwork-related ocular foreign bodies) and medical implants or devices (such as cardiac pacemakers, aneurysm clips, cochlear implants) that are contraindicated (see Magnetic Resonance Imaging (MRI)).
• A history of severe allergic reaction (collapse or airway obstruction) to MRI contrast agents, if contrast is required.

What are the relative contraindications for a prostate MRI?

• Previous mild allergic reactions to MRI contrast.
• Renal impairment with eGFR <30, if contrast is used.
• Morbid obesity.
• Severe claustrophobia.

What are the adverse effects of a prostate MRI?

Major contrast reactions (anaphylaxis) are very rare (roughly 1 in 10,000).

There is a very small risk of rectal perforation if an endorectal coil is used for the scan.

Is there any specific post-procedural care required after a prostate MRI?

There is no specific post-procedural care required after a prostate MRI

Are there alternative imaging tests, interventions or surgical procedures to a prostate MRI?

Ultrasound has a low sensitivity for diagnosing prostate cancer and is used for guidance of biopsies only. Contrast-enhanced ultrasound is showing promise, but at the time of writing is still unproven.

If a patient is unable to have an MRI (such as those with pacemakers), then staging is carried out using a combination of computed tomography (CT) and bone scan.

CT scanning is used in the staging of prostate cancer to identify distal/metastatic disease. A nuclear medicine bone scan is used to show bony metastases.

Further information about prostate MRI:

If the MRI shows abnormal areas, a biopsy (or a repeat biopsy) might be indicated. Normally this is done using ultrasound with the operator estimating as accurately as possible from the MRI images where in the gland the biopsy should be directed. Two recent advances have increased the accuracy of biopsies after an MRI scan:

• image fusion software, which fuses the MRI and ultrasound images; and
• MRI guided biopsy.

Neither of these techniques is, at the time of writing, widely available in Australia.

Useful websites about prostate MRI:

• American College of Radiology: www.radiologyinfo.org/en/info.cfm?pg=mr_prostate

*The author has no conflict of interest with this topic.

Page last modified on 26/7/2017.