Prostate MRI Information: How it is Done
What is MRI?
Magnetic Resonance Imaging (MRI) is a method of scanning used to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body.
Unlike X-rays or CT scanning, MRI does not use any ionizing radiation. In many cases, MRI gives information that cannot be seen on an X-ray, ultrasound, or computed tomography (CT) scan. There are no known side effects of an MRI scan.
MR imaging uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. The images can then be examined on a computer monitor.
Detailed MR images allow physicians to better evaluate various parts of the body that may not be assessed adequately with other imaging methods such as x-ray, ultrasound or CT scan.
Why Have an MRI Scan of the Prostate?
MRI provides excellent image quality for a more accurate look at the prostate gland.
The primary indication for MRI of the prostate is the evaluation of prostate cancer. The test is commonly used after a biopsy has confirmed prostate cancer. Biopsies identify cancer within the prostate, but it is also important to know whether any cancer has spread beyond the confines of the gland into the surrounding tissue. MRI is the most accurate noninvasive method of identifying so called locally advanced prostate cancer. This superior resolution offered by MRI can enable physicians to determine cancer stage, conclude whether the cancer is contained within the gland or has spread, and determine the most appropriate treatment path for the patient.
In order to intensify the signals and improve the clarity of images, several variations of MR coils are used. These MR coils can be placed on the surface of the body, e.g. a torso or pelvic MR coil, or inserted into a body orifice, e.g. an endorectal coil.
The endorectal coil helps focus on the prostate and surrounding structures. The increased signal from the endorectal coil helps to provide excellent image quality. It also enables the radiologist to perform magnetic resonance (MR) spectroscopy, which can provide additional information on the chemical makeup of cells present in the prostate gland.
What Is the Preparation for MRI of the Prostate?
Before requesting an MRI:
The MRI scanner uses a strong magnetic field to produce images of the body and although it is a very safe procedure, there are certain things which can interfere with MRI. People with the following implants cannot be scanned and should not enter the MRI scanning area. They are:
- cardiac pacemaker or defibrillator
- ear implants
- vascular clips ( brain or other )
You should tell the physician/technologist if you have medical or electronic devices in your body. These may interfere with the exam or potentially pose a risk, depending on their nature and the strength of the MRI magnet. Most important of them all are:
- artificial heart valves
- artificial limbs or metallic joint prostheses
- implanted nerve stimulators
- metal pins, screws, plates, stents or surgical staples
- implanted drug infusion ports
You will be asked questions about items which can interfere with MRI. The main concerns are brain surgery (hydrocephalus shunt), metallic fragments in your eyes, injury involving bullets or shrapnel, cosmetic surgery, tattoos, hearing aids and removable metal dental plates.
Those who have non-removable metal objects in certain parts of their bodies may require an x-ray prior to an MRI. Metal objects used in orthopedic surgery pose no risk during MRI provided they are not placed recently (less than a year). However, the radiologist’s decision will depend on the proximity of the metal implants to the area examined by the MRI.
Dyes used in tattoos may contain iron and could heat up during MRI, but this is rarely a problem. Usually tooth fillings and braces are not affected by the magnetic field.
Other contraindication, especially for an endorectal MRI, are having a history of rectal bleeding, rectal surgery, and inflammatory bowel diseases. Other conditions that your physician should be aware of are the history of chronic liver/kidney disease, use of anti- coagulant drugs and severe claustrophobia.
The Day Prior to Exam
To prepare for an MRI with the endorectal coil, you should eat light meals on the day prior to your exam. You will use an enema preparation such as Fleet, 3 hours prior to your exam to help clear the bowel. A good bowel preparation will help make it easier to insert the coil.
On the Day of Your Exam
You will be asked to fast for 8-12 hours before the exam. You may take your regular medications as usual with a sip of water.
If you have claustrophobia (fear of enclosed spaces) or anxiety, you may want to ask your physician for a prescription for a mild sedative which should be taken 30 minutes before the exam.
You may be asked to wear a gown during the exam.
Metal and electronic objects are not allowed in the exam room. Any metal containing items such as jewelry, watches, eyeglasses, pins, hairpins, removable dental work, pens, credit cards, coins and pocketknives and body piercings should be removed prior to the MRI scan.
You will be positioned on the moveable examination table. Straps and bolsters may be used to help you stay still and maintain the correct position during imaging.
Your scan requires the injection of MRI contrast fluid into a vein, which is delivered through a small tube placed into the arm or hand. This will be connected up to a pump containing the contrast fluid. The technologist may ask if you have allergies of any kind, such as allergy to iodine or x-ray contrast material, drugs, food, the environment, or asthma. However, the contrast material used for an MRI exam, called gadolinium, does not contain iodine and is less likely to cause side effects or an allergic reaction. A saline solution will drip through the IV to prevent blockage of the IV line until the contrast material is injected.
Your MRI exam involves the use of an endorectal coil, a thin wire covered with a balloon, placed inside the tail end of the large bowel, the rectum. You will be asked to lie on your side and the physician/nurse will lubricate the assembly and insert the coil into your rectum. Once inserted, the balloon is filled with a special liquid until it comes into contact with and conforms to the size and shape of the prostate. During insertion of the endorectal coil, it is not painful; however, it may cause some initial discomfort. You may feel pressure in your rectum similar to that experienced during a digital rectal exam.
Next, you will be asked to lie on your back and a special belt or the pelvic/torso coil will be placed on your abdomen. You will be moved into the magnet of the MRI unit and the radiologist and technologist will leave the room while the MRI examination is performed.
During the Exam
During the MRI scan, the patient lies in a closed area inside the magnetic tube.
Most MRI exams are painless. Some patients can experience a claustrophobic sensation during the procedure. Therefore, patients with any history of claustrophobia should relate this to the practitioner who is requesting the test, as well as the radiology staff. You will usually be alone in the exam room during the MRI procedure. However, the technologist will be able to see, hear and speak with you at all times using a two-way intercom.
Furthermore, there is usually a means of communication with the staff such as a buzzer held by the patient which can be used for contact if the patient cannot tolerate the scan.
During the exam you will hear a knocking sound, which is when you need to hold perfectly still. Some patients, however, find it uncomfortable to remain still during MR imaging. It is important that you remain perfectly still while the images are being recorded, which is typically only a few seconds to a few minutes at a time. The scan is noisy, so you will be given headphones to wear. If you enjoy any specific music and have it available on a CD, then we will be able to play it to you during the procedure.
It is normal for the area of your body being imaged to feel slightly warm, but if it bothers you, notify the radiologist or technologist.
After an initial series of scans, the contrast material will be injected into the intravenous line (IV). Additional series of images will be taken during or following the injection. It is normal to feel coolness and a flushing sensation for a minute or two when the contrast is been injected. The intravenous needle may cause you some discomfort when it is inserted and once it is removed, you may experience some bruising.
After the Exam
The entire examination is usually completed within one hour and 15 minutes. When the exam is complete, the balloon is deflated and the coil is removed and your intravenous line will be removed. You may resume your usual activities and normal diet immediately after the exam.
A few patients experience side effects from the contrast material, including nausea and local pain.
A radiologist will analyze the images and send a report to your physician, who will share the results with you.