An MRI-guided breast biopsy is a sophisticated medical procedure used to pinpoint and sample suspicious areas within the breast using the precision of Magnetic Resonance Imaging (MRI). This technique is particularly valuable for lesions that are difficult to detect with other imaging methods like mammography or ultrasound. This guide explains how an MRI-guided breast biopsy is performed, its common uses, preparation, and what to expect during and after the procedure.
What is an MRI-Guided Breast Biopsy?
When abnormalities or lumps are detected in the breast through physical exams, mammography, or other imaging tests, it’s not always possible to determine if they are benign or cancerous. A breast biopsy involves removing a small tissue sample from the suspicious area for laboratory analysis.
While surgical biopsies are an option, radiologists often prefer a less invasive approach: image-guided needle biopsy. This method uses a hollow needle guided by imaging technology to extract a small sample of the abnormality for further examination. MRI-guided breast biopsy uses magnetic resonance imaging to precisely guide the radiologist’s instruments to the site of the abnormal growth.
Alt text: Radiologist performing an MRI-guided breast biopsy, showing the patient positioned on the MRI table and the radiologist using imaging to guide the biopsy needle.
Common Uses of MRI-Guided Breast Biopsy
An MRI-guided breast biopsy is particularly useful when MR imaging reveals a breast abnormality, such as:
- A suspicious mass not visible through other imaging techniques.
- An area of distortion within the breast tissue.
- A region displaying abnormal tissue changes.
MRI guidance is employed in biopsy procedures that use various instruments, including vacuum-assisted devices (VADs) and thin guide wires for surgical biopsies.
How to Prepare for an MRI-Guided Breast Biopsy
Proper preparation is essential for a successful MRI-guided breast biopsy. Here’s what you need to do:
- Medical History: Inform your doctor about any existing health issues, recent surgeries, and the possibility of pregnancy.
- Metal Implants: While most orthopedic implants pose no risk, always notify the technologist about any medical devices or metal present in your body.
- Food and Medication: Guidelines for eating and drinking may vary. Unless instructed otherwise, continue taking your regular medications. Discuss all medications, including aspirin and herbal supplements, with your doctor, and disclose any allergies, especially to anesthesia or contrast materials.
- Blood Thinners: You may be advised to stop taking aspirin or blood thinners a few days before the procedure to minimize bleeding risk.
- Clothing and Jewelry: Wear loose, comfortable clothing and leave jewelry at home. You may be asked to wear a gown.
- Transportation: If you’re receiving sedation, arrange for someone to drive you home after the procedure.
Some MRI exams require a contrast material, often gadolinium. Inform your doctor if you have asthma or allergies to contrast material, drugs, food, or the environment. Patients with allergies to iodine contrast can often use gadolinium, though pre-medication may be necessary even with a known gadolinium allergy. Consult the ACR Manual on Contrast Media for more information.
Tell the technologist or radiologist if you have any serious health problems or recent surgeries. Some conditions, such as severe kidney disease, may make gadolinium unsafe. A blood test may be required to check kidney function.
Pregnant women should inform their doctor and technologist. While MRI has been used since the 1980s with no reported harm to pregnant women or their babies, it’s generally advised to avoid MRI in the first trimester unless the benefits outweigh the risks. Gadolinium contrast should be avoided unless absolutely necessary. See the MRI Safety During Pregnancy page for more information.
There are other important guidelines for patients to follow prior to undergoing MR imaging. For a list of these and a review of all preparations that should be made prior to MR imaging, please see MRI of the Breast.
What the Equipment Looks Like
The standard MRI unit is a large, cylinder-shaped tube surrounded by a circular magnet. You will lie on a table that slides into the tunnel toward the magnet’s center.
Alt text: A typical MRI machine used for medical imaging, showcasing the cylindrical shape and patient table.
Short-bore systems are designed so that the magnet does not completely surround you. Newer machines may have a larger diameter bore for comfort, especially for larger patients or those with claustrophobia. Open MRI units are open on the sides and are beneficial for larger patients or those with claustrophobia. However, open MRI may not be suitable for all exams.
Most MRI-guided breast biopsies are performed in closed MRI systems with a specially modified exam table that allows the breasts to hang freely into cushioned openings containing wire coils. These coils send and receive radio waves, creating the MR images.
How the Procedure Works
MRI does not use radiation like X-rays or CT scans. Instead, it uses radio waves to realign hydrogen atoms naturally present in the body. As these atoms return to their normal alignment, they emit varying amounts of energy based on the tissue type. The scanner captures this energy and creates detailed images.
A computer processes these signals into a series of images, each representing a thin slice of the body. The radiologist can then study these images from multiple angles. MRI often distinguishes between diseased and normal tissue more effectively than X-rays, CT scans, and ultrasound.
Guided by the MRI images, the radiologist precisely inserts the biopsy needle through the skin, advancing it into the lesion to collect tissue samples. For surgical biopsies, MRI may guide a wire into the mass to help the surgeon locate the excision area.
How is an MRI-Guided Breast Biopsy Performed?
MRI-guided breast biopsies are typically performed by a specially trained breast radiologist on an outpatient basis. Here’s a step-by-step breakdown:
- Patient Positioning: In most cases, you will lie face down on a movable exam table, with the affected breast positioned into an opening in the table.
- IV Line and Contrast: A nurse or technologist will insert an intravenous (IV) line into a vein in your hand or arm, and the contrast material gadolinium will be administered intravenously.
- Breast Compression: Your breast will be gently compressed between two plates, similar to a diagnostic MRI. The radiologist uses computer software to measure the lesion’s position relative to a grid on the compression plate, calculating the needle’s position and depth.
- Local Anesthesia: The doctor will inject a local anesthetic into the skin and deeper into the breast to numb the area.
- Needle Insertion: A small nick is made in the skin, and the biopsy needle is inserted and advanced to the abnormality’s location. MR imaging verifies the needle’s position.
- Tissue Sampling: Tissue samples are collected using a vacuum-assisted device (VAD). The vacuum pressure pulls tissue through the needle into a sampling chamber. The needle rotates to collect multiple samples without being withdrawn and reinserted. Typically, eight to ten samples are collected.
- Needle Removal and Marker Placement: After sampling, the needle is removed. If a surgical biopsy is planned, a wire may be inserted into the suspicious area to guide the surgeon. A small marker may be placed at the biopsy site for future location if needed.
- Wound Care: Pressure is applied to stop any bleeding, and the skin opening is covered with a dressing. No sutures are necessary.
- Confirmation: The doctor may use mammography to confirm the marker is in the proper position.
The entire procedure usually takes around 45 minutes.
What to Expect During and After the Procedure
During the biopsy, you will be awake and should experience minimal discomfort. Many women report little to no pain and no scarring. However, individuals with dense breast tissue or abnormalities near the chest wall or behind the nipple may experience more sensitivity.
Some women find lying on their stomach for the procedure’s duration uncomfortable. Strategically placed cushions can help ease this discomfort. Some may also experience neck and/or back pain due to head positioning.
You will feel a pinprick followed by a mild stinging sensation from the local anesthetic. You will likely feel some pressure during needle insertion and tissue sampling, which is normal. It’s crucial to remain still during imaging and the biopsy.
As tissue samples are taken, you may hear clicks or buzzing sounds from the sampling instrument, which are normal.
If you experience swelling and bruising post-biopsy, your doctor may recommend over-the-counter pain relievers and cold packs. Temporary bruising is normal.
Contact your doctor if you notice excessive swelling, bleeding, drainage, redness, or heat in the breast.
A marker left inside the breast to mark the biopsied lesion’s location will not cause pain, disfigurement, or harm. Biopsy markers are MRI compatible and won’t trigger metal detectors.
Avoid strenuous activity for at least 24 hours after the biopsy. Your doctor will provide more detailed post-procedure care instructions.
Interpreting Results and Follow-Up
A pathologist examines the removed specimen to make a final diagnosis. The radiologist or your referring physician will share the results with you. The radiologist will also evaluate the biopsy results to ensure the pathology and imaging findings align. If the pathology doesn’t match the imaging findings, surgical removal of the biopsy site and imaging abnormality may be recommended, even if cancer isn’t diagnosed.
A follow-up exam may be necessary to further evaluate a potential issue with more views or a special imaging technique or to monitor any changes over time. Follow-up exams are crucial for assessing treatment effectiveness or identifying problems requiring attention.
Benefits and Risks of MRI-Guided Breast Biopsy
Benefits:
- Less invasive than surgical biopsy, leaving little to no scarring.
- MRI is a noninvasive imaging technique without radiation exposure.
- Safe and accurate with a core needle.
- As effective as MR-guided wire localization without the complications and costs of surgery.
- Faster, less tissue damage, and less costly than surgical biopsy.
- Brief recovery time, allowing patients to resume usual activities quickly.
Risks:
- Risk of bleeding and hematoma formation (less than 1% of patients).
- Occasional discomfort, controlled by non-prescription pain medication.
- Risk of infection (less than one in 1,000).
- Slight risk of needle passing through the chest wall, causing lung collapse (extremely rare).
- Small chance of not providing a final answer to the imaging abnormality.
- Mothers should not breastfeed for 24-48 hours after contrast material is given, although recent studies suggest the amount of contrast absorbed by the infant is extremely low. For further information please consult the ACR Manual on Contrast Media and its references.
Limitations of MRI-Guided Breast Biopsy
MRI-guided tissue sampling is limited by the lesion’s position in the breast. Lesions in the extreme posterior region or small abnormalities can be difficult to target accurately.
Breast biopsy procedures may occasionally miss a lesion or underestimate the extent of the disease. If the diagnosis remains uncertain, surgical biopsy may be necessary.
The method cannot be used if the mass isn’t visible on an MRI exam. Calcifications within a cancerous nodule aren’t seen on Breast MRI, making it difficult to target small lesions accurately.
Its widespread use is limited by high cost, availability, and procedure length. MRI-guided biopsy shouldn’t be considered if the lesion is visible on mammography or ultrasound, where biopsy can be performed more easily with less patient discomfort. Stereotactic or ultrasound-guided biopsy are more appropriate in those cases.
Additional Resources
RTAnswers.org: Radiation Therapy for Breast Cancer
