Magnetic resonance imaging (MRI)-guided breast biopsy is a technique used to locate a breast abnormality and guide a needle to remove a tissue sample for microscopic examination, utilizing a strong magnetic field, radio waves, and a computer. This method avoids ionizing radiation and typically results in minimal or no scarring.
Prior to the procedure, it’s essential to inform your doctor about any health issues, recent surgeries, and potential pregnancy. While the magnetic field itself is not harmful, it can interfere with the function of certain medical devices. Most orthopedic implants pose no risk, but any devices or metal within the body should be disclosed to the technologist. Fasting guidelines may vary among facilities, so follow specific instructions provided. Continue taking your regular medications unless instructed otherwise. Inform your doctor about all medications you’re taking, including aspirin and herbal supplements, as well as any allergies, particularly to anesthesia or contrast materials. You may need to discontinue aspirin or blood thinners three days before the procedure. Wear loose, comfortable clothing and leave jewelry at home. A gown may be required. If sedation is planned, arrange for someone to drive you home afterward.
Understanding MR-Guided Breast Biopsy
Lumps or abnormalities detected in the breast through physical exams, mammography, or other imaging techniques may necessitate further investigation. While these tests can identify suspicious areas, they often cannot determine whether a growth is benign or cancerous. This is where “How Do They Do An Mri Guided Breast Biopsy” becomes a critical question.
Breast biopsy enables doctors to collect a small tissue sample from the suspicious area for laboratory analysis. A biopsy can be performed surgically, but radiologists commonly use a less invasive, image-guided needle biopsy. This needle biopsy takes a small sample of the abnormality for analysis, rather than removing the entire lesion.
Image-guided biopsy relies on imaging modalities like ultrasound, MRI, or mammography to guide the sampling of abnormalities. In MRI-guided breast biopsy, magnetic resonance imaging helps guide the radiologist’s instruments to the precise location of the abnormal growth.
Common Uses of MRI-Guided Breast Biopsy
An MRI-guided breast biopsy is particularly useful when MRI reveals a breast abnormality, such as:
- A suspicious mass that is not detectable by other imaging methods
- An area of distortion
- An area showing abnormal tissue changes
MRI guidance is used in biopsy procedures involving:
- Vacuum-assisted devices (VAD): These use vacuum pressure to draw tissue into the needle.
- Thin guide wires: These are used for surgical biopsies, guiding the surgeon to the correct location.
Preparing for the Procedure
Patients will be asked to change into a hospital gown to avoid image artifacts and comply with safety regulations related to the strong magnetic field.
Specific guidelines regarding eating and drinking before an MRI vary. Unless instructed differently, continue to take your food and medications as usual.
Contrast material may be injected during some MRI exams. The doctor may inquire about asthma or allergies to contrast material, drugs, food, or the environment. Gadolinium is a common contrast material used in MRI exams and is generally safer for patients with iodine contrast allergies. However, even with a known gadolinium allergy, it may be possible to use it after premedication.
Inform the technologist or radiologist of any serious health problems or recent surgeries. Severe kidney disease, for instance, may preclude the safe administration of gadolinium. A blood test may be necessary to assess kidney function.
Pregnant women should inform their doctor and technologist. While MRI has been used since the 1980s without reported harm to pregnant women or their babies, precautions are taken due to the strong magnetic field. MRI is generally avoided during the first trimester unless the benefits outweigh the potential risks. Gadolinium contrast is avoided during pregnancy unless absolutely necessary.
Prior to the needle biopsy, disclose all medications, including herbal supplements, and any allergies, particularly to anesthesia. Your doctor might advise you to stop taking aspirin, blood thinners, or certain herbal supplements three to five days before the procedure to minimize bleeding risk.
Inform your doctor about any recent illnesses or other medical conditions.
Consider having someone drive you home after the procedure, particularly if you receive sedation.
The Equipment Used
A traditional MRI unit is a large, cylinder-shaped tube encased in a circular magnet. The patient lies on a table that slides into the tunnel toward the magnet’s center.
Short-bore systems are designed so the magnet doesn’t completely surround the patient. Newer MRI machines may have wider openings for enhanced comfort, especially for larger patients or those with claustrophobia. Open MRI units, open on the sides, are also helpful for larger patients or those with claustrophobia, although they may not be suitable for all exams.
Most MRI-guided breast biopsies are done in closed MRI systems with a specialized exam table. This table allows the breasts to hang freely into cushioned openings containing wire coils that send and receive radio waves to create MR images.
Instruments used during the procedure may include:
- A vacuum-assisted device (VAD) uses vacuum power to pull tissue into the needle.
- A thin guide wire, used for surgical biopsies.
Sterile equipment such as syringes, sponges, forceps, scalpels, and specimen cups or microscope slides are also used.
How the Procedure Works
MRI does not involve radiation, unlike x-ray and computed tomography (CT) scans. Instead, it uses radio waves to realign hydrogen atoms within the body. As these atoms return to their usual alignment, they emit different amounts of energy depending on the tissue type. The scanner captures this energy and creates an image based on this information.
The magnetic field is typically created by passing an electric current through wire coils. Additional coils send and receive radio waves, producing signals detected by the machine. A computer processes these signals to create a series of images showing thin slices of the body, which the radiologist can study from different angles.
MRI often distinguishes between diseased and normal tissue better than x-ray, CT, and ultrasound.
Guided by MRI, the radiologist inserts the biopsy needle through the skin, advances it into the lesion, and removes tissue samples. MRI verifies the needle’s placement. For surgical biopsies, MRI may guide a wire into the mass, assisting the surgeon in locating the area for excision.
Steps of the Procedure
Image-guided, minimally invasive procedures like MR-guided breast biopsies are typically performed by a specialized breast radiologist.
Breast biopsies are typically outpatient procedures.
In most cases, the patient lies face down on a moveable exam table, with the affected breast positioned in an opening in the table.
A nurse or technologist inserts an intravenous (IV) line into a vein in the hand or arm, through which gadolinium contrast material is administered.
The breast is gently compressed between two compression plates (similar to those used in diagnostic MRI), one of which has a grid. Using computer software, the radiologist measures the lesion’s position relative to the grid and calculates the needle’s position and depth.
Local anesthetic is injected into the skin and deeper into the breast to numb the area.
A tiny nick is made in the skin where the biopsy needle will be inserted.
The radiologist inserts the needle, advances it to the abnormality’s location, and MRI is performed to confirm its position. The patient may remain in place or be moved out of the MRI scanner’s center depending on the type of MRI unit.
Tissue samples are removed using a vacuum-assisted device (VAD). Vacuum pressure draws tissue through the needle into a sampling chamber. The needle rotates positions and collects additional samples without being withdrawn and reinserted. The doctor usually collects eight to 10 tissue samples from around the lesion.
After sampling, the needle is removed.
If a surgical biopsy is planned, a wire is inserted into the suspicious area to guide the surgeon.
A small marker may be placed at the biopsy site for future identification, if needed.
Pressure is applied to stop any bleeding once the biopsy is complete, and the opening is covered with a dressing. Sutures are not required.
Mammography may be used to confirm the marker’s proper placement.
The procedure usually takes around 45 minutes.
What to Expect During and After the Procedure
Patients remain awake during the biopsy and typically experience minimal discomfort. Many women report little pain and no scarring. However, patients with dense breast tissue or abnormalities near the chest wall or behind the nipple may be more sensitive.
Lying on the stomach for the duration of the procedure can be the main source of discomfort for some women. Strategically placed cushions can alleviate this discomfort. Neck and/or back pain may also occur as the head is turned to position the breast.
The local anesthetic injection will feel like a pinprick, followed by a mild stinging sensation. Pressure will be felt during needle insertion and tissue sampling, which is normal.
The area will become numb within seconds.
Remaining still during imaging and the biopsy is essential.
Clicking or buzzing sounds from the sampling instrument are normal.
Swelling and bruising may occur following the biopsy. Over-the-counter pain relievers and cold packs can help. Temporary bruising is normal.
Excessive swelling, bleeding, drainage, redness, or heat in the breast should be reported to the doctor.
A marker left inside the breast to mark the biopsy site will not cause pain, disfigurement, or harm. Biopsy markers are MRI compatible and will not trigger metal detectors.
Strenuous activity should be avoided for at least 24 hours after the biopsy. The doctor will provide more detailed post-procedure care instructions.
Interpreting Results
A pathologist examines the removed specimen and provides a final diagnosis. The radiologist or referring physician will share the results. The radiologist also evaluates the biopsy results to ensure consistency between pathology and imaging findings. In some cases, surgical removal of the entire biopsy site and imaging abnormality may be recommended if the pathology does not align with the imaging findings, even if cancer is not diagnosed.
A follow-up exam may be necessary to further evaluate a potential issue or to monitor changes over time. Follow-up exams are essential for determining the effectiveness of treatment or addressing a problem.
Benefits vs. Risks
Benefits
- Less invasive than surgical biopsy, leaves little or no scarring, and takes less than an hour.
- MRI is a noninvasive imaging technique that does not involve radiation exposure.
- MRI-guided breast biopsy using a core needle is considered safe and accurate.
- The speed, accuracy, and safety of MRI-guided vacuum-assisted breast biopsy are comparable to MR-guided wire localization, without the complications and costs associated with surgery.
- MRI-guided biopsy does not use ionizing radiation.
- MRI-guided breast biopsy is faster, causes less tissue damage, and is less costly than surgical biopsy.
- Recovery time is short, and patients can quickly resume their usual activities.
Risks
- There is a risk of bleeding and hematoma formation at the biopsy site, although this risk is less than one percent.
- Occasional patients experience significant discomfort, which can be managed with over-the-counter pain medication.
- Any procedure involving skin penetration carries a risk of infection, but the chance requiring antibiotic treatment is less than one in 1,000.
- A biopsy of tissue located deep within the breast carries a slight risk of the needle passing through the chest wall, potentially causing a collapsed lung, though this is extremely rare.
- There is a small chance that the procedure will not provide a definitive explanation for the imaging abnormality.
- IV contrast manufacturers advise against breastfeeding for 24-48 hours after contrast material administration, although recent studies suggest the amount of contrast absorbed by the infant during breastfeeding is minimal.
Limitations of MRI-Guided Breast Biopsy
MRI-guided tissue sampling is limited by the abnormality’s location in the breast. Lesions in the extreme posterior region or small abnormalities can be difficult to target accurately.
Breast biopsy procedures can occasionally miss a lesion or underestimate the extent of disease. Surgical biopsy may be necessary if the diagnosis remains uncertain after a technically successful procedure.
The MR-guided breast biopsy method is only effective if the mass is visible on an MRI exam. Calcifications within a cancerous nodule are not visible on breast MRI, making it difficult to accurately target small lesions.
The widespread use of this technique is limited by its high cost, availability, and the length of the procedure. MR-guided biopsy should not be considered if the lesion is visible on mammography or ultrasound, where the biopsy can be performed more easily with less patient discomfort. In such cases, stereotactic biopsy or ultrasound-guided biopsy are more appropriate.
