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Magnetic Resonance (MRI)-Guided Breast Biopsy

Magnetic resonance- or MR-guided breast biopsy uses a powerful magnetic field, radio waves and a computer to help locate a breast lump or abnormality and guide a needle to remove a tissue sample for examination under a microscope. It does not use ionizing radiation and leaves little to no scarring.

Tell your doctor about any health problems, recent surgeries and whether there’s a possibility you are pregnant. The magnetic field is not harmful, but it may cause some medical devices to malfunction. Most orthopedic implants pose no risk, but you should always tell the technologist if you have any devices or metal in your body. Guidelines about eating and drinking before your exam vary between facilities. Unless you are told otherwise, take your regular medications as usual. Tell your doctor about any medications you’re taking, including aspirin and herbal supplements, and whether you have any allergies – especially to anesthesia. You will be advised to stop taking aspirin or blood thinner three days before your procedure. Wear loose, comfortable clothing and leave jewelry at home. You may be asked to wear a gown. If you are to be sedated, plan to have someone drive you home afterward.

What is MR-Guided Breast Biopsy?




In MRI-guided breast biopsy, magnetic resonance imaging is used to help guide the radiologist's instruments to the site of the abnormal growth.

What are some common uses of the procedure?

An MRI-guided breast biopsy is most helpful when MR imaging shows a breast abnormality such as:

  • a suspicious mass not identified by other imaging techniques
  • an area of distortion
  • an area of abnormal tissue change

MRI guidance is used in four biopsy procedures:

  • fine needle aspiration (FNA), which uses a very small needle to extract fluid or cells from the abnormal area.
  • core needle (CN) which uses a large hollow needle to remove one sample of breast tissue per insertion.
  • wire localization, in which a guide wire is placed into the suspicious area to help the surgeon locate the lesion for surgical biopsy.

How should I prepare?






Prior to a needle biopsy, you should report to your doctor all medications that you are taking, including herbal supplements, and if you have any allergies, especially to anesthesia. Your physician may advise you to stop taking aspirin, blood thinners, or certain herbal supplements three to five days before your procedure to decrease your risk of bleeding.



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 does the equipment look like?




The majority of MRI-guided breast biopsies are currently performed in closed MRI systems with a specially modified exam table. This moveable examination table allows your breasts to hang freely into cushioned openings, which contain wire coils that send and receive radio waves to help create the MR images.

One of four instruments will be used:

  • A vacuum-assisted device (VAD), a vacuum-powered instrument that uses pressure to pull tissue into the needle.
  • A thin guide wire, which is used for a surgical biopsy.


How does the procedure work?





Using MRI guidance to calculate the position of the abnormal tissue and to verify the placement of the needle, the radiologist inserts the biopsy needle through the skin, advances it into the lesion and removes tissue samples. If a surgical biopsy is being performed, MRI may be used to guide a wire into the mass to help the surgeon locate the area for excision.

How is the procedure performed?

Image-guided, minimally invasive procedures such as MR-guided breast biopsies are most often performed by a specially trained breast radiologist.

Breast biopsies are usually done on an outpatient basis.


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 given intravenously.

Your breast will be gently compressed between two compression plates (similar to those used in a diagnostic MRI exam), one of which is marked with a grid structure. Using computer software, the radiologist measures the position of the lesion with respect to the grid and calculates the position and depth of the needle placement.



The radiologist then inserts the needle, advances it to the location of the abnormality and MR imaging is performed to verify its position. Depending on the type of MRI unit being used, you may remain in place or be moved out of the center or bore of the MRI scanner.

Tissue samples are then removed using one of three methods:


After this sampling, the needle will be removed.

If a surgical biopsy is being performed, a wire is inserted into the suspicious area as a guide for the surgeon.




This procedure is usually completed within 45 minutes.

What will I experience during and after the procedure?




The area will become numb within a few seconds.







Who interprets the results and how do I get them?



What are the benefits vs. risks?


  • MRI-guided breast biopsy using a core needle is considered both safe and accurate.
  • The speed, accuracy and safety of MRI-guided vacuum-assisted breast biopsy are as good as MR-guided wire localization without the associated complications and cost of surgery.
  • Compared with stereotactic biopsy, the MRI-guided method avoids the need for ionizing radiation exposure.
  • MRI-guided breast biopsy, using either the core needle method or the vacuum-assisted device, takes less time than surgical biopsy, causes less tissue damage, and is less costly.



What are the limitations of MRI-Guided Breast Biopsy?

MRI-guided tissue sampling is limited by the position of the abnormality in the breast. Breast lesions located in the back of the breast or small abnormalities can be difficult or impossible to accurately target using MR.


The MR-guided breast biopsy method cannot be used unless the mass can be seen on an MRI exam. Calcifications within a cancerous nodule are not shown as clearly with MR as with x-rays. Small lesions may be difficult to target accurately by MR-guided breast biopsy.

The widespread use of this technique is limited by its high cost, availability, and length of the procedure. MR-guided biopsy should not be considered if the lesion can be seen on mammography or on ultrasound, where the biopsy can be performed more easily with less patient discomfort. In those cases, stereotactic biopsy or ultrasound-guided biopsy are the more appropriate methods of tissue sampling.

Additional Information and Resources Radiation Therapy for Breast Cancer

This page was reviewed on January 25, 2017


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