What is a MRI Guided Breast Biopsy?
Lumps or abnormalities in the breast are often detected by physical examination, mammography, or other imaging studies. However, it is not always possible to tell from these imaging tests whether a growth is benign or cancerous. A breast biopsy is performed to remove some cells—either surgically or through a less invasive procedure involving a hollow needle—from a suspicious area in the breast and examine them under a microscope to determine a diagnosis. Image-guided needle biopsy is not designed to remove the entire lesion, but most of a very small lesion may be removed in the process of biopsy. Image-guided biopsy is performed by taking samples of an abnormality under some form of guidance such as ultrasound, MRI or mammographic guidance. 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 to Expect?
The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. You will lie on a movable examination table that slides into the center of the magnet. One of four instruments will be used:
•A fine needle attached to a syringe, smaller than needles typically used to draw blood.
•A core needle, also called an automatic, spring-loaded needle, which consists of an inner needle connected to a trough, or shallow receptacle, covered by a sheath and attached to a spring-loaded mechanism.
•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.
Unlike conventional x-ray examinations and computed tomography (CT) scans, MRI does not depend on ionizing radiation. Instead, while in the magnet, radio waves redirect the axes of spinning protons, which are the nuclei of hydrogen atoms. The magnetic field is produced by passing an electric current through wire coils in most MRI units. Other coils, located in the machine and in some cases, placed around the part of the body being imaged, send and receive radio waves, producing signals that are detected by the coils. A computer then processes the signals and generates a series of images, each of which shows a thin slice of the body. The images can then be studied from different angles by the interpreting radiologist. Frequently, the differentiation of abnormal (diseased) tissue from normal tissues is better with MRI than with other imaging modalities such as x-ray, CT and ultrasound. 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.
Patient Preparation
Wear a gown during the exam or you may be allowed to wear your own clothing if it is loose-fitting and has no metal fasteners. Guidelines about eating and drinking before an MRI exam vary with the specific exam and also with the facility. Unless you are told otherwise, you may follow your regular daily routine and take food and medications as usual.
Some MRI examinations may require the patient to receive an injection of contrast material into the bloodstream. The radiologist or 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. The contrast material most commonly used for an MRI exam is called gadolinium. Because gadolinium does not contain iodine, it can be used safely in patients with contrast allergies.
The radiologist should also know if you have any serious health problems, or if you have recently had surgery. Some conditions, such as severe kidney disease may prevent you from being given contrast material for an MRI. If there is a history of kidney disease, it may be necessary to perform a blood test to determine whether the kidneys are functioning adequately.