X marks the spot: Good targeting can guarantee effective breast biopsy

NEW ORLEANS - Whether guided by stereotaxis or ultrasound, the success of a breast biopsy depends very much on accurate targeting, said Dr. Thomas Langer in a presentation at the Breast Imaging Conference on Oct. 7.

Langer, a radiologist at the Susan G. Komen Breast Cancer Center, Baylor University Medical Center in Dallas, outlined the three main areas that radiologists should consider before proceeding with a biopsy: patient selection, needle positioning issues, and, of course, targeting.

"It doesn’t matter whether you do the procedure with the patient prone or upright, or if you use digital or film x-ray, targeting is the same," Langer said. "It’s the single most important factor that allows us to have a successful biopsy."

Patient selection

"There’s really not much involved in patient selection for stereotactic biopsy," Langer said. "We used to get very concerned about which patients could have it and which couldn’t. We were concerned about patients from two aspects: Those patients who were at increased risk for infection and those who were at increased risk for bleeding."

The question of infection shouldn’t be an issue because both the procedure and the breast area are sterile, Langer said. As for bleeding, there is an increased hazard for those patients who are taking anticoagulants. Patients with liver diseases or clotting disorder also can be at risk for increased bleeding.

At his institution, Langer said these patients are approached in one of two ways. If the patient is taking an anticoagulant, he will ask her doctor to take her off the regimen one week prior to the biopsy. If that’s not possible, Langer will ice the patient before and after the procedure to reduce the risk.

"We’ll try to take fewer core pieces so that we will cause less injury to the breast tissue," he said. "We also perform the biopsy using sonographic guidance because that procedure is faster. With stereotactic, by the time you get into position and perform the biopsy, the breast may no longer be cooled down."

Targeting

There are two terms related to biopsy targeting that should be kept in mind. The "throw" or "stroke" is the distance that the needle moves when it is fired. The "stroke margin" is the distance from the image receptor to the tip of the needle after the needle has been fired.

"The stroke margin must always be positive -- greater than zero -- to avoid hitting the receptor," Langer said. "Take it from a man who hit a $200,000 digital imaging receptor with a needle. Your administrator will not look kindly upon this."

Another issue to keep in mind is the sampling site. If a mass is being biopsied, sampling should be done from the center of the mass on both pre-fire and stereo images. If calcifications are the intended target, Langer suggests using one of two strategies: Either zero in on a distinct calcification somewhere near the center and concentrate on that particular calcification, or draw an imaginary line around a cluster and then aim for the center of that cluster.

"When you aim for the center of the lesions and you miss a little, you are still going to be within the lesion," Langer said. "Be very careful when you aim for the margin of the lesion because if you are off a little bit, you may be sampling normal tissue next to it."

Next page: Positioning and removal techniques

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