Ultrasound's Complementary Role in Breast Imaging

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Breast ultrasound is making its mark - namely in characterizing palpable and non-palpable abnormalites found via mammography, determining whether a mass is fluid-filled or solid, guiding biopsies and interventions and examining problems in breast implants. The technology also is breaking new ground in radiation therapy planning, and a study is ongoing as to breast ultrasound's role in boosting breast cancer detection rates.

Current indications for breast ultrasound studies have not changed significantly over the past several years, but advances in equipment technology have enhanced image clarity and improved both diagnostic capability and facilitated interventional procedures. Ultrasound has proven a valuable adjunct to mammography in the diagnosis of breast cancer, particularly for women at high risk of developing the disease who also exhibit dense breast tissue.

USES FOR BREAST ULTRASOUND

Ellen Mendelson, MD, professor in the department of radiology and chief of the breast imaging section at the Feinberg School of Medicine of Northwestern University in Chicago, explains that the practice guidelines of the American College of Radiology dictate specific indications for the use of ultrasound in breast imaging. This imaging modality has proven valuable in the identification and characterization of palpable and non-palpable abnormalities and further evaluation of clinical and mammographic findings. Being able to detect whether a lesion is fluid filled or solid offers the clinician direction about next steps to take in the diagnostic process.

Ultrasound guidance of biopsies and other interventional procedures has proven to be an accurate method of performing these techniques.

William R. Poller, MD, FACR, associate director of the division of breast imaging in the Breast Care Center of Allegheny General Hospital in Pittsburgh, says, "Anytime we see anything on breast ultrasound, we may use a 25 gauge needle to aspirate contents up to an 8 gauge needle for biopsy."  He describes the necessity of being able to visualize the needle and the lesion with a system that is user friendly to facilitate accurate, fast sampling of the area of interest, followed by marking its location for future reference.

Poller uses the Philips Medical Systems iU22 system with a 5 to 12 MHz transducer.  He explains that higher frequencies produce better penetration, with greater detail. He uses power Doppler to examine vascularity of the lesion, and spatial compounding, called SonoCT, to enhance images.

Women with silicon breast implants may develop problems that require imaging visualization. While MRI is helpful in some circumstances, determining if a rupture has occurred outside the capsule is best imaged using ultrasound. Detecting whether a palpable mass is related to a wrinkle or bulge in the implant or an abnormality of the breast tissue is enabled through the use of this imaging technique as well.

A relatively new use of ultrasound involves treatment planning in preparation for radiation therapy. Mendelson explains that when breast conservation surgery has been employed, a fluid-filled area remains in the breast where the tumor was removed. The standard method of radiation therapy is to provide radiation to the entire breast, with a boost to the lumpectomy site. Ultrasound provides guidance about the correct location to deliver a boost of additional radiation for maximum effectiveness.

The last area where ultrasound becomes the imaging modality of choice involves the initial breast imaging technique for young patients under 30, lactating and pregnant patients. This reduces the need for x-ray exposure in this population of patients.

ULTRASOUND AS A SCREENING MODALITY FOR BREAST CANCER?

This spring, the American College of Radiology Imaging Network (ACRIN) in collaboration with the Avon Foundation, launched a multicenter clinical trial designed to evaluate the role of ultrasound as a supplemental screening tool for women with dense breasts as well as increased of developing breast cancer. ACRIN 6666 was first proposed by the principal investigator, Wendie Berg, MD, PhD, a breast imaging consultant at American Radiology Greenspring in Maryland, and was funded in part by the National Cancer Institute with half of the budget being provided by a grant from the Avon Foundation. Mendelson is co-director of this study. (See www.acrin.org/current_protocols.html#A6666)

Berg explains that the double-blind study protocol involves enrolling 2,808 women