Harmonic Ultrasound Improves Characterization of Breast Cysts

SEATTLE-Harmonic ultrasound (US) imaging may obviate the need to biopsy breast cysts that cannot be satisfactorily diagnosed on conventional (fundamental) ultrasound imaging, according to a study from University Health Network, Mt. Sinai Hospital, Toronto. Supriya Kulkarni, MD, a fellow at Mt. Sinai Hospital, presented the findings at the 101st Annual Meeting of the American Roentgen Ray Society (ARRS).

"Coded harmonics is a new technique now available on high-frequency linear transducers," Dr. Kulkarni said. Unlike traditional harmonic imaging, coded harmonic imaging completely preserves the second harmonic frequency band, she explained.

At left, a conventional ultrasound image of a breast cyst considered indeterminate. At right, the same cyst as seen in a coded harmonic ultrasound image obtained from the identical position. Images were obtained with a stationary 7-MHz linear transducer. Ultrasound images courtesy of Dr. Supriya Kulkarni, University Health Network, Mt. Sinai Hospital, Toronoto Canada.

Coded harmonic imaging also has increased sensitivity to weak harmonic signals, produces wideband resolution, and suppresses artifacts caused by fundamental imaging. As a result, she said, coded harmonic images can provide good detail and high resolution of target lesions.

Breast cysts often pose a diagnostic dilemma, Dr. Kulkarni noted. Simple cysts with hemorrhagic content may have worrisome features on conventional ultrasound. Conversely, solid breast nodules, including some malignancies, can mimic breast cysts on ultrasound. "There is a clear need for a modality that better visualizes and characterizes suspected cysts," she said.

The study included 117 image pairs from 30 consecutive patients with indeterminate cysts on conventional imaging. Each pair consisted of a conventional image and a harmonic image obtained from identical positions with a stationary 7-MHz linear transducer (see Figure). Indeterminate cysts were defined as cysts with internal echoes, ill-defined walls, or poor posterior enhancement.

For each image, two blinded reviewers assessed the cyst wall definition, cyst lumen (based on the presence of internal echoes), and posterior acoustic enhancement on 4-point scales. The reviewers later compared the image pairs side by side in a preference study.

Compared with conventional imaging, harmonic imaging produced a mean grade improvement in cyst wall definition in 42.7% of cases; in cyst lumen in 36.8% of cases; and in acoustic enhancement in 44.4% of cases, Dr. Kulkarni said.

In the preference study, the reviewers judged harmonic images superior to the corresponding conventional images for cyst characterization in 80% of image pairs. The cysts that were identified as simple cysts on harmonic imaging are being followed clinically, she said.

"Coded harmonic imaging improves characterization of breast cysts that are considered indeterminate on fundamental imaging," Dr. Kulkarni concluded. "This is particularly so for small cysts in the near field of the transducer or those deeply situated in the posterior third of the breast."

The availability of harmonic imaging on linear transducers makes it simple for sonographers to switch modalities, she explained. "In our institution, we use harmonic imaging on almost every case," she said. "It is available at the switch of a button. You just hit ‘Harmonic’ when you think you need to determine whether it is a cyst or not."

Improved characterization of cysts may spare some patients an unnecessary procedure. "Harmonic imaging will help in reducing the need for unnecessary fine-needle aspiration biopsy," Dr. Kulkarni concluded.