Elastrography Ultrasound Improves Breast Tumor Classification

The worldwide multicenter study, involving top clinicians in the breast radiology community, is evaluating the clinical benefits of ShearWave elastography in the ultrasonic evaluation of breast lesions.

The study has two objectives: The first is to demonstrate that images obtained using ShearWave elastography are reproducible. The second is to compare ultrasound alone versus the combination of ultrasound and ShearWave Elastography for breast lesion diagnosis. The goal of the latter is to improve lesion classification in categories BI-RADS (Breast Imaging-Reporting and Data System) 3 and BI-RADS 4 in order to better direct patients towards clinical follow-up or biopsy.

"This clinical investigation is the largest trial ever undertaken by an ultrasound imaging company as the recruitment will involve a targeted 2,300 breast lesion cases,” explained Claude Cohen-Bacrie, cofounder and scientific director of SuperSonic Imagine. "Today it is essential to obtain additional information on breast lesions to improve diagnosis. In an era of healthcare reform, being able to reduce the number of biopsies by correctly classifying lesions could save resources and spare women the anxiety and difficulty that surrounds invasive procedures. Better lesion classification also means improved diagnosis, which can lead to quicker and better treatment.”

Ultrasound imaging plays an important role in breast diagnosis. It is used on palpable masses, as a second intention exam after X-ray and magnetic resonance imaging (MRI) scanning, and as a modality of choice to guide biopsy. ShearWave elastography is a revolutionary technology that gives additional, important information about tissue elasticity. Unlike traditional elastography techniques, which rely on manual compression and measure tissue displacement, ShearWave elastography requires no manual compression and calculates true tissue elasticity by measuring the velocity of shear waves as they propagate in tissue. Shear wave propagation speed in tissue is directly related to tissue stiffness. This technology relies upon the generation of a shear wave and its subsequent capture. Shear wave propagation speed is then calculated and a color-coded real time ShearWave elastography map is produced showing tissue stiffness. Results are real-time, user-skill independent, reproducible, and quantifiable in kilopascals. ShearWave elastography is available only on the Aixplorer MultiWave ultrasound system.

A worldwide multicenter breast clinical study was launched in April 2008 with 17 American and European sites including: the Hammersmith Hospital Imperial College (London, UK), the Curie Institute of Paris (France), DKD Wiesbaden (Germany), and the academic hospitals Schleswig-Holstein (Kiel, Germany) and Greifswald (Germany), Yale Medical Center (New Haven, CT, USA), and Northwestern Memorial Hospital (Chicago, IL, USA). The study was conducted under the leadership of Prof. David Cosgrove (Imperial College, London, UK).

The first phase of the study was to define a scientific model on 1,000 cases to determine if ShearWave elastography data can complement ultrasound information in order to improve a diagnosis. To undertake this, it was necessary to identify the criteria of an elastography image that would, when added to ultrasound criteria, improve lesion characterization (in sensitivity and specificity when compared to ultrasound alone) and eventually improve a BI-RADS score. The ShearWave elastography criteria or features studied for each lesion were size, shape, average value of elasticity, homogeneity, orientation, and contrast of elasticity between lesion and fatty tissue.

The second phase of the study will consist of testing this scientific model on an independent set of lesions. This phase is currently ongoing.

The study's findings show that the ShearWave elastographic feature, when added to the ultrasound evaluation, improved the classification of the BI-RADS score of a lesion. The global evaluation is calculated on an analysis of the area under the ROC curve receiver operating characteristic (ROC). The larger the area under the curve, the better the BI-RADS score classification. The clinical results demonstrated that when two ShearWave Elastography features are added to the ultrasound evaluation, correct breast lesion classification rates soar to 87%, thus leading to more accurate results.

Scientifically evaluated, the results of this clinical study therefore demonstrate that ShearWave elastography features, when added to the BI-RADS score significantly improve the specificity and sensitivity of the diagnosis of the lesion. Associated with the BI-RADS score, these features increase the percentage of correctly classified lesions and improve lesion diagnosis.

Historically, ultrasound imaging was considered as an efficient method to differentiate solid lesions from liquid lesions. As a result of research over the last 15 years, ultrasound has become an important technique, with a very high negative predictive value, in the classification of lesions on the BI-RADS scale: 2 (benign) to 5 (highly suggestive of malignancy). The results of this multicenter study, according to the investigators, reveal that ShearWave elastography combined with ultrasound additionally improves lesion classification by significantly raising the percentage of lesions that are correctly classified and increases the specificity in the diagnosis while keeping a high negative predictive value and sensitivity.

Mr. Cohen-Bacrie concluded, "Our clinical objective is to confirm if ShearWave elastography, combined with ultrasound, leads to a more refined lesion classification of BI-RADS 3 and 4 and in turn leads to a better directed patient towards follow-up or biopsy.”

BI-RADS is a quality control system developed by the American College of Radiology (ACR; Reston, VA, USA) to assess breast lesions according to their degree of malignancy. Clinical sites of the study: United States: Denver, CO; Philadelphia, PA; Los Angeles, CA; Boston, MA; Baltimore, MD; Chicago, IL; New Haven, CT; U.K.: London; Italy: Gorizia; France: Paris, Marseille, Nice, Lyon; Germany: Wiesbaden, Osnabrück, Kiel, Greifswald.

SuperSonic Imagine has created, developed, and launched the Aixplorer innovative MultiWave ultrasound system with dedicated breast, thyroid, and abdomen applications. The unique technology developed by the company relies upon the combination of two waves: an ultrasound wave that offers the high quality of B-mode image, and a shear wave (ShearWave elastography).

SuperSonic Imagine holds the exclusive rights to 25 patents and submissions and this ensures the company is at the forefront of the medical imaging market. In addition to diagnostic applications, researchers at SuperSonic Imagine are currently developing ultrasound applications to be used in noninvasive therapy. This method is based on the Time Reversal Mirror technology, set up by Mathias Fink, a cofounder of SuperSonic Imagine.

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