Breast imaging researchers seek ultrasound-friendly compression

May 4, 1994

Paddle should improve x-ray/ultrasound correlationResearchers at the Indianapolis Breast Center are trying to makeit easier for sonographers to compare x-ray mammograms with breastultrasound images. Their work could eventually result in a

Paddle should improve x-ray/ultrasound correlation

Researchers at the Indianapolis Breast Center are trying to makeit easier for sonographers to compare x-ray mammograms with breastultrasound images. Their work could eventually result in a safeand effective way to use ultrasound to screen younger women forbreast cancer.

During a presentation at the American Institute of Ultrasoundin Medicine meeting in March, Dr. Elizabeth Kelly-Fry discussedthe center's progress in developing an ultrasound-friendly compressionpaddle that could help standardize positioning during mammographyand breast ultrasound studies.

Breast compression has been an important aspect of x-ray mammographysince the introduction of the first dedicated mammography devices.Compression immobilizes the breast, creating a uniform breastthickness that evens out x-ray penetration. Compression also reducesx-ray dosage and increases the contrast of mammograms.

Sonographers conducting ultrasound breast imaging have beenunable to use compression, however, because standard mammographypaddles attenuate ultrasound signals and cause multiple echoesthat create image artifacts.

Sonographers thus face a dilemma when correlating their imageswith those of mammograms because compression is used with onemodality and not the other. As a result, internal breast tissueis oriented differently on an ultrasound exam than on a mammogram.

In addition, most breast ultrasound studies are conducted withthe woman supine, which also contributes to changes in the orientationof internal breast tissue when compared to mammograms acquiredwhile she is standing up.

The Indianapolis Breast Center researchers are trying to overcomethe attenuation obstacle by developing a breast compression paddlethat will permit the transmission of ultrasound signals. At theAIUM meeting, Dr. Kelly-Fry presented the center's latest workon the paddles.

Dr. Kelly-Fry and her colleagues are using materials developedat Indiana University that permit the transmission of ultrasoundsignals without significant attenuation or creation of artifacts.Due to patent considerations, she did not disclose the compositionof the materials.

Indianapolis Breast Center researchers fabricated two compressionpaddles and retrofitted them onto a Bennett X-ray Contour mammographyunit. Patients were scanned through the paddles using an AcousticImaging AI 5200 B scanner and a 7.5-MHz transducer.

Dr. Kelly-Fry displayed images acquired with the compressiontechnique during her AIUM presentation. Breast compression conferreda number of advantages: ** By flattening breast tissue, sonographerswere able to use high-frequency transducers with better imageresolution;

** Manual scanning times were reduced because the transduceris easily traced across the surface of the paddle;

** The scanning process could be automated easily by developinga device that sweeps the transducer across the paddle mechanically;and

** The approach can image the breast in two additional viewsas well as the standard mediolateral and craniocaudal positions.

More importantly, the ultrasound images acquired with the techniquedisplay breast tissue in exactly the same orientation as in amammogram, making it easier for sonographers to match images whenlocalizing suspicious lesions.

"There is no question that ultrasound is very valuable,but it takes considerable expertise to correlate the data betweenthe modalities," Dr. Kelly-Fry said. "This techniquecan be used to make certain sonographers are looking at the sameinternal area of the breast in both images."

Dr. Kelly-Fry emphasized that clinical research on the techniqueis still in early stages. Dr. Patricia Harper, director of thebreast center, recently implemented a study to prove the utilityof the technique.

The center has stripped out the x-ray components from an oldermammography unit and replaced them with the experimental compressionpaddles. Clinicians wheel an ultrasound scanner up to the devicefor exams. The center will use a 10-MHz flat linear-array transducerrecently released by Acoustic Imaging to conduct the studies.

The researchers will scan two groups of women. The first groupconsists of women who have received an x-ray mammogram and havebeen referred for breast ultrasound. The researchers will conductboth conventional breast ultrasound as well as the compressedtechnique and will compare the two images.

The other group will consist of younger women who would notbe getting x-ray mammography because of their age, generally under40, but who have been scheduled for clinical ultrasound studiesto examine suspicious lumps. Again, the results of the conventionalultrasound technique will be compared to the compression approach.

The researchers do not have a corporate sponsor for their workbut are hoping to secure a grant from the National Cancer Institute.

In addition to improving breast image correlation, the IndianapolisBreast Center researchers hope that eventually the technique canlead to an ultrasound screening device for younger women, whohave dense breasts that are not easily visualized with x-ray mammography.

"My interest is to develop this technique so that it wouldbe appropriate to do screening," Dr. Kelly-Fry said. "Atthe present time, there is no screening available for young womenother than palpation. This technique would be effective and safefor screening young women."