Ultrasound is an accepted tool in the imaging of breast cancer.  The use of breast ultrasound is well established preoperatively and in interventional procedures.

In addition to mammography, sonography increases sensitivity for breast cancer detection especially in dense breasts.

Ultrasound is not yet a routine part of screening programs but is accepted in intensified programs for breast cancer detection in high risk women. In contrast to mammography, sonography is an examiner-dependent method and the examiner has to be present at the time of image acquisition. As a consequence, breast sonography is difficult to realize in a screening setting or in regions with low population density. In these cases an automated ultrasound system where the images are acquired by a technician and sent to specialists for evaluation could be helpful.

In our study we wanted to evaluate whether breast lesions could be detected and classified by independent radiologists with an automated breast ultrasound system (ABUS; SomoVu U-Systems, Inc., San Jose, CA, USA; EC Representative: Siemens AG, Medical Solutions, Erlangen, Germany) in comparison to handheld ultrasonography (HHUS).

Between June 11 and July 11, 2007, patients were selected for the study who were admitted for further work-up of unclear findings in breast diagnosis: palpable mass (n = 6), suspicious ultrasound (n = 6) and mammographical mass or density in the course of opportunistic screening performed elsewhere (n = 23).  Patients who were sent for further work-up of suspicious microcalcifications were excluded. All patients gave oral consent to the application of the ABUS.

A radiographer (RA) was trained how to perform the ABUS in five random patients who were not included in the study. She had no knowledge of the study patients. clinical history and mammography but was told by the radiologist which breast to scan. Depending on her subjective impression of the whole breast volume, the RA performed two or three views of the affected breast. ABUS images were acquired with the patient in supine position. The breasts were scanned with an 8MHz highfrequency linear transducer with an aperture of 14.5cm that is built in a rigid frame. The axial resolution for the 8MHz transducer is 0.4mm and the lateral resolution is 0.8mm. To minimize contact artifacts, the scanner frame is covered by a compressive polyester film sheet. Ultrasound gel is homogeneously distributed between the polyester film sheet and the patient.s skin. Handheld ultrasonography (HHUS) was performed with a 13MHz scanner (Antares Siemens, Erlangen, Germany) by one breast radiologist who had knowledge of each patient.s clinical history and mammography at the time of the examination.

Lesions detected with the ABUS or HHUS were classified according to the Breast Imaging Reporting and Data System (BI-RADS).  Lesions that were assessed as BI-RADS 4 or 5 lesions with the HHUS received histological or cytological work-up.

Five radiologists evaluated the ABUS independently without knowing the clinical findings and the results of the other imaging modalities. Their experience in breast sonography totaled 60, 24, 18, 6 and 6 months.

The images were analyzed on a separate viewing station with the cine function in three different planes (axial scanning plane, coronal and sagittal reconstructions).

The radiologists independently evaluated the ABUS according to the following criterion: Is a lesion detectable? If yes, the lesion was classified according to BI-RADS. The results were compared to the ones of HHUS and to histology. The concordance of BI-RADS classification with HHUS and the ABUS evaluation of each examiner was calculated with the Cohan.s Kappa test.