Current improvements in breast ultrasound, with a special focus on elastography
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- Tohno, E. & Ueno, E. Breast Cancer (2008) 15: 200. doi:10.1007/s12282-008-0052-1
Current improvements in the area of breast ultrasound are described. Digital beam formers contributed to improving both contrast and special resolution of B-mode images and enabled other techniques. Four-dimensinal images and CAD are still in progress. Elastography may reduce false-positives and unnecessary interventional procedures, especially in nonsymptomatic patients.
Breast ultrasound is one of the basic modalities for diagnosing diseases of the breast. In this paper, we discuss recently introduced technologies effective for lesion characterization and describe elastography results obtained in our institute.
B-mode images are fundamental to the analysis of lesion morphology. Of course, it is important to realize that only the ultrasonic characteristics of the lesions can be observed. The introduction of digital beam forming has improved the quality of B-mode images. In digital beam formers, analog/digital conversion is done at the level of the received signals in each element. This has led to advancements in many other techniques, such as digital focusing as well as harmonic imaging, flow imaging, and elastography.
In matrix array transducers, the elements are arranged in a multiple array rather than a single one, and this has resulted in improved resolution in an elevational direction.
Malignant lesions tend to be accompanied by neovascularity, and information about vascular flows in the lesion helps differentiate breast cancers from benign lesions. Because the sensitivity for flow signals has increased, it is possible to detect not only the flow signals of malignant lesions, but also those of benign lesions. To differentiate between these lesions, morphological or quantitative analysis is required . The use of intravenous contrast enhances information regarding vascularity, but the use of new contrast agents that remain in the circulation for longer is not yet permitted for breast lesions by Japanese health insurance.
CAD (computer-aided diagnosis or detection)
Ultrasound examination is commonly performed in real time, and the diagnosis depends on the examiner. To aid diagnosis, CAD is now conducted via the analysis of substantial data . A trial for studying the effectiveness of ultrasound in breast screening is currently underway. If ultrasound is used for screening, whole-breast automatic scanning with CAD may be useful when there is a shortage of staff and for the prevention of erroneous oversight.
Materials and methods
Between April 2005 and March 2006, 1,533 breast ultrasounds were performed in Tsukuba University Hospital. Elastography was subsequently applied in routine ultrasound examinations mainly for lesions that were suspected to be malignant or difficult to diagnose. Elastography images were obtained using a digital ultrasound scanner (EUB-8500; Hitachi Medical, Tokyo, Japan). The elastography scores were judged at the time of examination and noted in the ultrasound reports. We analyzed the data retrospectively, but the elastography scores were determined prospectively. When the same lesions were examined twice or more in the indicated period, the elastography scores obtained in the first examination were used. When multiple masses were observed close to each other, especially in the same quadrant, the largest lesions were selected because one-to-one correspondence with histological results is otherwise difficult. Finally, the objects of this study were 517 lesions in 417 cases.
If the lesions were judged as having score 1, they were not subjected to either additional interventional diagnosis (fine-needle aspiration cytology and/or core biopsy) or follow-up ultrasound examination. So the number of the cases with score 1 that were subjected to interventional diagnosis or follow-up ultrasound after more than 6 months is relatively small and counted to be 70 lesions.
Distribution of each score
No. of lesions (%)
No. of malignant lesions (%)
Summary of the breast cancer cases with score 1
Ultrasound size of the lesion (mm)
Opposite breast cancer postoperative state
Bloody nipple discharge
IDC (predominant intraductal component)
Multiple masses in the same segment
Bloody nipple discharge
Ultrasound equipment that can also be used to conduct real-time elastography is now commercially available, and the manner in which to exploit elasticity data is under discussion. In the previous report, we reported that when a cutoff point between scores 3 and 4 was used, elastography had 86.5% sensitivity, 89.8% specificity, and 88.3% accuracy . Zhi et al.  recently reported even better results: ultrasound elastography was found to be the most specific (95.7%) and had the lowest false-positive rate (4.3%). Elastography scores certainly provide additional information to that provided by B-mode images. In this paper, we analyzed cases in which the elastography score was 1. We focused on score 1 lesions for the following reasons. Ultrasound detects many nonpalpable lesions, and it is less specific when used for breast screening. Elastography may be helpful to obtain additional information based on which we can decide whether we should request the women to return for additional examination. Moreover, in clinical situations, elastography may be useful for determining whether to apply interventional methods or conduct follow-up. In addition, although it is sometimes difficult to differentiate between scores 2 and 3 (because their difference is distribution of blue area), it is easy to judge a lesion as having score 1 because no blue area is observed. In our first report, there were no score 1 lesions, but at that time, the scores were judged by only two persons with experience in elastography. The results provided in this paper were obtained by several examiners who used elastography daily. Our results showed that the elastography score is less helpful in cases of bloody nipple discharge and ductal carcinoma in situ (DCIS) and that very few invasive ductal carcinomas have a score of 1.
Recent improvements in breast ultrasound equipment technology have been overviewed. Breast ultrasound is still being developed further, and this will lead to better diagnosis.