Automated Whole Breast Ultrasound

A Review of Supplemental Screening Ultrasound for Breast Cancer: Certain Populations of Women with Dense Breast Tissue May Benefit

Breast density has been shown to be a strong, independent risk factor for breast cancer. Unfortunately, mammography is less accurate on dense breast tissue compared to fattier breast tissue. Multiple studies suggest a solution to this by demonstrating the ability of supplemental screening ultrasound to detect additional malignant lesions in women with dense breast tissue but negative mammography. In particular, supplemental screening ultrasound may be beneficial to women with dense breast tissue and intermediate or average risk for breast cancer, women in specific ethnic populations with greater prevalence of dense breast tissue, and women living in resource-poor healthcare environments. Although magnetic resonance imaging is currently recommended for women with high risk for breast cancer, not all women can access or tolerate a magnetic resonance imaging examination. Notably, ultrasound does not require intravenous gadolinium and may be an alternative for women with socioeconomic or medical restrictions, which limit their access to magnetic resonance imaging. Limitations of supplemental screening ultrasound include a substantial rate of false-positives, increased cost, and limited resource availability, particularly in regard to the time required for image interpretation. Additional clinical experience with this application of ultrasound, improved patient selection criteria, and new technology, such as the promising results seen with automated whole breast ultrasound, may address these limitations. In light of recent legislation in some states that has called for discussing supplemental imaging with patients who have dense breast tissue, the optimal role for supplemental screening ultrasound merits further exploration.

Automated Breast Ultrasound: Dual-Sided Compared with Single-Sided Imaging

The design and performance of a mammographically configured, dual-sided, automated breast ultrasound (ABUS) 3-D imaging system are described. Dual-sided imaging (superior and inferior) is compared with single-sided imaging to aid decisions on clinical implementation of the more complex, but potentially higher-quality dual-sided imaging. Marked improvement in image quality and coverage of the breast is obtained in dual-sided ultrasound over single-sided ultrasound. Among hypo-echoic masses imaged, there are increases in the mean contrast-to-noise ratio of 57% and 79%, respectively, for spliced dual-sided versus superior or inferior single-sided imaging. The fractional breast volume coverage, defined as the percentage volume in the transducer field of view that is imaged with clinically acceptable quality, is improved from 59% in both superior and inferior single-sided imaging to 89% in dual-sided imaging. Applying acoustic coupling to the breast requires more effort or sophisticated methods in dual-sided imaging than in single-sided imaging.

In situ validation of VEGFR-2 and α v ß 3 integrin as targets for breast lesion characterization

Vascular endothelial growth factor receptor 2 (VEGFR-2) and α v ß 3 integrin are the most frequently addressed targets in molecular imaging of tumor angiogenesis. In preclinical studies, molecular imaging of angiogenesis has shown potential to detect and differentiate benign and malignant lesions of the breast. Thus, in this retrospective clinical study employing patient tissues, the diagnostic value of VEGFR-2, α v ß 3 integrin and vascular area fraction for the diagnosis and differentiation of breast neoplasia was evaluated. To this end, tissue sections of breast cancer (n = 40), pre-invasive ductal carcinoma in situ (DCIS; n = 8), fibroadenoma (n = 40), radial scar (n = 6) and normal breast tissue (n = 40) were used to quantify (1) endothelial VEGFR-2, (2) endothelial α v ß 3 integrin and (3) total α v ß 3 integrin expression, as well as (4) the vascular area fraction. Sensitivity and specificity to differentiate benign from malignant lesions were calculated for each marker by receiver operating characteristics (ROC) analyses. Whereas vessel density, as commonly used, did not significantly differ between benign and malignant lesions (AUROC: 0.54), VEGFR-2 and α v ß 3 integrin levels were gradually up-regulated in carcinoma versus fibroadenoma versus healthy tissue. The highest diagnostic accuracy for differentiating carcinoma from fibroadenoma was found for total α v ß 3 integrin expression (AUROC: 0.76), followed by VEGFR-2 (AUROC: 0.71) and endothelial α v ß 3 integrin expression (AUROC: 0.68). In conclusion, total α v ß 3 integrin expression is the best discriminator between breast cancer, fibroadenoma and normal breast tissue. With respect to vascular targeting and molecular imaging of angiogenesis, endothelial VEGFR-2 appeared to be slightly superior to endothelial α v ß 3 for differentiating benign from cancerous lesions.

Early prediction of pathological outcomes to neoadjuvant chemotherapy in breast cancer patients using automated breast ultrasound

OBJECTIVE

Early assessment of response to neoadjuvant chemotherapy (NAC) for breast cancer allows therapy to be individualized. The optimal assessment method has not been established. We investigated the accuracy of automated breast ultrasound (ABUS) to predict pathological outcomes after NAC.

METHODS

A total of 290 breast cancer patients were eligible for this study. Tumor response after 2 cycles of chemotherapy was assessed using the product change of two largest perpendicular diameters (PC) or the longest diameter change (LDC). PC and LDC were analyzed on the axial and the coronal planes respectively. Receiver operating characteristic (ROC) curves were used to evaluate overall performance of the prediction methods. Youden's indexes were calculated to select the optimal cut-off value for each method. Sensitivity, specificity, positive and negative predictive values (PPV and NPV) and the area under the ROC curve (AUC) were calculated accordingly.

RESULTS

ypT0/is was achieved in 42 patients (14.5%) while ypT0 was achieved in 30 patients (10.3%) after NAC. All four prediction methods (PC on axial planes, LDC on axial planes, PC on coronal planes and LDC on coronal planes) displayed high AUCs (all>0.82), with the highest of 0.89 [95% confidence interval (95% CI), 0.83-0.95] when mid-treatment ABUS was used to predict final pathological complete remission (pCR). High sensitivities (85.7%-88.1%) were observed across all four prediction methods while high specificities (81.5%-85.1%) were observed in two methods used PC. The optimal cut-off values defined by our data replicate the WHO and the RECIST criteria. Lower AUCs were observed when mid-treatment ABUS was used to predict poor pathological outcomes.

CONCLUSIONS

ABUS is a useful tool in early evaluation of pCR after NAC while less reliable when predicting poor pathological outcomes.

Current status of automated breast ultrasonography

Breast ultrasonography (US) is currently considered the first-line examination in the detection and characterization of breast lesions. However, conventional handheld US (HHUS) has several limitations such as operator dependence and the requirement of a considerable amount of radiologist time for whole-breast US. Automated breast US (ABUS), recently approved by the United States Food and Drug Administration for screening purposes, has several advantages over HHUS, such as higher reproducibility, less operator dependence, and less required physician time for image acquisition. In addition, ABUS provides both a coronal view and a relatively large field of view. Recent studies have reported that ABUS is promising in US screening for women with dense breasts and can potentially replace handheld second-look US in a preoperative setting.

The evolution of breast imaging: past to present

The practice of breast imaging has transitioned through a wide variety of technologic advances from the early days of direct-exposure film mammography to xeromammography to screen-film mammography to the current era of full-field digital mammography and digital breast tomosynthesis. Along with these technologic advances, organized screening, federal regulations based on the Mammography Quality Standards Act, and the development of the American College of Radiology Breast Imaging Reporting and Data System have helped to shape the specialty of breast imaging. With the development of breast ultrasonography and breast magnetic resonance imaging, both complementary to mammography, additional algorithms for diagnostic workup and screening high-risk subgroups of women have emerged. A substantial part of breast imaging practice these days also involves breast interventional procedures-both percutaneous biopsy to obtain tissue diagnosis and localization procedures to guide surgical excision. This article reviews the evolution of breast imaging starting from a historical perspective and progressing to the present day.