Ultrasound-Based Noncontrast Microvascular Imaging for Evaluation of Breast Lesions: Imaging Techniques and Review of Diagnostic Criteria

Abstract

Vascularity plays a pivotal role in the progression of breast lesions and may be associated with their aggressiveness and likelihood of being malignant. Contrast-enhanced imaging techniques are necessary to evaluate vascularity due to the limited sensitivity of conventional color Doppler techniques, in which motion artifacts are eliminated using wall filters. However, in this process, low-flow signals from small vessels also get removed unintentionally. Advancements in technology have revolutionized the way ultrasound images are generated, resulting in tremendous improvements in Doppler imaging techniques. The new, ultrasound-based noncontrast microvascular imaging techniques overcome the limitations of conventional Doppler, and are highly sensitive for detecting microvessels and low flow. The resultant high Doppler sensitivity leads to detection of vascularity in more breast lesions. It is important for radiologists to understand the imaging principles and the clinical implications of the new techniques, to optimally utilize them and aid correct diagnosis. Angio-PLUS is one such recent advancement, which uses unfocused or plane waves and three-dimensional wall filtering to analyze tissue motion in time, space, and amplitude domains that effectively distinguish between blood flow and tissue. The information is beneficial for assessing the lesion vascularity without using contrast. This article aims to explain the Doppler imaging techniques, their clinical applications, scanning methods, and review the common Doppler-based diagnostic criteria used in the evaluation of breast lesions.

Keywords: Angio-PLUS; Doppler imaging; breast cancer; breast lesions; ultrasound-based microvascular imaging.

Fig. 1

Angio-PLUS image showing irregular, disordered vasculature in a malignant mass (histopathological evaluation: malignant phylloides tumor).

Fig. 2

Angio-PLUS image showing marginal vessels in a benign mass (histopathological evaluation: fibroadenoma).

Fig. 3

Color Doppler ( A ) and Angio-PLUS ( B ) images of the same mass (histopathological evaluation: infiltrating ductal carcinoma) demonstrating richer vascularity on Angio-PLUS.

Fig. 4

Color Doppler ( A ) and a Angio-PLUS ( B ) images of a small mass (histopathological evaluation: infiltrating ductal carcinoma) demonstrating the value of Angio-PLUS in showing penetrating vessels.

Fig. 5

Color Doppler images: ( A ) At 4 cm/sec velocity scale showing radial vessel and ( B ) at 2 cm/sec velocity scale showing twisted vessels in the same malignant mass (histopathological evaluation: infiltrating ductal carcinoma).

Fig. 6

Grayscale image ( A ) of a small (5.4 × 5.3 mm size mass) and Angio-PLUS image ( B ) of same mass (histopathological evaluation: infiltrating ductal carcinoma) demonstrating value of Angio-PLUS in showing intralesional vascularity.