Ultrasonic Elasticity Imaging as a Tool for Breast Cancer Diagnosis and Research

Abstract

Ultrasonic elasticity imaging is a promising new tool for breast cancer diagnosis and management. Ultrasound is applied to sense small local tissue deformations noninvasively to image stiffness and thus exploit the large intrinsic stiffness contrast generated during the progression of many diseases in vivo. This paper briefly reviews several related approaches to breast elasticity imaging to explain some of the observed variability in breast imaging results. Preliminary clinical results from a population of 13 patients with small and nonpalpable breast lesions obtained with a low noise elasticity imaging algorithm developed in our group are then reported. All the benign lesions exhibited normal elasticity ranges. About half of the malignant lesions were undetected with elasticity imaging most likely because of their small size (<7mm) or softening from the addition of fatty-replaced tissue. Other malignant lesions were clearly identified as areas with extreme elasticity values compared to their surroundings. We observed that some malignant lesions did not exhibit any desmoplasic stiffening while others showed an uncommon softening. It is clear that by broadening the study population to include small and nonpalpable lesions, we see much variability in elasticity image findings.

Viscoelasticity imaging using ultrasound: parameters and error analysis

“…No significant differences were found for acquisition times <90 s indicating that the linear term can be ignored. This is the range of most clinical imaging (Pellot-Barakat et al 2006). We assumed a first-order discrete model for these gelatin phantom measurements, resulting in stable T 1 values for 20 s ≤ T a ≤50 s and biased estimates for longer acquisition times (figure 8).…”

“…For example, at the lowest stress frequencies in the stimulus bandwidth of quasi-static elasticity imaging, elastic strain images can be formed that can be valuable for differentiating benign and malignant palpable breast masses (Garra et al 1997, Hall et al 2003. However, recent studies on earlystage non-palpable masses show that elastic strain can also be non-specific for cancer (Lorenzen et al 2003, Insana et al 2004, Pellot-Barakat et al 2006. In those cases, lesion discriminability may be enhanced by adding strain information from slightly higher stress stimulus frequencies; e.g., by imaging viscoelastic features from time-varying strain following a compress-hold-release stress stimulus.…”

A novel haptic robotic viscogram for characterizing the viscoelastic behaviour of breast tissue in clinical examinations

“…Since viscoelastic properties also reflect normal and diseased tissue types in addition to tissue elasticity, detecting these parameters may improve the accuracy of the diagnosis (10,11). The strain contrast of the lesion can be a nonspecific indicator, as it varies appreciably depending on the local tissue environmental factors (12). For example, malignant tumours decrease proteoglycan production in stromal collagen relative to benign lesions (13), which causes noticeable variation in the viscoelastic properties of the tissue.…”

Elasticity Imaging of Polymeric Media

“…The question of interpreting VE parameters for images obtained during large, nonlinear deformations is open [54]. Anecdotal evidence from imaging [17,24] shows there is little change in contrast even for large compressions where nonlinear responses are clearly expected. While interpretation of parameters in terms of polymer structure may require linearity, detection of features in imaging based on contrast may not.…”

“…Stiffening is common because of edema, cellular hyperplasia, and characteristic increases in stromal collagen concentration and cross-linking. However, cancers can also appear softer than the background tissue [17] because the magnitude, spatial homogeneity, and temporal variation of the strain response depend on the physiology [18] and tumor microenvironment [6] of a specific patient. In addition, images of viscoelastic features show both lower [19] and higher [2,3] respondance times for malignant masses as compared to benign masses.…”