Quantitative ultrasound imaging of soft biological tissues: a primer for radiologists and medical physicists

Abstract

Quantitative ultrasound (QUS) aims at quantifying interactions between ultrasound and biological tissues. QUS techniques extract fundamental physical properties of tissues based on interactions between ultrasound waves and tissue microstructure. These techniques provide quantitative information on sub-resolution properties that are not visible on grayscale (B-mode) imaging. Quantitative data may be represented either as a global measurement or as parametric maps overlaid on B-mode images. Recently, major ultrasound manufacturers have released speed of sound, attenuation, and backscatter packages for tissue characterization and imaging. Established and emerging clinical applications are currently limited and include liver fibrosis staging, liver steatosis grading, and breast cancer characterization. On the other hand, most biological tissues have been studied using experimental QUS methods, and quantitative datasets are available in the literature. This educational review addresses the general topic of biological soft tissue characterization using QUS, with a focus on disseminating technical concepts for clinicians and specialized QUS materials for medical physicists. Advanced but simplified technical descriptions are also provided in separate subsections identified as such. To understand QUS methods, this article reviews types of ultrasound waves, basic concepts of ultrasound wave propagation, ultrasound image formation, point spread function, constructive and destructive wave interferences, radiofrequency data processing, and a summary of different imaging modes. For each major QUS technique, topics include: concept, illustrations, clinical examples, pitfalls, and future directions.

Quantitative ultrasonography as a tool for the evaluation of breast tumor response to neoadjuvant chemotherapy

“…Although these images can show some qualitative and quantitative information, most of the information on the microstructure of the tissue is lost. QUS makes it possible to use all information contained in the RF signal (15) . Through the quantitative analysis of RF signals based on, e.g.…”

Association of Backscattered Ultrasonographic Imaging of the Tongue With Severity of Obstructive Sleep Apnea in Adults

“…The backscatter coefficient is the backscatter intensity returned by a tissue within a region of interest, expressed in cm/steradian. 32 As BUI is related to the brightness on grayscale images, it is more sensitive to subtle changes in tissue pathology. Clinical research that has already taken advantage of BUI include noninvasive characterization of the following: (1) carotid arteries, (2) breast cancer cells, 33 (3) pediatric and adult hepatic fat, [34][35][36] (4) cancellous and cortical bone, 27,37,38 and (5) cervical remodeling during pregnancy.…”

“…Specifically, BUI represents the information from ultrasound waves and tissue microstructure. The backscatter coefficient is the backscatter intensity returned by a tissue within a region of interest, expressed in cm/steradian . As BUI is related to the brightness on grayscale images, it is more sensitive to subtle changes in tissue pathology.…”

Implementing the quantitative study of ultrasound imaging of skin

“…The attenuation coefficient has been used to characterize the skin extracting the slope of the attenuation coefficient from backscattered signals. As a complement the backscattering coefficient is used to get microstructural information related to the scatterer diameters, concentrations, shapes, and impedances inside the tissue [31][32][33][34].…”