Expressiveness of temperature-induced changes in backscattered energy in conventional B-mode images

Abstract

Changes on conventional B-Mode images have been correlated with temperature, aiming to develop a reliable method for non-invasive temperature estimation. The assumption is that temperature variations induce wave propagation changes that modify the backscattered ultrasound signal and these changes have an expression in ultrasonographic images. One of the main effects is the change on the image intensity that is mainly caused by temperature-related changes in backscattered energy (CBE) from tissue inhomogeneities. It is reported that CBE is dependent on medium speed-of-sound and density, behaving in different ways for lipid or aqueous scatterers. In this paper we demonstrate that CBE has an expression on B-mode images recorded from conventional ultrasound scanners. We observed that different regions have positive, negative or undefined correlations with temperature, and that this behavior is due to the dependence of CBE with scatterers type. This differentiated behavior enables the segmentation of different structures inside the same tissue. Our experimental setup consisted in the temperature elevation from 36 to 44 °C (hyperthermia range) of ex-vivo tissue samples. We considered bovine muscle and porcine muscle and fat. For both samples we observed coherent segmentations of the different structures, pointing for a potential clinical application of the proposed analysis. © 2013 Acoustical Society of America.