Attenuation correction in ultrasound contrast agent imaging: elementary theory and preliminary experimental evaluation.

Progress in imaging and quantification of tissue perfusion using ultrasound (US) and microbubble contrast agents has been undermined by the lack of an effective automatic attenuation correction technique. In this article, an elementary model of the US attenuation processes for microbubble contrast enhanced imaging is developed. In the model, factors such as nonlinear bubble scattering, nonlinear attenuation, attenuation to both fundamental and harmonic and the US beam profile are considered. Methods are proposed for fast formation of images with automatic attenuation correction based on the model. In the proposed method, linear tissue echoes are extracted and filtered and then used to compensate for the attenuation in nonlinear bubble echoes at the same location to produce quantities that are a truer representation of bubble concentration. The technique does not require additional measurements and can be implemented in real time. Preliminary experiments on laboratory phantoms consisting of bubbles and tissue-mimicking materials are presented and the effectiveness of the proposed method is supported by improvements in image quality compared with unprocessed data. This development is an important step towards real-time quantitative contrast US imaging.