Geometric distortion of area in medical ultrasound images

Abstract

Medical ultrasound scanners are typically calibrated to the soft tissue average of 1540 m s −1 . In regions of different sound speed, for example organs and tumours, the B-mode image then becomes a distortion of the true tissue cross-section, due to the misrepresentation of length and refraction. We develop a ray model to predict the geometrical distortion of a general elliptical object with atypical speed of sound, and quantify the ensuing image distortion as a function of the key parameters, including the speed of sound mismatch, the object size and its elongation. Our findings show that the distortion of area can be significant, even for relatively small speed of sound mismatches. Our findings are verified by ultrasound imaging of a test object.

Fabrication and Characterization of Tissue-Mimicking Phantoms for Ultrasound-Guided Cannulation Training

“…Moreover, the visible artifacts and geometric distortion in sil-iocne10 D might be due to the discrepancies between the SOS in water versus silicone which can cause high refraction of sound waves at the boundary and result in misinterpretation of the length of an object and thus, distorted images. [38][39][40] The varying brightness in PVA scans might be due to the physical crosslinking and consequent crystal formation in the polymer bulk dependent on the applied FTCs. 30 Meanwhile, varying the applied FTCs did not significantly affect the quality of the generated scans, neither did it affect the pixel gray values, which agrees with previous work reporting a 1.4% increase in the SOS values between FTC1 to FTC5.…”