Radiation force imparted on a kidney stone by a Doppler‐mode diagnostic pulse

Detection of kidney stones and estimation of their sizes is an important part of the lithotripsy treatment. Fluoroscopy is often used to target stones, but not every stone is radio‐opaque and, in addition, fluoroscopy produces ionizing radiation. Acoustic waves offer an alternative way to visualize stones. The acoustic impedance of kidney stones typically differs significantly from that of surrounding tissue. A useful consequence of the impedance mismatch is the possibility to target stones with diagnostic mode ultrasound. Another consequence is that radiation force pushes the stone. Stone displacement may be responsible for the twinkling artifact that has been observed by several authors in color Doppler mode of ultrasound imaging. This effect can be used to detect not only renal and ureteral stones, but also calcifications in other organs (e.g., breast). In this paper we model the radiation force associated with the Doppler diagnostic pulse. The problem is divided into three parts: (1) acoustic scattering; it is solved in finite differences; (2) radiation force calculation; (3) stone velocity estimation supposing the stone sits in soft tissue. [Work supported by NIH DK43881, DK55674, NSBRI SMS00402, and RFBR.]