Use of Solid Nanoparticles as Contrast Agent for Ultrasound Imaging

The feasibility of using solid nanoparticles as ultrasound contrast agent have been called into question on the ground that the size of a nano-particle is much smaller than the wavelength of ultrasonic wave, therefore, backscattering from these particles will obviously be poor and hence, poor echogenicity would give poor image quality. However, appropriate size metal nanoparticles exhibit some important properties, such as, bio-conjugation and Enhanced Permeability Retention (EPR) effect.

Due to different acoustic impedance of solid nanoparticles than that of the biological tissues, the solid nanoparticles become a better ultrasound contrast agent than that of microbubbles. When solid nanoparticles are exposed to ultrasound waves during imaging they remain stable. In present work, we have synthesized solid nano-particles of gold to study its applications as Ultrasound Contrast Agent (USCA). With existing ultrasound technology, it appears that gold nano-particles of size 10 nm may not be suitable for Ultrasound Contrast Agent (USCA) as it failed to improve image brightness or even image quality. The size of nanoparticles are very small, therefore, it circulate inside the region of interest (human body) for sufficient duration to complete the imaging process.