RELATIONSHIP BETWEEN SIZE OF INJECTED MICROSPHERES AND ULTRASOUND IMAGING OF HEART BY PLSR

Purpose. To investigate the enhancement in ultrasound signal (US) in h eart, for diagnostic purposes, as a function of size and number of inj ected air-filled microspheres by multivariate statistical methods. Met hods. The US enhancement in left ventricle was measured after injectio n of 31 suspensions of air-filled albumin microspheres divided on and injected in six dogs. The relationship between the size of microsphere s between 1-38 mu m and the US enhancement was explored by Pearson's p roduct moment correlation analysis, ordinary least-squares regression, principal component regression (PCR) and partial least-squares regres sion (PLS). Results. Relative advanced algorithms such as PCR and PLS were required to achieve accurate in vivo/in vitro correlation. The mo st effective microsphere sizes contributing to US enhancement in left ventricle in dogs were estimated to be in the 7-15 mu m range. Conclus ions. In general, the effective in vivo sizes are dependent on the typ e of formulation due to the surprisingly large active in vivo sizes fo und for the tested concept. PCR and PLS are suitable methods for in vi vo/in vitro correlation, especially for covariated and noisy data.