Parametric imaging of blood perfusion with low-cost diagnostic ultrasound equipment

Developments on ultrasound contrast-specific imaging methods make it possible to detect the deep microvessel and evaluate blood perfusion noninvasively. In this study, we attempt to implement the perfusion parametric imaging to quantitatively assess blood perfusion of organs with the low-cost diagnostic ultrasound equipment. A novel ultrasound contrast imaging method called pulse inversion harmonic sum squared differences (PIHSSD) is proposed, which combines pulse inversion harmonic (PIH) method with pulse inversion sum squared differences (PISSD) method. Time-intensity curves (TICs) in each small region of interest (ROI) are gained from a sequence of PIHSSD images. The perfusion parametric images are acquired based on the parameters estimated from TICs. The perfusion parametric imaging was implemented using the modified diagnostic ultrasound equipment with pulse inversion transmit/receive mode. The flow phantom was used to validate the PIHSSD method for the perfusion parametric imaging, and the results suggested that the PIHSSD method can provide 11.9 to 17.5 dB higher contrast-to-tissue ratio (CTR) than PIH method. The experiments of the kidney of the rabbit were performed while keeping the relative position between transducer and organ basically unchanged during the examination. The results also showed that the CTR of PIHSSD images were higher than that of PIH images. The perfusion parametric images of the kidney of the rabbit were obtained including peak intensity (PI), area under curve (AUC), peak intensity time (PIT) and mean transit time (MTT). It was indicated that the parametric images based on PIHSSD method can possess more accurate assessment for blood perfusion. The perfusion parametric imaging method proposed in this paper can be easily realized on low-cost diagnostic ultrasound equipment and has promise to be widely applied clinically.