Improved Estimation of Ultrasound Thermal Strain Using Pulse Inversion Harmonic Imaging
Xuan Ding1, Man M Nguyen2, Isaac B James3
1Department of Bioengineering, University of Pittsburgh School of Engineering, Pittsburgh, Pennsylvania, USA; Medical Scientist Training Program, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, Pennsylvania, USA; Department of Medicine and Heart and Vascular Institute, Center for Ultrasound Molecular Imaging and Therapeutics, University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.
Abstract:
Thermal (temporal) strain imaging (TSI) is being developed to detect the lipid-rich core of atherosclerotic plaques and presence of fatty liver disease. However, the effects of ultrasonic clutter on TSI have not been considered. In this study, we evaluated whether pulse inversion harmonic imaging (PIHI) could be used to improve estimates of thermal (temporal) strain. Using mixed castor oil-gelatin phantoms of different concentrations and artificially introduced clutter, we found that PIHI improved the signal-to-noise ratio of TSI by an average of 213% or 52.1% relative to 3.3- and 6.6-MHz imaging, respectively. In a phantom constructed using human liposuction fat in the presence of clutter, the contrast-to-noise ratio was degraded by 35.1% for PIHI compared with 62.4% and 43.7% for 3.3- and 6.6-MHz imaging, respectively. These findings were further validated using an ex vivo carotid endarterectomy sample. PIHI can be used to improve estimates of thermal (temporal) strain in the presence of clutter.
