High Intensity Focused Ultrasound (HIFU) Thermal Lesion Detection Using Local Harmonic Imaging

Local Harmonic Imaging (LHI) is an ultrasound-based method that can detect HIFU thermal lesions. This technique relies on the delivery of an acoustic radiation force to induce localized harmonic oscillations (LHO). LHO are tracked using high frame rate ultrasound imaging. In this study, it was hypothesized that the LHO amplitude for HIFU coagulated tissue is smaller than the LHO amplitude for normal tissue due to changes in the Young’s modulus. LHO amplitudes at three tissue stages were compared in porcine muscle tissue (normal: 6.53± 0.68 µm, 2 minutes HIFU: 5.01± 0.88 µm, and 4 minutes HIFU: 2.96± 0.59 µm). The Young’s moduli at these tissue stages were 11.28± 1.57 kPa, 24.21± 2.66 kPa, and 40.38± 4.38 kPa, respectively. It was concluded that the decrease in the LHO amplitude is proportional to the increase in Young’s modulus. Additionally, a theoretical model that represents the LHI technique was developed and validated.