Harmonic motion imaging for abdominal tumor detection and high-intensity focused ultrasound ablation monitoring: an in vivo feasibility study in a transgenic mouse model of pancreatic cancer

Abstract

Harmonic motion imaging (HMI) is a radiation force-based elasticity imaging technique that tracks oscillatory tissue displacements induced by sinusoidal ultrasonic radiation force to assess relative tissue stiffness. The objective of this study was to evaluate the feasibility of HMI in pancreatic tumor detection and high-intensity focused ultrasound (HIFU) treatment monitoring. The HMI system consisted of a focused ultrasound transducer, which generated sinusoidal radiation force to induce oscillatory tissue motion at 50 Hz, and a diagnostic ultrasound transducer, which detected the axial tissue displacements based on acquired radiofrequency signals using a 1D cross-correlation algorithm. For pancreatic tumor detection, HMI images were generated for pancreatic tumors in transgenic mice and normal pancreases in wild-type mice. The obtained HMI images showed a high contrast between normal and malignant pancreases with an average peak-to-peak HMI displacement ratio of 3.2. Histological analysis showed that no tissue damage was associated with HMI when it was used for the sole purpose of elasticity imaging. For pancreatic tumor ablation monitoring, the focused ultrasound transducer was operated with a higher acoustic power and longer pulse length than that used in tumor detection to simultaneously induce HIFU thermal ablation and oscillatory tissue displacements, allowing HMI monitoring without interrupting tumor ablation. HMI monitoring of HIFU ablation found significant decreases in the peak-to-peak HMI displacements before and after HIFU ablation with a reduction rate ranging from 15.8% to 57.0%. The formation of thermal lesions after HIFU exposure was confirmed by histological analysis. This study demonstrated the feasibility of HMI in abdominal tumor detection and HIFU ablation monitoring.

Elasticity mapping of murine abdominal organsin vivousing harmonic motion imaging (HMI)

“…These measurements were also significantly lower than the ones obtained in low fibrotic groups. Previous reports by our group (Chen et al 2015a) also reported that the feasibility of this technique for in vivo tumor detection in the same PDA murine model with similar results. Normal pancreas showed HMI displacement 3.2 times higher than malignant pancreas.…”

“…This work shows that HMI can answer the need for an elastography technique for screening and small animal studies due to its low cost, efficient noise filtering and deep penetration. Moreover, previous work showed that the short duration of the acoustic exposure (0.2 s) prevents any damage to the tissue (Chen et al 2015a). …”

High-intensity focused ultrasound monitoring using harmonic motion imaging for focused ultrasound (HMIFU) under boiling or slow denaturation conditions

“…Ongoing efforts include translating the acquisition sequences presented herein onto the recently developed 2D platform [67] in order to perform multi-dimensional and parametric studies, such as real-time mapping of the focal cavitation response as well as quantitative mapping of depth-dependent attenuation change during HIFU [68]. Other application-specific ongoing studies include HMIFU monitoring assessment in pathological tissues such as breast [69] and pancreatic tumors detection and monitoring in vivo [70]. …”

Elastographic Assessment of Xenograft Pancreatic Tumors

“…Despite these encouraging results, endoscopic ultrasound elastography is invasive and currently only available on one commercially available system, Hitachi’s EUB-8500 system. To overcome these issues, Chen et al (2015) determined that non-invasive elastographic techniques like harmonic motion imaging could also improve the differential diagnosis of pancreatic cancer.…”