Three-Dimensional H-Scan Ultrasound Imaging For Acute Detection Of Breast Cancer Response To Neoadjuvant Treatment - Initial Results Using A Preclinical Animal Model

Abstract Introduction: The use of noninvasive ultrasound (US) for tumor tissue characterization is an exciting prospect for anticancer treatment response monitoring. To that end, our group has developed a new technology termed H-scan US imaging, which links differences in the raw backscattered US signals to various-sized tissue structures. The purpose of this research project was to develop a 3-dimensional (3D) H-scan US imaging system and method for tissue characterization in volume space and evaluate using a preclinical animal model of breast cancer. Methodology: Preliminary studies were conducted using female nude athymic mice (N = 20, Charles River Laboratories) implanted in the mammary fat pad with 1 million breast cancer cells (MDA-MB-231, ATCC). Once tumors reached about 1 cm in size, animals were sorted into four groups so that mean tumor size in each was comparable (N = 5 per group). Animals were then US imaged at baseline and before receiving intraperitoneal injections, namely: (1) 0.3 mg sterile saline (control), (2) 0.2 mg of agnostic TRA-8 monoclonal antibody to human death receptor 5 (DR5) + 0.1 mg sterile saline, (3) 0.1 mg paclitaxel + 0.2 mg sterile saline, and (4) 0.1 mg TRA-8 + 0.2 mg paclitaxel. Image data was acquired using a programmable US scanner (Vantage 256, Verasonics Inc) equipped with a volumetric imaging transducer (4DL7, Vermon) at baseline and again every 24 hours for 3 days. To generate the H-scan US images, a set of Gaussian-weighted Hermite filters were convolved with the radiofrequency (RF) data to measure the relative strength of the received signals. The signal envelope for each of the filtered signal then was calculated using a Hilbert transformation. Finally, the lower frequency backscattered signals were assigned to a red (R) channel and the higher frequency components to a blue (B) channel. The unfiltered original RF signal was assigned to the green (G) channel to complete the RGB colormap and 3D H-scan US image display. After US imaging on day 3, animals were humanely euthanized and tumors excised for histological processing using the TUNEL HRP-DAB assay and immunofluorescent staining for activated caspase-3, PARP1, Ki-67, and DAPI. Results: The in vivo results show that 3D H-scan US imaging is considerably more sensitive to tumor changes after neoadjuvant treatment as compared to traditional B-scan US. While there was no difference at baseline (p = 0.52), repeat H-scan US results from treated tumors exhibited progressive increases in image intensity (164.9 ± 23.4%, 180.29 ± 11.6%, and 229.2 ± 14.6% for groups 2, 3, and 4 at day 3, respectively; p < 0.05) due to cancer cell nuclear condensation and apoptotic activity. Moreover, 3D H-scan US exhibited less variance than planar measurements due to increased sample size and statistical averaging. Histological findings also confirmed increased apoptosis and decreased proliferation that matched H-scan US data trends. Conclusions: 3D H-scan US imaging is a promising technique that allows visualization of the heterogenous tissue microenvironment and improves the evaluation of treatment at an early stage of therapy as validated by histologic findings. Citation Format: Haowei Tai, Shreya Reddy, Jane Song, Mawia Khairalseed, Kenneeth Hoyt. Three-dimensional H-scan ultrasound imaging for acute detection of breast cancer response to neoadjuvant treatment - Initial results using a preclinical animal model [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS3-28.