Results suggests that future applications utilizing ultrasound imaging to monitor tumor response to therapy may be able to provide earlier insight into tumor behavior from metrics of microvascular density rather than anatomical tumor size measurements.

Noninvasive in vivo imaging technologies enable researchers and clinicians to detect the presence of disease and longitudinally study its progression. By revealing anatomical, functional, or molecular changes, imaging tools can provide a near real-time assessment of important biological events. At the preclinical research level, imaging plays an important role by allowing disease mechanisms and potential therapies to be evaluated noninvasively. Because functional and molecular changes often precede gross anatomical changes, there has been a significant amount of research exploring the ability of different imaging modalities to track these aspects of various diseases. Herein, we present a novel robotic preclinical contrast-enhanced ultrasound system and demonstrate its use in evaluating tumors in a rodent model. By leveraging recent advances in ultrasound, this system favorably compares with other modalities, as it can perform anatomical, functional, and molecular imaging and is cost-effective, portable, and high throughput, without using ionizing radiation. Furthermore, this system circumvents many of the limitations of conventional preclinical ultrasound systems, including a limited field-of-view, low throughput, and large user variability.

A cost-effective method for serial in vivo imaging of tumor microvasculature has been developed.We evaluated acoustic angiography (AA) for visualizing and assessing non-small cell lung tumor (A549) microvasculature in mice prior to and following tumor vascular disruption by vasculartargeted gold nanoparticles (GNPs) and radiotherapy. Standard B-mode and microbubbleenhanced AA images were acquired at pre-and post-treatment time points. Using these modes, a new metric, 50% Vessel Penetration Depth (VPD 50 ) was developed to characterize the 3D spatial heterogeneity of microvascular networks. We observed an increase in tumor perfusion after radiation-induced vascular disruption, relative to control animals. This was also visualized in vessel morphology mode, which showed a loss in vessel integrity. We found that tumors with poorly perfused vasculature at day 0 exhibited a reduced growth rate over time. This suggested a new method for reducing in-group treatment response variability by using pre-treatment microvessel maps to objectively identify animals for study removal.

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This study presents a novel dual-modality imaging system for assessing cancer progression in rodents. The system incorporates bioluminescence imaging (BLI), used to assess tumor growth, and contrast-enhanced ultrasound (CEUS), used to assess anatomical information and map microvasculature. The combination of the two modalities has previously been shown to reduce inter-user variability of BLI quantification, and in this work, we demonstrate that a dual BLI/US system can provide a more holistic assessment of disease. NSG (NOD/scid/gamma) female mice were implanted with luc-tagged lymphoma cells (BCBL-1, RRID: CVCL_0165, 1x105 cells, intraperitoneal (IP) injection, N = 8 mice) and imaged using the US and BLI hybrid modality system (SonoVol, Inc.), and a BLI-alone system (Perkin Elmer, Inc.) for comparison to a widely available commercial BLI system. BLI sensitivity was evaluated using a weakly luminescent tritium phantom to find the shortest exposure required to detect signal. In vivo studies consisted of an IP injection of D-luciferin (250 µL at 15 mg/mL) and serial captures of images with exposure times of 60 s every 3 min. Acoustic Angiography (AA), a high-resolution CEUS technique, was used to acquire 3D volumes in the abdomen surrounding the tumor site to assess angiogenesis-induced vascular remodeling associated with tumor growth. In vitro BLI sensitivity experiments showed that the dual-modality system required an exposure of 3 sec to detect signal (p < 0.05) and the BLI-alone system required an exposure of 1 sec (p< 0.05). For in vivo studies, the change in luminescence occurring between week 2 and 3 post-cell implantation was calculated (a surrogate measurement for tumor growth), and the difference in signal was 17.15 ± 10.1 photons/sec and 16.04 ± 7.6 for the dual-modality and BLI-alone systems, respectively. Images of the vascular remodeling arising during the first two weeks of tumor growth were captured with AA and demonstrated an increase in perfusion in the vicinity of BLI signal by a factor of 1.4 ± 0.38, with vascular remodeling being evident even at the periphery of BLI signal. This work demonstrates that non-invasive measurements of in vivo microvascular remodeling can be precisely mapped to changes in tumor growth with a hybrid modality system. The system has comparable sensitivity to a BLI-alone system and provides similar assessments of longitudinal tumor growth. Adding quantitative metrics for vascular remodeling to the widely used luminescent imaging could provide a more comprehensive assessment for tumor functional status than either modality could individually. This should prove valuable when using antiangiogenic therapies because changes in vasculature will precede cell death, and the ability to monitor both the cells and their blood supply might help to elucidate underlying biological processes. Citation Format: Juan D. Rojas, Rajalekha Rajamahendiran, Tomasz J. Czernuszewicz, Brian Velasco, Jonathan Perdomo, Max Harlacher, Graeme O'Connell, James Butler, Blossom Damania, Paul A. Dayton, Ryan C. Gessner. Tracking angiogenesis induced microvascular changes in a lymphoma model via a new high throughput non-invasive dual modality imaging platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1935.