ObjectivesComputed tomography (CT) imaging is considered relatively safe and is often used in preclinical research to study physiological processes. However, the sum of low-dose radiation, anesthesia, and animal handling might impact animal welfare and physiological parameters. This is particularly relevant for longitudinal studies with repeated CT examinations. Therefore, we investigated the influence of repeated native and contrast-enhanced (CE) CT on animal welfare and tumor physiology in regorafenib-treated and nontreated tumor-bearing mice.Material and MethodsMice bearing 4T1 breast cancer were divided into 5 groups: (1) no imaging, (2) isoflurane anesthesia only, (3) 4 mGy CT, (4) 50 mGy CT, and (5) CE-CT (iomeprol). In addition, half of each group was treated with the multikinase inhibitor regorafenib. Mice were imaged 3 times within 1 week under isoflurane anesthesia. Behavioral alterations were investigated by score sheet evaluation, rotarod test, heart rate measurements, and fecal corticosterone metabolite analysis. Tumor growth was measured daily with a caliper. Tumors were excised at the end of the experiment and histologically examined for blood vessel density, perfusion, and cell proliferation.ResultsAccording to the score sheet, animals showed a higher burden after anesthesia administration and in addition with CT imaging (P < 0.001). Motor coordination was not affected by native CT, but significantly decreased after CE-CT in combination with the tumor therapy (P < 0.001). Whereas tumor growth and blood vessel density were not influenced by anesthesia or imaging, CT-scanned animals had a higher tumor perfusion (P < 0.001) and a lower tumor cell proliferation (P < 0.001) for both radiation doses. The most significant difference was observed between the control and CE-CT groups.ConclusionRepeated (CE-) CT imaging of anesthetized animals can lead to an impairment of animal motor coordination and, thus, welfare. Furthermore, these standard CT protocols seem to be capable of inducing alterations in tumor physiology when applied repetitively. These potential effects of native and CE-CT should be carefully considered in preclinical oncological research.

Purpose Publication numbers reporting that ultrasound can stimulate immune reactions in tumors steadily increase. However, the presented data are partially conflicting, and mechanisms are difficult to identify from single publications. These shortcomings can be addressed by a systematic review and meta-analysis of current literature. As a first step, we here present the methodology and protocol for a systematic review to answer the following research question: Does ultrasound alter the immune reaction of peripheral solid tumors in humans and animals compared to control conditions without ultrasound? Procedures We designed a protocol to perform a systematic review and meta-analysis. The suitability of the protocol to detect and sort relevant literature was tested using a subset of publications. We extracted study characteristics, ultrasound parameters, and study outcomes to pre-evaluate the differences between publications and present the data as a scoping review. Results From 6532 publications detected by our preliminary literature search, 320 were selected for testing our systematic review protocol. Of the latter, 15 publications were eligible for data extraction. There, we found large differences between study characteristics (e.g., tumor type, age) and ultrasound settings (e.g., wavelength 0.5–9.5 MHz, acoustic pressure 0.0001–15,000 W/cm2). Finally, study outcomes included reports on cells of the innate (e.g., dendritic cells, macrophages) and adaptive immune system (e.g., CD8-/CD4-positive T cells). Conclusion We designed a protocol to identify relevant literature and perform a systematic review and meta-analysis. The differences between extracted features between publications show the necessity for a comprehensive search and selection strategy in the systematic review to get a complete overview of the literature. Meta-analyses of the extracted outcomes can then enable evidence-based conclusions.

Introduction: Ultrasound (US) imaging enables tissue visualization in high spatial resolution with short examination times. Thus, it is often applied in preclinical research. Diagnostic US, including contrast-enhanced ultrasound (CEUS), are considered to be well tolerated by laboratory animals although no systematic study has been performed to confirm this claim. Therefore, the aim of this study was to screen for possible effects of US and CEUS examinations on welfare of healthy mice. Additionally, the potential influence of CEUS and molecular CEUS on well-being and therapy response to regorafenib was investigated in breast cancer-bearing mice. Material and Methods: 40 healthy Balb/c mice were randomly assigned for examination with US or CEUS (3x/week) for four weeks. Untreated healthy mice and mice receiving only isoflurane anesthesia served as controls (n= 10/group). Ninety-four 4T1 tumor-bearing Balb/c mice were allocated randomly to the following groups: no imaging, isoflurane anesthesia, CEUS and molecular CEUS. They either received 10 mg/kg regorafenib or vehicle solution daily by oral gavage. Animals were examined three times within two weeks. CEUS measurements were performed using phospholipid-microbubbles and phospholipid-microbubbles targeting the vascular endothelial growth factor receptor-2 were applied for molecular CEUS. Welfare evaluation was performed by daily observational score sheets, measuring the heart rate, Rotarod performance and fecal corticosterone metabolites twice per week. On the last day, pathological changes of serum corticosterone concentrations, hemograms, and organ weights were obtained. Moreover, a potential influence of isoflurane anesthesia, CEUS and molecular CEUS on regorafenib response in tumor-bearing mice was examined. Analysis of variance and Dunnett post hoc test were performed as statistical analyses. Results: Severity parameters were not altered after repeated US and CEUS examinations of healthy mice, but spleen sizes were significantly lower after isoflurane anesthesia. In tumor-bearing mice, no effect on animal-welfare after repeated CEUS and molecular CEUS could be observed. However, leukocyte counts and spleen weights of tumor-bearing mice were significantly lower in animals examined with CEUS and molecular CEUS compared to the control groups. This effect was not visible in regorafenib-treated animals. Conclusions: Repeated US and (molecular) CEUS have no detectable impact on animal welfare in healthy and tumor-bearing mice. However, CEUS and molecular CEUS in combination with isoflurane anesthesia might attenuate immunological processes in tumor-bearing animals and may consequently affect responses to anti-tumor therapy.