New Enclosure for in vivo Medical Imaging of Zebrafish With Vital Signs Monitoring

Abstract

Lately, the use of zebrafish has gained increased interest in the scientific community as an animal model in preclinical research. However, there is a lack of in vivo imaging tools that ensure animal welfare during acquisition procedures. The use of functional imaging techniques, like Positron Emission Tomography (PET), in zebrafish is limited since it requires the animal to be alive, representing a higher instrumentation complexity when compared to morphological imaging systems. In the present work, a new zebrafish enclosure was developed to acquire in vivo images while monitoring the animal's welfare through its heartbeat. The temperature, dissolved oxygen, and pH range in a closed aquatic environment were tested to ensure that the conditions stay suitable for animal welfare during image acquisitions. The developed system, based on an enclosure with a bed and heartbeat sensors, was tested under controlled conditions in anesthetized fishes. Since the anesthetized zebrafish do not affect the water quality over time, there is no need to incorporate water circulation for the expected time of PET exams (about 30 min). The range of values obtained for the zebrafish heart rate was 88-127 bpm. The developed system has shown promising results regarding the zebrafish's heart rate while keeping the fish still during the long imaging exams. The zebrafish enclosure ensures the animal's well-being during the acquisition of in vivo images in different modalities (PET, Computer Tomography, Magnetic Resonance Imaging), contributing substantially to the preclinical research.

Keywords: Zebrafish physiology; non-invasive sensors; small animal imaging; vital signs monitoring; zebrafish heart rate.

FIGURE 1

Anesthesia protocol followed in the present work.

FIGURE 2

Enclosure prototype developed (A) Bed support block to accommodate zebrafish (B) Block to seal the container.

FIGURE 3

Zebrafish in the bed with a sponge to improve immobilization and positioning of zebrafish.

FIGURE 4

Sensor arrangement relative to the zebrafish (front view). Adapted from (Yoshida, Hirano and Shima, 2009).

FIGURE 5

Block diagram of the heartbeat and water temperature measurement and display.

FIGURE 6

Block diagram of the analysis applied to the acquired signals, both by the sensors and the video.

FIGURE 7

Graphical interface developed, during the signal acquisition.

FIGURE 8

Interface of the computer vision software and ROI selection.

FIGURE 9

Variation of the (A) concentration of dissolved oxygen and (B) pH over time with zebrafish and without (control).

FIGURE 10

Water temperature evolution during a zebrafish trial.

FIGURE 11

Comparison of the heart rate values obtained by the developed system's sensors and a commercial heart rate meter in one volunteer.

FIGURE 12

(A) Signal acquired from zebrafish 1 (B) Signal acquired from zebrafish 2.