A non-invasive restraining system for awake mouse imaging

Abstract

Background Preclinical neuroimaging allows for the assessment of brain anatomy, connectivity and function in laboratory animals, such as mice and rats. Most of these studies are performed under anesthesia to avoid movement during the scanning sessions. Method Due to the limitations associated with anesthetized imaging, recent efforts have been made to conduct rodent imaging studies in awake animals, habituated to the restraint systems used in these instances. As of now, only one such system is commercially available for mouse scanning (Animal Imaging Research, Boston, MA, USA) integrating the radiofrequency coil electronics with the restraining element, an approach which, although effective in reducing head motion during awake imaging, has some limitations. In the current report, we present a novel mouse restraining system that addresses some of these limitations. Results/Comparison to other methods The effectiveness of the restraining system was evaluated in terms of three-dimensional linear head movement across two consecutive functional MRI scans (total 20 min) in 33 awake mice. Head movement was minimal, recorded in roughly 12% of the time-series. Respiration rate during the acclimation procedure dropped while the bolus count remained unchanged. Body movement during functional acquisitions did not have a significant effect on magnetic field (B0) homogeneity. Conclusion/novelty Compared to the commercially available system, the benefit of the current design is two-fold: 1) it is compatible with a range of commercially-available coils, and 2) it allows for the pairing of neuroimaging with other established techniques involving intracranial cannulation (i.e. microinfusion and optogenetics).

Automatic Skull Stripping of Rat and Mouse Brain MRI Data Using U-Net

“…We observed the similar skull stripping performance for T2 W (Dice = 0.97) and EPI (Dice = 0.96), indicating that the model is adequately trained and not susceptible to ghosting artifacts in EPI. Rodent EPI data is also less prone to motion because the subjects are either under anesthesia and secured with ear and tooth bars ( Atay et al, 2008 ; Albaugh et al, 2016 ; Van Den Berge et al, 2017 ; Broadwater et al, 2018 ; Grandjean et al, 2019 , 2020 ; Sirmpilatze et al, 2019 ; Mandino et al, 2020 ) or awake and tightly restrained ( Madularu et al, 2017 ; Ma et al, 2018 ). Indeed, none of the dataset available on online repository suffers from severe EPI ghosting.…”

System‐specific activity in response to Δ9‐tetrahydrocannabinol: a functional magnetic resonance imaging study in awake male rats

“…Detailed description of the acclimation and imaging protocols can be found elsewhere (Madularu et al ., ,b, , ; Kenkel et al ., ). Briefly, prior to the first imaging session, all rats were acclimated to the imaging system environment before being placed into the scanner itself, over five consecutive days.…”

“…Briefly, prior to the first imaging session, all rats were acclimated to the imaging system environment before being placed into the scanner itself, over five consecutive days. Rats were secured into a mock holding system similar to the actual coil system (Animal Imaging Research, Holden, MA, USA) and placed into a mock scanner (a black box with a tape recording of MRI pulses) for 30 min at a time to reduce physiological effects of the scanner environment on the autonomic nervous system (King et al, 2005;Madularu et al, 2017). To deliver the test articles remotely, all animals in both groups had a piece of polyethylene tubing (PE-20) approximately 1 m in length positioned and secured prior to placement in the magnet with the tip placed for intraperitoneal (i.p.)…”

Mapping stress networks using functional magnetic resonance imaging in awake animals

“…These procedures often include a training period to acclimate animals to the scanning environment. Acclimation procedures have been utilized by a number of labs and have been shown on multiple occasions to diminish the motion and stress level of animals, measured by stress hormone levels, respiratory rate, heart rate and behavior ( Madularu et al, 2017 ; Schultz-Darken et al, 2004 ; Duyn, 2011 ; King et al, 2005 ; Ferenczi et al, 2016 ; Liang et al, 2014 ). These methods make it possible to image fully awake animals and allow for task-based designs to functionally map stress response in the brain, as well as a more accurate determination of resting-state functional networks related to stress processing in animals.…”