An Investigation of motion tracking for freely moving animals in PET

Stereo optical motion tracking has been shown to b e a feasible and accurate way of measuring head pose in positron emission tomography (PET) studies of minimally restrained awake animals. The aim of this work was to determine the number and arrangement of binocular trackers to optimize continuity of head tracking for a freely moving animal. We established a performance criterion for continuous tracking of a freely moving subject based on head motion measurements obtained from tube-bound rats. By measuring the angular detection capability of a single tracke r we were able to simulate the tracking performance of a variety of multi-tracker configurations. Based on these simulations, tracking can be maintained 96% of the time using four elevated and symmetrically positioned trackers compared with 70% of the time using two elevated trackers on opposite sides of the gantry. A pilot experiment tracking a freely moving rat using the latter configuration resulted in successful head tracking 85% of the time. We conclude that an ensemble of commercial trackers may provide sufficient tracking performance for the freely moving animal, avoiding the need to develop a customized system. This work is an important step towards implementing motion tracking for freely moving animals in PET.4 page(s

Developing a system for the molecular imaging of freely moving rats

Using molecular imaging to obtain time-activity data from the organs of living animals that are free to move, behave and respond to stimuli is a tantalising prospect for preclinical investigations. Here we report the current status of a system designed in our laboratory to realise this goal in positron emission tomography (PET) of rats

A motion adaptive animal chamber for PET imaging of freely moving animals

Small animal positron emission tomography (PET) is a potentially powerful tool for understanding the molecular origins of debilitating brain disease such as dementia, depression and schizophrenia. However, its full potential in such investigations has not yet been realized due to the use of anaesthesia to avoid motion artifacts. Anaesthesia alters biochemical pathways within the brain and precludes the study of animal behavior during the imaging study. Previously we have reported a motion correction approach for conscious animal PET imaging that employs motion tracking and line of response (LOR) rebinning. We are currently extending this technique to allow PET imaging of freely moving animals, enabling the non-invasive measurement of biochemical processes in the brain of a fully conscious rat while simultaneously observing its behavior. As a first step we report a robot-controlled motion adaptive animal chamber which translates in the horizontal plane based on the head position reported by a motion tracking system to compensate for gross animal movement and keep the head within the field of view (FOV) as long as possible during the scan. In a pilot animal study within a simulated microPET environment, thecontrol algorithm increased the time the head spent centrally in the FOV from 38% to 83% without any apparent disturbance to the animal’s behaviour. We conclude that a robot-controlled motion adaptive chamber is a feasible approach and an important step towards imaging freely moving animals

Developing a system for the molecular imaging of freely moving rats

Using molecular imaging to obtain time-activity data from the organs of living animals that are free to move, behave and respond to stimuli is a tantalising prospect for preclinical investigations. Here we report the current status of a system designed in our laboratory to realise this goal in positron emission tomography (PET) of rats