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, the control 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.