Molecular imaging of conscious, unrestrained mice with AwakeSPECT

Area of Science:

• Neuroscience
• Molecular Imaging
• Radiochemistry

Background:

• Current molecular brain imaging in mice often requires anesthesia, which can alter physiological conditions and radiotracer uptake.
• Developing imaging techniques for conscious, unrestrained animals is crucial for understanding natural brain states and behaviors.

Purpose of the Study:

• To introduce AwakeSPECT, a novel Single-Photon Emission Computed Tomography (SPECT) imaging system designed for conscious, unanesthetized, and unrestrained mice.
• To evaluate the system's capability for motion-corrected molecular brain imaging and assess the impact of anesthesia on radiotracer binding.

Main Methods:

• Development of AwakeSPECT with integrated head tracking and motion correction technologies.
• Validation using phantom studies, bone imaging with (99m)Tc-methylene diphosphonate, and dopamine transporter (DAT) binding potential measurement with (123)I-ioflupane.
• Assessment of stress levels in awake animals via plasma corticosterone measurements.

Main Results:

• AwakeSPECT produced high-resolution bone images comparable to CT.
• Dopamine transporter binding potential in awake mice was approximately 50% of that under isoflurane anesthesia, aligning with prior non-primate studies.
• Stress levels in awake animals were comparable to those in other behavioral and imaging studies.

Conclusions:

• AwakeSPECT demonstrates the feasibility of high-quality SPECT molecular brain imaging in conscious, unrestrained mice.
• The study highlights the significant influence of isoflurane anesthesia on radiotracer uptake in the mouse brain.
• This technology enables more naturalistic studies of brain function and disease in mice.