Functional Ultrasound Imaging

Preclinical Imaging of the Brain

In the brain, functional ultrasound imaging measures transient changes in blood volume at better spatiotemporal resolution than any other functional brain imaging technique. The readout is based on the well-known doppler effect where waves are reflected from red blood cells moving through blood vessels. The signals are directly proportional to relative cerebral blood volume (rCBV). It is a novel technique that was developed to identify regions of brain activation. One of the first study’s to use fUS explored whisker-evoked cortical and thalamic responses of epileptiform seizures in the brain of an awake rat.

Figure 1: Structural fUS scan of a rat brain, 3D MIP

Three Major Preclinical Imaging Applications

There are three major ways functional ultrasound imaging can be used to characterize animal models of neurological and neurodegenerative diseases:

1. Pharmaco-fUS: response to acute pharmacological challenge (e.g., nicotine cortical activation in mice) or altered receptor binding
2. Stimulation-fUS: altered stimulus-evoked activation by loss and/or restoration of functionality (e.g., somatosensory whisker stimulation with electrical stimulation to study pathologies in the trigeminal pathway such as migraine and neuropathic pain)
3. Resting-state-fUS: altered neurotransmitter systems and changes in functional connectivity (e.g., requires no stimulation, a relaxed animal to obtain resting state data with no interference from the environment)

Figure 2: fUS is used as a structural imaging tool in rats for visualization of the ischemic area in thromboembolic stroke (TBE).

Frequently Asked Questions (FAQs) Functional Ultrasound Imaging