title: Functional ultrasound imaging of the brain: theory and basic principles.
abstract: Hemodynamic changes in the brain are often used as surrogates of neuronal activity to infer the loci of brain activity. A major limitation of conventional Doppler ultrasound for the imaging of these changes is that it is not sensitive enough to detect the blood flow in small vessels where the major part of the hemodynamic response occurs. Here, we present a μDoppler ultrasound method able to detect and map the cerebral blood volume (CBV) over the entire brain with an important increase in sensitivity. This method is based on imaging the brain at an ultrafast frame rate (1 kHz) using compounded plane wave emissions. A theoretical model demonstrates that the gain in sensitivity of the μDoppler method is due to the combination of 1) the high signal-to-noise ratio of the gray scale images, resulting from the synthetic compounding of backscattered echoes; and 2) the extensive signal averaging enabled by the high temporal sampling of ultrafast frame rates. This μDoppler imaging is performed in vivo on trepanned rats without the use of contrast agents. The resulting images reveal detailed maps of the rat brain vascularization with an acquisition time as short as 320 ms per slice. This new method is the basis for a real-time functional ultrasound (fUS) imaging of the brain.
authors.affiliation: Institut Langevin, CNRS UMR7587, Inserm U979, Université Paris VII, Ecole Superieure de Physique et de Chimie Industrielles de Paris, Paris, France. emilie.mace@inserm.fr
authors.forename: Emilie
authors.initials: E
authors.lastname: Mace
authors.forename: Gabriel
authors.initials: G
authors.lastname: Montaldo
authors.forename: Bruno-Felix
authors.initials: BF
authors.lastname: Osmanski
authors.forename: Ivan
authors.initials: I
authors.lastname: Cohen
authors.forename: Mathias
authors.initials: M
authors.lastname: Fink
authors.forename: Mickael
authors.initials: M
authors.lastname: Tanter
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply; D001931:Brain Mapping / Q000379:methods*; D002533:Cerebral Angiography; D002560:Cerebrovascular Circulation; D004453:Echoencephalography / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D018608:Ultrasonography, Doppler / Q000379:methods*