Emmanuel Barbier

Comparative overview of brain perfusion imaging techniques

Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are: Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), Xenon-enhanced Computed Tomography (XeCT), Dynamic Perfusion-computed Tomography (PCT), Magnetic Resonance Imaging Dynamic Susceptibility Contrast (DSC), Arterial Spin-Labeling (ASL), and Doppler Ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow (CBF) or volume (CBV). All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview, established by consensus among specialists of the various techniques. For clinicians, this paper should offers a clearer picture of the pros and cons of currently available brain perfusion imaging techniques, and assist them in choosing the proper method in every specific clinical setting.

PO2 Matters in Stem Cell Culture

About a century ago, conditions were worked out for maintaining growing tissue and cells outside the body. From the beginning, care was taken to maintain cultures at a physiological temperature, and to include precise concentrations of salts and other compounds, but the oxygen concentration in the culture medium was simply the result of letting the medium equilibrate with air. This approach was a reasonable first approximation, given that values of partial pressure of oxygen (PO2) in animal tissues were not measured until over a decade later, and all that mattered seemed to be to provide cells with “enough” oxygen.

Brain, Head, and Neck

MRI in neuroradiology has evolved in the last 30 years, becoming faster, more precise, and more specific. The latest additions, including magnetic resonance spectroscopy (MRS), diffusion imaging, diffusion tensor imaging, functional MRI, and dynamic susceptibility contrast perfusion imaging, have expanded the applications for MR imaging. Currently, fluid attenuation inversion recovery (FLAIR) imaging, thin-section 3D volumetric imaging with spoiled gradient techniques, and the others mentioned above permit not only the precise localization of brain lesions, but also the evaluation of their metabolic profile, their location relative to eloquent regions of the cortex and subcortical white matter, and the relative blood volume and permeability of the vasculature that supplies the lesion. Thus, cellular, vascular, functional and anatomic information are obtained in one examination session and are available to treating physicians in their office, operating room, or radiation therapy suite.

Evaluation du métabolisme et du débit sanguin cérébral en réanimation

L’ischemie constitue la voie finale commune et redoutee de nombreuses agressions cerebrales (1). Son impact sur le devenir des patients est bien documente, notamment chez les traumatises crâniens graves (2). Ainsi, l’evaluation du debit sanguin cerebral (DSC) et du metabolisme cerebral est devenue une preoccupation centrale en neuroreanimation. En pratique clinique, cette preoccupation trouve une reponse dans le monitoring au lit du patient et dans l’imagerie de la perfusion cerebrale (RMN ou TDM), tandis que les techniques d’imagerie metabolique sont des outils de comprehension physiopathologique en recherche experimentale et clinique.