Evaluating Brain Activation: A Methodological Perspective

Conference paper
Part of the Syllabus book series (SYLLABUS)


Commonly used methods for measuring cerebral blood flow (CBF) stem from the nitrous oxide method. The method developed by Kety and Schmidt [1] first provided a means for measuring CBF and rates of glucose and oxygen consumption in the human brain [2]. The Kety and Schmidt method is based on the Fick Principle. Given a compartment (W) with one entrance and one exit, the relationship among the instantaneous (at any time t) concentration values of a tracer in the in-flowing (Ca) and out-flowing (Cv) liquid (blood), the flow rate of the blood perfusing the compartment, and the concentration of the dye within the compartment (Ci) is expressed by the following equation:
$$ dCi/dt = F/W\left( {Ca - Cv} \right) $$
The equation defines the parameters to be measured in order to calculate flow, expressed per unit of mass of tissue (F/W). The principle is applied to the brain, which satisfies the requirements imposed by the model. Assessments of the blood concentrations of a suitable indicator are performed in samples drawn from the in-coming arterial and out-coming jugular blood. The tissue concentrations of the indicator are inferred from the venous concentrations of a freely diffusible tracer according to the blood-tissue exchange theory [1]. Blood flow values, however, refer to the brain as a whole. The Kety and Schmidt method is ineffective in resolving the heterogeneity of the brain.


Cerebral Blood Flow Gamma Camera Regional Cerebral Blood Flow Cereb Blood Flow Diffusible Tracer 
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Copyright information

© Springer-Verlag Italia, Milano 1996

Authors and Affiliations

  • F. Orzi
    • 1
  1. 1.I.N.M. Neuromed, Pozzilli (IS) and Dipartimento Scienze NeurologicheUniversità “La Sapienza”RomeItaly

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