Quantification in brain SPECT: Noninvasive cerebral blood flow measurements using 99mTc-labeled tracers

Abstract

An absolute cerebral blood flow (CBF) measurement is necessary for detection of diffuse cerebral involvement and helpful for management of patients. Of the various measurement methods that have been employed in single photon emission computed tomography (SPECT), a noninvasive method using radionuclide angiography of 99mTc-labeled tracers has been widely used because of its simplicity without the need for any blood sampling. Brain perfusion index (BPI) is determined by graphical analysis of time-activity curves for the aortic arch andbrain within 30 s immediately after bolus injection of the tracer. This BPI is converted to global CBF using a regression line equation between BPI and global CBF measured using 133Xe-SPECT. Then, regional CBF is calculated from global CBF, a linearization correction factor, and global mean SPECT counts. Obtained CBF values show good correlations with those obtained by other invasive methods with arterial blood sampling. This noninvasive technique has been applied to various neuropsychiatric diseases including cerebrovascular diseases, neurodegenerative disorders, and mood disorders for the early and differential diagnosis and objective evaluation of therapeutic effects.