Functional CT : physiological models Ting

0167-7799/02/$ – see front matter ©2002 Elsevier Science Ltd. All rights reserved. PII: S0167-7799(02)02027-9 Ladurner and colleagues [1] were the first to use computed tomography (CT) to study physiological function in the human brain by measuring cerebral blood volume with intravenously injected X-ray contrast agent (an iodinated compound that preferentially stops X-rays more effectively than tissue).They used an equilibrium technique in which CT scanning was done at a time when the injected contrast agent had established an equilibrium distribution throughout the whole body. An alternative technique, called dynamic CT, uses serial CT scans at the same location to study the distribution of contrast agent in the brain as a function of time, and was first used by Traupe et al. [2]. From these early beginnings, dynamic CT methodology has evolved through several generations of technological advances in CT technology [3], and dynamic CT has become the dominant CT method in the evaluation of (physiological) function within the human body.The technique has thus been termed functional CT.The important advantages of functional CT in comparison to other imaging modalities, such as magnetic resonance imaging or positron emission tomography, are its accessibility and simplicity. Functional CT makes use of conventional CT scanners in radiology departments so it is available to patients 24 hours per day. In addition, the method only involves the intravenous injection of conventional contrast agent and CT scanning, enabling the study to be easily performed without extensive additional training of staff.