Use of a pencil-shaped ionization chamber for measurement of exposure resulting from a computed tomography scan

A simple method of comparing and/or monitoring the radiation output level of a Computed Tomography (CT) system, using a specially developed pencil-shaped ionization chamber, is presented. When the measurement is made with a phantom for the period of one tomographic scan, the result can be interpreted as the average exposure along the chamber axis resulting from the entire series of scans to be performed by the CT system. An interesting feature of this method is that no detailed knowledge of the beam distribution or slice thickness is necessary in order to measure the radiation output level, to compare the performance of CT systems or the estimate patient's exposure for a particular combination of CT operation parameters.