Factors affecting the use of quantitative information from a CT scanner.

Computed tomography can be used quantitatively in a variety of ways in both diagnosis and therapy. However, the successful use of CT numbers depends on the appreciation of several features of CT scanning, including the diagnostic viewer. It is also possible to employ the quantitative output of a CT scanner to improve the accuracy of isodase curve computations for photon (or electron) beam radiotherapy. A quality-control program is mandatory for anyone wishing to use CT numbers for this purpose.