ABSTRACT
R. L. Dixon originally proposed an alternative to circumvent the limitation by using a helical scan of length L to translate a phantom containing a short ion chamber through the computed tomography (CT) beam plane, thereby collecting essentially the same integral as would a pencil chamber, but rather integrated over an arbitrary length. A rigorous theoretical basis for CT phantom dosimetry has also been developed. Investigators have applied the method and equations successfully and/or supplied additional related data in various phantoms and applications using a variety of detectors. Measurements are made using both the small ion chamber method and the pencil chamber method in order to compare the results of the two methodologies at the short scan lengths corresponding to these pencil lengths. Validation is provided by comparison with pencil chamber results at the appropriate L.
