[A comparison of the performances between the ionization chamber dosimeters used in radiation therapy].

The structural principles and technical performances of different ionization chamber dosimeters used in radiotherapy have been briefly introduced in this paper. In the mean time, a comparison of technical performances of four different kinds of ionization chamber dosimeter used in hospitals in China has also been made. The data show their quality meet the required specification specified by IEC731 and JJG912-96, so they can be used as field survey dosimeters in hospitals.

[Evaluation method of CT number linearity].

Objective: To explore the method for computed tomography (CT) number linearity evaluation.

Methods: The model CTP401 of Catphan500 phantom was adopted to test 43 sets of CT scanners under the same scanning conditions. 1- and 2-order curve fitting of the testing results of each scanner were performed, with the bending of the 2-order fitted curve defined as the degree of CT number non-linearity and the slope of the linear fitting as contrast scale.