[Dosimetric calibration of CT pencil chamber in cobalt beams].
OBJECTIVE
To explore the dose-length product calibration method for pencil ionization chamber in cobalt beams.


METHODS
The PTW TM30009 ionization chamber was placed into the central hole of T40017 head phantom and irradiated 60 s in 20 cm x 20 cm cobalt beam. The charge was collected with UNIDOS electrometer. Absorbed doses were measured with TM30013 0.6 mL farmer-type chamber under the same condition. The CT chamber calibration factor was expressed in dose-length product. Dose linearity and spatial response were also investigated.


RESULTS
The calibration factor in dose-length product was derived from measured data. Dose linearity and spatial response were good in cobalt beams.


CONCLUSIONS
It is feasible to calibrate the CT chamber in cobalt beams for patient dose evaluation in MVCT.
Yi
Y
Li
Junliang
J
Wang
Yunlai
Y
Wang
D002138:Calibration; D011834:Radiation Monitoring / Q000379:methods*; D011839:Radiation, Ionizing; D011874:Radiometry; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*