Dosimetric calibration of CT pencil chamber in cobalt beams / 中国医疗器械杂志

ABSTRACT

<p><b>OBJECTIVE</b>To explore the dose-length product calibration method for pencil ionization chamber in cobalt beams.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>The calibration factor in dose-length product was derived from measured data. Dose linearity and spatial response were good in cobalt beams.</p><p><b>CONCLUSION</b>It is feasible to calibrate the CT chamber in cobalt beams for patient dose evaluation in MVCT.</p>