Dose verification in carcinoma of uterine cervix patients undergoing 3D conformal radiotherapy with Farmer type ion chamber.

External beam radiotherapy (EBRT) for carcinoma of uterine cervix is a basic line of treatment with three dimensional conformal radiotherapy (3DCRT) in large number of patients. There is need for an established method for verification dosimetry. We tried to document absorbed doses in a group of carcinoma cervix patients by inserting a 0.6 cc Farmer type ion chamber in the vaginal cavity. A special long perspex sleeve cap is designed to cover the chamber for using in the patient's body. Response of ionization chamber is checked earlier in water phantom with and without cap. Treatment planning was carried out with X-ray computed tomography (CT) scan and with the chamber along with cap in inserted position, and with the images Xio treatment planning system. Three measurements on 3 days at 5-6 fraction intervals were recorded in 12 patients. Electrometer measured charges are converted to absorbed dose at the chamber center, in vivo. Our results show good agreement with planned dose within 3% against prescribed dose. This study, is a refinement over our previous studies with transmission dosimetry and chemicals in ampules. This preliminary work shows promise that this can be followed as a routine dose check with special relevance to new protocols in the treatment of carcinoma cervix with EBRT.