Radiation transmission measurements in clinical teletherapy beam for quality assurance of dose delivery during treatments

An accuracy within 5% in dose delivery to target volume is essential to achieve good treatment outcome in clinical external beam radiotherapy. Most of the cobalt machines have only mechanical or digital timers and the treatment is subject to manual errors. Paliwal et al (1996) recommended consistency checking monitor system in accelerator. A similar monitoring may be useful in cobalt machines also. In telecobalt machines, parallel opposed patient treatments are planned based on physical thickness. There is need for measuring the radiological effective thickness for calculating correct dose delivery