Dosimetric Conformity of Cobalt-60 (Co) Beams

Objective: The radiation dosimetry is the output measurement of radiation generating source/ machine and its ambition is to ensure that the teletherapy units’ outputs are within limits. In the current article, the dosimetry of Cobalt-60 (Co 60 ) teletherapy units at Nuclear Institute of Medicine and Radiotherapy (NIMRA), Jamshoro Pakistan was studied. As Co 60 is undergo decay process, the output (dose rate) also decreases, therefore regular output measurement is obligatory to deliver appropriate dose to patient. The over dosage leads to hazards of radiation and under dosage may cause inadequate cancer treatment. This study highlights constancy between actual output and output acquired using decay method. Material and Methods: In the present study, the evaluation and comparison in the measurement of actual dose rate and expected output using decay method of Co60 teletherapy units has been done. Results: The evaluation and comparison of the values of output obtained by the two methods (actual and the expected outputs by decay method) shows constancy. Most of the values obtained by actual dosimetry are within ±2% of the expected measurements. Conclusions: The variation in measurements obtained by two methods is within the tolerable limits according to standard protocols and codes. Thus our study shows a homogenous trend in dose rate and a better patient dose delivery to avoid over or under dosage. Keywords-Radiotherapy, Medium, Ionization Chamber, Cobalt-60 (Co 60 ), Dosimetry, Output, Dosimetric Constancy, Radioisotope