Evaluation of the physical characteristic of Cerrobend blocks used for radiation therapy

Background: in radiation therapy, the sparing of normal tissues can be performed using either multi-leaf collimators or cerrobend blocks. the current work focuses on the physical characteristics of cerrobend blocks including attenuation coefficient, effective penumbra width and isodose curves undula- tion in penumbral regions. materials and methods: all measurements were performed using a dual energy linac and the cerrobend blocks designed and fabricated using a commercial cerrobend material. data were collected using a calibrated ionization chamber as well as edr2 films. results: the results showed that the attenuation coefficient was found to be 0.4475 and 0.4276 cm-1 for photon beams 6mv and 15 mv, respectively, and a potential air bubble with a diameter greater than 3 mm affects beam attenuation significantly. the optimum cerrobend block width was found to be around 16 mm. the isodose curves scalloping achieved for secondary collimator jaws, were also similar. conclusion: if cerrobend blocks are used as a basic method to protect normal tissues, its physical characteristics will be recommended to be taken into account compre- hensively.