Methodology for shielding design and evaluation in radiotherapy facilities

The Government of the Republic of Cuba has decided to carry out a wide programme concerning the purchase of more than a dozen dual linear accelerators and, also; more than a dozen cobalt-60 units. Due to the lack of a national methodology for the design and calculation of shielding enclosures for radiotherapy units, the medical physicists from different hospitals began to use different methodologies, e.g. those in: a) Medical Physics Publishing. Shielding Techniques for Radiation Oncology Facilities. Patton H. McGinley. 1998.; b) National Council on Radiation Protection and Measurements, Structural shielding design and evaluation for medical use of X-rays and gamma-rays of energies up to 10 MeV, Report No. 49, NCRP, Washington, DC (1976).; c) National Council on Radiation Protection and Measurements, Radiation Protection Guidelines for 0.1 - 100 MeV Particle Accelerator Facilities, Report No. 51, NCRP, Washington, DC (1977). In some cases this caused the overestimation of the shielding thickness, when applying the values of dose constraints required by the Cuban regulations. The objective of the present work is to provide the medical physicists, the Radiation Safety Officers and other related professionals with a consistent methodology for the design and remodelation of bunkers hosting radiotherapy units but not using shielding doors. This work shows the validity of the above mentioned methodology, and the feasibility of designing door less bunkers for radiotherapy purposes. This methodology is considered to be self consistent and therefore no other complementary materials for its application are required. The experience so far confirms that; entry of realistic input data, and adequate application of sound engineering concepts when using this methodology leads to the achievement of enclosure shielding designs for radiotherapy units that comply with the dose constraints established by the Cuban regulations. Radiation shielding is attained having no over expenses on construction materials and shielding doors. (author)