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Radiation Shielding


The safety of patients, staff and the general public is a primary consideration in the implementation of a radiation treatment program. The radiation beams and sources used in radiotherapy have the potential to injure those within or in the proximity of the facility if not properly managed. Radiation safety has two primary components: an intrinsically safe facility design with adequate shielding and other physical safeguards against accidental exposure and policies and procedures which, when followed, will ensure the radiation exposure to staff is kept As Low As Reasonably Achievable social and economic factors being taken into account. Site planning addresses the first issue, that of an intrinsically safe facility design.

Important Principles

In almost all jurisdictions the use of ionising radiation for any purpose, including therapeutic, is tightly regulated. The first step in preparing for a radiotherapy facility, or indeed changing equipment or practice in an existing facility, is to identify the appropriate regulatory authority and obtain copies of the current regulations. These regulations will state the minimum design criteria including requirements on annual and instantaneous dose equivalent rates, interlocks and other radiation safety measures. The architectural design of the facility may then commence. The shielding design is both complex and critical and must be supervised by a qualified medical physicist experienced in this specialised area. It is always advisable to have the design checked by a second knowledgeable physicist prior to submission to the regulator for approval. It is important to note that the references cited here do not adequately address the shielding requirements for newer, high monitor unit treatment techniques such as Intensity Modulated Radiation Therapy and Stereotactic Body Radiation Therapy.  If there are plans to implement these techniques the recent peer reviewed literature should be referred to during facility design.

Introduction to References

Both the IAEA and NCRP reports provide the data and detailed calculation methods for the shielding design of radiotherapy facilities. The book by Prof McGinley is a respected reference text for radiation shielding specialists. More information can be found here.