The Science of Radiation Shielding An introduction to the science of radiation shielding Steven Johnston Ph.D. AIA Chicago Healthcare Knowledge Community 23 rd July 2013

Plan view of example direct-entry room Linac head Patient Isocenter Door

Primary X-ray radiation Strong photon radiation coming from the linac head, through the patient towards a primary barrier

Weak photon radiation coming from the linac head in all directions. Treated as if coming from isocenter. For high energy linacs there is also neutron leakage radiation. Leakage radiation

Patient scatter radiation Weak photon radiation scattering from patient in all directions.

Plan view of example brachytherapy room Door Patient Brachytherapy equipment

Weak photon radiation coming in all directions from the patient during treatment.

Plan view of an example multi-room proton center Patient Cyclotron Beam-lineEnergy selection Fixed beam room Gantry treatment room Fixed beam room

The cyclotron and energy selection equipment are strong sources of high energy neutrons. The beam-line, treatment room and patient are weak sources of neutrons. The beam can only be directed into one treatment room at a time.

Material Effective Photon Shield Effective Neutron Shield VeriShield V-250 VeriShield V-300 Concrete Steel Lead Borated polyethylene Earth

Concrete (147 lb/cf) V-250 (250 lb/cf) V-300 (300 lb/cf)

Protected SpaceOccupancy (T) Perpetually occupied areas (e.g. offices), controlled areas1 Treatment/exam rooms1/2 Corridors, staff rooms, lounges1/5 Vault doors1/8 Unattended waiting rooms, restrooms, storage, mechanical1/20 Low-occupancy outdoor areas, rooftops1/40

Ceiling Earth Turndown Wall Door Wall Ceiling Duct Duct shielding Section Plan Section

Direct-EntryMaze-entry ProConProCon Faster access to inside the room Patient anxiety with thick door Thinner door required Takes up a lot of space Has smallest room footprint Time spent walking down the maze

Lead Borated Polyethylene Modular block

Advancing the Science of Radiation Shielding