Radiation therapy systems and their components, including secondary radiation shields. At least some versions of the disclosed systems combine a radiation delivery device, a primary radiation shielding device, and a secondary shielding layer into an integrated, modular unit. This is accomplished by using a small direct beam shield capable of blocking a primary beam from a radiation delivery device. In turn, a thinner shielding layer can be used to surround the radiation delivery device and primary shielding device, enabling a single modular unit to be delivered to an installation site. In some embodiments, a bed may be disposed within the secondary shielding layer. In some embodiments, the system is configured to provide up to 4-pi (4π) steradians of radiation coverage to the bed from the radiation delivery device.