Pennsylvania Code
Title 25 - ENVIRONMENTAL PROTECTION
Part I - Department of Environmental Protection
Subpart D - Environmental Health and Safety
Article V - Radiological Health
Chapter 228 - RADIATION SAFETY REQUIREMENTS FOR PARTICLE ACCELERATORS
RADIATION SAFETY REQUIREMENTS FOR ACCELERATORS USED IN THE HEALING ARTS
Section 228.67 - Beam symmetry

(a) In new equipment inherently capable of producing useful beams with asymmetry exceeding 5%, at least four different parts of the radiation beam shall be monitored before the beam passes through the beam limiting device.

(b) If the difference in dose rates between two of the different parts required in subsection (a) exceeds 10%, the irradiation shall be terminated.