AAPM Medical Physics Practice Guideline 18.a: Superficial radiation therapy using low-energy kilovoltage x-rays

Superficial radiation therapy (SRT), utilizing low-energy kilovoltage (kV) x-rays typically in the 50-100 kVp range, is a well-established modality in dermatology and radiation oncology clinics for the management of non-melanoma skin cancer and various benign dermatological conditions. The comprehensive medical physics practice guidelines presented in this report are designed to facilitate adherence to minimum standards for SRT delivery. A technical overview of commercially available SRT systems in the United States is provided. Detailed guidelines for commissioning and routine quality assurance are presented, specifying daily, monthly, and annual tests, alongside established action limits. The SRT clinical workflow is delineated, encompassing patient simulation, treatment time or monitor unit calculations, data entry, independent treatment plan review, and radiation delivery. A summary of typical state regulatory requirements for x-ray machines is included. Adherence to relevant state regulations is emphasized and radiation safety considerations, comprising structural shielding, radiation surveys, personnel monitoring, signage, periodic spot checks, and machine operation, are discussed to ensure a safe and effective clinical environment. References to relevant societal practice guidance are provided to support standardized clinical implementation.