Hauptabstrahlung

Hauptabstrahlung, literally “primary radiation” in German, refers to the direct X-ray photons produced by an X-ray tube before they interact with matter. It constitutes the primary beam that travels from the tube toward the patient and the image receptor, and under routine imaging conditions is what creates the diagnostic image.

The spectrum and quality of the Hauptabstrahlung are determined by several factors, including the tube potential (kVp), added and inherent filtration, the anode material and geometry, and the window design. Higher kVp shifts the spectrum toward higher energies, while filtration removes low-energy photons to reduce patient dose and modify beam quality. Collimation and field size shape the spatial distribution of the primary beam and the region of interest in the image.

In radiation protection, Hauptabstrahlung is distinguished from secondary radiation (Streustrahlung), which arises from scattering within the patient or surrounding materials, and from leakage radiation that escapes through the X-ray tube housing. The primary beam is typically the most intense component along its intended path, and shielding calculations for barriers are often based on the characteristics and maximum exposure of this primary radiation.

Characterization of the Hauptabstrahlung is important for dose optimization, shielding design, and quality assurance in radiology. The term is common in German-language radiology and shielding literature and is often used interchangeably with Primärstrahlung or Primärstrahlung in English-language texts.