Measured scattered x-ray energy spectra for simulated irradiation geometries in diagnostic radiology.

In this study, scattered x-ray distributions were produced by irradiating an anthropomorphic pelvis phantom under fluoroscopic conditions using incident beams generated at tube potentials between 61 kVp and 112 kVp. Both overcouch and undercouch x-ray tube orientations were used when irradiating the phantom. The energy spectrum of the scattered x rays was measured with a germanium x-ray detector. Two measurement geometries were employed: (i) the detector placed at 90 degrees to the incident x-ray beam to determine the energy spectra incident on the trunk region of staff and (ii) the detector placed at 45 degrees to the x-ray beam, measuring spectra incident on the head and neck region. The effect of irradiation area on the scattered spectra was also investigated. Spectral distributions, along with mean energy and half-value layer (HVL) in mm Al, are presented for each spectrum. Energy spectra measured at 90 degrees to the incident x-ray beam were found to have HVLs approximately 10%-15% greater than the corresponding primary incident spectrum, for both overcouch and undercouch irradiations. The magnitude of the irradiation area had negligible effect on the mean energy and HVL of the spectra.