MAMMOGRAPHY SPECTRUM MEASUREMENT USING AN X-RAY-DIFFRACTION DEVICE

The use of a diffraction spectrometer developed by Deslattes for the d etermination of mammographic kV is extended to the measurement of accu rate, relative x-ray spectra. Raw x-ray spectra (photon fluence versus energy) are determined by passing an x-ray beam through a bent quartz diffraction crystal, and the diffracted x-rays are detected by an x-r ay intensifying screen coupled to a charge coupled device. Two nonline ar correction procedures, one operating on the energy axis and the oth er operating on the fluence axis, are described and performed on measu red x-ray spectra. The corrected x-ray spectra are compared against ta bulated x-ray spectra measured under nearly identical conditions. Resu lts indicate that the current device is capable of producing accurate relative x-ray spectral measurements in the energy region from 12 keV to 40 keV, which represents most of the screen-film mammography energy range. Twelve keV is the low-energy cut-off, due to the design geomet ry of the device. The spectrometer was also used to determine the ener gy-dependent x-ray mass attenuation coefficients for aluminium, with e xcellent results in the 12-30 keV range. Additional utility of the dev ice for accurately determining the attenuation characteristics of vari ous normal and abnormal breast tissues and phantom substitutes is anti cipated.