In mammography, the use of a molybdenum (Mo) anode is essential due to its ability to produce characteristic X-rays at energies between 17-20 keV. The Mo filter is also deemed ideal because it selectively absorbs certain X-ray energies while allowing others to pass through, particularly when thin enough to prevent complete absorption. The mechanisms involved in X-ray production include core-level excitation (K-edge excitation) and the bremsstrahlung process, with the latter having a lower probability of absorption compared to K-edge X-rays. This selective absorption is crucial for optimizing image quality in mammographic imaging.
PREREQUISITESThis discussion is beneficial for medical physicists, radiologists, and engineers involved in mammography technology, as well as researchers focused on improving imaging techniques and filter design.
BobP said:In mammography, an Mo anode is used because it produces characteristic X-rays at about 17-20 keV.
Apparently, the ideal filter is also Mo. Why is this? Surely all the x-rays would just be re-absorbed by the filter?
Thank you
Well exactly. if we consider the brehmsstrahlung radiation, the probability of absorption is less than k-edge x-rays so they should be absorbed less? no? hence the k-edge x-rays are absorbed MORE than the other radiation?ZapperZ said:How thick is the filter?
Typically, the mechanism for x-ray production in such devices is via two different processes: core-level excitation (i.e. K-edge excitation) and bremsstrahlung process. So already, via the latter, the energy may not match the Mo states. But even via the former, if the Mo filter is thin enough, the absorption isn't 100%.
Zz.
BobP said:Well exactly. if we consider the brehmsstrahlung radiation, the probability of absorption is less than k-edge x-rays so they should be absorbed less? no? hence the k-edge x-rays are absorbed MORE than the other radiation?