The discussion centers on the use of molybdenum (Mo) anodes and filters in mammography, specifically exploring why Mo is considered ideal for filtering X-rays produced during the imaging process. The conversation touches on the mechanisms of X-ray production and the implications of filter thickness on absorption characteristics.
Participants express uncertainty and pose questions regarding the effectiveness of Mo as a filter and the mechanisms of absorption, indicating that multiple competing views remain without a clear consensus.
The discussion includes assumptions about the interaction of X-rays with the Mo filter, the dependence on filter thickness, and the unresolved nature of the absorption probabilities for different types of radiation.
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?