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?
Mo anode X-ray filtering works by using a thin layer of molybdenum on the anode of the X-ray tube. This layer selectively filters out lower energy X-rays, allowing only higher energy X-rays to pass through and reach the patient. This results in a higher contrast image with better tissue differentiation, making it ideal for mammography.
Mo anode is ideal for mammography because it has a characteristic X-ray emission spectrum that is well-suited for imaging breast tissue. It has a high atomic number, which means it can effectively filter out lower energy X-rays, resulting in a clearer image with less scatter radiation. Additionally, Mo has a lower melting point compared to other anode materials, making it more cost-effective and easier to manufacture.
Mo anode X-ray filtering improves image quality in mammography by reducing the amount of scatter radiation that reaches the image receptor. This results in a higher contrast image with better tissue differentiation, allowing for the detection of smaller lesions and abnormalities. It also reduces the patient's radiation exposure, making it safer for frequent screenings.
While Mo anode X-ray filtering has many benefits, it is not suitable for all types of mammography imaging. It is most effective for imaging dense breast tissue, but may not be as effective for fatty breast tissue. Additionally, it is not suitable for larger breast sizes as the X-rays may not penetrate deep enough to produce a clear image.
Yes, there are alternative materials to Mo anode for mammography, such as rhodium and tungsten. These materials also have high atomic numbers and can effectively filter out lower energy X-rays. However, they may be more expensive and have a higher melting point, making them less practical for routine use in mammography. Mo anode remains the most commonly used material for mammography imaging.