A molybdenum filter attenuates photons to shape the beam. Which energy range is attenuated?

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Molybdenum filtration shapes the X-ray beam by removing the low-energy photons that contribute mostly to patient dose without improving image quality. The absorption in molybdenum is much stronger at low energies, and there is a K-edge near 20 keV, so photons with energies below this threshold are preferentially absorbed as the beam passes through the filter. The result is a “hardened” beam with a higher average energy and fewer soft photons. Therefore, the energy range most attenuated is the lower-energy portion of the spectrum (below roughly 20 keV), not the higher-energy photons. This is why filtration reduces dose while preserving usable diagnostic photons.