How much does the presence of bone decrease the dose behind the bone for a 10 MV X-ray beam per centimeter?

When considering the impact of bone on the dose distribution from a 10 MV X-ray beam, the presence of bone tissues significantly attenuates the X-ray beam due to their higher atomic number and density compared to surrounding soft tissues. This attenuation results in a reduction in the dose that is delivered to tissues located behind the bone.

In the context of clinical practice in radiation therapy, for a 10 MV X-ray beam, studies and clinical data have indicated that the dose reduction observed for each centimeter of bone encountered is approximately 2%. This percentage takes into account the additional scatter and absorption effects that occur as the beam interacts with denser bone material, effectively lowering the dose to downstream tissues.

Understanding this dose attenuation is crucial in treatment planning, as it allows dosimetrists to account for changes in dose distribution caused by varying tissue densities, ensuring that adequate doses are delivered to the tumor while minimizing exposure to healthy tissues. Being aware of this specific rationale aids medical dosimetrists in accurately calculating and predicting dose distributions during therapy.