For high-energy clinical photon beams greater than 60 Co, skin dose is typically what?

In the context of high-energy clinical photon beams, especially those greater than cobalt-60, skin dose is typically less than peak dose. This is due to the energy characteristics of photon beams, which allow for significant penetration into tissue.

As photon energy increases, the dose distribution becomes more complex due to factors like beam quality, scatter, and the relationship between depth and dose. The peak dose refers to the maximum radiation dose delivered at a specific depth, often beyond the skin surface. As such, the dose delivered to the skin, which is the surface layer of tissue, does not receive the same level of radiation energy absorption as deeper tissues where the peak dose is observed.

Consequently, the skin dose tends to be lower than the peak dose because as photons penetrate, they deposit energy in a more uniform manner through the tissue, resulting in higher doses at greater depths compared to the skin surface. This is a critical aspect when considering treatment planning, as it informs clinicians about the potential for skin reactions and the overall tissue response to radiation therapy.