We are very pleased that our Hallway Conversations in Physics submission [1
] has motivated community discussion on the topic of peak skin dose. Dr. Morillo [2
] raises good points about the complexity of some corrections and classification of patients into dose bands as an effective way to manage appropriate follow-up. A caveat to using the cumulative air kerma (CAK) at the reference point as a risk measure is that careful consideration would be needed on how these values translate to the radiation risks presented by Balter et al. [3
], which are specific to peak skin dose. It would be reasonable to make some corrections, which may be large, such as distance to the skin surface, to more appropriately group individual cases. At hospitals with high volumes of these interventional procedures, applying the thresholds presented by Balter et al. to CAK may lead to unnecessary follow-up for patients who might otherwise be at low risk of skin injury. For example, in a recent study, Liu et al. [4
] found no skin injuries in patients who received a CAK of less than 9 Gy and only lower-grade injuries in 3 of 17 patients with CAK greater than 9 Gy. This suggests that CAK alone may not be a reliable indicator of injury risk to skin.
With respect to measurement uncertainties, a 35% accuracy requirement for the air kerma is a large source of variance and could be reduced by more frequent recalibrations, though that may rely on available physics expertise. Additional corrections for table attenuation, backscatter, and beam geometry could improve dose estimates in cases of large gantry angles but do require accurate and reliable knowledge of system setup and geometry, which can be challenging to gather [5
]. It is possible for a peak skin dose to be a gross approximation of the actual skin dose received during the procedure and, if done correctly, these estimates should reduce uncertainty instead of adding to it.