"The cumulative air kerma (CAK), also known as the reference air kerma (Ka,r), is the air kerma accumulated over a procedure at the interventional reference point (IRP) 4,5. For isocentric C-arm systems, the IRP lies 15 cm from the isocentre towards the x-ray source, a position that approximates the skin entrance surface of an average adult 4. CAK is not measured directly but is calculated by the system and displayed alongside KAP 4. As the IRP is fixed in space and the value excludes backscatter, table and mattress attenuation and beam movement, CAK is only an indication of skin dose and may over- or underestimate it 5,10."
"The peak skin dose (PSD) is the highest absorbed dose to any single area of skin and is the best predictor of deterministic effects (i.e. tissue reactions) 9,10. Its calculation is more complex, starting from CAK or KAP and accounting for backscatter, table attenuation, the actual source-to-skin distance, beam angulation and the degree to which projections overlap 5,10."
"The cumulative air kerma (CAK), also known as the reference air kerma (Ka,r), is the air kerma accumulated over a procedure at the interventional reference point (IRP) 4,5. For isocentric C-arm systems, the IRP lies 15 cm from the isocentre towards the x-ray source, a position that approximates the skin entrance surface of an average adult 4. CAK is not measured directly but is calculated by the system and displayed alongside KAP 4. As the IRP is fixed in space and the value excludes backscatter, table and mattress attenuation and beam movement, CAK is only an indication of skin dose and may over- or underestimate it 5,10."