Dose Area Product (DAP) Meters



Rearranging, we get: SFR = SSD x (RFR/SID)

Plugging in the values we know...

SFR = 49cm x (15.25cm/100cm)

So the Skin Field Radius (SFR) equals 7.5cm.

The area of a circle is 3.14 x radius² (e.g. pi-r-squared) so the exposed area at the patient's skin is 3.14 x (7.5)² or 176.6 cm².