An experimental check of published depth dose tables (HVL: 0.8-2.5 mm Cu)

The author has compared the absorbed dose rate (at a depth of 5 cm in water) of 89 different X-ray beams (HVL: 0.8-2.5 mm Cu) determined from the free-in-air exposure rate values with those measured directly in a water phantom. A total of 16 X-ray units from the four different types used in Hungary were involved in the intercomparison. The ratio of the two dose values were 1.005 if depth dose tables of Brit. J. Radiol., Suppl. 11. (open ended applicators) were used, for Wachsmann-Drexler tables it was 1.019. The agreement was poor (0.898) if the absorbed dose rate was determined on the base of the Hungarian Standard (the tables of it are taken from the Brit. J. Radiol., Suppl. 10., closed ended applicators). The difference was explained mainly by the different relative depth dose values.