Filter and modified stepwedge bootstrap sensitometry in medical radiography

Two new bootstrap methods for determining characteristic curves of radiographic screen/film systems are presented : filter bootstrap sensitometry and modified stepwedge bootstrap sensitometry. Both are intensity-scale sensitometries since the radiation intensity can be varied through use of a combination of inverse square and metal filters. Characteristic curves obtained by these methods are compared with those from screen/film systems using inverse square sensitometry as a reference standard of accuracy. The precision of all three methods is better than ± 2 % with agreement among generally being within 3 % over the useful density range. By these bootstrap methods, it is possible to obtain characteristic curves agreeing well with those using the inverse square method for a relatively short distance, and make radiographic sensitometry practical and convenient at most medical institutions. (author)