A new stepwedge has been developed for bootstrap sensitometry, which is used for determining the characteristic curve of radiographic screen/film systems. Since each step of the stepwedge is separated by the lead septum, flare generated under one step will not penetrate the region of another step. The metal of the stepwedge can be changed with various materials. Characteristic curves obtained with new stepwedge bootstrap (NSB) and conventional stepwedge bootstrap (CSB) techniques were compared with those obtained for screen/film systems with inverse sqare sensitometry. The inverse square method was used as the reference standard for accuracy. The NSB method provided characteristic curves that agreed well with those obtained using the inverse square method. The slope of the curve in the CSB method was lower than that in the inverse square or NBS method, because of scatter radiation. The shape of the characteristic curve from the NSB method did not vary with the materials of step metals (aluminum and copper). The cumulative error involved when using the bootstrap method is also discussed.
Radiographic screen/film systems