stepwedge

stepwedge

 [step´wej]
a device used for comparing exposure intensities in photography or radiography; a series of tones from white to black (photography) or plates of increasing thickness (radiography) are placed between the energy sources and the film and differences in exposure are noted.
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Briefly, samples were positioned onto an occlusal phosphor plate with an aluminium stepwedge. Focus (TM) X-ray (Instrumentarium Dental, Tuusula, Finland) was used to obtain radiographic images of all samples.
The optical density study was conducted by digital radiography means, and the bony parts were simultaneously placed parallel to an aluminum scale (stepwedge) fabricated of a specific and internationally standardized alloy (aluminum alloy 2026, ABNT, Brazil), constituted of eight degrees, with a thickness of 1 mm in each increment, used as a densitometric reference.
To measure relative bone density, an aluminum stepwedge is normally used in research as a unit of reference for density measurement, which enables a correlation between the values of bone and metal.
For the radiographic exposure, each acrylic plate containing a cement sample was positioned with another acrylic plate (1.3 cm x 4.5 cm x 1 mm), which contained a graduated aluminum stepwedge varying from 1 to 10 mm in thickness and uniform steps of 1 mm each.
Both materials overcame 3 steps from the aluminum stepwedge, which is the minimum recommended by ANSI/ADA specification 57 [24], whereas the pozzolan Portland cements did not meet this requirement (109.40 [+ or -] 3.50 mm Al).
For the radiographic exposure, each acrylic plate containing the cements was positioned together with another acrylic plate (1.3 cm x 4.5 cm x 1 mm), which contained a graduated aluminum stepwedge varying from 1 to 10 mm in thickness, and uniform steps of 1 mm each.
Both cements overcame 3 steps from the aluminum stepwedge, which is the minimum recommended by the ANSI/ADA [15] (Table 2).
Intensity calibration was carried out using an intensity stepwedge prior to gel image capture.
Beyer-Olsen, Orstavik [1] (1981) included in their studies a reproducible comparison standard using a 2-mm-increment aluminum stepwedge to determine the radiopacity of several root canal sealers.
Bone mineral density measurements were performed on the panoramic radiographs with the help of a five-step copper stepwedge phantom, attached to each film cassette, which was calibrated before hand by DEXA.
Exposure times were determined using a stepwedge to calibrate densities of the three film-speed/collimator combinations to a particular step on the wedge.