Line pair phantom
Line pair image
(d)
Low contrast detectability:
A test object, consisting of 19 discs, each of diameter 11 mm, mounted on a
perspex plate, is used. The discs produce a range of calibrated x-ray contrasts
when used with a calibrated x-ray beam of 70 or 75 kVp. The test object and
an image of it are shown below:
The low contrast detectability can be assessed by counting the number of discs
visible in the image during screening.
(e)
Image geometry and sizing:
A test object that consists of a wire matrix of 20 mm square spacing with 10
mm diameter interpolations, mounted on a perspex plate, is used. It is
positioned as closed to the I.I. as possible but must cover the whole field. An
image is then taken with low kVp.
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