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U.S. Department of Health and Human Services

Radiation-Emitting Products

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Under the regulations can the “added” test object used to perform the image contrast test be placed in positions other than on top of the phantom?

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It is the intent of the regulation that the test object be placed on top of the phantom in a consistent, and if possible, permanent location in the image area. Consistency in positioning the added test object is necessary to achieve a meaningful operating level density difference between the background of the phantom and the added test object that must not vary by more than +/- 0.05 OD of the established operating level. However, the position of the test object is not specified in the regulations. If a facility believes it beneficial to place the "added" test object in a different position (e.g., adjacent to the phantom), it will have to assure consistent positioning of the "added" test object, as well as provide the additional x-ray attenuation needed to give a background OD equal to that of the phantom.

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