Deliberate Underexposure in Cases of Radiography of Suspected Ingested Highly Visible Foreign Bodies-A Preliminary Study.

Introduction: Because of the linear response of digital detectors, it was hypothesized that large radiopaque foreign bodies would remain visible even when the image is grossly underexposed, meaning that dose could be greatly reduced without compromising diagnostic usefulness of the image.

Methods: Several metallic objects were placed over the abdominal area of an adult anthropomorphic phantom and imaged at different exposure levels ranging from 16.8 milliampere-seconds (mAs) to 0.5 mAs at a film-focus distance of 170 cm. The resulting images were subjectively scored for ease of visualization of anatomical features and metallic objects. In addition, the detection performance of three observers was assessed for the images obtained at 0.5, 1.25, and 2.5 mAs.

Results: All foreign bodies could be detected, even at the lowest exposure level. One observer failed to detect a screw projected over the spine at the lowest exposure setting.

Conclusion: The findings suggest that in cases where radiography is used to detect a large radiopaque object, the normal exposure may be reduced by around 70%, although further research using patients should be conducted before firm conclusions can be reached.