Adjustment to X-rays for X-ray through cast?

• A. 1.5x
• B. 0.5x
• C. 1x
• D. 2x

Answer: (A)

When imaging through a cast, you must compensate for the extra attenuation the cast material adds to the X-ray beam. The cast acts like an additional dense layer that reduces the amount of radiation reaching the film, so the image can come out underexposed if you use standard exposure factors. To counter this, increase the exposure by about 1.5 times. In practice, that means raising the mA or exposure time (mAs) by roughly 50% while keeping the kVp appropriate for bone detail. This 1.5x adjustment is a commonly used general rule to obtain adequate receptor exposure through a cast, though the exact factor can vary with the material (plaster vs fiberglass) and cast thickness.