CAMRT Radiography Practice Exam

To improve radiographic contrast in a repeat exposure of an AP shoulder, what changes should be made?

1. Increase the SID

2. Lower the kVp and adjust mAs

3. Use a longer exposure time

4. Change to a non-grid technique

The correct answer is: Lower the kVp and adjust mAs

Improving radiographic contrast is essential for better visualization of anatomical structures. When it comes to adjusting exposure factors in radiography, the kilovolt peak (kVp) plays a crucial role. Lowering the kVp reduces the energy of the x-ray photons, which enhances the contrast by increasing the differential absorption of the tissues. Tissues with different densities, such as muscles, fat, and bones, will absorb x-rays differently, producing a clearer distinction between structures. In a repeat exposure for an AP shoulder, if the initial image was too low in contrast, decreasing the kVp while increasing the milliampere-seconds (mAs) helps to compensate for the reduction in x-ray penetration. This results in an image where soft tissue outlines and bony structures are more distinguishable, providing better diagnostic information. While the other options may influence the image quality, they do not directly enhance contrast in the same effective manner. For instance, increasing the source-to-image distance (SID) often results in increased image sharpness but does not significantly improve contrast. Using a longer exposure time can risk motion blur, especially if the patient cannot remain still, whereas adopting a non-grid technique can reduce scatter but may also lower image detail, which may not be suitable