With digital imaging, underexposure causes quantum noise. Which procedure could be acceptable if intentionally underexposed?

• A. Chest radiograph
• B. Follow up scoliosis examination
• C. Knee radiograph
• D. Pelvic radiograph

Answer: (B)

Digital imaging quality is affected by exposure because underexposure creates quantum noise that blurs detail. Some studies tolerate more noise if the exam’s goal is not to reveal the finest anatomy but to monitor change over time, and if the technique is kept consistent.

A follow-up scoliosis examination fits this form. Its primary purpose is to measure spinal curvature and track progression, not to reveal every tiny soft-tissue detail. The vertebral landmarks needed for Cobb angle measurement are typically still discernible even when the image has more noise, especially when the projection and patient positioning are consistent. In contrast, chest radiographs rely on clear lung and mediastinal detail, knee radiographs depend on precise joint and bone edges, and pelvic radiographs require crisp pelvic bone and joint space visualization; underexposure would compromise diagnostic usefulness in those cases.

So, intentionally underexposing is most acceptable for a follow-up scoliosis study because the diagnostic task allows some noise without sacrificing clinically meaningful measurements.