In which examination should 70 kV not be exceeded?

In the context of radiographic examinations, the use of kilovolt peak (kVp) settings is crucial for optimizing image quality while minimizing patient radiation exposure. For an intravenous urogram (IVU), which is a specialized imaging study of the kidneys, ureters, and bladder using contrast material, it is recommended that the kVp not exceed 70 kV.

This limit is mainly due to the sensitivity of the abdominal structures to radiation, as well as to ensure that the bony structures, which might obscure the visualization of soft tissues and contrast pathways, do not overly attenuate the x-ray beams. Lower kVp settings facilitate better contrast and detail for the imaging of soft tissue structures like kidneys and ureters without overexposing the patient.

In contrast, higher kVp settings are often used for examinations like upper gastrointestinal series or barium enemas, where sufficient penetration through denser tissues is often required. Thus, using a kVp that exceeds 70 for these procedures would be more acceptable and would not typically pose the same risks associated with overexposure in soft tissue studies like an IVU.