If the KVP is increased from 75 to 90, what must be adjusted to maintain comparable radiograph quality?

When the kilovolt peak (kVp) is increased from 75 to 90, the quality and penetration power of the X-ray beam are enhanced. This increase allows for greater absorption of X-rays by the structures being imaged, which typically results in a darker radiograph if no adjustments are made to other factors.

To maintain comparable radiograph quality, it is crucial to adjust the milliampere-seconds (mAs), which is a product of the milliampere (mA) and exposure time (seconds). By increasing kVp, the overall exposure and the density of the radiograph also increase because higher energy X-rays are produced and have a greater ability to penetrate tissues. If mA and time aren't adjusted in conjunction with the increase in kVp, the image will become overexposed, leading to a loss of detail and diagnostic quality.

Decreasing mA and time in response to an increase in kVp allows for the control of the total amount of radiation that reaches the film or detector, ensuring that the radiograph maintains an appropriate density without becoming too dark. Reducing these parameters compensates for the increased penetrating power of the beam, ultimately preserving the diagnostic quality of the radiographic image.