Image Production

kVp is the primary controller of radiographic contrast; higher kVp lowers contrast (long scale), lower kVp raises contrast (short scale).

Increasing kVp lengthens the gray scale, producing lower (long-scale) contrast with many shades of gray.

Increasing kVp also increases the quantity of x-rays produced, so it secondarily raises receptor exposure even though mAs is the prime quantity controller.

As kVp increases, more scatter radiation (especially Compton scatter) is produced, adding fog and reducing image contrast.

kVp affects both photon quantity and beam penetration, so its effect on receptor exposure is not directly proportional; small kVp changes can produce large exposure changes.

kVp must be high enough to penetrate the part so the beam reaches the receptor; insufficient kVp yields a light, underpenetrated image regardless of mAs.