 So the subject contrast is said to be higher in the chest than in the abdomen.In order to image the body so that the maximum information will result, higher subject contrast areas require a higher kVp so as to result in a low radiographic contrast image, and vice versa.Although the product of tube current and exposure time, measured in milliampere-seconds (mA·s), is the primary controlling factor of radiographic density, kVp also affects the radiographic density indirectly.