How can high (short scale) contrast in X-rays be achieved?

High contrast, or short scale contrast, in X-rays refers to the presence of distinct differences between the various shades of gray in the image, leading to a more pronounced separation between light and dark areas. This effect can be achieved primarily by manipulating the kilovoltage peak (kVp) used during the radiographic procedure.

When kVp is decreased, the energy of the X-rays produced is also lowered. This results in fewer X-rays being able to penetrate the dense structures of the teeth and bone, producing fewer shades of gray and thus enhancing the contrast. The reduced energy contributes to a higher likelihood that the X-rays are either absorbed or scattered rather than passing through, which emphasizes the differences between adjacent structures. Consequently, this leads to an image with high contrast.

On the other hand, increasing kVp typically results in lower contrast (or long scale contrast) due to a wider range of gray shades being captured in the image, which is not desirable when high contrast is needed. The adjustments to the milliampere-seconds (mAs) affect the overall exposure but do not play a direct role in increasing contrast in the same manner as kVp adjustments. Therefore, decreasing the kVp is the appropriate method to achieve high contrast in X-rays.