This is a prime example of an issue that WC apologists are simply unable to explain and that they therefore ignore. The white patch is over 1,000 times brighter than the same area in a normal skull x-ray. Equally suspicious is that the white patch's location covers most of the area of the right-rear part of the skull where dozens of witnesses reported seeing a large wound. Another suspicious aspect of the patch is its size and shape: it is relatively oval and about 3 inches in diameter at its widest point.
The brightness of the white patch means that the bone in that area is far, far thicker than the bone in the same area on human skulls, an obvious impossibility. Tellingly, no such patch appears on any of JFK's pre-mortem x-rays.
Of course, the white patch is clear evidence of alteration. But WC apologists will never admit this because they are not interested in facts but in defending the lone-gunman myth.