“There is an area of increased hypoattenuation in the right parietal lobe.”

“increased hypoattenuation” sounds awkward to me. Similar to saying “increased decreased attenuation”.

This example sentence was not made in reference to a prior study, so “There is an area of hypoattenuation in the right parietal lobe” would suffice.

If I was trying to describe a hypoattenuating area that had become even lower in attenuation, I’d say “more hypoattenuating”. Something like “Left parietal lesion is more hypoattenuating than on the prior exam.”