Terminology & image display

Nuclear images are most commonly depicted in grayscale, although studies can be depicted in color as well. 

On grayscale images, by most conventions, areas of high radiotracer uptake are displayed in black, and areas of low uptake are white, with varying intermediate shades of gray.  Areas of high uptake are commonly called “hot or radiotracer avid”.  Areas of low uptake are called “cold or photopenic”.

The bone scan image on the left shows a hot spot in the medial left knee (red arrow) due to increased tracer uptake from bone turnover related to osteoarthritis. The patient then had a total knee replacement using a metal prosthesis. The bone scan on the right, done post-operatively, shows a cold spot in the left knee (yellow arrow) corresponding to the metal prosthesis, which cannot take up any tracer.