<s>[INST] I just had a PET/CT scan.  I got to see the PET scan and it showed lots of dark spots.  Are the dark spots just areas that hold moisture and are active?  Such as brain, kidneys, liver, etc.?  Only the back portion of my brain was black, what does that mean? [/INST] Howell come to ChatDoctorThank for asking really appreciate your concern, beside the radiologist it is not possible to read the radio imaging, and the most important is clinical history of the patients, the dark area may be normal or abnormal it is all depends upon the anatomy of organ and related pathological changes, without studying the image it is not at all possible to comment or predict or say anything hope this information helps. </s>