PMC

Making a magnetic resonance image

In these composite PET images of smokers and nonsmokers, arrows demonstrate lower concentrations of the enzyme monoamine oxidase in many of the smokers’ organs ().

The striatum of the healthy control (left) is largely red, indicating the highest level of receptor availability, while that of the cocaine abuser has little red.

PET studies in methamphetamine abusers show that brain metabolism is depressed in the thalamus and striatum shortly after quitting methamphetamine but partly recovers in the thalamus after protracted abstinence ().

In this comparison of a healthy subject (left) and a cocaine abuser, red represents the highest and blue and purple the lowest level of metabolic activity, as measured by ¹⁸FDG.

Arrows point to the anterior cingulate area, which is activated (yellow) in cocaine-addicted patients (left) but not in healthy volunteers (right) ().

In this illustration based on PET studies, cocaine blocks the dopamine transporter, preventing it from pulling dopamine back into the sending cell. As a result, dopamine molecules accumulate in the intercellular space, striking the receiving cell’s receptors and causing an intensified response within the receiving cell.

After study subjects were given [¹¹C] cocaine, PET showed that their reports of how high they felt rose and fell in very close parallel with the passage of the drug in and out of the brain area called the striatum ().

The yellow and red area in the central brain view indicates reduced gray matter density in the right middle frontal cortex (). The same deficit is shown from other perspectives in the flanking views.

The prefrontal cortex is the focal area for cognition and planning. The ventral tegmental area (VTA) and nucleus accumbens (NAc) are key components of the brain’s reward system. The VTA, NAc, amygdala, and hippocampus are major components of the limbic system, which coordinates drives, emotions, and memories.

(A) Chemists replace a naturally occurring carbon 12 atom in the cocaine molecule with a carbon 11 atom to make [¹¹C] cocaine, a radiotracer that acts just like natural cocaine in the body and brain. [¹¹C] cocaine decays by positron emission, resulting in two energetic photons that are detected by a PET scanner to produce an image of glucose metabolism in the brain. (B) Chemists replace a hydroxyl (-OH) group on the glucose molecule with fluorine-18 to make ¹⁸FDG, a radiotracer which is used to measure brain glucose metabolism.