PET scanning agents

Fowler and coworkers have recently reviewed the development of [ C]- and [ F]-labeled PET-scanning agents targeted to MAO activity [108]. 

Dihydroxyphenylalanine (DOPA) (99) is produced by tyrosine hydroxylase-catalyzed hydroxylation of Tyr. Recent interest in the use of [18F]-6-F-DOPA (100) as a PET scanning agent for regional dopaminergic brain function is based on its conversion, in the brain, to [,8F]-6-F-dopamine (101)161. The fact that fluorine in the 6-position of DOPA, dopamine and other catecholamines retards methylation by catechol-O-methyl transferase presumably increases the biological half-life of the tracer. In contrast, fluorine in the 5-position increases the rate of methylation162. 

Frmctional imaging such as PET scanning and SPECT scanning is also likely to be explored for detecting early activity of these cytostatic agents just as PET scanning documented the early activity of Gleevec in patients with G1 stromal tumors. ... 

Figure 35.8 Distribution of the drug fluconazole. Once taken in, compounds distribute themselves to various organs within the body. The distribution of the antifungal agent fluconazole has been monitored through the use of positron emission tomography (PET) scanning. These images were taken of a healthy human volunteer 90 minutes after...

That is where we are headed now. In our lab at UCLA, for example, we conducted studies using PET scans for predicting the effectiveness of each of the major classes of cytotoxic chemotherapy agents used to fight breast, as well as many other, cancers. We tagged each of these drugs with a radioactive isotope of fluorine so that we could... 

If and when such research is fully translated into human use, patients could get PET scans with these kinds of tracer drugs. Potentially, we would know which chemotherapy agent or combination of agents work for an individual and which do not before the large side-effect-producing doses are taken. 

PET scans rely on radiopharmaceuticals as contrast agents, which can be used for imaging of tumor metabolism. The radioactive tracers are formed by labelling cell metabolites (for example, peptides, glucose, or nucleic acids) with positron-emitting isotopes ( C or (Fig. 1). Early diagnosis can be accomplished by observing radiopharmaceuticals that undertake metabolic processes associated with the diseases. 

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