Technetium radioimaging

Radioactive labels are -emitters selected on the basis of half-lives, the energies emitted, decay products, ease of labeling, availability and expense. Iodine isotopes 121,123, and 124, Indium 111, and Technetium 99 are the labels most widely used. The short half-lives of these labels (hours to days) means that radioimaging reagents are prepared immediately prior to treatment. Radioimaging of diseased tissue also provides useful information on the design of therapies that localize radioisotopes or toxins at tumor sites for therapy. 

Technetium and rhenium coordination chemistry associated with the introduction of Tc into radiotherapy and radioimaging agents is of active current interest, and the application of nit/o-carbaborane hgands has recently been explored. Microwave heating assists the formation of rhenium jj -carbaborane complexes in aqueous solution, and similar conditions are effective at the tracer level for the preparation of 99mTc complexes. ... 

Substitution of a phenyl by the CpRe(CO)3 moiety, bulkier and not easily oxidizable but more lipophilic (log 4-3 for (Z)-30d 3.2 (Z)-OH-tamoxifen) thus produces complexes with an antiestrogenic effect very close to that of OH-tamoxifen itself, an effect that is not influenced by the length of the side chain or by the isomer used. Radioactive forms of these complexes could be envisaged for use either as Re p emitters in radiotherapy, or, since the chemical behavior of technetium is known to be similar to that of rhenium, as technetium y emitters for use in radioimaging. Owing to the very short half-life required in radioisotopes for medical applications, new synthetic routes will have to be found that allow the radioactive entity to be incorporated easily and in good yield at the final step of the synthesis. 

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