Radiochemical imaging

Fluorinated Aromatics. Fluorinated aromatics have found wide use as antibiotics, sedatives, important agrochemicals and radiochemical imaging agents. The best method is of course diazotization of an aromatic amine... 

Radiochemical tracers, compounds labeled with radioisotopes (qv), have become one of the most powerful tools for detection and analysis in research, and to a limited extent in clinical diagnosis (see Medical IMAGING TECHNOLOGY). A molecule or chemical is labeled using a radioisotope either by substituting a radioactive atom for a corresponding stable atom in the compound, such as substituting for H, for or for P, and for for... 

There are two aspects of resist sensitometry 1) the measuiement of resist response to radiation which involves measurements designed to determine the intrinsic radiation sensitivity of the materials from which the resist is constituted and 2) lithographic sensitivity which is a measure of the efficiency with which these radiochemical conversions can be expressed in relief image formation. 

Introduction of a fluorine-18 in )0-position to the pyridine nitrogen has been carried out in 37 % radiochemical yield by nucleophilic exchange for NO2 in the synthesis of a potential MAO-B imaging tracer (Scheme 48) [205]. 

This work was supported by the Intramural Research Program of the National Institutes of Health, National Institute of Biomedical Imaging and Bioengineering. The authors would like to thank Terry M. Phillips for his guidance and for his valuable assistance, especially with the sections on electrochemical and radiochemical detectors. 

Radiochemical purification, activation analysis and, 1 322-323 Radio-frequency plasmas commercial applications of, 17 110, 111 economics of, 17 111, 112 use of, in chemical synthesis, 17 89-112 Radioisotopes, use in medical diagnosis and imaging, 36 25-26... 

Fig. 6.26. Two electrode positions in a radiochemical technique. On the left, the electrode is lifted up for adsorbate equilibration and bulk counting rate measurement. On the right, the electrode is pressed down (squeezed) against the scintillator for surface counting rate measurement. (Reprinted with permission from M. E. Gamboa-Aldeco, K. Franaszczuk, and A. Wieckowski, Radiotracer Study of Electrode Surfaces, in Surface Imaging and Visualization, A. T. Hubbard, ed., Ch. 46, CRC Press, Boca Raton, FL, p. 635,1995, Fig. 46.4.)...

F]VUF 5000 was obtained in 23-34% radiochemical yield (decay corrected) within 3.5 hours and purified with HPLC. It was isolated with a radiochemical purity of > 99% and a specific activity of more then 2500 Ci/pmol [25], Biodistribution however showed a very low brain uptake after iv injection in the rat and so [1SF]VUF 5000 proved to be inappropriate for brain imaging with PET. 

In comparison to the conventional automated synthesis, the radiochemical yield and purity of the compound obtained by microreactor processing was higher and also had shorter synthesis time [21]. Multiple doses of2-deoxy-2-[18F]fluoro-D-glucose for positron emission tomography imaging studies in mice were prepared. Today, 2-deoxy-2-[18F]fluoro-D-glucose is routinely produced in about 50 min with the use of... 

To monitor tumor response to capecitabine therapy noninvasively, Zheng and co-workers, from the Indiana University School of Medicine, developed the synthesis of the fluorine- 18-labeled capecitabine as a potential radiotracer for positron emission tomography (PET) imaging of tumors.28 Cytosine (20) was nitrated at the C-5 position with nitric acid in concentrated sulfuric acid at 85°C, followed by neutralization to provide 5-nitrocytosine (27) in moderate yield. This nitro pyrimidine was then carried through the glycosylation and carbamate formation steps, as shown in the Scheme below, to provide the 6/s-protected 5-nitro cytidine 28 in 47% for the three-step process. Precursor 28 was then labeled by nucleophilic substitution with a complex of 18F-labeled potassium fluoride with cryptand Kryptofix 222 in DMSO at 150 °C to provide the fluorine-18-labe led adduct. This intermediate was not isolated, but semi-purified and deprotected with aqueous NaOH in methanol to provide [l8F]-capecitabine in 20-30% radiochemical yield for the 3-mg-scale process. The synthesis time for fluorine-18 labeled capecitabine (including HPLC purification) from end of bombardment to produce KI8F to the final formulation of [18F]-1 for in vivo studies was 60-70 min. 

NCA 125I and 123I in 50-70% radiochemical yield. 265 is specific for the benzodiazepine-GABA receptor in human brain imaging studies409. 

Radiolabelled benzodiazepine antagonists 346 useful for the in vivo imaging and quantitation of benzodiazepine-GABA receptor sites in the human brain327,328 have been synthesized in 50-70% radiochemical yield and >98% purity by a one-step Pd-catalysed reaction329 between bis(tributyltin) and Ro 16-0154, 347, followed by electrophilic iodination of the tributyl tin compound 348 with no-carrier-added 125I and 123I (equation 148). 

Figure 2.18. The surface-layer imaging process. Pattemwise exposure results in radiochemical modification of only a thin surface layer of the resist (i.e., the resist film is opaque at the exposure wavelength). The surface area modified by exposure is then metalated with an appropriate organometallic reagent, and the resulting structure is dry developed by treatment with oxygen RIE.

Neirinckx RD, Canning LR, Piper IM, Nowotnik DP, Pickett RD, Holmes RA, Volkert WA, Forster AM, Weisner PS, Mariott JA, Chaplin SB (1987) Technetium-99m d,l-HM-PAO a new radiopharmaceutical for SPECT imaging of regional cerebral blood perfusion. J Nucl Med 28 191-202 Noll B, Seifert S, Muenze R (1980) New Tc(IV) compounds with nitrilo-triacetic acid. Radiochem Radioanal Lett 43 215-218... 

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