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- Author or Editor: H. Machulla x
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Abstract
The diagnosis of the myocardial diseases with 17123I-heptadecanoic acid and recently 15-(p-123I-phenyl)-pentadeconoic acid has been applied successfully. A high labeling yield and short reaction time is desired for routine applications. The over-all yield of the complete procedure is the most important consideration. Different labeling approaches were evaluated to increase the yield of the entrire procedure. So each laboratory is able to select the method appropriate for their individual demands and possibilities.
Abstract
1,16-Diiodohexadecane was obtained by reaction of 1,16-hexadecanediol and potassium iodide. The14C-label was introduced into the 1,16-diiodohexadecan using a substitution reaction which replaced one of the terminal iodine with14C-cyanide. Hydrolysis and HPLC purification of 1-14C-17-iodoheptadecanoic acid yielded a product with a radiochemical yield of 17% and a specific activity of approx. 1850 MBq mol–1.
Abstract
By comparison of three halogenated nicotinic acid derivatives, viz. 2–18F-, 6–18F-and 6–123I-nicotinic acid diethylamide (2–18F-NADA, 6–18F-NADA, 6–123I-NADA) the biodistribution of18F-and123I-radioactivity in mice was determined. For the two fluoro-compounds the results indicate nearly similar time-activity curves in almost all organs investigated, while the iodo-derivative exhibits significant differences: for the brain and the heart a complete elimination of123I-radioactivity takes place within 4 hours, time-activity curves of the liver and the kidneys show higher maximal accumulations compared to the fluorinated derivatives and activity in the stomach increases continously within a time period of 2 hours to a maximum which is about 5 times higher than that of 6–18F-NADA. For the lung drastic differences can also be observed in case of 6–123I-NADA which accumulates with a dose of about 40%/g already 30 seconds after injection and exceeds the corresponding values for 2–18F-NADA and 6–18F-NADA by a factor of about 6, followed by a biexponential decrease. De-fluorination reactions from the aromatic ring can be excluded, as could be shown by the low accumulation of18F-radioactivity in bones after application of 6–18F-NADA.
Abstract
Using a distillation method for the separation of18F-fluoride from aqueous18F-solutions obtained after cyclotron irradiation of a water target by means of the16O(3He, p)18F reaction, the radiohalogen could be generated as a highly reactive species for nucleophilic substitution reactions. Thus, with the starting compounds 1,3,4,6-tetra-O-acetyl-2-O-trifluoromethanesulfonyl-
-D-mannopyranose and 1,2:5,6-di-O-isopropylidene-3-O-trifluoromethanesulfonyl-
-D-allofuranose18F-2-deoxy-2-fluoro-D-glucose (2-18FDG) and18F-3-deoxy-3-fluoro-D-glucose (3-18FDG) could be synthesized with radiochemical yields of 71.6% and 85.9%, respectively. Including purification by HPLC, the total preparation time was 70 min, yielding the glucose derivatives in a no-carrier-added state. Specific activities coold be calculated to be greater than 103 Ci/mmol.
Abstract
-Methyltyrosine was iodinated in position 3 of the aromatic ring by means of an electrophilic iodination method using chloramine-T in a phosphate buffer solution. In a mixture containing -methyltyrosine, chloramine-T and a small amount of NaI as a carrier the reaction was complete within 15 min at room temperature. After purification by radio high pressure liquid chromatography /HPLC/ radiochemical yields of 77.6±3.2% were obtained. Radiochromatograms also revealed a small amount of an impurity, probably chlorinated 3-123I--methyltyrosine. After dissolving in isotonic phosphate buffer and sterile filtration the solution was ready for nuclear-medical applications.
Abstract
The dependence of the radiochemical yield of [18F]fluoromisonidazole (1) on different reaction parameters such as reaction time, temperature and amount of precursor was investigated for the nucleophilic substitution of tosylate by [18F]fluoride and subsequent hydrolysis of the protecting group on 1-(2′-nitro-1′-imidazolyl)-2-O-tetrahydropyranyl-3-O-toluenesulfonylpropanediol as the precursor molecule (2). Highest yields (86%±6%) were obtained using 10 mg (2) at 100°C for 10 minutes, whereas both at 80 and 120°C the yields were lower (46%±11% and 29%±14%, respectively). A rapid decrease of the yield was observed when the reaction time exceeded 15 minutes, i.e., at 100°C using 5 mg (2) the radiochemical yield decreased from 61%±8% at 15 minutes to 18%±10% at 60 minutes.
Radiopharmaceuticals
I. Synthesis of radioiodinated phenylfatty acids for studying myocardial metabolism
Abstract
For studying the metabolism of fatty acids in the heart muscle in-vivo, ω-phenylpenta-decanoic acid (PPA) was labelled with radioiodine to the ortho and para position of the benzene ring with a radiochemical yield of 60%. The products were obtained in a relative isomer distribution of 29%ortho and 71%para radioiodinated PPA. The radiopharmaceutical quality control was performed by sequential radio high pressure liquid chromatography.
Abstract
Radiochemical quality control using high performance high pressure liquid chromatography and, to some extent, gas chromatography is described for a variety of carrier-free11C-,18F-and123I-labelled compounds and radiopharmaceuticals. The particular problems associated with the handling of carrier-free compounds labelled with short-lived radionuclides are outlined, and chromatographic data are given for the separation and purification of such products.
Abstract
For labeling reactions [18F]fluoride has to be separated from [18O]water and transferred into an organic solvent suitable for nucleophilic substitutions. An electrolytical method is described for depositing [18F]fluoride on a vitreous carbon electrode and releasing it directly into CH3CN or DMSO. In the presence of Et3N×3HF, [18F]fluoride is almost quantitatively released into acetonitrile. When using n.c.a conditions, i.e., Et3N.HCl, desorption of the 18F activity is almost 70% and 60% in acetonitrile and DMSO, respectively, already within 5 minutes.
Abstract
18F-labeling of aromatic compounds normally is achieved by electrophilic substitution. In that case [18F]fluoride cannot be applied although it is produced very efficiently at medical cyclotrons. By the use of electrochemical methods, however, benzene can be oxidized and thus, the electron density is reduced in a way that nucleophilic attack of [18F]fluoride occurs. For the first time benzene was shown to be labeled with [18F]fluoride after being electrochemically oxidized in a 2 ml electrolysis cell with 0.033M Et3N.3HF and 0.066M Et3N.HCl in CH3CN and benzene in various concentrations. After 50 Coulombs (60-90 min) maximum of labeling was reached. With the highest concentration of aromatic compound (1.0M) the radiochemical yields were 16±9% with specific activities up to 27 GBq/mmol.
