ABSTRACT
A Monte Carlo simulation code was written to analyze multi-layer targets for production of 15O. The code models beam-particle transport through the target and production and transport of generated radionuclides; it can be used to assess the effects on radionuclide production of several beam and target design variables. A pathlength correction feature is included that relaxes restrictions inherent in previous ion transport codes and a variance reduction procedure is implemented that significantly improves code efficiency.
Subject(s)
Monte Carlo Method , Oxygen Radioisotopes/chemistry , Radiochemistry/methods , Nuclear ReactorsABSTRACT
Astatine-211 is a 7.2 h half-life alpha-emitting radionuclide which has shown great promise for targeted radiotherapy. It is generally produced by cyclotron bombardment of bismuth metal targets with 28 MeV alpha-particles via the 209Bi(alpha,2n)211 At reaction. In order to provide 211At activity levels anticipated for clinical investigations, an internal target system has been designed and evaluated. The system has a grazing-angle configuration and leading- and trailing-edge monitors. Both aluminum and copper target backings were evaluated. With approx. 28 MeV alpha-particles, the 211At production efficiency was 41 +/- 7 MBq/microA.h, compared with 10.6 +/- 1.2 MBq/microA.h for an external target. Radionuclidic purity of 211At was high with no evidence of 210At.
Subject(s)
Astatine/chemistry , Bismuth/chemistry , Cyclotrons , Radioisotopes/chemistry , Astatine/isolation & purification , Bismuth/isolation & purification , Evaluation Studies as Topic , Half-Life , Radiochemistry/methods , Radioisotopes/isolation & purificationABSTRACT
There is a great need for a better pancreas-imaging agent. Studies with [1-14C] DL-valine have shown this amino acid to have a high pancreatic specificity in the four animal species examined. The tissue distribution was almost optimal by 30 min after injection, and no carrier effect was observed through a dose of 5 mg/kg. [1-11C] DL-Valine was synthesized in amounts up to 363 mCi using a rapid (T1/2 = 20.4 min for C-11), high-temperature, high-pressure modification of the Bücherer-Strecker amino acid synthesis. Purification was by anion-exchange followed by cation-exchange chromatography. [1-11C] DL-Valine was obtained in a 70% chemical yield with a total synthesis and purification time of 45 min. Studies in animals have demonstrated that it is a potentially useful new agent for clinical pancreatic imaging.
Subject(s)
Carbon Radioisotopes , Pancreas/diagnostic imaging , Valine , Animals , Cricetinae , Dogs , Fasting , Female , Isotope Labeling , Male , Mesocricetus , Rabbits , Radionuclide Imaging , Rats , Rats, Inbred F344 , Time Factors , Tissue Distribution , Valine/chemical synthesis , Valine/metabolismABSTRACT
High specific activity [11C] Carboxyl-labeled 1-aminocyclopentane-carboxylic acid ([11C] ACPC) was tested as a tumor-scanning agent in thirty-eight patients. This artificial amino acid clears the blood to a level of less than 12% within 45 min; thus, imaging is possible within the useful life of C-11. [11C] ACPC can be produced in amounts adequate for clinical scanning. Doses between 12 and 45 mCi were given by i.v. injection, and scans obtained only in the single-photon mode gave clinical information on the sites of tumors. There was no evidence of any toxic effects from [11C] ACPC, and the radiation doses as extrapolated from animal data are approximately 0.01 rad per mCi for the whole body and less than 0.06 rad per mCi for the pancreas. In all but five of the 38 patients [11C] ACPC scans were compared with those obtained with Ga-67 citrate. There were 19 positive [11C] ACPC scans and 24 positive Ga-67 scans. The results indicate that [11C] ACPC is likely to be of diagnostic value for cancer patients if used in conjunction with positron tomography instrumentation.
Subject(s)
Amino Acids , Carbon Radioisotopes , Cycloleucine , Neoplasms/diagnostic imaging , Cycloleucine/adverse effects , Cycloleucine/metabolism , Elementary Particles , Female , Humans , Isotope Labeling , Male , Neoplasms/metabolism , Radiation Dosage , Radionuclide Imaging , Time FactorsABSTRACT
Carboxyl-labeled 11C-1-aminocyclopentanecarboxylic acid (11C-ACPC) has been prepared in multimillicurie amounts. The conversion of H11CN to 11C-ACPC (t1/2 = 20.4 min) was accomplished by a rapid (20-min) two-step high-temperature modification of the Bücherer-Strecker amino acid synthesis technique, which should be applicable at other accelerator installations. Purification was by ion exchange techniques. Animal studies have indicated that 11C-ACPC is a potential tumor-localizing agent for detecting cancer in humans by nuclear medicine scanning techniques.
