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At least 271 records · Page 15Linked to original sources
PubMed1985

Carbon-11 choline: synthesis, purification, and brain uptake inhibition by 2-dimethylaminoethanol.

We report an improved method for the synthesis and purification of [11C]methylcholine from the precursors [11C]methyliodide and 2-dimethylaminoethanol (deanol). Preparation time, including purification, is 35 min postbombardment. Forty millicuries of purified injectable [11C]choline were produced with a measured specific activity of greater than 300 Ci/mmol and a radiochemical purity greater than 98%. The decay corrected radiochemical yield for the synthesis and purification was approximately 50%. Residual precursor deanol, which inhibits brain uptake of choline, is removed by a rapid preparative high performance liquid chromatography (HPLC) method using a reverse phase cyano column with a biologically compatible 100% water eluent. Evaporation alone did not completely remove the deanol precursor. Brain uptake of the [11C]choline product was six times greater after HPLC removal of deanol because doses of less than 1 microgram/kg significantly inhibit [14C]choline brain uptake.

Animals↗
PubMed1994

[Quantitative scintigraphic detection of 111In sources].

This paper reports on a quantitative scintigraphic method for 111In sources using counts from isoboundary regions of interest of source images. Accordingly, total counts from regions of the image excluding the counts below a given percentage of the maximum are recorded and attenuation correction is implemented using the Depth Independent Buildup Factor method which corrects the effects of Compton scattering on the transmission function of the photon flux leaving the source. The transmission function of both the 172 and the 247 keV photons of 111In was determined for a set of circular flat sources of varying diameter (33 to 111 mm), using counts recorded in isoboundary regions of interest of images of the sources placed in air and at various depths in water. The images were acquired using a gamma camera equipped with a parallel hole medium energy collimator. The influence of the isoboundary value on the shape of the transmission function was investigated, and thus the chosen isoboundary value was set to no more than 20% of the maximum count on the image. Two parallel and dimetrically opposed views were acquired to determine the unknown activity of the sources placed in a water phantom. This counting geometry was chosen to operate in conditions of depth independent of the source in the phantom. Our results show a high degree of accuracy, the experimental estimate of the activity obtained by using the counts in the regions of interest with the lowest isoboundary value exhibiting 4% error rate. The error rate increases with the increase in the isoboundary values. The method proved to be simple, practical and accurate. Moreover, it overcomes the problem of accurate estimation of sources size, a variable usually not known with sufficient accuracy in clinical scintigraphic studies.

Indium Radioisotopes↗
PubMedDate not supplied

[A solid-state reference sample of iodine radionuclide activity for checking radiometers and a method for its production].

This development relates to nuclear engineering, concerns the sources of ionizing radiation of iodine radionuclides and the ways of their manufacture. The iodine radionuclides are used for calibration of radiometers that measure the specific activity of iodine radionuclide in biological specimens, in particular for their use to identify noncancer diseases. The purpose of the paper is to design a routine activity sample for iodine radionuclide in the solid-state source for transfer of an iodine radionuclide activity unit from the reference iodine radionuclide activity unit to an operating meter with a simultaneous decrease in testing errors and an increase, in terms of iodine radionuclide half-life, in the life of the reference sample by stabilizing the activity unit of iodine radionuclide (in terms of its half-life) by eliminating the process of sublimation of iodine radionuclide from the working surface of the source. The objective is achieved by the fact that the radionuclide is replaced on the lower internal build-up part of the container, fixed with the upper internal build-up part, then kept for at least 10-12 hours at least at 18-20 degrees C, packed into a hollow container and sealed with epoxide resin. According to the proposed technical design, reference activity samples of iodine radionuclide in the solid-state radiometric source with a preset activity value have been prepared. The testing error for iodine radionuclide activity is minimal and equal to 1.0-3.0% at a 0.95 confidence.

Calibration↗