Search PubMed⌕ Search

Biomedical subjects

G D Robinson

Publications and source records attributed to G D Robinson.

27 records · Page 2Linked to original sources
PubMed1977

Production by compact cyclotron of radiochemically pure iodine-123 as iodide for synthesis of radiodiagnostic agents.

Iodine-123-labeled radiopharmaceuticals are desirable because they give a high flux of 159-keV photons and a low radiation exposure per millicurie. Procedures suited to a compact cyclotron were developed to produce 50-mCi batches of radiochemically pure iodine-123 as iodide. Iodine-123 is separated from proton-irradiated tellurium-124 by distillation. Aqueous iodide is readily obtained by reduction with thiosulfate. Anhydrous iodide is extracted from the distillate iwth methyl ethyl ketone. The procedures for isolating radiochemically pure iodide are trouble-free, convenient, and reliable. Iodine-123-labeled o-iodohippurate and 16-iodo-9-hexadecenoic acid prepared from our iodide are now being used in clinical trials.

Iodine Radioisotopes↗
PubMed1976

Collimation for imaging the myocardium. II.

Line-source response functions and modulation transfer functions (MTF) were used to compare the spatial resolutions obtained with an Anger camera system and four different nuclides used as myocardial-imaging agents: 99mTc, 123I, 201Tl, and 43K. The measurements were made with a low-energy converging collimator (LECY, a medium-energy converging collimator (MEC), and a pinhole collimator. The MTF values for 99mTc were very similar for all three collimator types, although the LEC collimator gave slightly higher values at hgih spatial frequencies and had 40% greater sensitivity. Iodine-123 was satisfactorily imaged only with the MEC and pinhole collimators, which in turn yielded MTF values comparable to those measured for 99mTc. Thallium-201 produced MTF curves that were similar for the MEC and pinhole collimators; the curve for th LEC collimator was slightly poorer. All three MTF curves for 201 Tl were inferior to those of 99mTc. For imaging with 43K, only the pinhole collimator provided marginally acceptable spatial resolution.

Iodine Radioisotopes↗
PubMed1976

Experimental basis of myocardial imaging with 123I-labeled hexadecenoic acid.

Progress in myocardial perfusion imaging has been slowed by the lack or radiopharmaceuticals with suitable physical and biologic characteristics. Hexadecenoic acid, terminally labeled with 123I, partially overcomes these limitations by providing a compound that concentrates in the myocardium in proportion to relative regional blood flow and carries a gamma-emitter with desirable detection and imaging qualities. After intravenous injection in experimental animals, the clearance half-times of hexadecenoic acid for blood and myocardium are 1.7 and 20 min, respectively. These values compare favorably with 18-carbon fatty-acid analogs labeled with 11C. In acute and chronic infarction, similar distribution patterns are found for hexadecenoic acid and 43K, which indicates that hexadecenoic acid is a suitable substitute for the potassium analogs now in use for myocardial imaging. Because of the high count rates obtainable with 123I-hexadecenoic acid, good-guality images can be acquired in as little as 2-3 min per view. Iodine-123-hexadecenoic acid is potentially a useful radiopharmaceutical for clinical application.

Animals↗
PubMed1976

Kit method of preparation of 4-lodoantipyrine (I-123) from Na123I: concise communication.

4-Iodoantipyrine (4-IAP), containing 123I, has been suggested as a radio-pharmaceutical for direct imaging of regional cerebral perfusion. In routine clinical use, a reliable source of the labeled compound is required. The 4-IAP (I-123) can be prepared by exchange between Na123I and 4-bromoantipyrine (4-BrAP) or 4-IAP with heating in aqueous acidic solution. Using an H3PO4 buffer system at pH 2.5 during labeling, with addition of NaOH for subsequent buffering at pH 7.0, a convenient reliable kit for routine preparation of 4-IAP (I-123) from commercially available Na123I has been developed.

Antipyrine↗
PubMed1975

Meteorological effects of environmental controls.

The solution of the continuity equation in practical applications is examined, and the values needed for approximate solutions are indicated. Models are adequate for investigating what could happen, but are less satisfactory for predicting what will happen. An example is given in relation to the distribution of SO2 over Connecticut. More knowledge is needed about atmospheric chemistry before better predictions can be expected. The effect of particulates on atmospheric opacity is reviewed.

Air↗
PubMed1975

Radioiodinated fatty acids for heart imaging: iodine monochloride addition compared with iodide replacement labeling.

Radioiodinated fatty acids have been proposed as agents for use in heart imaging. Previous studies in experimental animals and humans using 131I-oleic acid of low specific activity were marginally successful. Higher specific activity compounds offer potential improvement for use as imaging agents for normal myocardium. Methods for preparation of high specific activity, radioiodinated fatty acids by iodine monochloride addition to oleic, linoleic, and linolenic acids, and iodide replacement of terminal bromine in 6-bromohexanoic, 11-bromoundecanoic, and 16-bromo-9-hexadecenoic acids are presented and compared. Although both labeling procedures are suitable for use with 123I, the latter synthetic route gives labeled fatty-acid analog molecules and 16-iodo-9-hexadecenoic acid appears to show improved myocardial specificity in preliminary animal studies.

Caproates↗