Anhydrous F-18 labeled eslemental flurine for radiopharmaceutical preparation.

Interest in fluorine- 18 as a label in radiopharmaceutical studies has led to the development of a method for the production of decicuries of anhydrous 18F-F2 using the 20Ne(d, alpha) 18F reaction. The amount of anhydrous 18F-F2 that can be removed from the target is a function of target pressure and carrier cokncentration increasing with rising target pressure and decreasing with decreasing carrier concentration. At a target pressure of 24 atmospheres and a carrier concentration of 0.1% F2, nearly 95% of the theoretical yield of fluorine- 18 produced can be removed and up to 85% delivered through a 10o-m stainless steel tube to the reaction chamber. Other functions affecting yield--including target design, target-gas handling and purity--have been addressed. Thick target yields for 14.0- and 9.4-MeV deuterons on target were measured to be 82 and 67 mCl/microA at saturation. With the BNL 60-in. cyclotron, production okf 600-800 mCl of 18F-F2 with a specific activity of approximately 10 mCi/mumole has been in effect since 1976.

Radiopharmaceuticals XXVII. 18F-labeled 2-deoxy-2-fluoro-d-glucose as a radiopharmaceutical for measuring regional myocardial glucose metabolism in vivo: tissue distribution and imaging studies in animals.

18F-2-Deoxy-2-fluoro-D-glucose (18FDG) is rapidly extracted by the mouse heart, and the radioactivity in heart (3-4% per organ) remains relatively constant for 2 hr post injection. The brain uptake (2-3% per organ) remained relatively constant throughout the time course of the study. Liver, lungs, kidneys, small intestine, and blood all showed a rapid clearance of radioactivity after injection of 18FDG. At 120 min the heart-to-lung ratio was 12 and heart-to-liver ratio was 32. Urinary excretion of activity was approximately 16% of the injected dose at 60 min. The uptake of radioactivity by dog heart following the intravenous administration of 18FDG was 2.8-4.1% at 60 min and 2.4% at 135 min; it was regionally distributed, the areas of highest activity being the left ventricle and the interventricular septum. The brain activity was 2.1-3.5% at 120 min, with a ratio of gray matter-to-white matter of 2-3:1. Urinary excretion in dogs was 16% and 50% of the injected dose at 60 and 135 min. The chemical form of the activity in the urine, although unidentified, was not 18F-. Cross-sectional images of the myocardium of the dog after intravenous injection of 18FDG were obtained using emission tomography.

Opioid and benzodiazepine tolerance and dependence: application of theory to critical care practice.

Critical care clinicians frequently manage patient pain and agitation and promote ventilator stability through use of opioids and benzodiazepines. Often, doses of these drugs must be increased considerably over time as they lose their effectiveness-an indication of drug tolerance. Furthermore, patients can experience negative physiologic responses to withdrawal of these drugs-an indication of drug dependence. Withdrawal symptoms due to abrupt discontinuation of drug therapy can be profound and dangerous. It is important that clinicians understand the mechanisms of drug therapies and their potential negative sequelae. The purpose of this article is to present physiologic theories of opioid and benzodiazepine actions, as well as drug tolerance and dependence, as a basis of knowledge for clinical practice. A clinical scenario of an intensive care unit patient is presented, and a care plan is offered, to provide guidance to practitioners who care for patients experiencing the consequences of long-term opioid and benzodiazepine use.

Rare diffuse peritoneal malignant neoplasms: CT findings in two cases.

In the peritoneal cavity, diffuse serosal replacement by tumor is demonstrated usually by extensive carcinomatous involvement from gastric, colonic, or pancreatic tumors or less frequently by mesothelioma. Primary tumors other than mesothelioma are extremely rare in the peritoneum. The computed tomographic appearances of two cases of rare peritoneal tumors, epithelioid hemangioendothelioma and desmoplastic small round cell tumor, are described.

The [18F]fluorodeoxyglucose method for the measurement of local cerebral glucose utilization in man.

A method has been developed to measure local glucose consumption in the various structures of the brain in man with three-dimensional resolution. [18F]-2-deoxy-2-fluoro-D-glucose is used as a tracer for the exchange of glucose between plasma and brain and its phosphorylation by hexokinase in the tissue. A mathematical model and derived operational equation are used which enable local cerebral glucose consumption to be calculated in terms of the following measurable variables. An intravenous bolus of [18F]-2-deoxy-2-fluoro-D-glucose is given and the arterial specific activity monitored for a predetermined period of from 30 to 120 minutes. Starting at 30 minutes, the activity in a series of sections through the brain is determined with three-dimensional resolution by an emission tomographic scanner. The method was used to measure local cerebral glucose consumption in two normal volunteers. The values in gray matter structures range from 5.79 mg/100 g per minute in the cerebellar cortex to 10.27 in the visual cortex, whereas, in white matter structures, the values range from 3.64 mg/100 g per minute in the corpus callosum to 4.22 in the occipital lobe. Average values for gray matter, white matter, and whole brain metabolic rates, calculated as a weighted average based on the approximate volume of each structure, are 8.05, 3.80, and 5.90 mg/100 g per minute, respectively. The value of 5.9 mg/100 g per minute compares favorably with values previously reported.