Development of a non-radiometric method for measuring the arterial input function of a 11C-labeled PET radiotracer

Positron emission tomography (PET) uses radiotracers to quantify important biochemical parameters in human subjects. A radiotracer arterial input function (AIF) is often essential for converting brain PET data into robust output measures. For radiotracers labeled with carbon-11 (t1/2 = 20.4 min), AIF is routinely determined with radio-HPLC of blood sampled frequently during the PET experiment. There has been no alternative to this logistically demanding method, neither for regular use nor validation. A 11C-labeled tracer is always accompanied by a large excess of non-radioactive tracer known as carrier. In principle, AIF might be obtained by measuring the molar activity (Am; ratio of radioactivity to total mass; Bq/mol) of a radiotracer dose and the time-course of carrier concentration in plasma after radiotracer injection. Here, we implement this principle in a new method for determining AIF, as shown by using [11C]PBR28 as a representative tracer. The method uses liquid chromatography-tandem mass spectrometry for measuring radiotracer Am and then the carrier in plasma sampled regularly over the course of a PET experiment. Am and AIF were determined radiometrically for comparison. The new non-radiometric method is not constrained by the short half-life of carbon-11 and is an attractive alternative to conventional AIF measurement.

Elaboration of an environmentally appropriate technology of siderite ores concentration

Decrease of iron content in siderite ores, mined in mines stipulated a necessity to elaborate technologies of their concentration, which allow increasing iron content at least 35%. As a result of analysis of existing technologies of minerals concentration it was determined, that X-ray radiometric method is the most promising one for siderite ores concentration. Its essence is in a controlled supply of lump material of definite size, distribution of lump flows by streams and by the piece supply of ore lumps into analysis-division zone, in which the X-ray fluorescent analysis of main chemical elements takes place. Special microprocessor means of the measuring-control system make comparison of measuring results with the set threshold of separation and make decisions to direct the particular piece to one of the grading product. As the result, the particular piece comes to a chute either with rich product or by free fall comes to the chute of poor product. Tests of the technology of lump siderite ore separation accomplished by using industrial X-ray radiometric separators. Influence of ore size on the concentration process indices studied. It was determined, that at implementation the X-ray radiometric method of separation it is reasonable to limit by machine classes of 250– 100 mm and 100–30 mm. A technological flowchart proposed to provide the concentrate obtaining with the size of 30–10 mm and iron content of 35%. The concentrate can be used for reducing roasting of it in shaft furnaces. The formed screenings after concentration in the high intensity fields were proposed to subject to metallization in the rotating furnaces or rotating hearth furnaces. The metallized product can be smelted in an ore-thermal furnace to obtain steel semi-product used in large-scale EAF.