Dynamic measurement of newly formed carbonyl compounds in vapors from electronic cigarettes.

Recently, the formation of carbonyl compound within e-cigarettes usage has been reported. The aim of this study was to develop a new analytical method for the direct analysis of carbonyl compounds in vaporized liquids. Two different types of e-cigarettes and different puff's duration have been evaluated, using a modified smoking machine for vapor generation. An isotopic dilution approach, based on deuterated internal standard addition to the e-liquid before filling the e-cigarette tank, has been developed. Carbonyl compounds have been sampled in vapors using a direct, simple, solid-phase microextraction technique with on-fiber derivatization. Related oximes have been analyzed by gas chromatography/mass spectrometry technique. Results confirmed that new carbonyl compounds are formed during the vaping process, and that formation depends both from the heating device and from puffing topography.

Measurement of standard uptake value in dual-head coincidence system.

UNLABELLED: The standard uptake value (SUV) is an important semi-quantitative parameter in positron emission tomography (PET). But SUV is not available in dual-head coincidence imaging system (DHC) which is widely used in clinical practice. This study was designed to develop a method for measuring SUV in DHC system, and then compared SUV in DHC and SUV in PET. METHOD: Firstly, the calibration factor (CF) for converting the voxel count rate to radioactivity concentration was determined by a phantom study in DHC. Then the method for calculating SUV in DHC was formulated. Finally, SUV in DHC and SUV in PET were compared through another phantom study. The phantoms used in the comparing study were cylindrical and consisted of several hot lesions. RESULTS: The CF varied with the detected single count rate in a biquadratic polynomial; the lesion's radioactivity concentration was got based on the CF and the voxel count rate. From the lesion's radioactivity concentration, the lesion's SUV in DHC was obtained. The comparison study showed that SUV in PET was higher than SUV in DHC. The SUV in both DHC and PET increased with increasing sizes of lesions and were related with the reconstruction algorithm. CONCLUSIONS: SUV in DHC images could be obtained in our method; the value in DHC images was lower than that in PET image; and many factors, such as system performance, lesion's size, and reconstruction algorithm could influence the SUV accuracy in both DHC and PET.

Blood volume analysis: a new technique and new clinical interest reinvigorate a classic study.

Blood volume studies using the indicator dilution technique and radioactive tracers have been performed in nuclear medicine departments for over 50 y. A nuclear medicine study is the gold standard for blood volume measurement, but the classic dual-isotope blood volume study is time-consuming and can be prone to technical errors. Moreover, a lack of normal values and a rubric for interpretation made volume status measurement of limited interest to most clinicians other than some hematologists. A new semiautomated system for blood volume analysis is now available and provides highly accurate results for blood volume analysis within only 90 min. The availability of rapid, accurate blood volume analysis has brought about a surge of clinical interest in using blood volume data for clinical management. Blood volume analysis, long a low-volume nuclear medicine study all but abandoned in some laboratories, is poised to enter the clinical mainstream. This article will first present the fundamental principles of fluid balance and the clinical means of volume status assessment. We will then review the indicator dilution technique and how it is used in nuclear medicine blood volume studies. We will present an overview of the new semiautomated blood volume analysis technique, showing how the study is done, how it works, what results are provided, and how those results are interpreted. Finally, we will look at some of the emerging areas in which data from blood volume analysis can improve patient care. The reader will gain an understanding of the principles underlying blood volume assessment, know how current nuclear medicine blood volume analysis studies are performed, and appreciate their potential clinical impact.

Measurement of 18F-FDG concentrations in blood samples: comparison of direct calibration and standard solution methods.

OBJECTIVE: The purpose of this study was to compare the accuracy and reliability of 2 well counter methods for measuring the activity concentration of (18)F-FDG in blood samples. METHODS: Three to 5 blood samples from 154 patient studies were weighed and measured in a well counter. The (18)F-FDG activity concentration was derived using, first, a direct calibration factor to convert measured well counter readings into activity concentration and, second, a comparison of measured counts with those of a specified standard solution. RESULTS: The ratio between the activity concentration results of the 2 methods was 0.996 +/- 0.033, indicating that the methods provided equal results. CONCLUSION: Because the standard solution method is more prone to human error, less reproducible, and more labor intensive, preference should be given to the direct calibration method.

A parallel processing solid phase extraction protocol for the determination of whole blood folate.

We describe an improved whole blood folate analysis method that facilitates increased throughput compared to our previous method (Dueker et al. (2000) Anal. Biochem. 283, 266). Improvements include three items: first, a buffered solvent exchange to remove interfering amino acids, especially phenylalanine whose esters may interfere with the analysis because their retention times on the gas chromatography are close to those of the para-aminobenzoic acid (pABA) isotopomers; second, substituting an NH2 solid phase extraction step for an HPLC step permits the batch parallel processing of samples; third, replacing trifluoroacetyl derivatives of ethyl-esterified pABA isotopomers with heptafluorobutyl derivatives, which are better resolved on the GC column. The method measures pABA, a stable degradation product of folate. This simplifies sample handling and purification. Relative standard deviations are typically 5% or less and a single operator can process samples in batches of 40. Results from our GCMS method correlate (R = 0.98) with the Lactobacillus casei assay for whole blood folate. The modifications will facilitate the development of high throughput methods for whole blood folate. Our method holds promise for epidemiological and clinical studies, where accurate whole blood folate concentrations are needed. Because it is internally standardized, interlaboratory variation should be minimal.

[Quantitative radionuclide leakage control during isolated limb perfusion]. / Quantitative Leckkontrolle mit Radionuckliden bei der isolierten Extremitätenperfusion.

In order to reduce side effects of high-dose chemotherapy the penetration of the cytostatic substances into the main circulation should be prevented or limited. An efficient procedure for checking the leakage is generally based on the addition of a radionuclide to the perfusate. By scintillation probes the distribution of this radionuclide in the body of the patient is checked. A method is presented which continuously calculates the actual volume of the fluid which is penetrating into the main circulation during the perfusion. The values of momentary and cumulative volume crossover enables the surgical oncologist to detect a leakage readily and reliably and may be the basis for measures of confining it.

The matrix effect in particle beam liquid chromatography/mass spectrometry and reliable quantification by isotope dilution.

The transport efficiency of the particle beam liquid chromatography/mass spectrometer interface is influenced by analyte concentration contributing to a widely reported non-linearity. In this work, coeluting, isotope-labeled internal standards were investigated as 'carriers' to improve the transport efficiency and linearity. Three styrene metabolites--mandelic, phenylglyoxylic and hippuric acids--and their pentadeutero analogs were separated by reversed-phase liquid chromatography (LC) with an ammonium acetate-acetonitrile mobile phase. Selected positive ions produced by electron ionization were monitored to generate particle beam LC/MS calibration curves. The present study demonstrates that particle beam LC/MS not only is non-linear, but also is subject to a matrix effect presumably by the same mechanism responsible for non-linearity. Coeluting, isotope-labeled internal standards were ineffective at linearizing the particle beam liquid chromatograph/mass spectrometer detector response. Isotope dilution quantification, however, compensates for variable transport efficiencies, linearizes calibration and compensates for the matrix effect, affording reliable quantification of the styrene metabolites.

[Clinical evaluation of the RKA 3-01 radiocardioanalyzer]. / Klinicheskaia otsenka radiokardioanalizatora RKA 3-01.

Detection of cardiovascular diseases can be improved through the use of the radiocardioanalyser RKA 3-01. It measures automatically the volume of circulating blood, records radiocardiograms, performs their analysis, and computes circulation indices.

The use of a proprietary organic sample oxidiser to determine 14CO2 and 14C-carbonates of trace level specific radioactivity.

The specific radioactivity of 14CO2 (greater than 3 nCi mol-1) can be determined by conversion to an insoluble carbonate followed by re-evolution of the gas, using a mineral acid, through a proprietary organic sample oxidiser (Packard 306 Oxidiser, Packard Instruments Ltd, Caversham, Berks, U.K.).

A new rapid method for quantification of nitrogen in human serum employing the 14N(p,p' gamma)14N reaction: application to human pregnancy.

The total nitrogen concentrations in dried serum from 54 pregnant women and 17 newborn babies were determined by a new application of the 14N(p,p' gamma)14N reaction resonance at 3.9 MeV. The samples were bombarded in a He atmosphere by 4.1 MeV protons from a tandem Van de Graaff accelerator. The mean dry-weight nitrogen concentration in serum sampled during early pregnancy (6-12 weeks; 13.9 g per 100 g +/- 5.4%) was significantly higher than that in serum sampled during late pregnancy (38-42 weeks: 13.0 g per 100 g +/- 3.9%, p less than 0.001) and than that in serum taken from the umbilical cord (13.3 g per 100 g +/- 4.6%, p less than 0.01). The nitrogen levels measured using this rapid nuclear technique, applied for the first time to human serum analysis, agree well with parallel Kjeldahl analyses.

[Evaluation of the errors in analog recording of radionuclide dilution and clearance curves]. / Otsenka pogreshnosti analogovoi registratsii krivykh razvedeniia i klirensa radionuklidov.

The mathematical expression for the function of changes in the output signal of the analog medium frequency pulse meter (MFPM), supplied on the input of the dilution curve (clearance) of a radioactive indicator, is obtained. The graphs illustrating the deformation of the initial curve at different MFPM time constants and different rates of the increase and decrease in the input signal, corresponding to the real conditions occurring in the study of the regional cerebral and muscular blood flow with the use of 133Xe clearance and the study of the blood flow volume through heart and large vessels with the use of RISA-131 dilution, are plotted. The errors introduced by the MFPM to the obtained data of the basic informative parameters--a period of half-dilution, the maximum value and the area under the curve are calculated. The graphs of the errors versus the MFPM time constants are normalized by the time units relative to the maximum of the corresponding initial curves thus enabling one to use the graphs as a versatile means in the course of assessment of the dilution and clearance curves' distortions introduced by the analogous MFPM. The analysis of the results obtained is presented.

Device for monitoring 14CO2 in the expired air from beagle dogs: its use in the study of aminopyrine demethylation.

1. A device for serial collection of samples for determination of 14CO2 in the expired air of the beagle dog is described. 2. The device has been evaluated using [14C]aminopyrine as a model compound. The rate of 14C excretion in the expired air initially correlated with the plasma concentrations of aminopyrine rather than the plasma concentrations of 14C. 3. The dog demethylated aminopyrine at the slower rate than the rat. Both species demethylate the unchanged drug more readily than subsequent metabolites.