Impact Of Measurement Methods Research Articles

Liver fat volume fraction measurements based on multi-material decomposition algorithm in patients with nonalcoholic fatty liver disease: the influences of blood vessel, location, and iodine contrast

BackgroundIn recent years, spectral CT-derived liver fat quantification method named multi-material decomposition (MMD) is playing an increasingly important role as an imaging biomarker of hepatic steatosis. However, there are various measurement ways with various results among different researches, and the impact of measurement methods on the research results is unknown. The aim of this study is to evaluate the reproducibility of liver fat volume fraction (FVF) using MMD algorithm in nonalcoholic fatty liver disease (NAFLD) patients when taking blood vessel, location, and iodine contrast into account during measurement.MethodsThis retrospective study was approved by the institutional ethics committee, and the requirement for informed consent was waived because of the retrospective nature of the study. 101 patients with NAFLD were enrolled in this study. Participants underwent non-contrast phase (NCP) and two-phase enhanced CT scanning (late arterial phase (LAP) and portal vein phase (PVP)) with spectral mode. Regions of interest (ROIs) were placed at right posterior lobe (RPL), right anterior lobe (RAL) and left lateral lobe (LLL) to obtain FVF values on liver fat images without and with the reference of enhanced CT images. The differences of FVF values measured under different conditions (ROI locations, with/without enhancement reference, NCP and enhanced phases) were compared. Friedman test was used to compare FVF values among three phases for each lobe, while the consistency of FVF values was assessed between each two phases using Bland–Altman analysis.ResultsSignificant difference was found between FVF values obtained without and with the reference of enhanced CT images. There was no significant difference about FVF values obtained from NCP images under the reference of enhanced CT images between any two lobes or among three lobes. The FVF value increased after the contrast injection, and there were significant differences in the FVF values among three scanning phases. Poor consistencies of FVF values between each two phases were found in each lobe by Bland–Altman analysis.ConclusionMMD algorithm quantifying hepatic fat was reproducible among different lobes, while was influenced by blood vessel and iodine contrast.

Impact of measurement method on interobserver variability of apparent diffusion coefficient of lesions in prostate MRI

PurposeTo compare the inter-observer variability of apparent diffusion coefficient (ADC) values of prostate lesions measured by 2D-region of interest (ROI) with and without specific measurement instruction.MethodsForty lesions in 40 patients who underwent prostate MR followed by targeted prostate biopsy were evaluated. A multi-reader study (10 readers) was performed to assess the agreement of ADC values between 2D-ROI without specific instruction and 2D-ROI with specific instruction to place a 9-pixel size 2D-ROI covering the lowest ADC area. The computer script generated multiple overlapping 9-pixel 2D-ROIs within a 3D-ROI encompassing the entire lesion placed by a single reader. The lowest mean ADC values from each 2D-small-ROI were used as reference values. Inter-observer agreement was assessed using the Bland-Altman plot. Intraclass correlation coefficient (ICC) was assessed between ADC values measured by 10 readers and the computer-calculated reference values.ResultsTen lesions were benign, 6 were Gleason score 6 prostate carcinoma (PCa), and 24 were clinically significant PCa. The mean±SD ADC reference value by 9-pixel-ROI was 733 ± 186 (10−6 mm2/s). The 95% limits of agreement of ADC values among readers were better with specific instruction (±112) than those without (±205). ICC between reader-measured ADC values and computer-calculated reference values ranged from 0.736–0.949 with specific instruction and 0.349–0.919 without specific instruction.ConclusionInterobserver agreement of ADC values can be improved by indicating a measurement method (use of a specific ROI size covering the lowest ADC area).

A study of unexpected autoignition temperature trends for pure n-alkanes

An experimental study of minimum autoignition temperatures (AIT) reveals unexpected behavior of pure, higher-carbon-number n-alkanes (C16 and larger) not predicted by current AIT prediction methods nor current phenomenological understanding of autoignition processes. The well-documented AIT trend for normal alkanes shows high AIT values for smaller members of the family with decreasing AIT, as carbon chain length increases, to a roughly constant value for C7 and larger. Measurements in this work show that values start to increase again at C16 and show a dramatic and previously unexplained step increase between C25 and C26.The impact of measurement methods on AIT values is discussed. Experimental modifications to compensate for AIT measurements at altitude are presented. Measured values for several n-alkanes using the ASTM E-659 method are reported and compared to data from other sources. Temperature-versus-time plots, external autoignition experiments, lag times, and decomposition measurements using differential scanning calorimetry are also reported and examined for several n-alkanes to illucidate the unexpected trends. A mechanistic explanation of these trends is proposed. Finally, the implications of this behavior for trends in other chemical families are discussed.

Testosterone and cardiometabolic risk in the general population – the impact of measurement method on risk associations: a comparative study between immunoassay and mass spectrometry

Low total testosterone (TT) serum concentrations in men have been associated with various cardiometabolic risk factors. But given error-prone immunoassays used for TT assessment, upcoming mass spectrometry methods question the validity of these risk associations. Thus, we performed the first comparative study quantifying potential differences in the association of TT with cardiometabolic risk factors between the two methods. We used data from 1512 men aged 20-81 years, recruited for the cross-sectional population-based Study of Health in Pomerania (SHIP), Germany. TT concentrations were repeatedly measured by chemiluminescent immunoassay (CLIA, Immulite 2500) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). We tested for significant differences between coefficients from CLIA- and LC-MS/MS-based multiple linear regression models associating TT with major cardiometabolic risk factors including adiposity, lipid metabolism, blood pressure, diabetic status, and inflammation. TT measurements by CLIA and LCMS/MS yielded a pearson correlation coefficient of 0.84. only three of the ten tested associations for tt with cardiometabolic risk factor showed significant differences between the two measurement methods: in comparison to LC-MS/MS, CLIA-based TT assessment significantly underestimated risk associations of TT with waist circumference (β: -0.54 vs -0.63), BMI (β: -0.19 vs -0.22), and serum glucose levels (β: -0.006 vs -0.008). In this comparative study, the CLIA platform showed a reasonable measurement error and yielded comparable risk associations, providing little support to measure TT concentrations in men from the general population exclusively by LC-MS/MS.

Použiteľnosť elektronických pomôcok pre buzolové meranie v lesníckom mapovaní a výskume

Abstract The paper contains output of the research aimed on applicability of compass measurement using laser range-finder Impulse LR 200 and electronic compass LTI MapStar Compass Module in forestry mapping and research. The research was aimed on the impact of measurement methods and also methods of computation on the final precision of the position evaluation. Because the combination of instruments, with the Field-Map software, is also used in forestry research (forest inventory, research of natural forests), the paper shows also the methods of evaluation referring to this field of use of compass measurement. In dependence to measurement and evaluation methods there is a quite wide interval of mean position error mxy values (0.15 - 0.60 m). In general it can be stated, that compass measurement in areas without negative effects on the natural magnetism is applicable method for the under-canopy forestry mapping and research. The best of output values have shown the theoretical possibility of use in forest area cadastral mapping (4th accuracy class), especially in combination with other measurement methods

Clinician-Assessed Depression and HAART Adherence in HIV-Infected Individuals in Methadone Maintenance Treatment

The impact of measurement methods on the relationship between depression and HIV treatment adherence has not been adequately examined. The purpose of this paper is to examine the relationship between clinician- and patient-rated depression and HIV medication adherence. The participants were 91 HIV-infected individuals in methadone maintenance. Depression was assessed via clinician ratings (Clinical Global Impression Scale and Montgomery Asberg Depression Rating Scale) and self-report (Beck Depression Inventory-Short Form). Clinicians rated substance abuse using the Clinical Global Impression Scale and a structured interview. HIV medication adherence was measured over the following 2 weeks using electronic caps. Each unit increase in the Clinical Global Impression Scale was associated with 75% increased odds of nonadherence (OR=1.75, p=0.002, 95% CI=1.23-2.48). Similarly, for each standard deviation Montgomery Asberg Depression Rating Scale increase, there was a 2.6-fold increased odds of nonadherence (OR=2.60, p=0.001, 95% CI=1.45-4.67). Substance abuse and self-reported depression severity were not significantly related to adherence. Clinician-rated depression severity was a strong predictor of nonadherence. Assessment methods may influence the relationship between depression and HIV nonadherence.