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R H Nord

Publications and source records attributed to R H Nord.

8 recordsLinked to original sources
PubMed2000

Measurement precision of body composition variables using the lunar DPX-L densitometer.

The objective of the study was to determine the precision of total- and regional-body composition measurements from a total-body scan using dual-energy X-ray absorptiometry (DXA). This is critical information necessary to determine the smallest change from baseline that could be detected with statistical significance when conducting longitudinal measurements of body composition variables in an individual. Twenty volunteers were scanned once each day for 4 consecutive days using a Lunar DPX-L densitometer and manufacturer-supplied software (version 1.3z). Coefficients of variation (CV, %) derived from data using the (preferred) extended research mode of analysis were 0.62, 1.89, 0.63, 2.0, 1.11, 1.10, and 1.09% for total-body bone mineral density (BMD), total percentage fat, total body tissue mass, fat mass, lean mass, bone mineral content (BMC), and total bone calcium, respectively. Regional measurements (arm, leg, trunk, pelvis, and spine) were less precise than total body measurements, with CVs in the range of 1% to 3% (but fat mass for arms was 4.26%, trunk 3.08%, BMC 3.65%). Small but statistically significant differences in mean values for most body composition variables were found when data were compared between extended and standard modes of analysis. Inconsistent use of analysis mode in a cohort or when following a patient longitudinally may negatively affect precision. We conclude that the measurement precision of total and regional body composition variables was generally comparable to the precision limits typically associated with lumbar spine and proximal femur BMD data.

Absorptiometry, Photon↗
PubMedDate not supplied

DXA body composition properties: inherent in the physics or specific to scanner type?

Experimental results with DXA body composition are partly attributable to the DXA technology itself (X-ray physics) and partly to the particular implementation (Lunar DPX, Hologic QDR, etc). This paper identifies a number of advantages and disadvantages of DXA body composition measurement, distinguishing between those which are common to all DXA and those which are specific to particular instruments.

Absorptiometry, Photon↗
PubMedDate not supplied

Body composition stability in Lunar DPX.

This study examines how well a Lunar DPX can compensate for certain aging changes in its X-ray source. Total body scans were done on a phantom having variable soft tissue composition. Aging of the X-ray source was simulated by placing a thin aluminum foil over the beam exit window, and by deliberately misadjusting the high voltage power supply. The % fat measurement was found to change by up to 12%, but returned to within about 2% afer recalibration.

Absorptiometry, Photon↗