Thirty-two magnetic resonance imaging examinations of the lungs were performed in 16 subjects after inhalation of 1-2 L of helium 3 gas that was laser polarized to 10%-25%. The distribution of the gas was generally uniform, with visualization of the fissures in most cases. Ventilation defects were demonstrated in smokers and in a subject with allergies. The technique has potential for evaluating small airways disease.

CLASEY, JODY L., CLAUDE BOUCHARD, C. DAVID TEATES, JILL E. RIBLETT, MICHAEL 0. THORNER, MARK L. HARTMAN, AND ARTHUR WELTMAN. the use of anthropometric and dual-energy X-ray absorptiometry (DXA) measures to estimate total abdominal and abdominal visceral fat in men and women. Obes Res. 1999; 7:256-264. Objective: A single-slice computed tomography (CT) scan provides a criterion measure of total abdominal fat (TAF) and abdominal visceral fat (AVF), but this procedure is often prohibitive due to radiation exposure, cost, and accessibility. In the present study, the utility of anthropometric measures and estimates of trunk and abdominal fat mass by dual-energy X-ray absorptiometry (DXA) to predict CT measures of TAF and AVF (cross-sectional area, cm2) was assessed. ference and abdominal sagittal diameter were the anthropometric measures most strongly associated with TAF (r=0.87 to 0.93; Standard Error of Estimate (SEE) =60.7 to 75.4 cm') and AVF (r=0.84 to 0.93; SEE=0.7 to 30.0 cm'). The least predictive anthropometric measure of TAF or AVF was the commonly used waist-to-hip ratio (WHR). DXA estimates of trunk and abdominal fat mass were strongly associated with TAF (Y = .94 to 0.97; SEE = 36.9 to 50.9 cm2) and AVF (r=0.86 to 0.90; SEE=4.9 to 27.7 cm2). Discussion: The present results suggest that waist circumference and/or abdominal sagittal diameter are better predictors of TAF and AVF than the more commonly used WHR. DXA trunk fat and abdominal fat appear to be slightly better predictors of TAF but not AVF compared to these anthropometric measures. Thus DXA does not offer a significant advantage over anthropometry for estimation of AVF. Research Methods and Procedures

We examined the validity of percent body fat (%Fat) estimation by two-compartment (2-Comp) hydrostatic weighing (Siri 2-Comp), 3-Comp dual-energy X-ray absorptiometry (DEXA 3-Comp), 3-Comp hydrostatic weighing corrected for the total body water (Siri 3-Comp), and anthropometric methods in young and older individuals (n = 78). A 4-Comp model of body composition served as the criterion measure of %Fat (Heymsfield 4-Comp; S. B. Heymsfield, S. Lichtman, R. N. Baumgartner, J. Wang, Y. Kamen, A. Aliprantis, and R. N. Pierson Jr., Am. J. Clin. Nutr. 52: 52-58, 1990.). Comparison of the Siri 3-Comp with the Heymsfield 4-Comp model revealed mean differences of /= r = 0.997, total error values

Dual energy x-ray absorptiometry (DEXA) measures bone mineral content (BMC), bone mineral density (BMD), fat-free mass (FFM), and provides estimates of percent body fat. Changes in scan mode geometry (pencil beam vs array) may impact these measures and body composition estimates using multi-compartment models. Forty-one adults, ages 59-79 yr, were scanned in each mode and also underwent hydrostatic weighing and measurement of total body water (tritiated water dilution). The effect of scan mode on measurement of DEXA BMC, BMD, FFM, and percent body fat (DEXA %Fat) was examined. The effect of scan mode on percentage body fat determined by a 4-compartment body composition model (4 Comp %Fat) and comparison of DEXA %Fat and 4 Comp %Fat were also examined. BMC and DEXA %Fat were greater (1.3% and 3.9%, respectively, P < 0.01), and BMD and FFM were lower (1.1% and 1.9%, respectively, P < 0.01) with the array scan mode. The 4 Comp %Fat was significantly greater (0.2%) when the array scan mode measurements of total body bone mineral were used; however, these differences were physiologically inconsequential. Comparison between DEXA %Fat and 4 Comp %Fat measures revealed a total error of +/-5.0% in the older adults examined. These results indicate significant scan mode differences in total body BMC, BMD, FFM, and DEXA %Fat measurements and demonstrate the importance of using a single DEXA scan mode for clinical investigation, particularly with longitudinal studies. For all investigations with DEXA, the scan mode should be reported. Furthermore, the error associated with using DEXA alone to estimate percent fat in an older population suggests that this technique is unacceptable in a research setting.