In vivo precision of the GE Lunar iDXA densitometer for the measurement of total body composition and fat distribution in adults.

In vivo precision for body composition measurements using dual energy X-ray absorptiometry (DXA; GE Lunar iDXA, GE Healthcare, Bucks, UK) was evaluated in 52 men and women, aged 34.8 (s.d. 8.4; range 20.1-50.5) years, body mass index (25.8 kg/m(2); range 16.7-42.7 kg/m(2)). Two consecutive total body scans (with re-positioning) were conducted. Precision was excellent for all measurements, particularly for total body bone mineral content and lean tissue mass (root mean square 0.015 and 0.244 kg; coefficients of variation (CV) 0.6 and 0.5%, respectively). Precision error was CV 0.82% for total fat mass and 0.86% for percentage fat. Precision was better for gynoid (root mean square 0.397 kg; CV 0.96%) than for android fat distribution (root mean square 0.780 kg, CV 2.32%). There was good agreement between consecutive measurements for all measurements (slope (s.e.) 0.993-1.002; all R(2) = 0.99). The Lunar iDXA provided excellent precision for total body composition measurements. Research into the effect of body size on the precision of DXA body fat distribution measurements is required.

Validity of foot-to-foot bio-electrical impedance analysis body composition estimates in overweight and obese children.

OBJECTIVES: To examine the validity of body composition estimates obtained using foot-to-foot bio-electrical impedance analysis (BIA) in overweight and obese children by comparison to a reference four-compartment model (4-CM). SUBJECTS/METHODS: 38 males: age (mean +/- sd) 13.6 +/- 1.3 years, body mass index 30.3 +/- 6.0 kg.m(-2) and 14 females: age 14.7 +/- 2.2 years, body mass index 32.4 +/- 5.7 kg.m(-2) participated in the study. Estimates of fat-free mass (FFM), fat mass (FM) and percentage body fat (PBF) obtained using a Tanita model TBF-310 and a 4-CM (derived from body mass, body volume, total body water and total body bone mineral measurements) were compared using bias and 95% limits of agreement (Tanita minus 4-CM estimates). RESULTS: Body composition estimates obtained with the Tanita TBF-310 were not significantly different from 4-CM assessments: for all subjects combined the bias was -0.7kg for FM, 0.7kg for FFM and -1.3% for PBF. However, the 95% limits of agreement were substantial for individual children: males, up to +/-9.3kg for FFM and FM and +/-11.0% for PBF; females, up to +/-5.5kg for FFM and FM and +/-6.5% for PBF. CONCLUSIONS: The Tanita TBF-310 foot-to-foot BIA body composition analyser with the manufacturer's prediction equations is not recommended for application to individual children who are overweight and obese although it may be of use for obtaining group mean values.

Exercise during childhood and adolescence: a prophylaxis against cystic fibrosis-related low bone mineral density? Exercise for bone health in children with cystic fibrosis.

Inadequate bone mineral accrual during growth and accelerated bone demineralisation in adulthood are recognised as additional and serious complications for patients with cystic fibrosis (CF). However, little attention has been given to preventative strategies for this population. Inadequate bone accrual during childhood and adolescence, and premature bone loss, lead to a failure to attain an optimal peak bone mass, osteoporosis and fracture in patients with CF. Pharmaceutical treatments may assist in the improvement of bone in patients with CF, but these are usually not preferable for use in children. Evidence indicates that regular, weight-bearing exercise significantly enhances bone accrual in healthy children. This paper reviews the literature concerning the potential for weight-bearing exercise to improve bone mineral accrual in children with CF. All relevant literature since 1979 was obtained and reviewed from the Medline, PubMed, Cochrane and PEDro data base. Evidence concerning the efficacy of exercise for bone health in CF is lacking. There have been no controlled trials investigating the value of weight-bearing exercise for bone accrual in children with CF. As exercise may offer an effective and enjoyable strategy to improve the bone development in children who have CF, exercise should be a high priority for randomised controlled trials in this population.

Can ultrasound propagate in the joint space of a human knee?

A large body of evidence supports the principle that the use of low-intensity pulsed ultrasound with a frequency of 1.5 MHz can reduce fracture healing time. It is hypothesized that similar therapeutic benefits may be achieved in damaged articular cartilage. This study looks specifically at a 22-mm circular ultrasound transducer delivering ultrasound with a frequency of 1.5 MHz. A human cadaver knee was imaged using CT, the resulting images were used to help map a number of hydrophone positions in the joint from which measurements were taken. The experimental results suggest that at best there is a 30-mm window in which to place the ultrasound transducer for ultrasound to propagate through the joint space. In terms of a clinical device delivering an I(SATA) of 30 mW cm(-2) to anterior regions of the joint, the I(SATA) in posterior regions will at best be in the region of 10 mW cm(-2). The clinical implications of this are not known and require further investigation.

Low lumbar spine bone mineral density in both male and female endurance runners.

There have been many reports of low bone mineral density (BMD) in female endurance runners. Although there have been several reports of low BMD in male runners, it is unclear how comparable the problem is to that in females. We compared BMD between male and female endurance runners and with a reference population. One hundred and nine endurance runners (65 females, 44 males) aged 19-50 years participated and had been training regularly for at least 3 years (32-187.2 km week(-1)) in events from 3 km to the marathon. BMD was measured at the lumbar spine (L2-L4) and hip by DXA. A questionnaire assessed training and menstrual status. Lumbar spine T scores were similar in male and female runners (-0.8 (0.8) versus -0.8 (0.7); f = 0.015; P = 0.904) as were total hip T scores (0.6 (7.9) versus 0.5 (9.2); f = 0.192; P = 0.662). The proportion of male runners with low lumbar spine BMD (<-1.0) (n = 16 from 44) compared to that of females (n = 27 from 65) (P = 0.675). Males had lower spine T scores than eumenorrhoeic females (-0.8 (0.7) versus -0.4 (0.7); f = 5.169; P = 0.03). There were moderate negative correlations between weekly running distance and lumbar spine BMD in males and females (r(2) = 0.267; 0.189; P < 0.001), independent of menstrual status in females (r(2) = 0.192; P < 0.001). Lumbar spine but not hip T scores were greater in runners who participated in resistance training at least twice-a-week (male: -0.4 versus -1.1; female: -0.5 versus -1.1; P < 0.01). Using multiple regression, running distance (-) and BMI (+) together best predicted lumbar spine T scores (r(2) = 0.402; P < 0.01) in females. Although weak, BMI (+) best predicted hip T scores (r(2) = 0.167; P < 0.05). In males, running distance and training years (-) together best predicted lumbar spine T scores (r(2) = 0.400; P < 0.01). Training years (-) best predicted hip T scores (r(2) = 0.361; P < 0.01). To conclude, our findings suggest that male runners face the same bone threat at the spine, as female runners. Further research in male athletes is required. Incorporation of regular resistance training into an athlete's training programme may be a useful preventative strategy.

Pediatric in vivo cross-calibration between the GE Lunar Prodigy and DPX-L bone densitometers.

Dual energy x-ray absorptiometry (DXA) machine cross-calibration is an important consideration when upgrading from old to new technology. In a recent cross-calibration study using adult subjects, close agreement between GE Lunar DPX-L and GE Lunar Prodigy scanners was reported. The aim of this work was to cross-calibrate the two machines for bone and body composition parameters for pediatrics from age 5 years onwards. One-hundred ten healthy volunteers aged 5-20 years had total body and lumbar spine densitometry performed on DPX-L and Prodigy densitometers. Cross-calibration was achieved using linear regression and Bland-Altman analysis. There was close agreement between the machines, with r2 ranging from 0.85 to 0.99 for bone and body composition parameters. Paired t-tests demonstrated significant differences between machines that were dependent on scan acquisition mode, with the greatest differences reported for the smallest children. At the lumbar spine, Prodigy bone mineral density (BMD) values were on average 1.6% higher compared with DPX-L. For the total body, there were no significant differences in BMD; however, there were significant differences in bone mineral content (BMC) and bone area. For small children, the Prodigy measured lower BMC (9.4%) and bone area (5.8%), whereas for larger children the Prodigy measured both higher BMC (3.1%) and bone area (3.0%). A similar contrasting pattern was also observed for the body composition parameters. Prodigy values for lean body mass were higher (3.0%) for small children and lower (0.5%) for larger children, while fat body mass was lower (16.4%) for small children and higher (2.0%) for large children. Cross-calibration coefficients ranged from 0.84 to 1.12 and were significantly different from 1 (p<0.0001) for BMC and bone area. Bland-Altman plots showed that within the same scan acquisition modes, the magnitude of the difference increased with body weight. The results from this study suggest that the differences between machines are mainly due to differences in bone detection algorithms and that they vary with body weight and scan mode. In general, for population studies the differences are not clinically significant. However, for individual children being measured longitudinally, cross-over scanning may be required.

Effect of oral bisphosphonates on bone mineral density and body composition in adult patients with cystic fibrosis: a pilot study.

BACKGROUND: Approximately two thirds of adult patients with cystic fibrosis have reduced bone mineral density and up to one quarter have osteoporosis at one or more sites. Any bone mineral deficits are likely to be exacerbated in patients following lung transplantation by their immunosuppressive regimen. Vertebral collapse and rib fractures will impair the ability to cough and the efficacy of physiotherapy treatments. METHODS: Patients attending the Leeds Regional Adult Cystic Fibrosis Unit with either osteopenia or osteoporosis on dual energy x ray absorptiometry (DXA) scanning were offered treatment with oral bisphosphonates after exclusion of abnormal vitamin D, calcium, or phosphate levels, abnormal thyroid function, or hypogonadism. Those declining treatment or patients with a normal initial DXA scan formed the control group. A second DXA scan was performed after a mean of 2.4 years in the treatment group and 2.9 years in the non-treatment group. Patients in the active group were asked to complete a short questionnaire detailing their adherence to treatment. RESULTS: The medians of the differences in annual changes in bone parameters between treatment and control groups showed significant differences in bone mineralisation in favour of the treatment group at the lumbar spine (L2-L4), the femoral neck, and for total body measurements. There were no significant differences in weight, height, or body composition in either patient group. Most treated patients stated that they adhered to treatment most of the time. CONCLUSION: Treatment with oral bisphosphonates may improve bone mineralisation in adult patients with cystic fibrosis. The results of this pilot study need to be further explored in a randomised controlled trial.

Bone density, body composition and menstrual history of sedentary female former gymnasts, aged 20-32 years.

Few studies have examined the effects of retirement from sports involving regular, high impact and weight bearing activity on bone mass. This cross-sectional study compared total body and regional areal bone mineral density (aBMD, g/cm(2)) within female former gymnasts and women who had never participated in structured sport or exercise, and explored relations between aBMD of these former gymnasts and their duration of retirement. Eighteen sedentary female former gymnasts (GYM) and 18 sedentary controls (CON) were recruited. GYM displayed a broad range of duration of retirement (3-12 years) and a wide age range (20-32 years). GYM and CON were paired individually to match for age, body mass and stature. GYM had commenced training at least 3 years pre-menarche and had trained post-menarche for 2 or more years. They had trained continuously for 5-12 years and had retired between age 14 and 22 years. Measurements of aBMD and body composition were made using dual energy X-ray absorptiometry (DXA). Group mean values of physical and skeletal characteristics were compared using paired t-tests. Linear regression was used to explore possible relations of aBMD within GYM to duration of retirement. GYM displayed a higher aBMD than CON at all measurement sites, which ranged in magnitude from 6% for the total body ( P=0.004), to 11% for the total femur ( P=0.006). Elevations of aBMD within GYM equated to T-scores ranging from +0.8 (arms) to +1.7 (legs). There were no differences in body composition or age of menarche between groups, although 11 of 18 GYM reported a history of irregular menses. There was no significant decline of aBMD with increasing duration of retirement in GYM. The results suggested that an elevated bone mass in female former gymnasts was retained during early adulthood, in spite of a cessation of training for up to 12 years.

Comparison of body composition methods in overweight and obese children.

The objective of the present study was to investigate the accuracy of percent body fat (%fat) estimates from dual-energy X-ray absorptiometry, air-displacement plethysmography (ADP), and total body water (TBW) against a criterion four-compartment (4C) model in overweight and obese children. A volunteer sample of 30 children (18 male and 12 female), age of (mean +/- SD) 14.10 +/- 1.83 yr, body mass index of 31.6 +/- 5.5 kg/m, and %fat (4C model) of 41.2 +/- 8.2%, was assessed. Body density measurements were converted to %fat estimates by using the general equation of Siri (ADPSiri) (Siri WE. Techniques for Measuring Body Composition. 1961) and the age- and gender-specific constants of Lohman (ADPLoh) (Lohman TG. Exercise and Sport Sciences Reviews. 1986). TBW measurements were converted to %fat estimates by assuming that water accounts for 73% of fat-free mass (TBW73) and by utilizing the age- and gender-specific water contents of Lohman (TBWLoh). All estimates of %fat were highly correlated with those of the 4C model (r > or = 0.95, P < 0.001; SE < or = 2.14). For %fat, the total error and mean difference +/- 95% limits of agreement compared with the 4C model were 2.50, 1.8 +/- 3.5 (ADPSiri); 1.82, -0.04 +/- 3.6 (ADPLoh); 2.86, -2.0 +/- 4.1 (TBW73); 1.90, -0.3 +/- 3.8 (TBWLoh); and 2.74, 1.9 +/- 4.0 DXA (dual-energy X-ray absorptiometry), respectively. In conclusion, in overweight and obese children, ADPLoh and TBWLoh were the most accurate methods of measuring %fat compared with a 4C model. However, all methods under consideration produced similar limits of agreement.

Estimates of percentage body fat in young adolescents: a comparison of dual-energy X-ray absorptiometry and air displacement plethysmography.

OBJECTIVE: To evaluate the accuracy of percentage body fat (%fat) estimates from air displacement plethysmography (ADP) against an increasingly recognised criterion method, dual-energy X-ray absorptiometry (DXA), in young adolescents. DESIGN: Cross-sectional evaluation. SETTING: Leeds General Infirmary, Centre for Bone and Body Composition Research, Leeds, UK. SUBJECTS: In all, 28 adolescents (12 males and 16 females), age (mean+/-s.d.) 14.9+/-0.5 y, body mass index 21.2+/-2.9 kg/m(2) and body fat (DXA) 24.2+/-10.2% were assessed. RESULTS: ADP estimates of %fat were highly correlated with those of DXA in both male and female subjects (r=0.84-0.95, all P<0.001; s.e.e.=3.42-3.89%). Mean %fat estimated by ADP using the Siri (1961) equation (ADP(Siri)) produced a nonsignificant overestimation in males (0.67%), and a nonsignificant underestimation in females (1.26%). Mean %fat estimated by ADP using the Lohman (1986) equations (ADP(Loh)) produced a nonsignificant underestimation in males (0.90%) and a significant underestimation in females (3.29%; P<0.01). Agreement between ADP and DXA methods was examined using the total error (TE) and methods of Bland and Altman (1986). Males produced a smaller TE (ADP(Siri) 3.28%; ADP(Loh) 3.49%) than females (ADP(Siri) 3.81%; ADP(Loh) 4.98%). The 95% limits of agreement were relatively similar for all %fat estimates, ranging from +/-6.57 to +/-7.58%. Residual plot analyses, of the individual differences between ADP and DXA, revealed a significant bias associated with increased %fat (DXA), only in girls (P<0.01). CONCLUSIONS: We conclude that ADP, at present, has unacceptably high limits of agreement compared to a criterion DXA measure. The ease of use, suitability for various populations and cost of ADP warrant further investigation of this method to establish biological variables that may influence the validity of body fat estimates.

Cross-calibration of GE/Lunar pencil and fan-beam dual energy densitometers--bone mineral density and body composition studies.

OBJECTIVE: In vitro and in vivo comparisons of bone mineral density (BMD) and body composition between GE/Lunar pencil (DPXL) and fan-beam (PRODIGY) absorptiometers. DESIGN: Comparison of BMD, bone mineral content (BMC) and area of lumbar spine (L2-L4), femoral neck and total body. Total body composition compartments tissue (TBTissue), fat (TBF), lean tissue (TBLean) and %TBF were also compared. SETTING: Centre for Bone and Body Composition Research, University of Leeds. PHANTOMS/SUBJECTS: A range of spine phantoms, a variable composition phantom (VCP) and total body phantom. A total of 72 subjects were included for the in vivo study. RESULTS: In vitro: A small significant underestimation of BMD by the Prodigy compared to the DPXL ranging from 0.7 to 2% (p<0.05-0.001) for the spine phantoms. The Prodigy underestimated the VCP %Fat. Although the Prodigy underestimated phantom TBBMD by 1.1+/-1.0%, TBBMC and area were reduced by 8.2+/-1.4 and 7.3+/-1.0%, respectively. The Prodigy overestimated TBTissue 1508 g (2.2%), TBLean 588 g (1.2%), TBF 919 g (4.8%) and %TBF (0.8%). In vivo: BMD cross-calibration was only required in the femoral neck, DPXL(BMD)=0.08+0.906*PRODIGY(BMD). The Prodigy had higher estimates for TBTissue 1360 g (2.3%), TBLean 840 g (2.0%), TBF 519 g (3.4%), TBBMC 32.8 g (1.3%) and %TBF (0.3%). Cross-calibration equations were required for TBTissue(DPXL)=-1158+0.997*TBTissue(PRODIGY) and TBBMC(DPXL)= 89.7+0.949*TBBMC(PRODIGY). CONCLUSIONS: Small differences between the two absorptiometers for both BMD and body composition can be made compatible by use of cross-calibration equations and factors. The discrepancy in body composition compartments requires further research.

Differences in bone density, body composition, physical activity, and diet between child gymnasts and untrained children 7-8 years of age.

Strategies that enhance the acquisition of bone mass may be protective against osteoporosis. BMD was compared in 20 artistic gymnasts (10 boys; 10 girls) and 20 untrained children ages 7-8 years. Higher regional values of BMD were observed in female gymnasts than untrained girls. If retained to adulthood, this higher BMD may protect skeletal integrity in later life. Strategies that enhance the acquisition of bone mass in children may assist with the prevention of osteoporosis. This study explored the effects of regular high-impact and weight-bearing activity before the age of 7 years on total and regional bone mineral density (BMD). Twenty artistic gymnasts (10 boys and 10 girls) and 20 untrained children, 7-8 years of age, were recruited. The untrained children were matched to gymnasts by sex, height, weight, and age. Female gymnasts trained 8-10 h per week and had trained regularly for 3-4 years. Male gymnasts trained 4-6 h per week and had trained for 1-2 years. Measurements of bone mineral density were made using DXA for total body BMD (TBBMD); lumbar spine, both areal (aSBMD) and volumetric (vSBMD); total spine; pelvis; arms; and legs. Significant mean differences (8-10%) in aSBMD, vSBMD, arm BMD, and TBBMD were observed between female gymnasts and untrained girls (p < 0.05: aSBMD, vSBMD, and TBBMD body mass (BM); p < 0.01: arm BMD). A nonsignificant trend toward a higher TBBMD/BM and arm BMD was observed in male gymnasts compared with untrained boys. Trends toward a higher BMD within the pelvis, legs, and total spine were also observed in gymnasts. There were no differences in total and regional BMD between untrained boys and untrained girls. The results suggest that gymnastics training before the age of 7 years enhances the acquisition of bone mass at selected skeletal sites. The magnitude of this enhancement seems to be linked to the cumulative volume of such training. If retained during adolescence and young adulthood, a surfeit of bone acquired through high-impact and weight-bearing activity in early childhood may protect skeletal integrity in later life.

The measurement of total body potassium in patients on peritoneal dialysis.

OBJECTIVES: To assess the validity of measuring total body potassium (TBK) to estimate fat-free mass (FFM) and body cell mass (BCM) in patients on peritoneal dialysis (PD). METHODS: We studied 29 patients on PD (14 men, 15 women) and 30 controls (15 men, 15 women). We calculated TBK by using a whole-body counter to measure 1.46 MeV gamma-ray emissions from naturally occurring 40K. We measured total body water (TBW) by deuterium oxide dilution, and extracellular water (ECW) from bromide dilution. These measurements allowed us to estimate intracellular water (ICW), fat-free mass dilution (FFM(Dilution)), and body cell mass dilution (BCM(Dilution)). RESULTS: The FFM(TBK) in male PD patients (55.7 +/- 7.0 kg) did not differ from that in male controls (57.0 +/- 10.9 kg). The FFM(TBK) in female PD patients (38.4 +/- 6.8 kg) was less than that in female controls (44.7 +/- 4.5, p < 0.01). The FFM(Dilution) did not differ from the FFM(TBK). Correlation of FFM(TBK) and FFM(Dilution) was r = 0.90, p < 0.0001 for all subjects; r = 0.90, p < 0.0001 for PD patients; and r = 0.90, p < 0.0001 for controls. Bland-Altman comparison of FFM(Dilution) with FFM(TBK) in individuals showed bias 0.6 kg, range -8.5 kg to 9.7 kg for the whole group; bias 1.4 kg, range -7.9 kg to 10.7 kg for PD patients; and bias -0.2 kg, range -9.0 kg to 8.6 kg for controls. The BCM(TBK) in male PD patients (30.1 +/- 4.5 kg) did not differ from that in male controls (31.9 +/- 6.2 kg). The BCM(TBK) in female PD patients (19.0 +/- 4.4 kg) was less than that in female controls (23.1 +/- 2.9 kg, p < 0.01). The BCM(Dilution) results did not differ from those for the BCM(TBK). Correlation of BCM(TBK) and BCM(Dilution) was r = 0.90, p < 0.0001 for all subjects; r = 0.87, p < 0.0001 for PD patients; and r = 0.93, p < 0.0001 for controls. Bland-Altman comparison of BCM(Dilution) with BCM(TBK) in individuals showed bias 0.1 kg, range -5.9 kg to 6.1 kg for the whole group; bias 0.0 kg, range -6.9 kg to 6.9 kg for PD patients; and bias 0.1 kg, range -5.0 kg to 5.2 kg for controls. The [K+]ICW did not differ between PD patients and controls (148.0 +/- 25.1 mmol/L vs 148.1 +/- 14.3 mmol/L, p = nonsignificant). CONCLUSIONS: Total body potassium is a valid, noninvasive technique for measuring FFM and BCM in PD patients. In our PD patient group, depletion of FFM and BCM as compared with controls was identified in the women but not in the men.

Osteoporosis and osteopenia in adults and adolescents with cystic fibrosis: prevalence and associated factors.

BACKGROUND: Patients with cystic fibrosis (CF) have many risk factors for reduced bone mineral density (BMD). The aim of this study was to determine the prevalence of osteoporosis and osteopenia in a large cross section of patients and to identify risk factors. METHODS: All patients attending the regional centre were invited to participate in the study. Bone mineral density was measured at the lumbar spine, femoral neck, and for total body with a Lunar DPX-L densitometer. Multiple indices of disease severity were investigated, and liver and thyroid function, blood calcium, phosphate, 25-OH vitamin D, follicle stimulating and luteinising hormone, oestradiol, and testosterone levels were measured. Patients completed a four day prospective dietary diary. Exercise was assessed by a seven day activity recall questionnaire. Sexual development and treatment histories were obtained. The relationship between all these variables and BMD measurements was analysed. RESULTS: Sixty six percent of 114 patients assessed had osteopenia or osteoporosis. The Shwachman-Kulczycki (SK) clinical score (higher score = less severe disease) correlated significantly with BMD at the lumbar spine and femoral neck, and with total body BMD (p<0.001). There was a predicted increase of 0.0032 g/cm(2) in lumbar spine BMD for every unit increase in the SK score. Oral steroid use was significantly associated with reduced BMD at the lumbar spine (p = 0.017) and femoral neck (p = 0.027). CONCLUSIONS: Osteopenia and osteoporosis are common findings in a heterogeneous population of adults with CF. Patients at most risk are those with severe disease and those who have used corticosteroids.

Limited ileal resection in infancy: the long-term consequences.

BACKGROUND/PURPOSE: The longer-term sequelae of short bowel syndrome in infancy are reasonably well documented, but little is known about the long-term nutritional and metabolic effects of limited (less than 50 cm) ileal resection. This makes it difficult to formulate a rational follow-up policy in such children. METHODS: All children who underwent limited ileal resection for either necrotizing enterocolitis (NEC) or intussusception at our institution between 1984 and 1992 were invited to attend a detailed clinical, anthropometric, hematologic, and biochemical assessment, together with a biliary and renal ultrasound scan and measurement of bone mineral density. RESULTS: Twenty-four children (NEC, 17; intussusception, 7) of median age 7.4 years (range, 5.5 to 13.7 years) agreed to participate. Nine previously had undergone an isolated ileal resection, and 15 also had had variable lengths of colon removed. The length of resected ileum ranged from 3 to 44 cm, with a median of 10 cm. Seven control subjects in whom neonatal NEC developed but recovered without surgery were also evaluated. Median height, weight, and body mass index after ileal resection were between the 25th and 50th percentiles; no child was stunted or wasted. After ileal resection, one boy was found to have asymptomatic vitamin B12 deficiency, and three children had low plasma concentrations of vitamin A. Hematologic and biochemical parameters were otherwise normal apart from a few marginally low trace element levels in both subjects and controls. No renal calculi were detected, and bone mineral density measurements were normal in all except one child. Four children had cholelithiasis, all of whom had previously undergone limited ileal resection for NEC (two isolated, two ileocolic). Thus, the prevalence of cholelithasis after limited ileal resection for NEC was 24% at a median age of 7.0 years. CONCLUSIONS: Growth and nutritional status are well preserved after limited ileal resection in infancy. Limited ileal resection for NEC is associated with a subsequent high prevalence of cholelithiasis and a risk of vitamin B12 deficiency. These findings are important when planning strategies for long-term follow-up.

Broadband ultrasound attenuation in the os calcis and its dependence on the receiver aperture size.

The broadband ultrasonic attenuation (BUA) was measured in 10 os calces on the same site with two transducer separations and five different receiving apertures built from perspex. The results displayed relative differences greater than 40%. However, a clear trend (increasing or decreasing BUA) with smaller aperture size or transducer separation was not observed and hence the differences do not seem to be predictable. The cause for this may be the influence of four factors--averaging, phase cancellation, diffraction and scattering--which are interactive and frequency dependent. This means that values measured with different equipment and experimental set-up are not directly comparable and hence the introduction of measurement standards seems to be necessary.

An evaluation of the reproducibility and responsiveness of four 'state-of-the-art' ultrasonic heel bone measurement systems using phantoms.

This paper evaluates four modern ultrasonic heel bone scanners: the Osteometer DTU-one, Hologic Sahara, CUBA Clinical and Lunar Achilles+. Six phantoms, ranging in porosity from 50% to 83%, were used to evaluate the range of values of broadband ultrasonic attenuation (BUA), speed of sound (SOS) and Stiffness/quantitative ultrasound index (where available) from each machine. Differences in inter-system variability between the lowest and highest porosity phantoms up to a factor of 3.8 were demonstrated. The reproducibility of each system was measured using a single phantom and gave values of 0.03-0.15% for SOS, 0.39-1.6% for BUA and 0.73-1.11% for Stiffness. This contrasted with values of range normalized standard deviation (CX) of 0.2-1.19% for SOS, 0.71-1.86% for BUA and 0.83-1.12% for Stiffness when the output range of the measurement is taken into account. Measures of all quantities differed between machines and care should be taken when expressing and comparing results from different systems.

Comparison of in-vivo body composition using two Lunar dual-energy X-ray absorptiometers.

OBJECTIVE: To compare in-vivo composition analysis between two dual energy X-ray absorptiometers, a DPX and a DPX/L, from the same manufacturer (LUNAR), pre(Study A) and post(Study B) hardware changes on both absorptiometers. DESIGN: Comparison of (1) quality assurance (QA) data: air-counts low (38 keV), air-counts high (70 keV), air-counts ratio, percent spillover, R-delrin; and (2) total body compartments: total body tissue (TBTISS), total body fat (TBF), percent total body fat (%TBF), total body lean (TBLEAN), total body bone mineral content (TBBMC) and total body bone mineral density (TBBMD), between the two absorptiometers. SETTING: Centre for Bone and Body Composition Research, University of Leeds. SUBJECTS: Study A, 14 normal subjects and Study B, a different cohort of 19 normal subjects, were scanned on both machines on the same day. RESULTS: In Study A, large significant differences were observed in the QA parameters between the two machines. The DPX, air-counts low and air-counts high, being 25% and 22% lower than the DPX/L. The Bland Altman method of analysis indicated that the DPX was significantly higher for TBTISS (0.3 kg), %TBF (2%) and TBF ( 1.4 kg) and correspondingly lower for TBLEAN (-1.0 kg). No significant difference was observed in TBBMC. After the hardware changes (Study B) a marked reduction in the differences in QA air-counts was observed. The DPX air-counts low was now 1% higher and air-counts high 8% lower than the DPX/L. The DPX had now only small significant negative differences for %TBF (-0.6%) and TBF (-0.4 kg) and a small significant positive difference for TBLEAN (0.4 kg), compared to the DPX/L. TBBMC difference although slightly increased, was still non-significant. CONCLUSIONS: The closer agreement observed in the QA parameters after the hardware changes was associated with a reduction in the mean differences, 95%CI of the mean differences and limits of agreement of the comparison of body composition analysis from the Lunar machines using the Bland-Altman method. The study indicates that the QA limits set for bone mineral analysis may require more stringent limits for body composition.