Measured Bone Mineral Research Articles

Influence of Region Size on Bone Mineral Measurements along Femoral Stems in THA

The influence of regional size on the precision error in the evaluation of bone mineral changes along femoral components in uncemented THA's was studied methodologically using Dual Energy X-ray Absorptiometry (DEXA) and with a review of the literature. A significant negative relation between region size and precision error was found in experimental studies and the precision error was shown to vary with type of DEXA scanner when reviewing the literature. When using Gruen's zones we found that the precision was best at the tip and poorest in the proximal regions. Guidelines based upon calculations of the approximate percentage changes necessary in a single individual to be statistically significant in a longitudinal study with 95% probability were made for three different types of DEXA scanners.

Comparison of adult and paediatric spine and whole body software for the Lunar dual energy X-ray absorptiometer.

Simple phantoms were devised to compare the performance of adult (software 3.64) and paediatric (software 3.8 g) spine and whole body software developed for the Lunar dual energy X-ray absorptiometer. Rectangular slabs of aluminium with high (1.18 g cm-2) and low (0.57 g cm-2) density were used to represent bone mineral. For spine measurements, the phantoms were scanned in water at depths of 5-20 cm. For whole body measurements, the phantoms were scanned with known amounts of oil and water to represent fat and lean tissue. This simulated tissue depths of 5.5-19.7 cm and body composition ranging from 14-29% fat. There were systematic differences in spine and whole body bone mineral content (BMC), bone area (BA) and bone mineral density (BMD) measurements and also between adult and paediatric software versions. The magnitude and direction of these differences were dependent on BMD of the phantom and tissue depth. Similar systematic differences were observed in vivo when volunteers were scanned using adult and paediatric software. Paediatric software enabled measurements to be made at low tissue depths. The weights of fat, lean and total soft tissue measured by the adult and paediatric whole body software were similar to the values calculated from the known composition of the phantom. Precision estimates for all softwares were excellent. In conclusion, paediatric software should improve bone mineral measurements of children but the discrepancies between adult and paediatric softwares may cause problems in longitudinal studies of skeletal growth and when compiling reference data from infancy through to adulthood.

Anomalies in dual energy X-ray absorptiometry measurements of total-body bone mineral during weight change using Lunar, Hologic and Norland instruments.

A previous study showed that measurements of total-body bone mineral changes made with a Hologic QDR 1000W were unreliable when the subjects underwent weight change. The study has been extended to dual energy X-ray absorptiometry (DXA) apparatus from other manufacturers. Re-analysis of published results during weight loss using a Lunar DPX showed that they varied with the software used. Using the Extended mode, there was a 1% loss of bone mineral areal density (BMD), but no significant change in bone mineral content (BMC) or bone area (BA) following a weight loss of 16 kg, whereas the use of the Standard mode led to a larger fall of BMC and BMD. Similar findings arose from the consideration of two studies using Norland XR 26 HS absorptiometers. On the other hand, separation of two groups with similar weight changes from the population studied with a Hologic QDR 1000W confirmed that BMC changed directly with weight, but there was an inverse relationship for BMD, owing to an inappropriate change of BA. The use of Hologic Enhanced and Standard software modes led to significant differences in initial readings and measured changes. With each instrument there was a strong correlation between changes in BA and changes in BMC. When 6 kg of lard was wrapped around the limbs of volunteers or a semi-anthropomorphic phantom to simulate weight change, there were spurious increases of measured BMC and BA by about 5% with each instrument. There were no changes of BMD with Lunar, variable results with Norland, but decreases with Hologic. The results observed in vivo could be explained by the effects of fat changes, without there being any real change of bone mineral. Changes of BMD in the skeleton of the phantom were underestimated with all three brands. The anomaly observed with the Hologic QDR 1000W is less apparent with a Lunar DPX or a Norland XR 26, but there are sufficient uncertainties for all total-body measurements during weight change to be treated with suspicion.

Dual X-Ray absorptiometry in pediatric studies: changing scan modes alters bone and body composition measurements.

The use of dual X-ray absorptiometry (DXA) for measurement of bone mineral and body composition in pediatric subjects faces a major technical issue: body size dictates choice of scan mode. However, different scan modes change results in the same subject, thus affecting the accuracy of bone/body composition measurements and especially the capacity to measure changes owing to either growth or intervention. To evaluate the effect of scan mode selections on measurements of bone mineral and body composition, 13 children with weights at the cutoff point between the pediatric large and adult medium scan modes of Lunar DPX or DPXL (Lunar, Madison, WI) with software 3.6 g (35.3 +/- 0.9 kg or 77.7 +/- 2.0 lb) were scanned by both modes. Adult medium mode gave significantly higher results than pediatric large mode for total body fat mass (11.1%), fat% (10.5%), bone mineral content (8.1%), and bone area (1.3%) (p < 0.02). The differences between pediatric large and adult medium modes in fat measurements increased with increasing body mass index ([BMI], kg/m(2)), body surface area ([BSA], m(2)), and trunk size (mm), whereas the differences in bone mineral measurement tended to be greater only with increasing BMI and BSA. None of the differences were correlated to body weight. This study suggests that scan mode selections based on trunk size, BMI, or BSA instead of body weight may improve continuity of bone and body composition measurements by the DXA technique in pediatric subjects.

Previous milk consumption is associated with greater bone density in young women

Dietary calcium and milk intakes at specific ages may influence bone mineral measures at specific sites during development of peak bone mass. Relations of previous milk intake and current calcium intake to current bone mineral measures were investigated in young women. A food-frequency interview and recall of previous milk intake from early childhood to 12 y of age and during adolescence (13-19 y) were completed in a cross-sectional analysis in young women (age 18-31 y; n = 224). Three levels of previous milk intake were defined: 1) infrequently or never, 2) sometimes, and 3) at every or almost every meal. Total body (TB), femoral neck, radius (R), and spine (S) bone mineral density (BMD) and bone mineral content (BMC) were determined by using dual-energy X-ray absorptiometry. Childhood and adolescent milk intakes were positively correlated (r = 0.66). Childhood and adolescent milk intakes correlated with current calcium intakes (r = 0.26 and 0.33, respectively). Adolescent milk intake correlated with RBMD (r = 0.16). When weight was controlled for, adolescent milk intake correlated with TBBMD (r = 0.16), TBBMC (r = 0.21), SBMC (r = 0.16), RBMD (r = 0.18), and RBMC (r = 0.15). Current calcium intakes correlated with SBMC (r = 0.17). Regression analyses supported these results. Results were consistent with the hypothesis that higher milk intake during adolescence is associated with greater total body, spine, and radial bone mineral measures during development of peak bone mass, whereas current calcium intakes may influence SBMC. In addition, milk intake at a younger age may contribute to similar habits of milk intake later in life.

Clinical assessment of bone mass, quality and architecture.

An increasing awareness of osteoporosis and the development of treatments with proven efficacy is likely to increase the demand for management of patients with osteoporosis. This in turn will demand facilities for the diagnosis and assessment of osteoporosis. Measurements of bone mineral are a central component of any provision that arises from the definition of osteoporosis. The internationally agreed definition of osteoporosis is: a progressive systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture [1]. This definition captures the notion that low bone mineral density is an important component of the risk of fracture, but that other abnormalities occur in the skeleton that contribute to skeletal fragility. Thus, ideally the assessment of osteoporosis should encompass aspects of bone mass and quality. This review summarizes and updates the extent to which this is possible in clinical practice [2].

Effects of continuous infusion of PTH on experimental tooth movement in rats.

Development of new methods for accelerating orthodontic tooth movement has been strongly desired for shortening of the treatment period. The rate of orthodontic tooth movement is dependent on the rate of bone resorption occurring in the compressed periodontium in the direction of orthodontic force applied to the tooth. In the present study, we examined the effects of continuous infusion of parathyroid hormone (PTH) on tooth movement. Male rats weighing 350-400 g were treated with subcutaneous of vehicle or hPTH(1-84) at 1-10 micrograms/100 g of body weight/day. When the upper right first molar (M1) was moved mesially for 72 h by the insertion of an elastic band between the first and second molars, M1 movement was accelerated by PTH infusion at 10 micrograms. PTH infusion caused a 2- to 3-fold increase in the number of osteoclasts in the compressed periodontium of M1, indicating that such treatment accelerated tooth movement by enhancing bone resorptive activity induced in the compressed periodontium. When M1 was moved mesially by an orthodontic coil spring ligated between upper incisors and M1 for 12 days, PTH(1-84) infusion at 10 micrograms caused a 2-fold increase in the rate of M1 movement. PTH(1-34) infusion at 4 micrograms had an effect comparable to that of PTH(1-84). However, intermittent injection of PTH(1-34) did not accelerate M1 movement. PTH infusion for 13 days did not affect either bone mineral measurements or the serum calcium level. These findings suggest that continuous administration of PTH is applicable to accelerate orthodontic tooth movement.

Does paracentesis of ascites influence measurements of bone mineral or body composition by dual-energy x-ray absorptiometry?

Measurements of bone mineral content (BMO) and density (BMD) by dual-energy x-ray absorptiometry (DXA) may be affected by changes in soft tissue overlying bone. Furthermore, the accuracy error for body composition determined by DXA may be high in the trunk region due to the complex bone geometry. Our objective was to evaluate the impact of paracentesis on measurements of bone mineral and body composition by DXA. DXA (Norland XR-36; Norland, Fort Atkinson, WI) scans were performed in six patients with cirrhosis of the liver before and after treatment of ascites by paracentesis. There were no significant differences in the spinal BMC (change [Δ] = 0.04%) and BMD (Δ = −0.9%) ( P > .05), nor in total body BMC ([TBBMC] Δ = 1.9%) and BMD ([TBBMD] Δ = 0.4%) ( P > .05). The median volume of ascites drained (6.8 L; range, 1.6 to 14.7) was not significantly different from the median change in total (5.8 kg; range, 2.0 to 16.1) or trunk lean tissue mass ([LTM] 5.8 kg; range, 1.9 to 11.9) ( P > .05). The changes in body weight correlated with the changes in trunk LTM ( r = .93, standard error of the estimate [SEE] = 1.8 kg, P = .007). Total and regional fat mass were not changed significantly by the paracentesis. We conclude that measurements of total body and spinal bone mineral by DXA are unaffected by large changes in the soft tissue composition and height of the trunk. Furthermore, the change in body composition induced by ascites drainage was accurately determined as a change in total body and trunk LTM on a group level.

Whole-body bone mineral measurements in 15-year-old Swedish adolescents.

Bone mineral area (BA), total bone mineral content (TBMC) and total bone mineral density (TBMD) were assessed by dual-energy X-ray absorptiometry (DXA) in 396 randomly selected, healthy 15-year-old Swedish boys and girls. The influence of body size, pubertal development, physical activity level (PAL), total energy expenditure (TEE), dietary intake of energy, calcium and vitamin D, and alcohol and smoking habits on TBMC and TBMD were examined in bi- and multivariate analyses. In bivariate analyses BA, TBMC and TBMD showed strong correlations with weight, height and TEE in both sexes. In boys but not in girls these bone variables were significantly correlated with dietary intakes of energy, calcium and vitamin D. No significant correlations were found between PAL and the three bone variables. In multivariate analyses with TBMC as dependent variable BA, height, weight and Tanner stages explained 88% and 87% of the variance in boys and girls respectively. In similar analyses with TBMD as dependent variable the corresponding figures were 50% and 54%. The major part of the variance in all these models was explained by BA, and only a few percent by all the other independent variables. No significant reduction was found when TEE or daily intakes of calcium or vitamin D were introduced into the models. These results illustrate the importance of including BA, weight and height as independent variables in regression models of TBMC to avoid spurious associations with other variables in the analyses. The results may also indicate that in normal Swedish adolescents environmental factors such as dietary intake of nutrients play a minor role as determinants of bone mineralization. High levels of physical activity and bone mineral measures possibly explain the lack of significant correlations between these variables and do not imply a lack of association.

人骨資料を用いた骨粗鬆症の診断への基礎的研究

人骨資料を用いた骨粗鬆症の診断への基礎的研究

Dietary calcium, protein, and phosphorus are related to bone mineral density and content in young women

Dietary factors have been implicated in modifying bone health, although the results remain controversial, particularly in young women. The objective of the study was to determine relations of selected dietary factors and anthropometric measurements to bone mineral density (BMD) of the spine, femoral neck, trochanter, Ward's triangle, radius, and total body and the bone mineral content (BMC) of the spine, radius, and total body. The study was a cross-sectional analysis of 215 women aged 18-31 y. Weight, height, and lean mass were correlated with bone mineral measures at every site (r = 0.17-0.78). Postmenarcheal age (years since onset of menses) was positively correlated with total-body BMD and BMC, radius BMD and BMC, and spine BMC, and negatively correlated with Ward's triangle BMD. Radius BMD was correlated with protein, calcium, and phosphorus intakes, and spine BMD and BMC were correlated with energy, protein, calcium, and phosphorus intakes. These correlations remained significant when postmenarcheal age, lean mass, and fat mass were controlled. A pattern emerged in multiple regression analyses that showed a complex relation among calcium, protein or phosphorus, and the calcium-protein or calcium-phosphorus ratio and spine or total-body BMC and BMD. All 3 variables (calcium, protein or phosphorus, and calcium-protein or calcium-phosphorus ratio) were required in the model for significance. Anthropometric measures were predictors of bone mass. A single ratio of calcium to phosphorus or protein did not optimize bone mass across the range of calcium intakes.

Bone mineral density is a predictor of survival.

The purpose of this study was to examine the relationship between bone mineral density (BMD) and survival in both sexes and to compare BMD with other established risk factors such as blood pressure and cholesterol. A population-based prospective study of 1924 individuals (850 men, 1074 women) was performed in Göteborg from 1980 to 1983. Measurements of BMD were obtained in 1468 (76%) of the participants (653 men, 815 women). This selection of individuals generated 10,965 person years, and death was registered for 289 men and 197 women in the 7-year period (2661 days) after bone mineral measurement. Later information on date of death was obtained from the official population register. This information covers 7 years from the time of survey of the last examined participant (in Dec. 1983). At the beginning of the study, BMD was measured in the calcaneus by dual photon absorptiometry (DPA), and blood pressure, serum cholesterol, serum triglycerides, and body mass index (BMI) were also recorded. The study was coordinated with the National Register of Causes of Death and the National Cancer Register. A modified version of the Cox proportional hazards model was used to calculate and determine the age-adjusted relations between nontrauma mortality and BMD. When the various quartiles of BMD were compared prospectively from 70, 75, and 79 years of age with survival figures during the 2661-day follow-up period, the first and the second quartiles with the lowest BMD at entry showed the lowest survival rate in both men (P = 0.01) and women (P = 0.01). A decrease of 1 SD of BMD in a univariate analysis was associated with a 1.39-fold increase in mortality in both men (95% confidence interval 1.25-1.56, P < 0.001) and women (95% confidence interval 1.22-1.58, P < 0.001), and a multivariate analysis demonstrated a relative risk of 1.23 (95% confidence interval 1.10-1.41, P < 0.001) in men and 1.19 (95% confidence interval 1.02 to 1.39, P = 0.019) in women. All relations were adjusted for sex, age, and follow-up. This study indicates that BMD is a predictor of survival, especially for subjects over 70. Bone mineral density was found to be a better predictor of death than blood pressure and cholesterol. This study indicates that, after adjustments have been made for diseases, low bone mass is an independent predictor of mortality and might be a marker of general health or functional aging. Its measurement might therefore be a valuable tool in general health investigations.

Distal radius fractures: mechanisms of injury and strength prediction by bone mineral assessment.

The strength of the radius depends on the mechanical properties of cancellous and cortical bone. By assessing both compartments quantitatively with bone densitometry, we tried to identify the specificity of each in predicting the load at which the distal radius will fracture. Twenty human cadaver forearms were scanned for bone mineral and geometric properties with quantitative computed tomography and dual x-ray absorptiometry. In both a neutral loading situation and one in which the wrist was extended 45 degrees, the load distribution was determined with pressure-sensitive films, and a fracture simulating a fall on the hand was produced with a material testing machine. Fractures that occur with the wrist in extension were produced by a central impact of the scaphoid onto the radiocarpal joint, and those that occur under neutral loading conditions were produced by a more commonly distributed loading pattern. The load at fracture was most specifically predicted (r2=0.74) by bone mineral and geometric measures of the cortex at the shaft of the radius. Bone mineral density measures of trabecular (r2=0.64) and total (r2=0.66) bone were less successful in predicting the fracture load. After adjustment for bone size, the geometric and density measures revealed similar specificity. Cortical bone, therefore, contributes significantly to the strength of the distal radius and may play an important role in the prediction of osteoporotic wrist fractures.

Anomalies in the measurement of changes in bone mineral density of the spine by dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry (DXA) is frequently used for longitudinal studies of bone mineral status because of the high precision obtained, but evidence is emerging that the accuracy of measurements of changes may be a limitation because of artefacts of the analysis procedure, in particular, a dependence of the measured bone area (BA) on the bone mineral content (BMC). Results of spine bone mineral measurements taken at intervals with two DXA scanners, a Hologic QDR 1000 W, and a Norland XR 26 HS, were examined. There was a consistent correlation between changes in BA and in BMC, with a slope of approximately 0.25 when expressed as percentages. A real change of BA of the magnitude observed is not feasible. There were no differences among the correlations for different instruments, genders, ages, or weight changes. There would appear to be an underestimation of changes in bone mineral density (BMD), but there is a possibility that some of the anomaly is manifested as an overestimation of a change in BMC. Phantom measurements were undertaken with the DXA scanners mentioned above and with a Lunar DPX. The phantoms consisted of simulations of the spine cut from aluminium sheet, so that the effective BMD could be varied. The dependence of the measured BA on BMC varied with the phantom outline, particularly the thickness of the transverse processes. Evidence was obtained of both an underestimate of BMD changes and an overestimate of BMC changes. There are errors in measuring spine changes, but these do not seem to be as serious as a previous report suggests for the Hologic scanner and are not likely to lead to misinterpretation of results.

Evaluation of bone mineral density using three-dimensional solid state phosphorus-31 NMR projection imaging.

A solid state magnetic resonance imaging technique is used to measure true three-dimensional mineral density of synthetic hydroxyapatite phantoms and specimens of bone ex vivo. The phosphorus-31 free induction decay at 2.0 T magnetic field strength is sampled following application of a short, hard radiofrequency excitation pulse in the presence of a fixed amplitude magnetic field gradient. Multiple gradient directions covering the unit sphere are used in an efficient spherical polar to Cartesian interpolation and Fourier transform projection reconstruction scheme to image the three-dimensional distribution of phosphorus within the specimen. Using 3-6 Gauss/cm magnetic field gradients, a spatial resolution of 0.2 cm over a field of view of 10 cm is achieved in an imaging time of 20-35 minutes. Comparison of solid state magnetic resonance imaging with dual energy X-ray absorptiometry (DXA), gravimetric analysis, and chemical analysis of calcium and phosphorus demonstrates good quantitative accuracy. Direct measurement of bone mineral by solid state magnetic resonance opens up the possibility of imaging variations in mineral composition as well as density. Advantages of the solid state magnetic resonance technique include avoidance of ionizing radiation; direct measurement of a constituent of the mineral without reliance on assumptions about, or models of, tissue composition; the absence of shielding, beam hardening, or multiple scattering artifacts; and its three-dimensional character. Disadvantages include longer measurement times and lower spatial resolution than DXA and computed tomography, and the inability to scan large areas of the body in a single measurement, although spatial resolution is sufficient to resolve cortical from trabecular bone for the purpose of measuring bone mineral density.

Experimental testing of a DEXA-derived curved beam model of the proximal femur.

This study was designed to test whether, using curved beam theory, a structural model of the proximal femur derived from two-dimensional dual energy x-ray absorptiometry could be used to predict femoral strength in an experimental simulation of a fall on the greater trochanter. A set of 22 fresh cadaveric femoral specimens were scanned with use of two-dimensional dual energy x-ray absorptiometry and then were tested to failure in a materials testing system, under three-point loading, with the ground impact vector aligned within the plane and along the bisector of the femoral neck-shaft angle. Failure locations generally corresponded to stress peak locations predicted by the curved beam model. Predicted failure loads correlated well with measured failure loads for femoral neck fractures (r=0.89; percent SE of estimate=23%) and some-what less well for intertrochanteric fractures (r=0.83; percent SE of estimate=29%). Overall predictions for failure load calculated from the maximum stress peak value over both locations corresponded to measured failure loads with an r value of 0.91 (percent SE of estimate=21%). This kind of structural approach to the analysis of data for hip bone mass has the potential to provide mechanistic interpretations of the statistical associations frequently shown between conventional bone mineral measures and either hip fracture risk in vivo or bone strength in vitro.

Book Review

Metabolic Bone Disease and Clinically Related Disorders. Louis V. Avioli and Steven M. Krane, Editors. Academic Press, San Diego, California, U.S.A., 1998. Metabolic Bone Disease and Clinically Related Disorders is a multiauthored book, now in its third edition (published some 8 years after the second edition). This volume has become the definitive comprehensive book in the area of metabolic bone disease and is thus an important textbook. The first edition (1977) was much shorter and contained only 7 chapters. In the current edition, 26 chapters cover all the fundamental metabolic bone disorders of humans, and each chapter is written by a senior authoritative figure in the field of divalent mineral metabolism and calcium endocrinology. The explosion of new information concerning bone formation and remodeling is comprehensively and effectively reviewed. The first 10 chapters cover calcium, phosphorus, and vitamin D metabolism and their biologic functions with several chapters emphasizing direct approaches to bone development and a better understanding of bone mineral measurement. From Chapters 11–26, a variety of metabolic bone diseases are discussed in depth. In contrast with previous editions, the current edition includes expanded information regarding the molecular biology of both normal bone and of human disorders of bone. A number of key figures in the field of molecular biology related to bone metabolism, especially Drs. Edward Brown, Eduardo Slatopolsky, David Rowe, Greg Mundy, Mike Econs, and Francis Glorieux have written up-to-date chapters regarding the entirety of disorders that affect bone and mineral desposits. Chapter 18, entitled “Bone Disease and Hyperthyroidism,” by Douglas S. Ross is a particularly useful chapter because few textbooks of endocrinology or bone disease discuss the full spectrum of hyperthyroid bone disease. Another important contribution is Chapter 22, “Hypercalcemia of Malignancy” by Dr. Gregory Mundy. This chapter contains the latest information regarding the remarkable story of the hypercalcemia of malignancy which has evolved so dramatically over the past 20 years. Dr. Mundy has interwoven the effect of various interleukins in the stimulation of osteoclasts. This chapter presents a most complete and compelling story regarding this serious complication of malignancy. In the third edition of Metabolic Bone Disease, Avioli and Krane have greatly expanded the information in a number of areas in the textbook itself. It is more thorough and broadly composed than the two previous editions. In summary, this text is useful in acquiring a deep knowledge of metabolic bone disease. Its greatest strength is the experience and contributions of the various authors of the chapters, many of whom have been in the field of metabolic bone disease for more than 30 years. In addition, it contains a great deal of information concerning the molecular biology of various conditions which has greatly enhanced this edition of the book. Certainly it should be on the shelf of all physicians who care for patients with metabolic bone disease, be they nephrologists, endocrinologists, or oncologists.

Total body bone mineral measurements in children with Prader-Willi syndrome: the influence of the skull's bone mineral content per area (BMA) and of height.

Background. The aim of this study was to investigate the influence of body height and growth on total body measurements with dual energy X-ray absorptiometry (DEXA) in children. Material and methods. Seventeen children with Prader-Willi syndrome were studied as part of a clinical investigation of the effect of growth hormone (Genotropin) treatment. Bone mineral areal mass (BMA), in g/cm2, was studied with DEXA at 0, 12, 24 and 30 months after the start of the study. The effect of increased bone volume on BMA was studied by making a rough estimate of bone width, which was correlated with BMA. Results. There was a weak correlation between total body BMA and body height (r = 0.58), which increased after exclusion of the head (r = 0.84). The BMA of the head was more than twice as high as that of the rest of the body. In the shortest children more than 50 % of the total bone mineral was contained in the skull, which decreased with height to below 20 % in the tallest children. The correlation between the so-called bone width and BMA (total body, head excluded) was 0.97. Conclusion. The results indicate that (a) the bone mineral content (BMC) of the head and (b) the bone volume and body height have a major influence on BMA measurements with DEXA in children. A theoretical method for evaluating the relative bone density (g/cm3) has also been described.

Composition analysis of pork carcasses by dual-energy x-ray absorptiometry.

Dual-energy x-ray absorptiometry (DXA) was used as a noninvasive method to measure the composition of pig carcasses. A total of 181 half-carcasses (10 to 51 kg, from pigs slaughtered at approximately 30, 60, 90, and 120 kg) were scanned using a Lunar (Madison, WI) DPX-L densitometer. The DXA measurements of fat, lean, bone mineral, and total tissue mass were compared with chemical analysis for fat, water, protein, total ash, and scale weight. The mean value for total tissue mass by DXA was slightly less than the mean carcass weight (32.3 kg vs 33.6 kg, P > .05, R2 = .998). Although highly correlated (R2 = .81), the DXA measurement of the percentage of fat in the half-carcass was less (P < .001) than the chemical measurement (19.5 vs 24.9%). The DXA measurement of lean tissue mass (total mass less fat and bone mineral) was correlated with carcass protein (R2 = .97) and water (R2 = .99) content. The correlation (R2) between DXA bone mineral content and carcass ash content was only .68; however, DXA bone mineral content was more highly correlated with carcass weight (R2 = .93) than was carcass ash content (R2 = .70). When we used the DXA R value (ratio of the attenuation coefficients for fat and lean) to predict percentage of fat in the carcass, the mean value for predicted carcass fat was 25.9% (P > .05). Similarly, carcass protein and water content were predicted from DXA lean. Using DXA region of interest analysis, estimates of the fat content of the shoulder and ham regions were close to chemical values; however, DXA underestimated the fat content of the loin and side regions by 20 and 28%, respectively. When prediction equations were used to evaluate DXA measurements of the half-carcasses of 28 gilts and 37 boars slaughtered at approximately 120 kg, the half-carcasses of gilts contained more fat (33.9 vs 27.8%, P < .001), less protein (14.1 vs 16.1%, P < .001), and less water (45.9 vs 52.1%, P < .001) than those of boars. These results indicate that DXA could be a valuable research tool for measuring the composition of pig carcasses. On the basis of the results of this study, prediction equations were revised for the DXA estimation of fat, protein, and water content of the half-carcass: Fat (%) = 450 - (315 x DXA R value), Protein (g) = -145 + (.23 x DXA lean), and Water (g) = 150 + (.73 x DXA lean). Furthermore, it seems that separate prediction equations are needed for regional analysis.

Bone mineral measurement in Japan.

Various methods for evaluating bone mineral in appendicular, and axial bone or in the whole skeleton have recently become available. As bone mineral is one of the major determinants of bone strength, its exact measurement should be useful for the diagnosis of osteoporosis, as well as for the prediction of fracture risk and monitoring of therapeutical response. The aims of this paper are to review the fundamental performance of bone mineral measurements, the improvements in DXA systems, and the progress in site-specific bone mineral instruments for the radius and calcaneus used in Japan, and to introduce diagnostic criteria for primary osteoporosis, and report on annual rates of bone loss in Japanese females.