Dual-energy X-ray absorptiometry versus single photon absorptiometry of the radius

Bone mineral density is related with previous renal dysfunction caused by cadmium exposure

Relationship between bone mineral density (BMD) and previous renal dysfunction caused by cadmium exposure was investigated. A total of 457 persons, living in polluted and control areas, were followed up in this study. The inhabitants living in exposure areas ceased ingesting cadmium-contaminated rice in 1996. Blood and urinary cadmium levels and BMD in 1998 and 2006 were measured. Urinary N-acetyl-β-d-glucosaminidase and albumin determined in 1998 and 2006 were used to evaluate kidney status. BMD of subjects with tubular damage was significant lower than those without damage in female (p < 0.05). The prevalence of osteoporosis was significantly different between those with and without kidney damage (p = 0.003, in total population; p = 0.039, in female) and those with and without tubular damage (p = 0.0005, in total population; p = 0.007, in female). The results suggested that BMD was correlated with previous kidney impairment caused by cadmium exposure, especially to tubular damage and especially for female.

A systematic review of interventions by healthcare professionals on community-dwelling postmenopausal women with osteoporosis

A systematic review was conducted to evaluate evidence concerning the effect of non-drug interventions by healthcare professionals on community-dwelling postmenopausal osteoporotic women. Evidence available indicates that such interventions are effective in improving the quality of life, medication compliance, and calcium intake, but effect on other outcomes is less conclusive.

INTRODUCTION

The purpose of this study is to conduct a systematic review to evaluate evidence concerning the effect of non-drug interventions by healthcare professionals on community-dwelling postmenopausal osteoporotic women.

METHODS

Randomized controlled trials (RCTs) published in English between year 1990 and 2009 were identified. Types of patient outcome used as assessment included quality of life (QOL), bone mineral density (BMD), medication compliance and persistence, knowledge level, and lifestyle modification.

RESULTS

Twenty four RCTs met the inclusion criteria. Seven studies assessed interventions by physiotherapists, six by physicians, seven by nurses, three by multi-disciplinary teams and one by dietitians. Variability in the types and intensity of interventions made comparison between each study difficult. Collectively, these studies provided some evidence to show that interventions by healthcare professionals improved the QOL medication compliance and calcium intake of patients but its effects on BMD, medication persistence, knowledge, and other lifestyle modifications were less conclusive.

CONCLUSIONS

From this review, it was found that some outcome measures of such non-drug interventions still required further studies. Future studies should use validated instruments to assess the outcomes, with focus on common definitions of interventions and outcome measures, more intensive one-to-one interventions, appropriate control groups, adequate randomization procedures, and also provide information on effect size.

Different molecular mechanisms underlie ethanol-induced bone loss in cycling and pregnant rats

Chronic ethanol (EtOH) consumption can result in osteopenia. In the current study, we examined the modulation of EtOH-induced bone loss during pregnancy. Nonpregnant and pregnant dams were intragastrically infused either control or EtOH-containing diets throughout gestation (gestation d 5 through 20 or an equivalent period of 15 d) by total enteral nutrition. The effects of EtOH (8.5 to 14 g/kg/d) on tibial bone mineral density (BMD), mineral content (BMC), and bone mineral area were assessed at gestation d 20 via peripheral quantitative computerized tomography. EtOH caused a dose-dependent decrease in BMD and BMC without affecting bone mineral area. Trabecular BMD and BMC were significantly lower in EtOH-treated, nonpregnant dams, compared with pregnant cohorts at the same infused dose of EtOH and urinary ethanol concentrations. Static histomorphometric analysis of tibiae from pregnant rats after EtOH treatment showed decreased osteoblast and osteoid surface, indicating inhibited bone formation, whereas EtOH-treated cycling rats showed higher osteoclast and eroded surface, indicative of increased bone resorption. Circulating osteocalcin and 1,25-dihydroxyvitamin D3 were lower in both EtOH-fed nonpregnant and pregnant rats. Gene expression of osteoclast markers, 70 kDa v-ATPase, and tartrate-resistant acid phosphatase were increased selectively in nonpregnant EtOH-treated rats but not pregnant rats. Moreover, only nonpregnant EtOH-fed rats showed induction in bone marrow receptor activator of nuclear factor-kappaB ligand mRNA and decreased circulating 17beta-estradiol levels. Our data suggest that EtOH-induced bone loss in pregnant rats is mainly due to inhibited bone formation, whereas in nonpregnant rats, the data are consistent with increased osteoclast activation and bone resorption concomitant with decreased estradiol levels.

Dual-energy X-ray absorptiometry in diagnosis of osteoporosis: basic principles, indications, and scan interpretation

Dual-energy x-ray absorptiometry is currently the most commonly used modality for the diagnosis of osteoporosis, allowing fast, accurate, and noninvasive measurements of bone mineral density. In this review we discuss the principles, applications, advantages, and limitations of this diagnostic technique.

Prediction of bone strength of distal forearm using radius bone mineral density and phalangeal speed of sound

This investigation compares quantitative ultrasound (QUS) measurement of the phalanges with peripheral quantitative computed tomography (pQCT) and dual X-ray absorptiometry (DXA) measurement of the forearm, to estimate the strength of the distal radius in 13 cadaveric forearms. The cadavers were scanned at the distal radius by pQCT and DXA for bone mineral density (BMD) and at the approximate phalanges by QUS for speed of sound (SOS). The distal radii were subjected to a simulated Colles fracture produced with a materials testing machine. The load at which the distal radius was fractured was considered as a representation of bone strength. The bone strength correlated significantly with SOS at different phalanges (r = 0.63-0.72), BMD at different regions of interest by DXA (r = 0.67-0.75), and cortical BMD at different sites by pQCT (r = 0.61-0.67). Standard stepwise regression analysis showed that adding phalangeal SOS into forearm densitometric variables significantly enhanced the statistical power for prediction of the strength of the distal radius. Our results suggest that, for assessment of site-specific distal forearm strength, QUS measurement of the phalanges is comparable to forearm densitometry. Phalangeal QUS may add clinical value if distal forearm strength has a high priority.

Bone mass, areal, and volumetric bone density are equally accurate, sensitive, and specific surrogates of the breaking strength of the vertebral body: an in vitro study

The validity of the bone mineral density (BMD) measurement depends on its accuracy as a predictor of the breaking strength of bone. As the breaking strength is proportional to the square of the apparent density, a small error in the calculation of BMD may result in a larger error in the predicted bone strength. The aims of this study were (i) to determine whether inaccuracies in the measurement of the dimensions, projected area, and volume of the vertebral body (used to derive the areal and volumetric BMD) result in errors in the predicted breaking strength and (ii) to compare the accuracy, sensitivity, and specificity of bone mineral content (BMC), areal BMD, volumetric BMD, and volumetric bone mineral apparent density (BMAD) as surrogates of bone strength. We measured the BMC (by densitometry), dimensions and volume (using calipers, densitometry, the Carter et al. and Peel and Eastell methods), and breaking strength (using the Instron 1114 apparatus, Newtons, N) of 22 vertebral body specimens. All methods resulted in errors in height, width, and depth between -11.3 +/- 1.0 and 30.4 +/- 1.8% relative to the "gold" standard caliper method. The vertebral body volume (of 38.0 +/- 1.2 cm3) measured by submersion was used as the gold standard to derive the volumetric BMD gold standard (of 0.162 +/- 0.01 g/cm3). All methods, except the Peel and Eastell method, resulted in errors ranging between -10.7 +/- 1.5 and 56.9 +/- 3.4% in vertebral body volume and -35.6 +/- 1.5 to 12.6 +/- 1.8% in volumetric BMD (all p < 0.0005). The same absolute value for volumetric BMD predicted a breaking strength that differed according to the method used to derive BMD. For example, a volumetric BMD of 0.162 g/cm3 predicted a breaking strength of 6208 N (submersion method), 5473 N (caliper method), 6095 N (Peel and Eastell method), 7697 N (DXA method), and 9470 N (Carter et al. method). The mean volumetric BMD derived by each method differed (0.181, 0.165, 0.133, and 0.104 g/cm3, respectively). However, all were accurate; each predicted a similar breaking strength (6177, 6217, 6209, and 6221 N respectively). Likewise, breaking strengths predicted by the mean BMC, areal BMD by calipers, and areal BMD by dual-energy X-ray absorptiometry (DXA) were 6267, 6214, and 6244 N, respectively. The methods were equally sensitive; a 1 standard deviation (SD) decrease in volumetric BMD resulted in a similar decrease in the breaking strength of 1818 (caliper), 2080 (Peel and Eastell), 2001 (DXA), and 1625 N (BMAD by Carter et al). A 1 SD decrease in BMC, areal BMD (using calipers) and areal BMD (using DXA) predicted a decrease in the breaking strength of 2019, 1738, and 1825 N, respectively. All methods were equally specific; the variance in bone strength explained by bone mass did not differ for volumetric BMD (38-61% depending on the method), BMC (58%), or areal BMD (48%). In conclusion, despite errors in the measurement of the dimensions of the vertebral body, bone mass, areal, and volumetric bone density are equally accurate, sensitive, and specific surrogates of the breaking strength of bone in vitro.

Accuracy and precision study in vitro for peripheral quantitative computed tomography

We evaluated the accuracy and precision of a peripheral quantitative computed tomography (pQCT) scanner, the Stratec XCT-960, using 12 human cadaveric forearms. The accuracy was determined by comparing the total bone mineral content (BMC) with the ash weight (AW). We scanned and ashed three consecutive slices (thickness 2.5 mm) at the standard position (s-position) and at 2.5 mm both proximal and distal to the s-position. The correlation coefficient between the AW and total BMC using slices at the s-position was r = 0.87 with an accuracy error (random component) of 15.5%. The correlation coefficient using all slices was r = 0.90 with an accuracy error of 14.3%. The correlation coefficient improved to r = 0.95 with an accuracy error of 9.7% after averaging the results of all three slices for each forearm. The short-term precision error expressed as the coefficient of variation (CV) of bone mineral density (BMD) and BMC was determined by measuring the forearms five times either with repositioning or without repositioning. The CVs with repositioning were 2.77 and 1.15 for total BMD and BMC, 1.85 for trabecular BMD; without repositioning they were 0.29, 0.58 and 0.69 respectively. To further evaluate the influence of positioning, additional scans were performed at 1, 2 and 5 mm proximal, and 1 and 2 mm distal to the s-position. BMD and BMC were greatly influenced by the scan location; for example, the percentage differences in trabecular BMD 1 mm distal and proximal relative to the s-position were 2.5% +/- 5.1% and 0.18% +/- 6.3%, respectively. The Stratec XCT-960 appears to be a moderately accurate and highly precise scanner with potential usefulness for evaluating BMC and BMD of ultradistal radius.

Correlations of dual-energy X-ray absorptiometry, quantitative computed tomography, and single photon absorptiometry with spinal and non-spinal fractures

Controversy continues as to which method of measuring bone mineral density (BMD) best detects osteoporosis and best correlates with fractures of the spine, hip and elsewhere. To answer these questions the prevalence of fractures was carefully determined among 90 subjects (70 with osteoporosis, 6 with mild primary hyperparathyroidism, 1 with osteomalacia and 13 normals) and simultaneous measurements were made using spinal computed tomography (QCT), spinal anteroposterior (AP) and supine lateral dual X-ray absorptiometry (DXA), femoral neck and total hip DXA, and distal third radial DXA and single photon absorptiometry (SPA). The DXA measurements which had the greatest sensitivity in detecting osteoporosis (defined as a BMD lower than -2.5 SD of peak bone mass at age 30 years) were the supine lateral spine DXA (84%) and femoral neck DXA (75%); less sensitive were the DXA measurements of the distal third of the radius (61%) and AP spine (51%). DXA measurements of the femoral neck and distal third of the radius were more useful than spinal measurements in detecting the osteopenia of mild primary hyperparathyroidism. Vertebral compression fractures (VCF) correlated well with spinal QCT (r = 0.38) and lateral spine DXA (r = -0.41), but poorly with AP spine DXA (r = -0.17) and distal third radial DXA (r = -0.02). Non-spinal fractures correlated best with the distal third radial DXA (r = -0.42). In conclusion, spinal QCT, supine lateral spine DXA and femoral neck DXA are the best BMD methods to screen for osteoporosis, whereas AP spine DXA is a poor screening method in women over 60 years of age. Spinal QCT and lateral spine DXA correlate well with VCFs, whereas correlations of VCFs with AP spine DXA, femoral neck DXA and distal third radial DXA are poor.

Dual x-ray absorptiometry forearm software: accuracy and intermachine relationship

An ash study was performed to analyze the accuracy of forearm measurements at the one-third site of three dual x-ray absorptiometry (DXA) systems using 20 cadavers. A Hologic QDR-2000, a Hologic QDR-1000/W, and a Lunar DPX-L system were used. The correlations between ash weight and DXA BMC were excellent for the three instruments (r > 0.97, p < 0.001), with accuracy errors < 5.2%. To perform a forearm cross-calibration of bone mineral content (BMC) and density (BMD) between the scanners, 10 healthy volunteers were additionally scanned at the distal one-third radius. The correlations among the DXA machines were excellent (r > 0.95); the absolute BMC and BMD values were significantly different between the two Hologics and the Lunar machine. The slope and intercept of both the BMC and BMD between the two Hologic systems were close to unity. In conclusion, the DXA forearm software packages provide accurate methods for assessing bone mineral content and density. The conversion of data among different manufacturers should be performed by careful cross-calibration measurements.

The site-specific effects of long-term unilateral activity on bone mineral density and content

This study assessed the site-specific effects of long-term tennis playing on the bone mineral density (BMD) and content (BMC) of upper extremities in male Finnish top-level players using a dual energy x-ray absorptiometric (DXA) scanner. In players (n = 20), the BMDs and BMCs were significantly higher in each bone of the playing right extremity (p < 0.05-0.001), the side-to-side difference being largest in the humeral shaft (BMD + 25.4%, BMC + 28.7%) and proximal humerus (BMD + 14.4%, BMC + 20.5%), and smallest in the ulnar shaft (BMD + 3.1%, BMC + 7.5%) and distal ulna (BMD + 6.3%, BMC + 7.8%). In sex-, age-, weight-, and height-matched controls (n = 20), the right-to-left differences were small ranging from 0.0% to + 6.4% (average +3%). The number of training sessions per week was the only variable in muscle strength and training history assessment which showed, in several anatomic sites, a significant correlation with the relative bone mineral variables (r = 0.460-0.627, p < 0.05-0.001). In conclusion, long-term unilateral tennis activity had a clearly positive effect on the BMD and BMC of the bones of the playing extremity. The effect was very site-specific, being greatest in the humerus and smallest in the ulna. The effect was always greater in BMC than BMD indicating that the excess mineral was used not only for condensation of the bone tissue, but also for enlargement of bone dimensions.(ABSTRACT TRUNCATED AT 250 WORDS)

Precision of measurement by dual-energy X-ray absorptiometry of bone mineral density and content in rat hindlimb in vitro

Dual-energy x-ray absorptiometry (DXA) is a precise and effective method for measuring bone mineral density (BMD) and content (BMC) at various skeletal sites in the human, but its precision for measuring low BMD and BMC in tiny rat bones has scarcely been evaluated. The short-term precision of DXA (Norland XR-26) for eight regions of interest (ROI) was determined by measuring dissected, not totally defleshed hindlimbs from four rats of differently weights 10 times consecutively. The accuracy of the BMD (area) measurement was also evaluated. The following average precision values (coefficients of variation) with negligible reanalysis error were obtained for BMD and BMC measurements: 0.7 and 1.2% (total); 0.9 and 1.2% (femur); 1.3 and 2.8% (tibia); 1.3 and 2.1% (foot); 2.1 and 4.7% (proximal femur); 1.4 and 2.9% (femoral shaft); 1.8 and 5.6% (distal femur); and 2.7 and 7.6% (proximal tibia). As for the accuracy, BMD measured in tiny bones is likely to be markedly underestimated. We conclude that the standard DXA technique without additional modification for small animal measurements is a precise method for BMD and BMC measurements at multiple sites in rat hindlimb in vitro.

A comparison of single photon and dual X-ray absorptiometry of the forearm in children and adults

We compared single photon absorptiometry (SPA) to dual x-ray absorptiometry (DXA) for determination of bone mineral content (BMC), bone mineral density (BMD), and bone width (BW) of the forearm. The SPA and DXA measurements were done on the same subjects, using Lunar densitometers. The measurements were performed over the proximal radius (1/3 shaft) of the nondominant arm in 285 healthy, Caucasian females and males, ages 9-53. Correlation, linear, and split regression analyses for all subjects, and for subgroups (adults and children), were performed to compare SPA and DXA measurements. Corresponding measurements performed on two densitometers were highly correlated: r = 0.987, 0.975, and 0.943 for BMC, BMD, and BW, respectively. The corresponding measurements were also very similar in value, ranging from 0.9% to 4.1% difference, although they were different statistically. Correlations dropped slightly when subjects were separated into adult and children subgroups, and therefore, split regression analysis was performed resulting in R2 (adjusted) values of 97.6%, 95.5%, and 89.0% for BMC, BMD, and BW, respectively. Because the group indicator was statistically significant (p < 0.001) only for the BMC measurements but not for BMD and BW, linear regression of the whole sample was done as well. The difference in fitted values between the two regression methods was insignificant; therefore, we concluded that linear regression was sufficient for description of the relationship between SPA and DXA measurements. The precision study showed that the DXA had better reproducibility than SPA. The DXA precision in vivo (CV%) for BMC, BMD, and BW was 1.06, 0.83, and 0.95, respectively; and the SPA precision for same variables was 2.08, 2.12, and 0.95, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Densitometry of the radius using single and dual energy absorptiometry

Though spinal and femoral measurements are typically preferred for evaluating skeletal density, an abundance of forearm data exists, primarily from single photon absorptiometry (SPA) devices. Most dual X-ray absorptiometry (DXA) scanners are capable of scanning the forearm and provide analysis tools to duplicate conventional SPA measurements. In this study, we have compared the radius density measurements from three commonly available densitometers: a Norland 278 SPA, a Lunar DPX-L, and a Hologic 1000/W. Radius bone mineral density (BMD) on the nondominant forearm was measured in 28 volunteers (21 women and 7 men) aged 24-78, with an average age of 51 +/- 17 years. Values were compared and regression relationships derived at corresponding measurement sites. SPA and DXA BMD values were found to be highly correlated (r = 0.99) with small standard errors (0.014 g/cm2-0.021 g/cm2), though significant absolute differences were observed at most measurement regions. Correlation slopes ranged from 0.85 to 1.04, with intercepts from 0.01 to 0.08 g/cm2. Using the resultant regression equations, SPA BMD values can be converted to DXA values with an expected error of roughly 3%. DXA BMD can also be interconverted between Lunar and Hologic with a similar expected error. In situations where this level of imprecision is acceptable, patient forearm measurements obtained on different systems can be interconverted.

Single X-ray absorptiometry of the forearm: precision, correlation, and reference data

The performance of a single X-ray absorptiometry (SXA) device incorporating an X-ray tube as a photon source was evaluated with respect to precision in vivo and in vitro, scan time, image quality, and correlation with an existing dual energy X-ray absorptiometry (DXA) device. SXA precision in vivo, expressed as a coefficient of variation (CV), was 0.66% for bone mineral content (BMC) and 1.05% for bone mineral density (BMD). Precision in vitro, based on 78 BMC measurements of a forearm phantom over 195 days, was 0.53%. Correlation with DXA at the 8 mm distal forearm site was high (r = 0.97 for BMC and r = 0.96 for BMD). A preliminary SXA reference database composed of 151 healthy Caucasian American women was developed to facilitate the interpretation of patient measurements. SXA scan time was 4 minutes and delivered a radiation exposure of 1.68 mrem. SXA image quality and spatial resolution were superior to SPA and comparable to DXA.

Geometric variables from DXA of the radius predict forearm fracture load in vitro

The purpose of this investigation was to determine the cross-sectional geometry of the radius in female and male cadaveric specimens using dual-energy X-ray absorptiometry (DXA), to measure the accuracy of this technique compared with a digitizing procedure, and to measure the correlation between these DXA-based geometric variables and the load required to produce a forearm fracture. Paired intact forearms were scanned at a distal site and at a site approximately 30% of the forearm length from the distal end. The cross-sectional area and the moments of inertia of two sections at 10 and 30% of the forearm length were computed from the X-ray attenuation data. One member of each pair was then sectioned at the 30% location, which is mostly cortical bone, and the section was traced on a digitizing pad. The other forearm was loaded to failure in a servohydraulic materials test system. The DXA-based area and moment of inertia at 30% correlated significantly with the digitized results (r2 = 0.93 for area; r2 = 0.95 for moment; P < 0.001). The conventional bone mineral density from DXA did not associate significantly with failure load, but the minimum moment of inertia and the cross-sectional area at 10% correlated in a strong and significant manner with the forearm fracture force (r2 = 0.67 for area; r2 = 0.66 for moment; P < 0.001). The determination of radial bone cross-sectional geometry, therefore, should have better discriminatory capabilities than bone mineral density in studies of bone fragility and fracture risk.

Precision of dual energy x-ray absorptiometry in the upper extremities

Dual energy x-ray absorptiometry (DEXA) has been shown to be a precise method for measuring bone mineral density (BMD) and content (BMC) in lumbar spine and proximal femur, but it has not been widely used in other skeletal sites. The in vivo day-to-day precision of DEXA (Norland XR-26) for seven anatomic sites in the upper extremities was evaluated by twice measuring both the right and left sides in ten subjects. For consistently defined regions-of-interest, the following precision values (coefficient of variation) were obtained for BMD and BMC: 0.8% and 1.0% (proximal humerus); 0.5% and 0.5% (humeral shaft); 0.7% and 0.5% (radial shaft); 1.3% and 1.1% (ulnar shaft); 0.7% and 1.0% (distal radius); 0.7% and 1.2% (distal ulna); 0.4% and 0.6% (hand). The initially observed relative side-to-side differences did not change significantly in the repeated measurements. Our results indicate that DEXA is a precise method for assessment of BMD and BMC also in the upper extremities.

Comparative assessment of bone mineral density of the forearm using single photon and dual X-ray absorptiometry

Forearm bone mineral density (BMD) was measured at proximal and distal sites by 125I single photon absorptiometry (SPA) and by dual energy X-ray absorptiometry (DXA) in 67 consecutive subjects, aged 18-75 years. Correlations and regression equations between these two techniques were determined. All forearm measurements were significantly correlated with each other (r = 0.599-0.926; P < or = 0.0001). Although SPA and DXA correct for fat in different ways, we found similar correlation and regression equations in women with body mass index measurements above and below the mean. In addition, forearm measurements by both techniques were moderately correlated with vertebral spine and hip BMD. We conclude that overall, SPA forearm measurements in a population can be calibrated to DXA measurements if necessary, and that DXA forearm measurements are as predictive of the remainder of the skeleton as SPA measurements.

Comparison of single-photon and dual-energy x-ray absorptiometry of the radius

We compared dual-energy x-ray absorptiometry (DXA) for measurement of the radius with the conventional single-photon absorptiometry (SPA) method. To evaluate reproducibility, 34 healthy male and female subjects were measured twice each by both methods. While the instruments measured bone mineral content (BMC) similarly, projected area was consistently lower by SPA and therefore bone mineral density (BMD) was higher by an average of 10%. We report similar coefficients of variation for the two methods, which are 0.8% (SPA) and 0.7% (DXA) for BMC (P = 0.71) and 0.8% (SPA) and 1.4% (DXA) for BMD (P = 0.02). We also evaluated the relationship between the methods with data from 196 clinic patients who were measured once each on both instruments. The BMD measurements from the two instruments were highly correlated (r = 0.97) in these patients, which permits the conversion of databases from SPA to DXA-equivalents. We conclude that DXA can replace SPA for radial bone densitometry.

Dual-energy x-ray absorptiometry of the forearm: reproducibility and correlation with single-photon absorptiometry

Although single-photon absorptiometry (SPA) has been the predominant tool used to assess bone mineral density (BMD) in the forearm, the development of dual-energy x-ray absorptiometry (DEXA) provides the benefits of greater source stability, reduced scanning time, and improved image resolution compared to SPA. In the present study we used the DEXA bone densitometer (Hologic, Inc., Waltham, MA) to (1) measure BMD in the one-third radius and ultradistal radius; (2) examine the reproducibility of these BMD measurements; and (3) compare the BMD at the one-third radius with SPA (SP2, Lunar Corp., Madison, WI). In 65 normal women (ages 22-74 years) we examined changes in the forearm DEXA BMD with age, revealing significant quadratic regression equations. The reproducibility of DEXA BMD (mean +/- SEM) in 7 normal subjects aged 22-50 years is 0.85 +/- 0.16% for the predominantly cortical one-third radius site and 0.97 +/- 0.15% for the more trabecular ultradistal site. The regression relationship between DEXA and SPA of the one-third radius in 26 subjects (ages 22-68 years) is DEXA BMD = 0.105 + 0.826 (SPA BMD); R = 0.97, R2 = 0.94, p less than 0.0001. Bone densitometry of the forearm using DEXA may be performed relatively rapidly, providing reproducibility and image resolution that are generally superior to those observed with SPA.