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.     

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by¹⁵³Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMD_DPA into BMD_DXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.     

Precision and Accuracy of Computed Digital Absorptiometry for Assessment of Bone Density of the Hand

Widespread osteoporosis testing and diagnosis are currently limited due to the high capital cost and reduced portability of many existing bone densitometry techniques. In this study we evaluated an inexpensive, low radiation, X-ray-based technique for assessing bone density of the middle phalanx. The technique, termed computed digital absorptiometry (CDA), is similar to radiographic absorptiometry (RA), using a single-energy X-ray source, an aluminum alloy step-wedge, and a charge-coupled device (CCD) detector system to automatically compute bone mineral content (BMC, g) and bone mineral density (BMD, g/cm²) in the middle phalanx of the third finger. The potential advantage of CDA over current RA techniques is that by using a filmless detector system, no off-site processing of radiographs is required and bone density results are obtained immediately after the test. Using human cadaveric specimens we determined the accuracy and short-term precision of CDA as well as its correlation with other hand and forearm bone densitometry methods. We obtained 26 cadaveric forearms (50% female, mean age 78 years, range 52–96 years). BMC and BMD of the middle phalanx of the third finger were determined using CDA and using RA. We assessed forearm BMC and BMD using single-energy and dual-energy X-ray absorptiometry (SXA and DXA). Precision of CDA was assessed by measuring ten of the specimens five times each with repositioning between measurements. Finally, the middle phalanx was dissected and incinerated to determine ash weight. BMC estimates from CDA and from RA were strongly correlated with ash weight (r = 0.89, p < 0.001 and r = 0.93, p < 0.001, respectively). The mean coefficients of variation using CDA were 1.36% and 0.70% for phalanx BMC and BMD, respectively. BMC and BMD measured by CDA were strongly correlated with hand and forearm bone mineral measurements performed by SXA, DXA and TA (r = 0.74–0.91). These results indicate that CDA accurately and precisely predicts BMC of the middle phalanx. Thus, with further clinical verification, this technique may prove to be a useful tool for the wide-spread testing and assessment of osteoporotic fracture risk.     

Precision and stability of dual-energy X-ray absorptiometry measurements

Summary This study was performed to determine the precision and stability of dual-energy X-ray absorptiometry (DEXA) measurements, to compare bone mineral density (BMD) of subjects measured by DEXA and radionuclide dual-photon absorptiometry (DPA), and to evaluate different absorber materials for use with an external standard. Short-term precision (% coefficient of variation, CV) was determined in 6 subjects scanned six times each with repositioning, initially and 9 months later. Mean CV was 1.04% for spine and 2.13% for femoral neck BMD; for whole-body measurements in 5 subjects, mean CV was 0.64% for BMD, 2.2% for fat, and 1.05% for lean body mass. Precision of aluminum phantom measurements made over a 9-month period was 0.89% with the phantom in 15.2 cm, 0.88% in 20.3 cm, and 1.42% in 27.9 cm of water. In 51 subjects, BMD by DEXA and DPA was correlated for the spine (r=0.98,P=0.000) and femoral neck (r=0.91,P=0.000). Spine BMD was 4.5% lower and femoral neck BMD 3.1% higher by DEXA than by DPA. An aluminum phantom was scanned repeatedly, in both water and in an oil/water (30∶70) mixture at thicknesses ranging from 15.2 through 27.9 cm. Phantom BMD was lower at 15.2 cm than at higher thicknesses of both water and oil/water (P=0.05, ANOVA). The phantom was scanned repeatedly in 15.2, 20.3, and 27.9 cm of water over a 9 month period. In 15.2 and 20.3 cm of water, phantom BMD did not vary significantly whereas in 27.9 cm of water (equivalent to a human over 30 cm thick), phantom BMD increased 2.3% (P=0.01) over the 9 months.     

Bone mineral density in feline mucopolysaccharidosis VI measured using dual-energy X-ray absorptiometry

Dual-energy X-ray absorptiometry (DXA) was used to determine the in vivo bone mineral density (BMD) and bone mineral content (BMC) of lumbar vertebrae in six cats affected with the inherited lysosomal storage disease mucopolysaccharidosis VI (MPS VI). DXA was also performed on MPS cats that had a bone marrow transplant (BMT) and total body irradiation (TBI) (MPS+BMT;n=7), normal cats that had a bone marrow transplant, and TBI (control+BMT; n=8) and normal cats (control; n=14). Following euthanasia, one of the lumbar vertebrae that had been scanned (L5) was harvested and bone volume (BV/TV%) was determined by histomorphometry. The in vivo BMD and BMD measurements were compared with the BV/TV%. There was a greater BMD and BMC in the MPS+BMT cats compared with the MPS cats but the difference was not statistically significant. However, there was a greater BV/TV% in the MPS+BMT cats compared with the MPS cats and the difference was significant (P=0.0152). Correlation between the noninvasive in vivo DXA measurements of BMD and BMC and the BV/TV% was significant (r ²=0.767, P<0.0001; r ²=0.504, P<0.0001). Noninvasive in vivo DXA was a rapid and precise method for measuring the lumbar BMD and BMC in cats and it correlated well with histomorphometric determination of bone mass. Further, the response of inherited storage diseases such as MPS VI to therapy, such as BMT, could be monitored in a longitudinal fashion using DXA.     

Bone densitometry of the forearm: Comparison of single-photon and dual-energy X-ray absorptiometry

Forearm bone mineral densitometry was performed initially by single-photon absorptiometry (SPA), but is now achievable by dual-energy X-ray absorptiometry (DXA) as well, with a good correlation between both measurements. However, it is still unknown whether: (1) short-term precision of DXA is superior to SPA and (2) identical regions of interest (ROT) are mandatory to correlate SPA with DXA. The aim of this study was to answer these questions using a commercial system for DXA (DXA-FAS) and to test an in-house system using spine DXA and a soft-tissue compensator (DXA-STC). In ten subjects, four measurements on the same day showed significantly lower (p < 0.05) coefficients of variation (CV) for bone mineral density (BMD) by DXA-FAS (proximal site: 0.74%; ultradistal site: 1.20%) than by SPA (1.26% and 2.25%). However, the CV for bone mineral content (BMC) were similar for DXA-FAS (0.73% and 1.58%) and SPA (0.79% and 1.34%). The significant difference (p < 0.05) for surface calculation by DXA-FAS (1.24% and 0.93%) compared with SPA (2.36% and 1.28%) explains all the advantages of DXA-FAS for short-term precision. The measurements taken on the same day on the ulna and the radius or on the radius alone by SPA, DXA-FAS, and DXA-STC on 108 subjects aged 18–80 years were highly correlated [r ranging from 0.925 to 0.995 (p < 0.0001) and standard error of the estimate from 3.15% to 8.89%]. The need for a manual adjustment of the ROT was found to be mandatory for BMC but not BMD assessment. The use of DXA-STC is a fast method for forearm bone densitometry and its correlation with SPA is very high. However, its short-term precision for BMC (3.00% and 1.54%), BMD (2.15% and 1.12%), and surfaces (1.99% and 1.12%) is significantly higher (p < 0.05) than that of DXA-FAS. We conclude that short-term precision of DXA is better than that of SPA only for BMD and surface measurement but not for BMC. ROT should be adjusted manually for the assessment of BMC but not for that of BMD.     

Sensitivity of dual-photon absorptiometry in spinal osteoporosis

Summary Lumbar spine bone mass and density were measured with Dual photon absorptiometry (DPA) in 60 patients with crush fractures and 60 age-matched normal women. Short-term reproducibility of bone mineral density (BMD) was 1.3% in normal women and 2.5% in osteoporotic women; long-term reproducibility in normal women was 2.2%. The reproducibility of bone mineral content (BMC) seemed to be poorer than that of BMD. In this study, aortic calcifications had no effect on BMD, and one or two crush fractures in the L2–L4 region increased BMD by an average of 3% (0–10%). Lumbar spine DPA provided high sensitivity for these younger crush fracture osteoporotic patients (x=65 years). The sensitivity at 95% specificity was 74% for BMD and 73% for BMC. This sensitivity is substantially better than that reported for DPA instruments giving higher variances or for quantitative computed tomography.     

The accuracy of volumetric bone density measurements in dual X-ray absorptiometry

New developments in dual x-ray absorptiometry (DXA) allow the performance of high precision anteroposterior (AP) and lateral scans of spinal bone mineral density (BMD, units: g/cm²) without the patient moving from the supine position. Data from both projections may be combined to give an estimate of the true volumetric bone mineral density (VBMD, units: g/cm³) of the lumbar vertebral bodies. This report presents a cadaver study designed to validate DXA measurements of volumetric bone density. Sections of whole lumbar spine were scanned in AP and lateral projections in a water tank to simulate soft tissue. Individual vertebrae were then divided to separate the vertebral body from the neural arch, and vertebral body volume was measured using the displacement of sand. The bone mineral content (BMC) of vertebral bodies and neural arches was measured by ashing at 250°C for 60 hours followed by 500°C for a further 24 hours. The results showed that DXA scanning systematically underestimated ashing data by 14% for AP BMC, 33% for vertebral body BMC, 23% for vertebral body volume, and 12% for VBMD. Despite these significant systematic errors, the DXA measurements and ashing values were highly correlated (r=0.979-0.992). The results suggested that after allowing for the systematic errors, lateral DXA parameters related closely to true BMC, volume, and VBMD.     

Dual-energy X-ray absorptiometry of the spine in anteroposterior and lateral projections

Dual-energy X-ray absorptiometry (DXA) of the lumbar spine provides an estimation of the bone mineral content (BMC) corrected by the projected area of the spine and expressed in g/cm². This two-dimensional estimate of the bone mineral density (BMD) is influenced by the skeletal size, assessed by the subject's height. In order to obtain an estimate of the volumetric BMD, we measured BMC with a new DXA device (Sophos L-XRA) equipped with 24 detectors and a rotating arm, thus allowing scanning of the lumbar spine in both an anteroposterior (AP) projection and a lateral (LAT) projection with the patient in a supine position. Comparison between the results obtained on the third (L3) and fourth (L4) lumbar vertebrae with automatic or manual analysis showed that the best precision was obtained with the lateral measurement of L3 alone with an automatic soft tissue baseline determination. Results were expressed in g/cm² and in g/cm³ (by dividing the g/cm² value by the width (AP area divided by the height of the vertebra) of L3), and were compared with those obtained by conventional AP scanning of L2–4 (g/cm²). The in vivo precision error evaluated by triplicate measurements on 10 controls was 17 mg/cm² (1.96%) and 5.2 mg/cm³ (2.31%) for LAT L3 as compared with 13 mg/cm² (1.15%) for AP L2–4. Volumetric BMD (g/cm³) measurement, assessed in vitro on a calibrated hydroxyapatite phantom, and the absolute values obtained in normal women were similar to those obtained by quantitative computed tomography (QCT). In 39 healthy adults (27±4 years) BMD expressed in g/cm² was correlated with height (r=0.36 for AP L2–4 andr=0.39 for LAT L3;p<0.05 for both) but not with LAT L3 BMD expressed in g/cm³ (r=0.02; NS). The age-related bone loss between 30 and 80 years of age, derived from the normal values for 101 healthy women (age range 19–73 years) was 36% for AP L2–4, 52% for LAT L3 (g/cm²) and 60% for LAT L3 (g/cm³). In a group of 22 women with untreated postmenopausal vertebral osteoporosis (one or more non-traumatic vertebral crush fractures) the mean decrease in BMD, expressed as a percentage of the age-adjusted normal value, was more pronounced (p<0.001) for LAT L3 BMD (–21% in g/cm²,Z-score –1.08; –22% in g/cm³,Z-score –0.94) than for AP L2–4 BMD (–9%,Z-score –0.66). We conclude that: 1) BMD measurement restricted to the vertebral body of L3 can be achieved with a low precision error with this new DXA device; 2) it allows an estimate of the volumetric density (g/cm³) which does not seem to be influenced by skeletal size; 3) lateral BMD appears to be more sensitive than conventional AP scanning for assessing age-related bone loss and should be useful in the investigation of trabecular osteoporosis.     

Precision of dual x-ray absorptiometry and peripheral computed tomography using mobile densitometry units

Irrespective of the method used for noninvasive bone mass determination, data comparison between different centers is a major problem as significant interunit variation may occur. We, therefore, have employed mobile densitometry units to reduce interunit variability in two large epidemiologic studies in Germany. Two cars were equipped with either two dual X-ray absorptiometry (DXA) instruments (QDR 1000 Hologic, USA) (car I) or a special purposed scanner for peripheral quantitative computed tomography (pQCT) (XCT 900, Stratec, FRG) (car II). The cars were moved across Germany 11,090 km and 1651 km during the studies over a period of 30 and 7 months, respectively. Precision in vitro was determined using hydroxyapatite phantoms. Forty-eight patients underwent duplicate measurements at the lumbar spine (n=22) and hip (n=26) for assessing reproducibility in vivo. Between the two series of scans, the car was moved 63 km. Long-term precision in vitro of the QDR 1000 instruments were 0.41% and 0.59% for BMD with no evidence of machine drift (rate of change per year 0.04% and 0.05%, respectively). Short-term reproductibility in vivo showed a coefficient of variation (cv) of 1.02% for spinal BMD (L2–L4) and 1.72% for femoral neck. Long-term precision in vitro of the pQCT scanner was 0.9%. Our study shows precision in vivo and in vitro and stability of the mobile densitometers similar to that achieved with stationary equipment. In conclusion, mobile densitometry may become a useful tool not only for epidemiologic surveys and clinical trials but also for routine evaluation in less densely populated areas.     

Comparison of nuclear magnetic resonance spectroscopy with dual-photon absorptiometry and dual-energy X-ray absorptiometry in the measurement of thoracic vertebral bone mineral density: Compressive force versus bone mineral

³¹P nuclear magnetic resonance spectroscopy (NMRS) measurements were made on human T2 and T3 vertebral bodies. The bone mineral content (BMC) of isolated vertebral bodies minus the posterior elements and disks was measured using (1) NMRS on a 3.5 T, 85 mm bore GE Medical Systems NT-150 superconducting spectrometer, (2) a Lunar Corporation DPX-L dual-energy X-ray absorptiometry (DXA) scanner in an anterior-posterior (AP) orientation, (3) a Norland Corporation XR26 DXA scanner, also in an AP direction, and (4) a Norland Corporation model 2600 dual-photon absorptiometry (DPA) densitometer in both the AP and superior-inferior (SI) directions. Vertebral body volumes were measured using a water displacement technique to determine volume bone mineral densities (VBMD). They were then compressed to failure using an electrohydraulic testing device, followed by ashing in a muffle furnace at 700 °C for 18 h. Correlations of BMC between NMRS and DPA, DXA and ashing were excellent (0.96r0.99); in a one-way analysis of variance (ANOVA) test, means were not statistically different at ap level of 0.757. The correlations of VBMD between NMRS and the other methods were not as good (0.83r0.95); in a one-way ANOVA test, means were not statistically different at ap level of 0.089. BMC was a better predictor of ultimate compressive failure than VBMD for all six methods. For NMRS, the regression coefficient for BMC wasr ²=0.806, compared withr ²=0.505 for VBMD. NMRS may prove an alternative to present methods of determing bone mineral.     

Single X-ray absorptiometry: Performance characteristics and comparison with single photon absorptiometry

The aim of the present study was to evaluate a new device for measurement of forearm bone mass using the technique of single X-ray absorptiometry (SXA, DTX-100; Osteometer A/S, Rødovre, Denmark), and to compare the performance with the more traditional single photon absorptiometry (SPA, DT 100; Osteometer A/S, Rødovre, Denmark). The SPA phantom measurements showed a coefficient of variation of 0.43% and 0.42% for bone mineral content (BMC) and bone mineral density (BMD), respectively (39 months including seven source changes). The SXA precision errors were slightly lower with values of 0.30% and 0.30%, respectively. The patient measurements showed SPA coefficients of variation of 0.85% and 0.99% (BMC and BMD) and SXA coefficients of variation of 0.56% and 0.83%, respectively. The correlation between SPA and SXA values performed in 377 individuals yielded r values of 0.99 an 0.98 for BMC and BMD, respectively. The correlations between SXA measurements of the dominant and non-dominant forearm yielded anr-value of 0.95, with a slope of 0.949 (p<0.001) and an intercept of 0.204 (p<0.05). The non-dominant forearm thus had approximately 3% lower BMC than the dominant (the same was true for BMD). Correlations to spine and femur ranged fromr=0.48 tor=0.75. In conclusion, the new single X-ray absorptiometry forearm bone densitometer described in this paper has performance characteristics which allows it to be used both for diagnostic purposes and for the follow-up of treatment.     

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.     

Accuracy and precision of in vivo bone mineral measurements in sheep using dual-energy X-ray absorptiometry

We evaluated the precision and accuracy of in vivo measurements of spine bone mineral density (BMD) and bone mineral content (BMC) in five ewes using dual-energy X-ray absorptiometry (DXA, Lunar DPX-L). The short-term in vivo reproducibility expressed as the coefficient of variation (CV) varied from 0.9 to 1.6% for spine BMD and from 1 to 3.1% for spine BMC. The ex vivo measurements, performed in 20 cm of water to simulate soft tissue thickness, correlated closely with the in vivo measurements, yielding an r value of 0.98 and 0.97 for spine BMD and BMC, respectively. The accuracy was determined by comparing the total BMC of each vertebra measured in vivo with the corresponding ash weight. The correlation coefficient between the two measurements was r = 0.98, with an accuracy error of 5.6%. We concluded that the DXA allows a precise and accurate measurement of spine bone mineral in live ewes using the methodology designed for humans. Received: 19 March 1999 / Accepted: 26 July 1999     

Accuracy and precision of bone mineral density and bone mineral content in excised rat humeri using fan beam dual-energy X-ray absorptiometry.

The aim of this study was the evaluation of fan beam dual-energy X-ray absorptiometry (DXA) for measuring bone mineral density (BMD) and bone mineral content (BMC) of isolated rat humeri. Defleshed rat humeri from male Lewis rats were examined with a Hologic QDR 4500 A (Hologic, Inc., Bedford, MA) high-resolution densitometer both in water and 0.9% saline solution. The small animal scan protocol with the regional high-resolution mode was used. BMC measured by DXA was compared with bone dry weight, ash weight, and bone calcium content. Furthermore, DXA BMD and BMC precision were determined. We also evaluated the effect of salinity of the water bath in which the bones were measured. Correlations (r(2)) of BMC, as determined by DXA with dry weight, ash weight, and bone calcium content, were 0.978, 0.988, and 0.890, respectively. DXA overestimated ash weight by 5%-9%. Precision errors for BMC (BMD) were 0.90% (0.76%) without and 1.3 (0.86) with repositioning. Changes in the salinity of the water bath had a significant influence on the DXA results: At the 0.9% physiological level, BMC (-4.4%) and area (-4.1%), but not BMD, values were significantly lower (p < 0.005) compared with measurements in tap water. Fan beam DXA is a highly accurate and precise technique for measuring BMC and BMD in excised small animal bones. A physiological saline concentration in the water bath had a significant impact on BMC and area, but not on BMD, and should therefore be strictly controlled to avoid an underestimation of BMC.     

Bone mineral content by photon absorptiometry of the mandible compared with that of the forearm and the lumbar spine

Summary A new method for measuring the bone mineral content (BMC) of the mandible by dualphoton absorptiometry (DPA) has recently been introduced. The purpose of the present investigation therefore was to examine the long-term precision for 32 monthsin vitro andin vivo for assessment of BMC in the mandible and to examine the relationshipin vivo among BMC of the mandible, the forearms, and the lumbar spine as measured by DPA and/or single-photon absorptiometry (SPA). For comparison, the relationship between forearm BMC as measured by DPA and SPA was studied. The long-term precision of the mandibular BMC was 0.8%in vitro, independent of age and change of radioactive source, and 2.1% by assessmentin vivo. A significant relationship (P<0.01) was found between BMC of the lumbar spine and the forearms and between the two sets of forearm BMC measured by DPA and SPA. Thus, relative BMC changes of the forearms can be compared without respect to type of forearm bone scanner used. The BMC changes of the mandible can only be evaluated by scanning of the mandible itself. The present DPA bone scanner is suitable for follow-up analyses of the BMC changes of the mandible and the forearms.     

Comparison of total-body measurements by dual-energy X-ray absorptiometry and dual-photon absorptiometry

Both dual-photon absorptiometry (DPA) using 153Gd and dual-energy x-ray absorptiometry (DEXA) can be used for measurement of bone mineral content (BMC) and bone mineral density (BMD) of the total skeleton and its seven major regions. The short-term precision (coefficient of variation, CV) of DEXA for total-body BMD using the medium (20 minute) and fast (10 minute) speeds was 0.34 and 0.68% in 5 normal subjects; the corresponding CV in 5 osteoporotic females were 0.70 and 1.04%. The CV for BMD using DPA was 0.82% in 8 normal subjects and 0.70% in 12 osteoporotic patients. The CV for regional BMD using DPA was similar to fast-speed DEXA, without significant differences (p NS); precision with medium-speed DEXA was superior to DPA, and the differences were statistically significant (p less than 0.05) for head, spine, trunk, ribs, and pelvis. Total-body measurements using both DPA and DEXA were done on 99 subjects (84 females and 15 males). Significant correlations (r = 0.98; p less than 0.001) were found between DEXA and DPA measurements of both BMC and BMD. There were also significant correlations (r = 0.94-0.98; p less than 0.001) between DEXA and DPA measurements of anatomic regions (head, trunk, spine, pelvis, ribs, arms, and legs). DPA and DEXA results for BMD of total skeleton, ribs, pelvis, and legs were similar (p NS), and statistically significant differences were found in head, spine, and arm measurements (p less than 0.01, p less than 0.01, and p less than 0.05, respectively); regression equations allowed adjustment of DEXA values in patients already measured with the earlier DPA method.     

Dual X-ray absorptiometry for the evaluation of bone density from the proximal femur after total hip arthroplasty: Analysis protocols and reproducibility

Summary Dual X-ray absorptiometry (DXA) instruments are now able to evaluate bone mineral density (BMD) of bone surrounding metal implants. The assessment of BMD around prosthetic components could provide additional information for the follow-up of total hip arthroplasty (THA). In this study, we evaluated the potential application of DXA in the field of THA. BMD was measured in the proximal femur of both THA and THA-free sides in 14 postmenopausal women 6–18 months after THA. The explored segment was divided into seven zones as proposed by Gruen et al. [18]. The precision error of BMD measurements ranged from 1.8 to 6.8% on the THA side and from 1.1 to 2% to the THA-free side. The reduction of BMD of the THA versus the THA-free side was significant in all seven zones (P < 0.01, t-test for paired data). These results showed significant differences in BMD around femoral components of THA with respect to contralateral healthy side, and demonstrate the sensitivity of DXA for detecting these changes.     

A population-based comparison of quantitative dual-energy X-ray absorptiometry with dual-photon absorptiometry of the spine and hip

Summary Dual photon absorptiometry (DPA) is currently the most widely used method for noninvasive bone mineral density (BMD) measurement of the axial skeleton. Dual energy X-ray absorptimetry (DEXA) is a recently developed technique that uses an X-ray tube as a photon source; it has demonstrated several significant advantages over DPA in preliminary studies. We report here a quantitative comparison of the DEXA and DPA technologies using a Hologic DEXA (Hologic QDR model 1000, Waltham, MA) scanner and a Lunar DPA (Lunar Radiation DP3, gandolineum-153 source) scanner at both the proximal femur and lumbar spine sites using bone density measurements from a populationbased sample of older white men and women who had complete DEXA and DPA measurements of the hip (n=217) or the spine (n=176). To examine the relationship of BMD measured by the DPA scanner to BMD measured on the DEXA scanner, normal least squares linear regression was used to regress the DPA BMD on the DEXA BMD for each site. DEXA values were consistently lower than DPA values, with an average difference of 16%. The squared multiple correlation (R²) values were at or above 0.95 for almost all sites, with Ward's triangle having the lowest value (0.89). The slope for all sites was similar, ranging from 0.94 to 1.1. Research and clinical centers that wish to change to DEXA technology because of its shorter examination time and greater precision can therefore compare DEXA with DPA values using representative convesion factors.     

Dual-energy X-ray absorptiometry of human metatarsals: Precision,least significant change and association to ex vivo fracture force

BackgroundFractures are common in foot bones, but clinicians lack adequate indices of bone strength.ObjectivesWe used dual-energy X-ray absorptiometry (DXA) to measure bone mineral density (BMD) and content (BMC) of excised human metatarsals, determined intra- and inter-rater measurement precision, and assessed associations between BMD/BMC and ex vivo bone fracture strength.MethodsTwo raters each made two measurements of whole-bone and sub-regional BMD and BMC in both second and third metatarsals from 10 cadavers. Variance components analysis was used to assess variability attributable to repeat measurements, raters, sub-regions, bones, sides, and cadavers. Root-mean-square standard deviation (RMS-SD) and least-significant change (LSC) were used to assess rater precision and ultimate forces during 3-point bending were tested for correlations with BMD and BMC.ResultsVariation due to repeat measurements and rater was low (<1% combined) for BMD and BMC. RMS-SD for whole metatarsal BMD of both metatarsals ranged from 0.004 to 0.010 g/cm² and 0.062 to 0.086 g for BMC. Whole metatarsal and sub-region BMD and BMC were strongly correlated to ex vivo fracture force (r² = 0.67–0.93).ConclusionsDXA measurements of BMD and BMC have high intra- and inter-rater precision and are strongly correlated to ex vivo bone strength.