Precision of total-body and regional bone mineral measurement by dual-energy X-ray absorptiometry.

The precision of total-body and regional bone mineral measurements from whole body scans obtained by dual-energy X-ray absorptiometry (DEXA) was determined in a phantom and two normal subjects. Whole body scans were performed once a week for three months at the speed of 80 mm/sec. Coefficients of variation for measurements of total-body bone mineral content (BMC) in the phantom and the subjects were 1.7% and 1.5% (average), respectively. Moreover, plots of total-body BMC values with time showed no significant slope, indicating the stability of the instrument. Regional BMC measurement from whole body scans, however, resulted in larger precision errors than total-body BMC measurement. This is attributed to the more rapid scan speed and coarser scan width used in whole body scanning as compared with regional scanning. Good precision of total-body BMC measurement by DEXA is of great clinical value in the assessment of metabolic bone disease.     

Intersite comparison of the Hologic QDR-1000 dual energy X-ray bone densitometer

We have compared results from 13 Hologic QDR-1000 bone densitometers: (i) by performing spine and hip scans on two normal volunteers; (ii) by acquiring sets of 10 sequential scans on a Hologic anthropomorphic spine phantom. For each QDR-1000 site visited a set of spine phantom scans was also acquired on a QDR-1000 at Guy's Hospital to serve as a control study. All scans were analysed using the Hologic scan comparison software. Radiographers at each site were asked to perform their own independent analysis of the scans of the two volunteers. The precision of the bone mineral density (BMD), bone mineral content (BMC) and projected area (Area) results for a set of 10 phantom scans was 0.11%, 0.14% and 0.12% respectively. The coefficient of variation (CV) between sites for the sets of phantom scans was 0.58% for BMD, 0.71% for BMC and 0.35% for Area. In comparison, CVs for the phantom scans acquired on a single QDR-1000 were 0.23%, 0.23% and 0.09% respectively. The CV for the BMD results on the two volunteers obtained using the scan comparison software averaged 1.4% for the spine and 2.1% for the femoral neck. The CV for the results obtained by site radiographers averaged 2.2% for the spine and 3.7% for the femoral neck. Significant differences in the technique used for hip analysis were found. Conclusions: (i) differences in calibration between systems were generally less than 1%; (ii) variations in results resulting from differences in analytical technique were more significant than those resulting from differences in calibration.     

Fundamental evaluation of bone densitometry using dual energy X-ray absorptiometry (DEXA)

A newly developed instrument based on dual energy X-ray absorptiometry (DEXA), Hologic QDR-1000, was evaluated fundamentally and clinically. Image quality was quite satisfactory though radiation exposure was minimal, 780.2 nC/kg (3.024 mR) for lumbar measurement. Reproducibility of the repeated measurement of a phantom was fairly good; 0.343 CV% in a same day and 0.520 CV% in a long period. Accuracy determined by measurement of potassium phosphate solution was also satisfactory. Bone mineral densities measured by this instrument were fairly correlated with those measured by single energy quantitative CT; coefficient was 0.740 for 17 patients. Mix-DP plates of more than 10 cm thick overestimated the bone mineral densities of a phantom. Bone mineral densities of Japanese normal volunteers were in the normal range (mean +/- 2SD) of the Americans though mostly lower than the mean. In patients with spondylosis deformans or prominent aortic calcification, bone mineral densities might be overestimated. Lateral view was obtainable though its reproducibility was not good. Positioning especially for measuring femoral neck was quite critical for reproducible measurement. In conclusion, this new instrument is quite accurate and satisfactory for clinical application to measuring bone mineral densities.     

Determination of vertebral bone mineral density with new dual energy X-ray absorptiometry using multiple detectors: fundamental studies.

Fundamental studies on the ability of a newly developed 90-detector dual energy X-ray absorptiometry (DEXA) system with a fan beam, the DCS-3000, to determine bone mineral density (BMD) were performed. This new system not only measured BMD precisely, resulting in a fast scan mode in CV of 0.89% and 1.63% for in vitro and in vivo studies, respectively, but also performed data acquisition in a greatly reduced examination time (24 sec). Furthermore, when a rod phantom was used, the linear regression equation obtained between BMD quantified with the QDR-1000 (x) and that quantified with the DCS-3000 (y) was y = 1.250x-0.242. In both healthy subjects and osteoporotic patients, significant positive correlations were obtained between radial BMD and vertebral BMD measured with the QDR-1000 and with the DCS-3000. The correlation for radial BMD was r = 0.533 (p less than 0.001, N = 76), and that for vertebral BMD was r = 0.985 (p less than 0.001, N = 56). Therefore, in addition to safety of operation, the performance of the DCS-3000 was considered to be equal to that of commercially available DEXA systems, indicating that it should be useful in the detection of vertebral bone loss.     

Comparative performance in vitro and in vivo of Lunar DPX and Hologic QDR-1000 dual energy X-ray absorptiometers.

The measured absolute bone mineral density values of spine and femur and their precision were compared on two dual energy X-ray absorptiometers, the Lunar DPX and the Hologic QDR-1000. There were systematic differences between the two systems, the Lunar DPX always giving a higher bone density value. The ratio of the mean Lunar DPX/Hologic QDR-1000 bone density measurements obtained in vivo was 1.13 g/cm2 for spine (L2-L4) and 1.20-1.43 g/cm2 for femur measurements. For both systems, short- and long-term precision (coefficient of variation) was below 0.5% for spine in vitro measurements and below 1.5% for neck of femur in vitro measurements. Precision of in vivo measurements was less good, especially for femur measurements. The coefficient of variation of spine measurements was dependent on bone density and deteriorated with decreased bone mineral density and increased body thickness.     

Vertebral bone mineral measurement using dual photon absorptiometry and computed tomography

The lumbar spine of 14 cadavers was studied both by 153Gd dual photon absorptiometry (DPA) and quantitative computed tomography (QCT) at 96 and 125 kVp. The intact spine and the individual vertebrae were analyzed. After these measurements the ash content of the vertebral body, the posterior elements, and the transverse processes was determined. The fat content of the vertebral body as well as its volume was also measured. With DPA, the bone mineral content (BMC) determined in situ as well as on excised spine specimens correlated highly with the amount of total vertebral ash (r greater than 0.92, SEE less than 3.2 g). The bone mineral density (BMD, area density) of 3 lumbar vertebrae correlated accurately with the mean ash density of the vertebral body (r greater than 0.81, SEE less than 0.015 g/cm3). The so-called corpus density and central density determinations were less accurate. No difference in accuracy was found between measurements when using 3 mm and 4.5 mm step intervals. Variations in the distribution of mineral between the vertebral body and the posterior elements contribute to the error in predicting vertebral body mineral with DPA. QCT gave a smaller error when a cylindric portion of the vertebral body with a 20 mm diameter was measured compared with one with a 9 mm diameter, when the dual energy technique was used (p less than 0.01). With dual energy QCT a correlation was found between a center segment of 3 vertebrae in the lumbar spine and the mean ash density of the vertebral body of r = 0.92 (SEE = 0.010 g/cm3).(ABSTRACT TRUNCATED AT 250 WORDS)     

Anteroposterior versus lateral bone mineral density of spine assessed by dual X-ray absorptiometry

Recently, it has been suggested that lateral (LAT) spine bone mass measurements by absorptiometry may be more sensitive for detecting bone loss than the standard anteroposterior (AP) projection. The aim of this study was to evaluate the precision of LAT spine dual-energy X-ray absorptiometry (DEXA) and its diagnostic sensitivity. A group of 1554 subjects with no risk factors that might affect bone metabolism and 185 osteoporotic patients with vertebral fractures were studied. Bone mineral density (BMD) was measured in the lumbar spine (standard AP and LAT projections) and proximal femur with a DEXA absorptiometer. The precision of the measurements was assessed in 15 volunteers. Diagnostic sensitivity was evaluated by the Z-score method. Comparing young people and the elderly, spine bone loss in the latter was similar for AP and LAT projections, when it was evaluated in absolute values (glcm²). However, when it was evaluated in percentage terms, bone loss was about twice as high in the LAT projection. LAT spine BMD correlated significantly with all the other areas assessed. The best correlation was found with the standard AP projection (r=0.67,P<0.0001). The precision in the LAT projection was found to be within an acceptable range (1.6% in normal subjects, 2% in osteoporotic patients), even though it was about twice that obtained in the AP projection. Diagnostic sensitivity was also better with the AP projection. It is concluded that LAT spine BMD measurements can be assessed with acceptable precision although it is about twice as high as for AP spine measurements. The percentage decrease in BMD in the elderly is greater for measurements made in the LAT projection than for measurements made in the AP projection. However, there is no enhancement of diagnostic sensitivity in osteoporosis. BMD measurements in the LAT projection are not as good as in the AP projection but they may offer complementary information of the regional evolution of spine bone mass.     

双能X线吸收法在肌少症诊治中的研究进展

肌肉减少症（简称肌少症）是以广泛的、渐进的骨骼肌质量和力量减少或丧失为特点,并可能导致机体残疾、生活质量下降、甚至死亡的综合征。肌少症可导致罹患者行动障碍、跌倒及骨折风险增加,从而造成日常生活能力丧失和残疾等严重后果。双能X线吸收法（DXA）具有经济、快速、可重复性强、辐射剂量小及能同时呈现肌肉、脂肪和骨量等优点,现已成为研究及临床应用中估测肌肉质量的首选方法。笔者就DXA肌肉质量测定在肌少症诊疗中的研究进展进行综述。     

Quantitative evaluation of bone mineral density of rat femur by using DEXA (dual energy x-ray absorptiometry)

BMD of rats was measured by using a collimator for small animals and HRSM-1 (high resolution scan module). There was a good correlation between obtained BMD and the known mineral content of hydroxyapatite phantoms. The presence of soft tissue and the positioning of bone did not affect BMD and BMC. There was also a good correlation between BMC and the total calcium by chemical analysis. This study confirmed high precision and accuracy of the rat femur BMD measurement.     

DXA椎体骨折评估联合腰椎侧位骨密度诊断老年性骨质疏松的临床研究

目的研究双能X线吸收检测法（DXA）椎体骨折评估（VFA）联合腰椎侧位骨密度诊断老年性骨质疏松的效能。方法选取我院DXA同时检测髋部、腰椎前后位、腰椎侧位骨密度及VFA的老年受检者86例,根据DXA骨密度低下或VFA有脆性骨折诊断骨质疏松。比较腰椎侧位骨密度联合VFA与常规DXA检测髋部及腰椎前后位骨密度诊断骨质疏松的检出率。检出率的比较采用χ2检验。结果所有受检者中,常规DXA检测髋部及腰椎前后位诊断出骨质疏松患者58例（58/76,76.3%）,侧位骨密度联合VFA诊断出骨质疏松患者76例（76/76,100%）,二者检出率差异有统计学意义（χ2=10.617,P < 0.001）。其中,股骨颈骨密度诊断骨质疏松疏检出率（55.3%）高于髋部整体（34.2%）,二者差异有统计学意义（χ2=6.812,P < 0.05）;髋部骨密度、腰椎前后位骨密度、腰椎侧位骨密度和VFA诊断骨质疏松症检出率分别为60.5%、47.4%、84.2%和78.9%,腰椎侧位骨密度与VFA的骨质疏松检出率比较,差异无统计学意义（χ2=0.700,P>0.05）,但二者均高于髋部骨密度的骨质疏松检出率（χ2=10.66、6.110,均P < 0.05）。结论DXA检测腰椎侧位骨密度联合VFA对老年性骨质疏松的诊断具有重要价值,能够避免骨质疏松的漏诊。     

Panoramic-based mandibular indices in relation to mandibular bone mineral density and skeletal status assessed by dual energy X-ray absorptiometry and quantitative ultrasound

OBJECTIVES: The panoramic-based indices (Mandibular Cortical Index-MCI, the height of mandibular inferior cortex-IC (mm), Panoramic Mandibular Index-PMI, Mandibular Ratio-MR) were used to evaluate their diagnostic efficacy and to determine whether they correlate with bone mineral density (BMD (g/cm(2))) of the mandible and hip, and with ultrasound parameters of the calcaneus and hand phalanges in postmenopausal, edentulous women. METHODS: Basing on MCI women were divided into three subgroups differed in the appearance of the mandibular cortex (C1 n=6, C2 n=16, C3 n=8). BMD of the hip (neck-BMD, Ward's-BMD, trochanteric BMD) and mandible (m-BMD) were measured by dual-energy X-ray absorptiometry (DXA). Calcaneus using Achilles (Speed of Sound-SOS (m/s), Broadband Ultrasound Attenuation-BUA [dB/MHz], Stiffness Index-SI [%]) and hand phalanges (amplitude dependent speed of sound-Ad-SoS (m/s)) using DBM Sonic 1200 were assessed by Quantitative Ultrasound (QUS). RESULTS: There were no significant differences between subgroups in parameters measured except for significant differences in m-BMD (P<0.01). Only m-BMD correlated significantly with DXA (r=0.43-0.45, P<0.05) and QUS (r=0.36-0.55, P<0.05) measurements excluding correlations with calcaneal SOS and trochanteric BMD. The ability of the mandibular variables to discriminate between normal and osteopenic/osteoporotic cases was assessed by calculating: specificity (ranging from 31 to 81%), sensitivity (ranging from 21 to 93%), negative and positive predictive values (ranging from 47 to 83% and 40 to 79%, respectively). CONCLUSION: MCI is a simple three-graded classification of changes in the cortex but is not able to distinguish normal and osteopenic/osteoporotic postmenopausal edentulous women. The efficacy of the panoramic-based mandibular indices in diagnosing osteopenia/osteoporosis is low to moderate.     

双能X射线骨吸收测量仪的辐射剂量评价

目的 评价双能X射线骨吸收测量仪（DXA）的辐射剂量。方法 使用美国Radcal公司多功能剂量仪（1 800 cc电离室）对美国Norland公司XR-800 DXA （笔形束扫描,100/46.8 kVp、1.3 mA）进行剂量检测,得到正位腰椎、髋关节、腕骨、下颌骨扫描的受检者入射体表剂量（ESD）;使用Radcal剂量仪对美国Hologic公司Discovery A DXA （扇形束扫描,140/100 kVp、2.5 mA）进行剂量检测,得到正位腰椎、髋关节扫描的受检者ESD;对比两种机器在不同扫描方式下骨密度检查受检者的ESD。使用美国Fluke公司451P巡测仪对这两台DXA仪器正位腰椎扫描分别在距床面模体中心1 m和地面高1 m处测量周围剂量当量率水平。结果 Radcal公司多功能剂量仪测得Norland XR-800 DXA受检者正位腰椎扫描的ESD为0.43 μGy （高速度）和0.73 μGy （标准速度）,髋关节、腕关节、下颌骨扫描的ESD分别为1.93（初扫+测量扫描）、0.40和1.06 μGy （初扫+测量扫描）。Radcal多功能剂量仪测得Hologic Discovery A DXA受检者正位腰椎、髋关节扫描的ESD分别为65.6和63.9 μGy。Norland XR-800 DXA 4个检查部位在不同扫描方式和不同扫描速度下,受检者ESD均<2 μGy,Hologic Discovery A DXA正位腰椎及髋关节受检者ESD均<66 μGy,与两台机器的操作手册给出的数据基本一致。使用451P巡测仪对两台DXA周围剂量当量率测量显示,扇形束机器高于笔形束机器65倍。结论 受检者做骨密度检查的ESD是医用X射线检查项目中较低的,笔形束扫描DXA常规腰椎及髋关节的受检者ESD约为扇形束扫描DXA检查剂量的1/153~1/33。笔形束DXA扫描的工作人员接受的剂量可忽略不计,扇形束DXA扫描的工作人员接受的剂量<20 mSv/年的个人剂量限值。     

Bone mineral measurement of phalanges: comparison of radiographic absorptiometry and area dual X-ray absorptiometry

With a standard, image-intensifier-based, digital radiographic system, high-spatial-resolution images of the hand were acquired for analysis of phalangeal bone mineral density with dual x-ray absorptiometry (DXA). Results with phalangeal DXA had precision of plus or minus 0.67% and accuracy of 4.1% and correlated well with those with radiographic absorptiometry. This phalangeal DXA technique is potentially useful for clinical diagnosis of osteoporosis.     

Triple-photon energy absorptiometry in the measurement of bone mineral

The feasibility of determination of bone mineral content using a triple-photon absorptiometric technique is presented. Using three different photon energies it is possible to correct the measured 'bone mineral' value for fat and lean soft tissue. The theoretical basis of the method, as well as the experimental determination of mass attenuation coefficients, is described. It is shown that the results are reproducible within 5 per cent, which means that the method could be of value in the management of metabolic bone diseases.     

Influence of anthropometric parameters and bone size on bone mineral density using volumetric quantitative computed tomography and dual X-ray absorptiometry at the hip

PURPOSE: To evaluate the influence of anthropometric parameters (age, height, and weight) and bone size on bone mineral density (BMD) using volumetric quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) in a group of elderly women. MATERIAL AND METHODS: BMD values were obtained with DXA and QCT at the spine and hip in a cohort of 84 elderly women (mean age 73 +/- 6 years). QCT measures included trabecular, integral, and cortical BMD assessed at the hip and spine as well as cross-sectional areas of the mid-vertebrae and proximal femora. Spinal integral and femoral neck BMD measures were well matched to the regions of bone quantified on anteroposterior (AP) spine DXA and the femoral neck region of hip DXA. RESULTS: When QCT parameters were linearly regressed against body height and weight, only the relationships with weight were found to be statistically significant. Except for cortical BMD at the femoral neck, all BMD and geometric parameters measured from both DXA and QCT showed statistically significant associations with body weight (r2 = 0.4, 0.0001 < P < 0.02). The strongest associations with weight were found for DXA Neck (DXA_NECK) and DXA lumbar spine (DXA_LSP) (r2 = 0.4, P < 0.0001). CONCLUSION: The relationship of DXA BMD is stronger than QCT BMD with body weight and it encompasses the response of both bone size and density to increasing body mass.