Standardization of spine and hip BMD measurements in different DXA devices

AIM: To compare BMD values of lumbar and hip regions measured in two different DXA scanners in one laboratory, and to investigate the efficiencies of implemented and specifically derived standardization formulas. MATERIALS AND METHODS: PA lumbar (L2-L4) and right femoral neck BMD values were obtained in 100 women (aged 26-75), consecutively in GE-Lunar DPX-NT and Hologic QDR 4500 C DXA scanners. Standardization of BMD values obtained in two different DXA devices was done according to the method developed by International DXA Standardization Committee (IDSC), using the European Spine Phantom (ESP) to obtain the specific constant value. Mean corrected standardized BMD (sBMD) values in two scanners have been compared with each other and with the mean reported sBMD values, respectively. RESULTS: The mean lumbar BMD values were 0.950+/-0.117 g/cm(2) for Hologic and 1.068+/-0.135 g/cm(2) for GE-Lunar (p<0.05); mean corrected sBMD values were 1.035+/-0.128 g/cm(2) for Hologic and 1.035+/-0.131 g/cm(2) for GE-Lunar (p>0.05). The mean femoral neck BMD values were 0.798+/-0.114 g/cm(2) for Hologic and 0.895+/-0.111 g/cm(2) for GE-Lunar (p<0.05); mean corrected sBMD values were 0.869+/-0.124 g/cm(2) for Hologic and 0.867+/-0.108 g/cm(2) for GE-Lunar (p>0.05). The difference between the mean values of BMD and sBMD, both corrected and reported, were statistically important in each scanner (p<0.05). The mean values of corrected and reported sBMD were also statistically different in each scanner (p<0.05; mean standard error in the spine was 1.3 for GE-Lunar and 1.8 for the Hologic device). CONCLUSION: The originally proposed standardization formulae may not optimally correct for manufacturer, model and device-specific differences. Therefore, use of sBMD is not recommended to compare results of individual patients obtained on scanners of different type and brand. The residual error of reported sBMD, however, is substantially smaller than for manufacturer-specific results, and therefore, reporting standardized results is useful for population studies.     

The correlation between R2' and bone mineral measurements in human vertebrae: an in vitro study

The aim of this study was to investigate whether MR imaging of trabecular bone structure using magnetic inhomogeneity measurements is related to the amount of bone mineral in human vertebrae. Weight, bone mineral content (BMC_DXA), bone mineral per area (BMA_DXA) and bone mineral density (BMD_CT) were determined in 12 defatted human lumbar vertebrae (L2–L4) by weighing, dual X-ray absorptiometry (DXA) and CT. Inhomogeneity caused by susceptibility differences between trabecular bone and surrounding water was studied with MR imaging at 1.5 T using the GESFIDE sequence. The pulse sequence determines the transverse relaxation rate R2^* and its two components, the non-reversible transverse relaxation rate (R2) and the reversible transverse relaxation rate (R2'; i. e. relaxation rate due to magnetic susceptibility) in a single scan. Voxel size was 0.9 × 1.9 × 5.0 mm. Positive significant correlations between R2' and weight, BMC_DXA, BMA_DXA and BMD_CT were observed (r > 0.61 and p < 0.05 for all). Unexpectedly, R2 was also positively correlated with weight, BMC_DXA and BMD_CT (r > 0.66 and p < 0.05 for all), but not with BMA_DXA. Thus, R2' measurements are related to the amount of bone mineral, but they also provide information which is not obtainable from bone mineral measurements. Received: 10 March 1998; Revision received: 18 June 1998; Accepted: 22 July 1998     

Methods of interpreting paediatric dual energy X-ray absorptiometry (DXA)

The purpose of this review is to discuss the difficulties in interpreting paediatric dual energy X-ray absorptiometry (DXA) scans and examine the methods used to overcome these problems. There are several approaches to aid interpretation of DXA results, however despite agreement that a method should be employed; there is currently no consensus as to which method is the most appropriate.     

Bone mineral density of skeletal remains: Discordant results between chemical analysis and DXA method

Dual-energy X-ray absorptiometry (DXA) scanning is a gold standard for bone mineral density measurement and diagnosis of primary and secondary osteoporosis in living persons. DXA is becoming widespread when analysing archaeological material, and is considered to provide an accurate diagnosis of osteoporosis in skeletal samples.The aim of this study was to explain the differences in results between bone mineral density (obtained with DXA) and chemical determination of calcium and phosphorus concentrations in skeletal remains. We examined bone mineral density (BMD) and mineral content of femoral bone samples exhumed from mass graves of the Second World War. BMD was determined by Hologic QDR 4500 C (S/N 48034) Bone Densitometer. Concentrations of calcium and phosphorus were determined with AAS (Atomic absorption spectroscopy) and UV/VIS (Ultraviolet–visible) spectroscopy.The results obtained in this study do not support the hypothesis according to which BMD measured by DXA scan has positive correlation with chemically determined concentrations of calcium and phosphorus in bones, especially in acidic soils where there was significant impact of diagenesis observed.     

Impact of bone mineral measurements on osteoporosis

Dual photon absorptiometry enables measurement of bone mineral to be carried out at the clinically relevant sites of the spine and femur. Few would argue that it provides a powerful research tool, but defining its role in clinical practice has been somewhat more difficult. With the advent of X-ray based systems, studies can be rapidly carried out with improved precision, which has led to increased clinical interest. It is probable that this technology will be incorporated into routine use in the near future. In the present review we have addressed the role of dual photon absorptiometry in areas pertinent to osteoporosis and the direction in which recent developments are leading with regard to future research.     

High correlation between quantitative ultrasound and DXA during 7 years of follow-up

Ultrasound is a quick, cheap and non-radiating device for assessing bone quality. We wanted to validate the method for clinical and epidemiological use.Eighty women, aged 53-73 years, with osteoporosis and/or fractures were followed repeatedly during 7 years. Quantitative ultrasound (QUS) measurements (LUNAR Achilles) were compared with bone mineral density (BMD) and bone mineral content (BMC) estimated by DXA (LUNAR) in regions of interest.Changes in the speed of sound, broadband ultrasound attenuation and stiffness were positively correlated with changes in BMD and BMC in all regions measured with DXA (r = 0.20-0.53; p = 0.09 to <0.0001). The QUS t-score at the left heel was positively correlated with the t-score at the right heel (r = 0.90, p < 0.0001). The DXA t-score of the left vs. the right femur was also positively correlated (r = 0.72-0.86; p < 0.0001).A t-score < −2.5 S.D. was found in 70% and 56% at baseline, and 74% and 65% at follow-up measured with QUS and DXA, respectively. The mean sensitivity of QUS vs. DXA was 79% and the mean specificity 45% over a 7-year period. A QUS t-score of <−3.65 S.D. was consistent with a DXA t-score of <−2.5 S.D.In conclusion, QUS was well correlated with DXA in all regions over the 7-year period. QUS can be used in settings without access to DXA and in epidemiological studies. The sensitivity was high but the specificity was low, implicating that DXA, if available, is recommended before treatment for osteoporosis. However, treatment can be started without DXA at a QUS t-score < −3.65 S.D., and especially in the presence of fractures.     

西安地区人群骨密度检测及骨质疏松分析

目的:研究西安地区人群骨密度(BMD)变化规律及骨质疏松(OP)的发病状况,为OP的防治提供依据。方法:采用美国SXA3000骨密度分析仪对西安地区23~76岁的人群522人进行跟骨BMD检测。结果:男女骨峰值均在21~30岁年龄段,随年龄段增高BMD逐渐下降,50岁以上女性和60岁以上男性骨量呈快速下降(P<0.01);骨量减少发生率男女性各年龄段均较高,60岁以上年龄组骨量减少发生率男性高于女性(P<0.01);而严重骨质疏松发生率则女性显著高于男性(P<0.01)。结论:骨质疏松发病率与年龄和性别相关。从青年起定期监测骨密度,并尽早调治骨量减少是预防老年性骨质疏松的重要措施。     

The interchangeability of radioisotope and X-ray based measurements of bone mineral density

Lumbar spine and femoral neck bone mineral density (BMD) were measured with a Novo radioisotope based dual photon densitometer and with a Lunar X-ray densitometer in 94 subjects attending a Metabolic Bone Disease Clinic. There was a strong correlation between results obtained from each machine for the same skeletal site. The correlation coefficients for the spine and femoral neck were 0.97 and 0.88, respectively. The differences between results from each machine were normally distributed with a mean bias of 37.5% for the spine and 27.8% for the femur, which arise principally from differences in machine calibration. In each case the BMD was greater when measured by X-ray absorptiometry. The range for the bias was approximately 25-50% for the spine and 10-45% for the femoral neck. The results from these two machines are not interchangeable. When subjects who are participating in long term studies using a radioisotope densitometer are transferred to an X-ray densitometer, an individual conversion factor must be measured at each site for each subject.     

年龄因素对中老年妇女腰椎双能X线骨密度测量重复性的影响

目的探讨年龄因素对中老年妇女腰椎双能X线骨密度(DXA)测量重复性的影响。方法用数字法随机选取90例中老年女性受检者,按年龄分为3组:45～55岁、56～65岁、66～75岁组,每组30例。每例受检者均在同一天内完成2次腰椎DXA测量,DXA机型为美国Lunar公司生产的Prodigy型骨密度仪。根据公式计算每例个体的标准差、变异系数及每组患者的平均骨密度、标准差,并对结果进行方差分析。用标准差代表精确性,P<0.05为差异有统计学意义。结果45～55岁、56～65岁、66～75岁各组的平均骨密度分别为(1.089±0.014)g/cm2、(0.992±0.010)g/cm2、(0.910±0.010)g/cm2,随年龄的增长,各年龄组的平均骨密度下降,56～65岁和66～75岁年龄组的标准差相同,但2年龄组的标准差低于45～55岁组的标准差。三组间骨密度差异有统计学意义(F=5.213,P<0.05)。45～55岁与56～65岁组、45～55岁与66～75岁组、56～65岁与66～75岁组间两两比较差异均有统计学意义(q值分别为0.035、0.035、0.500,P值均<0.05)。结论年龄因素可影响中老年女性腰椎DXA测量的精确性。     

Combining areal DXA bone mineral density and vertebrae postero-anterior width improves the prediction of vertebral strength

Objective

Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) is an important determinant of bone strength (BS), despite the fact that the correlation between aBMD and BS is relatively weak. Parameters that describe BS more accurately are desired. The aim of this study was to determine whether the geometrical corrections applied to aBMD would improve its ability for BS prediction. We considered new parameters, estimated from a single DXA measurement, as well as BMAD (bone mineral apparent density) reported in the literature.

Materials and methods

In vitro studies were performed with the L3 vertebrae from 20 cadavers, which were studied with DXA and quantitative computed tomography (QCT). A mechanical strength assessment was carried out. Two new parameters were introduced: $ vBM{D}_{min}=\frac{ aBMD}{W_{PA}^{min}} $ and $ vBM{D}_{av}=\frac{ aBMD}{W_{PA}^{av}} $ (W _PA ^min —minimal vertebral body width in postero-anterior (PA) view, W _PA ^av — average PA vertebral body width). Volumetric BMD measured by QCT (vBMD), aBMD, BMAD, vBMD_min, and vBMD_av were correlated to ultimate load and ultimate stress (P_max) to find the best predictor of vertebrae BS.

Results

The coefficients of correlation between P_max and vBMD_min, vBMD_av, as well as BMAD, were r?=?0.626 (p?=?0.005), r?=?0.610 (p?=?0.006) and r?=?0.567 (p?=?0.012), respectively. Coefficients for vBMD and aBMD are r?=?0.648 (p?=?0.003) and r?=?0.511 (p?=?0.03), respectively.

Conclusions

Our results showed that aBMD normalized by vertebrae dimensions describes vertebrae BS better than aBMD alone. The considered indices vBMD_av, vBMD_min, and BMAD can be measured in routine PA DXA and considerably improve BS variability prediction. vBMD_min is superior compared to vBMD_av and BMAD.     

Bone mineral measurements of subchondral and trabecular bone in healthy and osteoporotic rabbits

Introduction Experimental models of osteoporosis in rabbits are useful to investigate anabolic agents because this animal has a fast bone turnover with predominant remodelling over the modelling processes. For that purpose, it is necessary to characterize the densitometric values of each type of bony tissue. Objective To determine areal bone mass measurement in the spine and in trabecular, cortical and subchondral bone of the knee in healthy and osteoporotic rabbits. Design Bone mineral content and bone mineral density were measured in lumbar spine, global knee, and subchondral and cortical bone of the knee with dual energy X-ray absorptiometry using a Hologic QDR-1000/W densitometer in 29 skeletally mature female healthy New Zealand rabbits. Ten rabbits underwent triplicate scans for evaluation of the effect of repositioning. Osteoporosis was experimentally induced in 15 rabbits by bilateral ovariectomy and postoperative corticosteroid treatment for 4 weeks. Identical dual energy X-ray absorptiometry (DXA) studies were performed thereafter. Results Mean values of bone mineral content at the lumbar spine, global knee, subchondral bone and cortical tibial metaphysis were: 1934±217 mg, 878±83 mg, 149±14 mg and 29±7.0 mg, respectively. The mean values of bone mineral density at the same regions were: 298±24 mg/cm², 455±32 mg/cm², 617±60 mg/cm² and 678±163 mg/cm², respectively. Bone mineral content and bone density of healthy rabbits followed a normal distribution at the four skeletal regions studied. Precision after triplicate repositioning yielded a coefficient of variation ranging from 2.6% to 3.8%. The least significant change ranged between 7.3% and 10.7%. Bone mineral density measured at the four different skeletal regions correlated significantly. Bone mineral density in osteoporotic rabbits was significantly lower in the four regions studied than that in controls, rendering a T-score of, respectively, −2.0±1.1 in the lumbar spine, −2.2±2.1 in the global knee, −1.9±0.6 in the subchondral bone, and −5.7±3.1 in the cortical tibia (P<0.05). Conclusions DXA is a reliable and precise method to evaluate the bone mass in rabbits. Our results also suggest that subchondral bone is a bone of mixed densitometric characteristics with marked cortical bone predominance.     

严重急性呼吸综合征康复期患者相关骨密度及骨坏死分析

目的初步探讨严重急性呼吸综合征（SARS）康复期患者相关骨密度及骨坏死状况。方法共64例SARS康复期患者，其中男19例，平均年龄37岁（26—57岁）；女45例，平均年龄39岁（21～67岁）。所有患者均行腰椎及股骨近端骨密度测量分析，并按10岁1个年龄段分组同正常对照组比较。另外其中有55例患者进一步行双髋关节MR检查，根据有无骨坏死分为2组，并进行相应部位骨密度比较。随访问隔时间距患者康复出院10—12个月。结果19例男性SARS康复期患者按年龄分层后各部位骨密度与健康对照组相应部位对照显示：除40～49岁组腰椎（L2～4）骨密度高于健康对照组外（P=0．016），其余各年龄组各部位骨密度两组间差异均无统计学意义（P值均〉0．05）。45例女性SARS康复期患者按年龄分层后各部位骨密度与健康对照组相应部位对照显示：各部位骨密度总体趋势上高于健康对照组，并于20～29岁组股骨颈（P=0．0013）及40～49岁组大粗隆处（P=0．041）骨密度明显高于相应的健康对照组。55例行MR检查的康复期患者中共有6例可见骨坏死，有无骨坏死两组问各部位骨密度差异未见统计学意义（P值均〉0．05）。结论SARS康复期患者其骨密度在短期较大剂量使用糖皮质激素10～12个月后未见减低，且有个别部位骨密度高于健康对照组，其长期影响有待进一步随访观察。     

骨质疏松老年妇女腰椎骨密度及结构的多层螺旋CT研究

目的评价容积性定量CT(vQCT)技术测量的腰椎骨密度(BMD)参数区分骨质疏松性椎体骨折与无骨折老年妇女的能力,对骨质疏松老年妇女腰椎结构与正常老年妇女进行比较。方法将有骨质疏松脊椎骨折的26例老年妇女归为第1组,选择年龄与其相匹配的无脊椎骨折的30例骨质疏松妇女归为第2组。应用多层螺旋CT(MSCT)对56例病人腰椎L1、L2椎体行容积扫描,在横断面影像中经传统的QCT法测量L1、L2小梁骨BMD(2D-TRAB)、整体骨BMD(2D-INTGL);在经计算机工作站行容积再现(VR)三维处理的影像中应用直方图功能测量L1、L2椎体整体骨BMD(3D-INTGL)、皮质骨BMD(3D-CORT)、小梁骨BMD(3D-TRAB)。双能X线吸收仪(DXA)测量参数为腰椎正位BMD(AP-SPINE)、腰椎正位表观BMD(BMAD)。比较2组老年妇女间上述7组的BMD值。另对10例2D-TRAB正常的老年妇女在VR像中测量L1椎体中部边长为20mm的正方体内骨小梁容积比值,并与在56例妇女中随机选取的10例的数值比较。结果DXA测量中AP-SPINE、BMAD在第1组妇女为(0·796±0·170)g/cm2、(272·7±27·7)mg/cm3,与第2组妇女(0·817±0·140)g/cm2、(249·5±26·5)mg/cm3之间差异无统计学意义;vQCT中第1组的2D-TRAB为(70·4±22·2)mg/cm3、2D-INTGL为(138·3±35·1)mg/cm3、3D-INTGL为(139·4±34·9)mg/cm3、3D-CORT为(133·8±26·9)mg/cm3、3D-TRAB为(69·9±18·6)mg/cm3,比第2组数值(89·1±21·8)mg/cm3、(170·6±34·5)mg/cm3、(180·5±28·2)mg/cm3、(163·2±27·5)mg/cm3、(83·8±17·1)mg/cm3下降18%~23%。10例骨质疏松老年妇女L1椎体骨小梁容积比值为(8·12±1·96)%,明显低于正常老年妇女的(39·13±2·15)%,差异有统计学意义(P<0·01)。结论MSCT中vQCT参数区分骨质疏松性椎体骨折与无骨折老年妇女的能力优于DXA,三维重组影像显示的骨质疏松老年妇女椎体骨小梁容积明显低于正常老年妇女。     

我国定量CT骨量测量的临床评估

骨质疏松症是老年人常见的骨关节疾患,其骨折并发症严重地影响老年人的生活质量.为了早期预防骨质疏松症及其并发症,各国相关学者均对此给予了极大的关注,特别是对骨质疏松症诊断的骨矿含量测量进行了大量的研究工作.     

芳香化酶抑制剂对绝经后乳腺癌患者的骨量影响

目的探讨芳香化酶抑制剂治疗对绝经后乳腺癌患者骨密度的影响。方法采用法国CHALLENGER公司双能X线骨密度仪,测定47例应用芳香化酶抑制剂治疗和47例同年龄段非芳香化酶抑制剂治疗乳腺癌患者的腰椎（L2～4）及左髋部骨密度值。结果治疗组腰椎骨密度（BMD）较对照组明显降低,具有极显著性差异（P〈0．01）;左侧整体髋BMD也较对照组降低,两组有显著差异（P〈0．05）。两组患者骨量减少的发生率均占绝大多数,其次为骨质疏松的发生率。治疗组患者骨量减少和骨质疏松的发生率均高于对照组．但差异无显著性意义（P〉0．05）。结论绝经后乳腺癌患者不同程度存在骨量减少和骨质疏松,芳香化酶抑制剂治疗可使乳腺癌患者BMD明显下降,对接受芳香化酶抑制剂治疗的乳腺癌患者,定期监测BMD和适当采用预防性骨质疏松治疗是非常必要的。