南宁地区20899名壮族、汉族正常人群峰值骨量和年龄相关骨丢失的临床意义

目的探讨南宁地区壮族、汉族正常人群骨密度(bone mineral density,BMD)、峰值骨量(peak bone density,PBD)以及随增龄骨丢失率(rate of bone loss,RBL)的规律及临床意义。方法使用美国Hologic公司生产的双能X线吸收仪(dual energy X-ray absorptiometry,DAX),对南宁地区壮族、汉族正常体检人群的20899名的腰椎L1~4、左股骨颈上段BMD进行测定,按检测不同部位、性别、年龄分组统计出PBD的均值±标准差和RBL(%)。参照WHO的规定,对≥50岁男性和绝经后女性与本数据库人群中同性别、同部位PBD比较,-2.5T值-1.0为骨量减少,T值≤-2.5为骨质疏松。结果 (1)各部位PBD出现在25~27岁,腰椎PBD男性为1.066±0.153,女性为1.025±0.095;左股骨颈上段PBD,男性为0.920±0.136,女性为0.796±0.132。(2)女性在47岁前BMD处于平台期,围绝经后BMD加速丢失,以腰椎尤为显著,年RBL在1.13%~2%;男性累计RBL随年龄逐渐上升,年丢失率约在0.21%~0.68%,但各年龄段左股骨颈上段的RBL始终高于腰椎。(3)以本地区人群数据库作为参照,男性骨质疏松检出率为腰椎3.1%,左股骨颈上段9.47%;女性腰椎48.8%,左股骨颈上段5.02%。结论南宁地区老年人发生骨质疏松性骨折风险女性明显高于男性,女性的腰椎、男性的股骨颈可能骨折风险更高。     

跟骨定量超声法评价正常女性骨丢失和骨质疏松患病率

目的　评价正常女性跟骨超声随增龄骨量丢失及骨质疏松患病率。方法　用定量超声法测定了 2 72例正常女性右跟骨宽带超声衰减 (BUA) ,超声声速 (SOS)及骨硬度指数 (STI)。结果女性跟骨峰值骨量出现在 30～ 39岁。 5 0～ 84岁 3组与峰值组以及两两之间比较 ,差异均有显著性(P <0 0 1)。老年组骨质丢失率和骨质疏松患病率分别为 2 6 %～ 37%和 4 2 %～ 6 9%。在各个年龄组中 ,STI丢失率最高 ;STI和BUA骨质疏松检出率相近 ,均大于SOS。结论　跟骨超声的 3项指标均可用于区分绝经前、后的妇女 ;STI检测骨量丢失和OP患病率最敏感     

放射吸收法测量北京地区2884例健康人骨密度研究

目的 利用放射吸收(Radiographic absoptiometry，RA)方法测定骨密度(BMD)，建立北京地区RA测量骨密度参考值数据库。方法 选取北京地区10-92岁健康人2884例，男性1481例，女性1403例，研究对象均详细填写健康调查表格，排除因继发性骨病或服用影响骨代谢药物的病例。用美国CompuMed公司OsteoGram-2000骨密度仪测定所有对象非优势手的第2、3、4指中节指骨(MP2、MP3、MP4)的BMD值，按10岁一个年龄组进行统计分析。结果 峰值骨量(PBM)男性出现在20～29岁，女性20～39岁。男性BMD从30岁开始下降，随年龄增长各年龄段逐渐下降，女性从40岁开始下降。北京女性平均绝经年龄50岁，绝经后骨量快速丢失，绝经后第6～10年丢失最多，达21．38％，绝经后20年平均年骨量丢失率为1．35％。RA测量BMD数据与刘忠厚教授80年代末使用SPA测量40000中国人群中远1／3前臂骨(桡骨、尺骨)结果有极好的相关性。结论 RA测量北京地区健康人峰值骨量和骨量丢失规律与我国部分地区用DXA或SPA方法所得结果相似。     

住院精神病患者骨密度状况的分析研究

目的检测内蒙古精神卫生中心住院精神病患者手指骨密度(BMD),获得该地区精神病患者骨密度状况,为预防精神病患者骨质疏松提供科学依据。方法选取1191例住院精神病患者和1329例健康体检人员作为研究对象,使用M etriScaTM数字化成像骨密度仪测量受试者非优势手的2、3、4指中节指骨BMD值,进行统计分析。结果患病组骨密度降低与对照组相比有明显差异(P0.01)。两组中的女性骨密度值降低均较男性骨密度值降低明显(P0.01)。结论女性骨量丢失率较男性明显,尤其是精神病组骨密度降低更明显,应及早采取预防措施。     

新疆乌鲁木齐地区维吾尔族健康人群骨矿含量DXA测量分析

目的通过测量乌鲁木齐市1485人维吾尔族健康人群的骨密度(BMD),确定本市BMD正常参考值,并探讨BMD随年龄变化的规律。方法使用法国DMS公司生产的Lexxos型双能X线骨密度仪(Dual-energy X-ray absorptiometer,DXA)对乌鲁木齐市20岁以上的维吾尔族健康人腰椎前后位、左侧股骨近端的BMD进行测定。按不同性别每5岁分为1年龄组,得出BMD值、标准差及累计丢失百分率。结果男性及女性腰椎骨峰值年龄段组均出现在35～39岁组,而股骨近端男性及女性骨峰值年龄段组均出现在20～24岁组,峰值后随年龄增加而骨密度下降,女性在50～74岁呈加速下降趋势,而男性无明显加速下降现象。结论达到骨峰值后BMD随年龄增加而下降,女性绝经后骨量丢失明显加快,男性下降缓慢,女性骨质疏松发病率高于男性。提示预防和治疗骨质疏松的重点在中老年女性,同时老年男性也不容忽视。因此建立本地区健康维吾尔族人群骨峰值及诊断参考值,对于临床诊断早期原发性骨质疏松症有着重要参考意义。     

资阳地区定量超声跟骨骨量测定的流调分析

目的调查四川资阳地区健康人群骨密度值及骨质疏松患病率,为骨质疏松的诊断和防治提供科学依据。方法对资阳地区人群亚群抽样1976例,应用日本FURUNO公司生产的超声骨量测定仪CM100测试受试者的右跟骨的超声速度(SOS)值。结果男女骨量峰值(PBM)均出现在20～39岁组,随年龄增加骨量逐渐下降。女性50岁以后骨量丢失明显加快,60～69岁年龄组骨量丢失最快;男性70岁以后骨量丢失明显加快。80岁以前各年龄组女性骨量丢失明显高于男性,80岁以后男性骨量丢失高于女性,但累计骨量丢失女性仍明显高于男性。结论骨量随年龄增长而下降,骨质疏松发病率也随之增加。女性骨量丢失明显高于男性,女性骨质疏松发病率也明显高于男性。     

吉林省老年人群周围骨骨矿含量测定结果分析

目的通过测定所得骨矿含量数值更好的评估骨强度,监测骨质疏松的发生、发展,提高高危患者骨折风险识别能力。方法选取吉林省2375例50—89岁体检者运用美国OSTEOMETER DTX200周围骨骨密度测量仪测量受检者非受力侧前臂桡尺骨远端三分之一处的骨密度、骨矿含量,应用采用SPSS 17.0软件分析处理,数据用X±S表示。进行统计分析。结果男性50～59岁年龄组OP发生率为9.33%,女性为7.38%;60～69岁男性OP发生率为18.59%,女性为26.26%;70～79岁男性OP发生率为40.00%,女性为55.90%;80岁以上男性OP发生率63.93%,女性为71.42%。结论提示随着年龄增加,男女骨密度及BMC均呈下降趋势,女性下降速度明显较男性快,OP发生率也随之增加,各年龄组之间OP发生率女性亦均高于男性;T值大于-1的受检者中有5.74%骨量丢失率在13%～24%之间,亦为骨量减少范围,这类人群远期骨质疏松症的发病率及骨折的发生率很高,故骨矿含量(BMC)在临床骨质疏松症的诊断、治疗、预防骨质疏松骨折发生等方面起着重要作用。     

长春市16019例汉族人群骨密度调查及骨质疏松发病率分析

目的 调查长春市16019例汉族人群骨密度,分析本地区峰值骨量及骨密度变化的人群规律.方法 采用美国Osteometer Medi Tech公司生产的DTX-200型骨密度仪,检测受试者非受力侧前臂桡尺骨远端三分之一处骨密度(BMD).将16019例检测结果按不同性别每5岁为一年龄组,应用SPSS 13.0软件统计分析骨密度均值、T评分及骨量丢失百分率.结果 长春市男、女性人群骨密度峰值分别为0.625±0.109、0.506±0.058,其峰值年龄为30～39岁年龄段,40岁以后开始缓慢下降,50～59岁年龄段男性骨质疏松发病率为7.7%,女性为6.97%;60～69岁年龄段男性骨质疏松发病率为18.13%,女性为35.97%;70～79岁年龄段男性骨质疏松发病率为36.41%,女性为59.55%,80岁以上男性骨质疏松发病率为57.53%,女性为75.56%.结论 不同年龄及同年龄组两性之间比较骨密度测定值差异显著(P<0.01).50岁以后各年龄段女性骨质疏松发病率明显高于男性(P<0.01).本研究报告的骨密度峰值高于日本、丹麦同类型骨密度仪检测结果;与北京地区骨密度检测结果相近.与西双版纳傣族、西藏、甘肃东乡族比较,差异显著(P<0.01).     

青岛地区1206例骨密度调查研究

目的调查青岛地区部分人群骨密度,为骨密度正常参考值数据提供资料,为青岛乃至全国骨质疏松的预防、诊断、治疗提供科学依据。方法应用双能X线骨密度仪对青岛地区1206例受检对象进行骨密度检测,得出各年龄组骨密度值,计算骨量丢失率及患病率,用SPSS10.0分析软件进行统计学处理,进行各年龄组间差异比较。结果青岛地区男、女骨密度峰值均在25～29岁年龄组,女性50岁、男性60岁以后骨密度值明显降低,骨量丢失率增加,患病率升高。结论骨质疏松患病率与增龄呈明显正相关,女性50岁以后、男性60岁以后患病几率增大,应及早预防。     

浙江地区人群11926例跟骨骨密度研究

目的 探讨浙江地区人群骨量的分布规律和骨质疏松的患病情况.方法 采用美国进口Dove3000骨密度测量仪对11926例浙江居民的跟骨骨量进行测定,按年龄分成14组,SPSS10.0统计软件对各组数据进行处理.结果 浙江地区人群骨量约在25～35岁达到峰值,50岁开始随年龄的增加而逐年减少;20岁后男性骨密度明显高于女性(P＜0.01),女性骨量的丢失速率明显快于男性;女性绝经1～3年骨量开始快速丢失,约10年后趋缓;骨质疏松的患病率与年龄的变化呈正相关(r=0.99),女性患病率明显高于男性(P＜0.01).结论 浙江地区人群骨量25～35岁达到峰值,50岁后随年龄的增加而逐年减少;女性骨量低于男性,50岁后骨量丢失的速率明显快于男性;女性骨量丢失与绝经时间密切相关.     

身高、体重及体重指数对辽宁地区正常中老年人骨矿含量的影响

目的　调查分析身高、体重及体重指数 (BMI)对辽宁地区正常中老年人群骨矿含量的影响。方法　在辽宁地区年龄在 40～ 79岁的中老年人群中随机抽样 173 1例 ,除外可能导致继发性骨质疏松症的各种疾病 ,应用美国lunar公司生产的双能X线骨密度仪 ,分别测试受试者的腰椎及股骨上段的骨密度 (BMD) ,全部资料输入微机 ,用SPSS软件进行统计学处理。结果　身高与腰椎及股骨上段的BMD相关性较差 (r=0 0 87～ 0 197,P <0 0 5 ) ,体重与腰椎及股骨上段的BMD相关性较好(r=0 2 2 6～ 0 3 5 2P <0 0 1)。体重指数与腰椎的相关性最好 ,其次是大转子。腰椎及股骨颈的BMD在超体重组 (BMI>2 5kg/m2 )明显大于低体重组 (BMI≤ 19kg/m2 ) ,其差异有显著性 ,该特点在腰椎最为明显。结论　体重是影响中老年人骨矿含量的重要因素。对低体重的中老年人 (BMI≤ 19kg/m2 )可作为骨质疏松症的易发人群 ,及时监测BMD ,早期预防及治疗     

Peripheral Bone Mineral Density and Different Intensities of Physical Activity in Children 6–8 Years Old: The Copenhagen School Child Intervention Study

This study aimed to evaluate the association between objectively measured habitual physical activity and calcaneal and forearm bone mineral density (BMD, g/cm²), one mechanically more loaded and one less loaded skeletal region, in children aged 6–8 years. BMD was measured in 297 boys and 265 girls by peripheral dual-energy X-ray absorptiometry in the forearm and calcaneus. An accelerometer registered the level of physical activity during 4 days (2 weekdays and the weekend). Weight, height, and skinfold thickness were measured. In order to establish thresholds (count · min⁻¹) for bone-stimulating physical activity, we evaluated different definitions of vigorous physical activity. The boys had 3.2% higher distal forearm bone mineral content (BMC, P < 0.001) and 4.5% higher distal forearm BMD (P < 0.001) than the girls. They also carried out 9.7% more daily physical activity and spent 14.6–19.0% more time in vigorous physical activity (all P < 0.05) compared to the girls. In contrast, the girls had 3.8% higher calcaneal BMC (P < 0.01) and 2.5% higher calcaneal BMD (P < 0.05) than the boys. Both calcaneal and forearm BMD were significantly related to total time of daily physical activity as well as with intense physical activity above all the chosen cut-off points (all P < 0.05). The β value for mean count · min⁻¹ physical activity was significantly lower than that for all the chosen cut-off points of vigorous activity both for calcaneal and distal forearm BMD. This study suggests that both habitual daily physical activity and amount of vigorous physical activity in children aged 6–8 years are associated with appendicular BMD.     

DXA测定诊断骨质疏松症的敏感指标

目的探索双能X线吸收法（DXA）骨密度测定仪测定诊断骨质疏松症（OP）的敏感指标.方法随机抽取成都地区年龄20岁以上健康男、女1456名（其中女性793名）,准确测定身高（H）、体重（W）后,采用美国Lunar公司生产DPX-L型DXA测定受试者腰椎和髋部的骨矿含量（BMC）、骨密度（BMD）.全部资料输入微机,用SPSS软件进行统计学处理.结果男、女在峰值骨量后,随年龄增加,BMC、BMC/W、BMD均逐渐下降,BMC、BMD、BMC/W累积丢失率在40岁以上组均随年龄增加而增加,女性丢失更明显（P＜0.05）,同部位、同年龄组三指标累积丢失率差异无显著性（P＞0.05）.OP检出率以BMD为参照指标最高,明显高于BMC/W、BMC二指标（P＜0.05）.结论DXA测定中BMD能较好反应BMC、BMC/W变化,是诊断OP的敏感指标.     

体重、身高对成都地区青壮年腰椎、髋部骨量的影响

目的　研究体重、身高对青壮年腰椎、髋部骨量的影响。方法　随机抽取成都地区年龄在 2 0～ 39岁 ,排除心肝肺肾、内分泌等慢性病、骨代谢疾病及脊椎畸形者 2 37名 (其中男性 10 8名 ,女性 12 9名 ) ,采用美国Lunar公司生产DPX L型双能X线骨密度仪测定受试者腰椎和髋部的骨矿含量 (BMC)、面积 (AREA)、骨密度 (BMD)。全部资料输入微机 ,用SPSS软件进行统计学处理。结果　体重、身高、体重指数 (BMI)与腰椎、髋部的BMC、Area、BMD呈正相关 ,其中体重与腰椎、髋部的BMC、Area中等程度相关 (r=0 39～ 0 5 5 ,P <0 0 1) ,身高与腰椎 (L2 - 4)AREA相关性最好 (r=0 75 8,P <0 0 1) ,体重、身高与BMD相关性差 (r=0 15 2～ 0 2 2 5 ,P <0 0 5 )。男性腰椎及髋部的BMC、AREA均明显高于同年龄组女性 (P <0 0 1) ,男、女L2 - 4BMD无显著性差异 (P >0 0 5 ) ,男性略低于女性。L2 - 4BMC与体重比值及L2 - 4AREA与体重比值 ,男、女无显著性差异 (P >0 0 5 )。L2 - 4Area与身高比值男性明显高于女性 (P <0 0 1)。结论　体重对青壮年BMC的影响大于身高 ,身高对L2 - 4AREA影响最大 ,男、女体重、身高的差异决定了峰值骨量的差异。BMC、Area、BMD 3项指标中 ,BMC更能反映体重、身高的差异 ,用BMC诊断骨质疏松     

Normalization of bone mineral content to height,weight, and lean body mass: Implications for clinical use

Summary The main object of the present study was to reduce the large biological variation in forearm bone mineral content (BMC) by correction for individual variation in gross morphology. In 315 normal females aged 45–54 years, determinations of height, weight, and 24-h urinary creatinine excretion rates were performed, and lean body mass was calculated. BMC was measured by photon absorptiometry on both forearms. BMC was correlated to height (r=0.19,P<0.01), to weight (r=0.09,P>0.05), to lean body mass (r=0.15,P<0.05), and to creatinine excretion rate (r=0.29,P<0.001). The biological variation in BMC of the 315 females was for raw BMC 15.8%; after correction of BMC for height 15.5%, for weight 15.8%, for lean body mass 15.6%, and for creatinine excretion rate 15.2%. Regression analysis with two independent variables (creatinine excretion and height or weight) increased in both cases the correlation coefficient to 0.32 and decreased the interindividual coefficient of variation of BMC to 15.0%. For diagnostic purposes BMC must be corrected for age and sex, but further corrections seem of minimal benefit.     

The effects of first gestation and lactation on bone metabolism in dairy goats and milk sheep

The goal of the present study was to compare mobilization rate of calcium (Ca) from bone in pregnant and lactating goats and sheep. Blood samples were collected from goats and sheep monthly during pregnancy and at 1, 2, and 4 weeks postpartum (pp) and monthly during lactation until 6 months after parturition. Total bone mineral content (BMC) and total bone mineral density (BMD) were quantified using peripheral quantitative computed tomography at the same intervals as the blood was taken. Bone resorption was assessed by immunoassays quantitating two epitopes of the carboxyterminal telopeptide of type I collagen (ICTP, CTX). Bone formation was estimated by quantifying serum osteocalcin (OC) and bone-specific alkaline phosphatase (bAP). In addition, Ca and 1,25-dihydroxy vitamin D (1,25-VITD) concentrations were determined in serum.

Mean ICTP and CTX concentrations of both animal species increased the first week after parturition. By the second week pp, the concentrations of both markers had decreased toward early gestation levels. In contrast, mean OC concentrations continually decreased until the 1st week pp. By the 2nd week pp, the mean concentrations of OC started to increase again. Mean bAP activities decreased during gestation and reached a nadir in the first week pp in goats and 4 weeks pp in sheep. Afterwards, mean bAP activities increased again in goats and sheep. 1,25-VITD concentrations peaked the first week pp and returned to early gestation values thereafter. Total BMC and BMD decreased from the 4th month of pregnancy until the 1st week pp in both species. Afterwards, BMC increased throughout the first month pp in goats and the first 3 months pp in sheep. BMD levels of sheep and goats returned to prepartum levels during lactation.

The resorptive phase of bone remodeling is accelerated at parturition and in early lactation and is uncoupled from the process of bone formation. This allows the animal to achieve Ca homeostasis at the expense of bone. Increased bone remodeling during lactation may represent physiological mechanisms to help replace the maternal skeleton lost as the animal adapted to enormously increased Ca losses to the fetus and milk in late gestation and early lactation.     

中国男女性骨大小和体积骨密度的探讨

目的　确定中国北方人群在腰椎和股骨部位峰值骨大小和体密度的性别差异 ,并分析影响其大小的因子。方法　年龄 15至 4 0岁 2 5 6例健康男性和 30 9例健康女性 ,他们的腰椎和股骨颈的骨大小和体积骨密度用双能X线骨密度仪测量。椎体和股骨颈近似为圆柱体 ,骨体积V =π× (宽度 2 ) 2 ×高度 ,vBMD =BMC 体积。结果　椎体峰值BMC ,体积和vBMD女性在 30～ 4 0岁达到峰值 ,而男性 15～ 17岁达到峰值。椎体和股骨颈的BMC男性比女性高 18 1%～ 2 6 7% ,而骨体积相应高 2 8 5 %～ 32 0 % ,这样vBMD男性比女性低 4 0 %～ 8 3% (P <0 0 1)。初潮较晚 (≥ 15岁 )绝经前妇女比来潮较早者 (≤ 12岁 ) ,BMC低 10 % (P <0 0 5 )。男性抽烟者与非抽烟者骨大小和vBMD没有统计学差异。饮酒也没有观察到明显的效应。结论　中国男性比女性有较低的vBMD ,这可能部分地解释中国男性有较高骨折发生率的原因     

Relationship between leg bone mineral values and muscle strength in women with different physical activity

This study examines whether knee extensor muscle isometric, isokinetic, and isoinertial strength values in women with different physical activity and body composition patterns are related to leg bone mineral density (BMD) and bone mineral content (BMC) values. A total of 129 women aged 17–40 participated in this study. They were divided into four groups: strength-trained (n = 33), endurance-trained (n = 32), normal weight sedentary (n = 41), and overweight sedentary (n = 23) women. In addition, the subjects were grouped as physically active (n = 65) or sedentary (n = 64) women. BMD and BMC for both legs (LBMD and LBMC, respectively) and for the dominant leg alone (DLBMC), body fat percentage and lean body mass (LBM), maximal knee extension isometric (ISOM) and isokinetic (ISOK) strength at the angular velocity of 60 deg·s⁻¹, and isoinertial leg explosive strengths (countermovement jump CMJ) were measured. In endurance-trained women, LBMD was dependent on body mass index (BMI) (33.7% of the variance, R² × 100), and in the physically active group and the total group with LBM (14.6% and 15.6%, respectively). In the overweight group, LBMD was dependent on ISOK strength (21.7% of the variance, R² × 100). In the sedentary and total groups, ISOM strength was more important (10.3% and 5.0%, respectively); in the strength-trained group, body weight influenced LBMC, accounting for 71.6% of the variance (R² × 100). In the endurance-trained women, height influenced LMBC (37.9%, R² × 100). In sedentary and overweight women, LBM accounted for 52.1% and 61.4% of the total variance in LBMC. In these groups, ISOM strength accounted for 15.3% and 25.9% of the variance in LBMC. In overweight women, ISOM and ISOK strength together influenced LBMC highly (64.8% of the variance, R² × 100). In the sedentary group, the influence of LBM on LBMC was higher than in the active group (82.1% and 50.5% of the variance, respectively). In the total group, LBM influenced LBMC, accounting for 54.5% of the variance (R² × 100). ISOM strength (22.7%) alone or in combination with ISOK strength (35.8%) and CMJ (41.7%) (R² × 100) in LBMC in the sedentary group explained the variance. In the total group, ISOM strength alone (13.2%) or in combination with CMJ (17.1%) influenced LBMC (R² × 100). Our results suggest that (1) muscle strength and anthropometrical parameters were associated with LBMD; (2) LBM and ISOM strength had a significant relationship with DLBMC and LBMC only in nonathletic women; and (3) strength measured with different regimens highly influenced LBMC compared with LBMD, especially in the sedentary groups.     

Precision of dual-photon absorptiometry

Summary Precision of dual-photon absorptiometry (DPA) measurements was determined in a lumbar spine phantom and in humans. Approximately half of the measurements were made before and half after a¹⁵³gadolinium source change. The phantom was measured with different amounts of acrylic, which simulates human soft tissue, in order to evaluate the influence of body thickness on bone mineral density (BMD). Results of scans analyzed with two software versions from Lunar Radiation Corp., the widely used 08B and a prototype 08C, are compared. DPA with a cold source significantly overestimated BMD in the phantom in the presence of large amounts (more than 25 cm) of soft tissue equivalent with version 08B but not with the newer version 08C. Similiarly, in nine subjects, there was a significant decrease in spine BMD after a source change when scans were analyzed with version 08B (mean difference 0.026 g/cm²,P=0.002) but not with 08C (0.01 g/cm²,P=0.234). No systematic effect of source change on femoral BMD measurements was observed. The SD of the mean difference of two measurements of the nine subjects was 0.019 g/cm² (1.6% of the mean value) for the spine with software version 08B and 0.024 g/cm² (2.0%) with version 08C, 0.03 g/cm² (3.3%) for the femur neck, 0.03 g/cm² (4.0%) for the greater trochanter, and 0.04 g/cm² (4.9%) for Ward's triangle region of the proximal femur. The spine phanton was scanned on two other commercial bone densitometers in order to assess inter-instrument variation. Phantom measurements of L2-4 BMD made on two Lunar Radiation Corp model DP3 scanners which differed by 2% were 10 and 12% higher than those with a Norland Corp. model 2600 scanner.     

Switching from DXA pencil-beam to fan-beam. I: Studies in vitro at four centers

The performance of the Hologic QDR-2000 DXA osteodensitometer was critically evaluated at four centers, using at all four centers one bone equivalent humanoid spine phantom supplied by the manufacturer. Results were compared with results from Hologic QDR-1000/W using that phantom tested at the same centers.

It appears that the concept of fan-beam scanning—as used in the QDR-2000: a fan-beam, a linear array detector above the phantom, and an x-ray tube located rather close to the spine below the phantom—creates problems due to the magnification effect of the fan beam. The effect of decreasing the distance between the “vertebrae” of the phantom and the couch are: bone mineral content (BMC) increases by 2.8% per cm, projected area (Area) by 2.8% per cm, and bone mineral density (BMD) is unchanged.

When QDR-1000/W is upgraded to QDR-2000, BMD is relatively constant, but there are shifts of BMC and Area which are partly due to the magnification effect of the fanbeam. Replacement of a QDR-1000/W with a QDR-2000 can invalidate longitudinal measurements, even for BMD, unless the proportionality factors of the QDR-2000 are checked and, if necessary, changed. This is true for switching from QDR-1000/W to pencil-beam mode of QDR-2000 or to fanbeam mode of QDR-2000.

Even with pencil-beam mode, the long-term precision error with phantoms is higher for QDR-2000 than for QDR-1000/W (for BMD, 0.47% versus 0.35%).