Hologic Systems Research Articles

Visceral adipose tissue reference data computed for GE HealthCare DXA from the National Health and Nutrition Examination Survey data set.

The National Health and Nutrition Examination Survey (NHANES) characterizes body composition representative of the US population using dual-energy x-ray absorptiometry (DXA) scans. These population-level trends of abdominal subcutaneous and visceral adipose tissue (SAT and VAT) are useful for identifying measures associated with increased disease risk. Recently, VAT and SAT data collected by Hologic DXA in NHANES were published online; however, there are known differences in the absolute calibration of DXA systems by make. The purpose of this study was to create reference tables suitable for calculating z scores and percentile values for GE HealthCare (GEHC) DXA systems. DXA scans were acquired on participants aged 8 to 59 years using Hologic systems. DXA measures were converted to GEHC and described using the least median squares curve fitting method in pediatrics (aged <20 years) and adults (aged 20-59 years). A total of 11,972 adults and 7298 pediatrics were included for this analysis. Adult and pediatric curves were generated by sex and by ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, Asian, Other) and were derived as a function of age. These results show the ability to generate VAT and SAT reference data for GEHC systems using Hologic DXA data representative of the US youth and adult population.

Standardization of dual-energy x-ray visceral adipose tissue measures for comparison across clinical imaging systems.

Excess visceral adipose tissue (VAT) is a major risk factor for metabolic syndrome (MetS) and clinical guidelines have been proposed to define VAT levels associated with increased risk. The aim was to standardize VAT measures between two dual-energy x-ray absorptiometry (DXA) manufacturers who provide different VAT estimates to support standardization of measures across imaging modalities. Scans from 114 individuals (ages 18-81 years) on GE HealthCare (GEHC) and Hologic DXA systems were compared via Deming regression to standardize VAT between the two systems, validated in a separate sample (n = 15), with κ statistics to assess agreement of VAT measurements for classifying patients into risk categories. The GEHC and Hologic VAT measures were highly correlated and validated in the separate data set (r2 = 0.97). VAT area measures substantially agreed for metabolic risk classification (weighted κ = 0.76) with no significant differences in the population mean values. VAT measures can be estimated from GEHC and Hologic scans that classify individuals in a substantially similar way into metabolic risk categories, and systematic bias between the measures can be removed using simple regression equations. These findings allow for DXA VAT measures to be used in complement to other imaging modalities, regardless of whether scans used GEHC or Hologic systems.

The Interference of Gamma Rays With Bone Mineral Density Measurements in 177Lu-PSMA and DOTATATE Therapy

The main purpose was to describe the interference of gamma radiation emitted by 177Lu with simultaneous bone mineral density BMD measures for patients undergoing 177Lu-PSMA and 177Lu DOTATATE therapy. A cohort of 9 patients underwent 177Lu-PSMA therapy were randomly selected to speculate the activity in the abdominopelvic region. So that, SPECT/CT scan at 24 h was used with attenuation and scatter correction. The activities were derived from the delineated ROIs over the abdominopelvic zone showing a range of 34−274 MBq. Next, a water path was placed under spine phantom mimicking L1-L4 vertebrae and followed by consecutive DEXA scans made by Hologic 4500 W and GE-Lunar DPX-NT systems. Five scans were performed without/and with different Lu-177 activities 37, 185, 370 and 555 MBq under the same geometric conditions. The obtained BMD readings of L1-L4 by the Hologic device were 1.027, 1.024, 1.021, 1.013, and 1.006 g/cm2 with presence of 0, 37, 185, 370, and 555 MBq 177Lu activity, respectively. Whereas, in Lunar device, it was found as higher as 1.163, 1.121, 1.09, 1.072, and 1.043, respectively. There was no statistically significant difference between both devices (pvalue ≥ 0.05). The fluctuation ranges in the L1-L4 BMD readings at the presence of 37−555 MBq were 0.3%−2%, and 3.6%−10.3% for Hologic and Lunar systems, respectively. It was emphasized that gamma radiation emitted by 177Lu relatively influence DEXA scans and the yielded BMD measures. Postponing DEXA scans as early as 8 d after 177Lu-PMSA and 11 d after 177Lu-DOTATATE therapies is recommended to avoid the erroneous contribution of gamma radiation and provide precise bone assessment.

Pediatric Reference Centiles of Bone Mineral Density and Body Composition of Lower Limbs

Localized neurological diseases such as spina bifida are often accompanied by normal upper limb and spinal bone mineral density (BMD), whereas regional BMD of the lower limbs may be decreased. Therefore, regional BMD measurements may be more accurate to quantify regional bone health. Until now, no pediatric reference centiles of bone mineral density and body composition of the lower extremities are available for Hologic DXA systems. The objective was to generate age-and sex specific reference centiles of DXA scans of lower limbs for Hologic DXA systems. Data from the National Health and Nutrition Examination Survey of the period 1999–2004 (age 8 – 20 years) were used to generate age-specific and sex-specific reference centiles for the non-Hispanic Black, non-Hispanic White and Mexican-American NHANES study population. The LMS method was used to calculate the reference centiles. Data of DXA scans of 2233 non-Hispanic black children (880 females), 1869 non-Hispanic white children (803 females) and 2350 Mexican American children (925 females) were used to create age-specific and sex-specific reference curves. We presented age-and sex-specific reference centiles for regional bone mineral density, bone mineral content, lean body mass and fat mass at the lower limbs for children and adolescents which were ethnicity specific and directly applicable to Hologic QDR-4500A fan-beam densitometer.

Muscle mass measurements in hip fracture patients and control general population depending on dual-energy X-ray absorptiometry device used: The General Electric Lunar and Hologic systems

ObjectivesThe prevalence of sarcopenia, an independent risk factor for fragility fractures, is high in geriatric hip fracture patients. We aim to compare patients with hip fractures to the general population using different dual-energy X-ray absorptiometry (DXA) devices – General Electric (GE) Lunar and Hologic. MethodsWe retrospectively reviewed data of patients diagnosed with osteoporotic hip fractures. At our institute, 252 patients with hip fractures were measured with the GE Lunar DXA. The control group included 252 matched individuals from a general population dataset whose data were measured with the Hologic DXA; controls were selected using nearest-neighbor propensity score matching. Measurements included appendicular lean mass (ALM), bone mineral density, and subsequent rates of sarcopenia and osteoporosis. ResultsThe BMD T-score was significantly lower in patients with hip fractures than in matched controls (−2.7 vs. −2.1, respectively; P < 0.001). However, mean lean body mass of the arm was significantly greater in the hip fractures group compared to the matched control groups (4.092 kg vs. 3.869 kg, respectively; P = 0.024). Additionally, mean lean body mass of the leg was similar between groups (11.565 kg vs. 11.986 kg, respectively; P = 0.084). ALM/height2 and subsequent sarcopenia rates were not different between groups (hip fractures and 6.257 kg/m2 and 38.5%; matched controls, 6.198 kg/m2 and 33.7%). ConclusionsDespite experiencing hip fractures, muscle mass measurements and sarcopenia prevalence were similar between the groups. Muscle mass measurements for evaluating sarcopenia present significant discrepancies according to the DXA used.

Quantitative texture analysis: robustness of radiomics across two digital mammography manufacturers' systems.

The robustness of radiomic texture analysis across different manufacturers of mammography imaging systems is investigated. We quantified feature robustness across mammography manufacturers using a dataset of 111 women who underwent consecutive screening mammography on both general electric and Hologic systems. In each mammogram, a square region of interest (ROI) directly behind the nipple was manually selected. Radiomic features describing parenchymal patterns were automatically extracted on each ROI. Feature comparisons were conducted between manufacturers (and breast densities) using newly developed robustness metrics descriptive of correlation, equivalence, and variability. By examining the distribution of these metric values, we propose the following selection criteria to guide feature evaluation in this dataset: (1)[Formula: see text] of feature ratios [Formula: see text], (2)standard deviation of feature ratios [Formula: see text], (3)correlation of features [Formula: see text], and (4)[Formula: see text]. Statistically significant correlation coefficients ranged from 0.13 to 0.68 in comparisons between the two mammographic systems tested. Features describing spatial patterns tended to exhibit high correlation coefficients, while intensity- and directionality-based features had comparatively poor correlation. Our proposed robustness metrics may be used to evaluate other datasets, for which different ranges of metric values may be appropriate.

Reference Standards for Lean Mass Measures using GE Dual Energy Xray Absorptiometry

Body composition (BC) assessments focus predominantly on fat mass, however lean mass (LM) measurements also provide useful information on clinical and nutritional status. LM measurements have been shown to be predictive of health outcomes, including sarcopenia, which has been associated with frailty and reduced quality of life. Dual energy x-ray absorptiometry (DXA) is an established technique used to assess BC, including total and regional LM. Reference values for LM derived from DXA are necessary for interpretation and detection of LM deficits and its associated health issues. Recently reference values for LM measures specific to Hologic DXA systems were developed, however it is known that BC, including LM measures differ by DXA manufacturer. There currently are no LM reference values available for GE-Healthcare DXA systems. PURPOSE:To develop reference values by age and sex for LM measures using with GE-Healthcare DXA systems. METHODS: A de-identified sample, considered exempt from IRB review, was obtained from Ball State University’s Clinical Exercise Physiology Laboratory and University of Wisconsin-Milwaukee’s Physical Activity & Health Research Laboratory. DXA scans of 2,076 women and 1,251 men were completed using a GE Lunar Prodigy or iDXA. Variables of interest included total LM and appendicular lean mass index (ALMI; leg lean mass + arm lean mass (kg)/height (m2)). Percentiles (%ile) were calculated and a factorial ANOVA was used to assess differences for each variable between age groups and sex, as well as the interaction between age and sex. RESULTS: Men had higher mean total LM and ALMI than women (p<0.01), across all age groups. Total LM and ALMI decreased over the 5 decades in men and women (p<0.01). The 50th %ile for total LM of men and women aged 20-29 years decreased from 63.9 and 42.5 kg to 54.2 and 39.1 kg for ages 70-79 years, respectively. The rate of decline in total LM during a 5 decade period was approximately 3% and 2% for men and women per decade, respectively. CONCLUSIONS: These age and sex-specific LM reference values are the first developed specifically for use with GE-Healthcare DXA systems. These reference values provide for a more accurate interpretation of DXA-derived LM measurements providing an initial resource to aid in the early detection and assessment of LM deficits.

Characterisation of noise and sharpness of images from four digital breast tomosynthesis systems for simulation of images for virtual clinical trials

In-depth evaluation of the noise and sharpness characteristics of FujiFilm Innovality, GE SenoClaire, Hologic Selenia Dimensions and Siemens Inspiration digital breast tomosynthesis (DBT) systems was performed with the intention of improving image simulation for virtual clinical trials. Noise power spectra (NPS) and modulation transfer function curves (MTF) were measured for planar modes and for the first and central projections for DBT modes. In DBT mode, the x-ray beam was blocked for the projections before the central projection in order to remove the influence of lag and ghosting from the previous images. A quadratic fit between the NPS and linearised pixel value gave the noise coefficients for planar and DBT imaging modes. The spatial frequencies corresponding to an MTF of 0.5 (MTF0.5) were calculated from the MTF measurements made on the breast support and at 40 mm above the breast support. This was done for the first and the central projections. The percentage of signal carried over from the first projection to subsequent images (lag) was measured using a slit. The noise associated with lag was also evaluated. The DBT modes typically had lower electronic noise coefficients but higher structural noise coefficients compared to the respective planar mode MTF0.5 measured 40 mm above the table was between 6% and 47% lower for continuous scanning systems compared to 1% lower for step and shoot systems. For wide angle DBT, the MTF0.5 of the first projection was 18% (FujiFilm) and 28% (Siemens) lower than for the central projection. Lag in the second projection was 2.2%, 0.3%, 0.8% for the FujiFilm, GE and Hologic systems respectively. In all cases, the noise associated with lag was negligible. Current modelling frameworks for virtual clinical trials of breast DBT systems need to be adapted to account for signals from lag and variations in the MTF at wide angles.

Radiation shielding calculation for digital breast tomosynthesis rooms with an updated workload survey

Purpose. To present shielding calculations for clinical digital breast tomosynthesis (DBT) rooms with updated workload data from a comprehensive survey and to provide reference shielding data for DBT rooms. Methods. The workload survey was performed from eight clinical DBT (Hologic Selenia Dimensions) rooms at Massachusetts General Hospital (MGH) for the time period between 10/1/2014 and 10/1/2015. Radiation output related information tags from the DICOM header, including mAs, kVp, beam filter material and gantry angle, were extracted from a total of 310 421 clinical DBT acquisitions from the PACS database. DBT workload distributions were determined from the survey data. In combination with previously measured scatter fraction data, unshielded scatter air kerma for each room was calculated. Experiment measurements with a linear-array detector were also performed on representative locations for verification. Necessary shielding material and thickness were determined for all barriers. For the general purpose of DBT room shielding, a set of workload-distribution-specific transmission data and unshielded scatter air kerma values were calculated using the updated workload distribution. Results. The workload distribution for Hologic DBT systems could be simplified by five different kVp/filter combinations for shielding purpose. The survey data showed the predominance of 45° gantry location for medial-lateral-oblique views at MGH. When taking into consideration the non-isotropic scatter fraction distribution together with the gantry angle distribution, accurate and conservative estimate of the unshielded scatter air kerma levels were determined for all eight DBT rooms. Additional shielding was shown to be necessary for two 4.5 cm wood doors. Conclusions. This study provided a detailed workload survey and updated transmission data and unshielded scatter air kerma values for Hologic DBT rooms. Example shielding calculations were presented for clinical DBT rooms.

Mammographic density assessed on paired raw and processed digital images and on paired screen-film and digital images across three mammography systems.

BackgroundInter-women and intra-women comparisons of mammographic density (MD) are needed in research, clinical and screening applications; however, MD measurements are influenced by mammography modality (screen film/digital) and digital image format (raw/processed). We aimed to examine differences in MD assessed on these image types.MethodsWe obtained 1294 pairs of images saved in both raw and processed formats from Hologic and General Electric (GE) direct digital systems and a Fuji computed radiography (CR) system, and 128 screen-film and processed CR-digital pairs from consecutive screening rounds. Four readers performed Cumulus-based MD measurements (n = 3441), with each image pair read by the same reader. Multi-level models of square-root percent MD were fitted, with a random intercept for woman, to estimate processed–raw MD differences.ResultsBreast area did not differ in processed images compared with that in raw images, but the percent MD was higher, due to a larger dense area (median 28.5 and 25.4 cm2 respectively, mean √dense area difference 0.44 cm (95% CI: 0.36, 0.52)). This difference in √dense area was significant for direct digital systems (Hologic 0.50 cm (95% CI: 0.39, 0.61), GE 0.56 cm (95% CI: 0.42, 0.69)) but not for Fuji CR (0.06 cm (95% CI: −0.10, 0.23)). Additionally, within each system, reader-specific differences varied in magnitude and direction (p < 0.001). Conversion equations revealed differences converged to zero with increasing dense area. MD differences between screen-film and processed digital on the subsequent screening round were consistent with expected time-related MD declines.ConclusionsMD was slightly higher when measured on processed than on raw direct digital mammograms. Comparisons of MD on these image formats should ideally control for this non-constant and reader-specific difference.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0787-0) contains supplementary material, which is available to authorized users.

WE‐DE‐207B‐09: Scatter Radiation Measurement From a Digital Breast Tomosynthesis System and Its Impact On Shielding Consideration

Purpose:To accurately measure the scatter radiation from a Hologic digital breast tomosynthesis (DBT) system and to provide updated scatter distribution to guide radiation shielding calculation for DBT rooms.Methods:A high sensitivity GOS‐based linear detector was used to measure the angular distribution of scatter radiation from a Hologic Selenia Dimensions DBT system. The linear detector was calibrated for its energy response of typical DBT spectra. Following the NCRP147 approach, the measured scatter intensity was normalized by the primary beam area and primary air kerma at 1m from the scatter phantom center and presented as the scatter fraction. Direct comparison was made against Simpkin's initial measurement. Key parameters including the phantom size, primary beam area, and kV/anode/target combination were also studied.Results:The measured scatter‐to‐primary‐ratio and scatter fraction data closely matched with previous data from Simpkin. The measured data demonstrated the unique nonisotropic distribution of the scattered radiation around a Hologic DBT system, with two strong peaks around 25° and 160°. The majority scatter radiation (&gt;70%) originated from the imaging detector assembly, instead of the phantom. With a workload from a previous local survey, the scatter air kerma at 1m from the phantom center for wall/door is 0.018mGy/patient, for floor is 0.164mGy/patient, and for ceiling is 0.037mGy/patient.Conclusion:Comparing to Simpkin's previous data, the scatter air kerma from Holgoic DBT is at least two times higher. The main reasons include the harder primary beam with higher workload, added tomosynthesis acquisition, and strong small angle forward scattering. Due to the highly conservative initial assumptions, the shielding recommendation from NCRP147 is still sufficient for the Hologic DBT system given the workload from a previous local survey. With the data provided from this study, accurate shielding calculation can be performed for Hologic DBT systems with specific workload and barrier distance.

Scatter radiation intensities around a clinical digital breast tomosynthesis unit and the impact on radiation shielding considerations.

To measure the scattered radiation intensity around a clinical digital breast tomosynthesis (DBT) unit and to provide updated data for radiation shielding design for DBT systems with tungsten-anode x-ray tubes. The continuous distribution of scattered x-rays from a clinical DBT system (Hologic Selenia Dimensions) was measured within an angular range of 0°-180° using a linear-array x-ray detector (X-Scan 0.8f3-512, Detection Technology, Inc., Finland), which was calibrated for the x-ray spectrum range of the DBT unit. The effects of x-ray field size, phantom size, and x-ray kVp/filter combination were investigated. Following a previously developed methodology by Simpkin, scatter fraction was determined for the DBT system as a function of angle around the phantom center. Detailed calculations of the scatter intensity from a DBT system were demonstrated using the measured scatter fraction data. For the 30 and 35 kVp acquisition, the scatter-to-primary-ratio and scatter fraction data closely matched with data previously measured by Simpkin. However, the measured data from this study demonstrated the nonisotropic distribution of the scattered radiation around a DBT system, with two strong peaks around 25° and 160°. The majority scatter radiation (>70%) originated from the imaging detector assembly, instead of the phantom. With a workload from a previous survey performed at MGH, the scatter air kerma at 1 m from the phantom center for wall/door is 1.76 × 10(-2) mGy patient(-1), for floor is 1.64 × 10(-1) mGy patient(-1), and for ceiling is 3.66 × 10(-2) mGy patient(-1). Comparing to previously measured data for mammographic systems, the scatter air kerma from Holgoic DBT is at least two times higher. The main reasons include the harder primary beam with higher workload (measured with total mAs/week), added tomosynthesis acquisition, and strong small angle forward scattering. Due to the highly conservative initial assumptions, the shielding recommendation from NCRP Report 147 is still sufficient for the Hologic DBT system given the workload from a previous survey at MGH. With the data provided from this study, accurate shielding calculation can be performed for Hologic DBT systems with specific workload and barrier distance.

Hip Structure Analysis Precision and Agreement between the Hologic and GE-Lunar DXA Systems

Hip Structure Analysis Precision and Agreement between the Hologic and GE-Lunar DXA Systems

SU-E-I-47: Quality Survey Using DIGIMAM Phantom for Digital Mammographic Systems

Purpose: This study aimed to evaluate the quality performance of digital mammographic systems based on the national survey data in Taiwan. Methods: On-site inspections were conducted on 120 mammographic units during 2014 survey in Taiwan. Quality performance of digital mammographic systems evaluated by DIGIMAM phantom (Artinis) complied with the European guidelines for quality assurance program were performed on 56 digital units, including 35 CR and 21 DR systems. The phantom was exposed with clinical techniques on-site for further investigate geometric distortions, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) with for-processing images, and dynamic range and chest wall missed tissue with for-presentation images. Results: Geometric distortion ranged from 0.3%∼12.5% for chest wall-anterior and from 0.8%∼14.1% for left-right direction. Mean CNR for 0.1 mm and 0.2 mm Al were 0.06±0.02 and 0.11±0.04, respectively. SNRs for DR may deviate from systems of different manufacturer/model and had a mean value of 69.87±15.02. As for CR systems, larger SNR variations were found between different manufacturers as compared to DR ones. For investigating the dynamic range in the low contrast inserts within fatty, normal and dense tissue, only 4 of 10 Hologic systems failed to distinguish the inserts for all the three test patterns. Evaluations of missed tissue at chest wall side showed that most DR systems had missed tissue less than 5 mm with the exception of 2 Hologic systems. Total pass rate according to European guidelines for chest wall missed tissue was 84.78%. Conclusion: Feasibility for quality survey using commercialized digital phantom were investigated in this study. Further analysis may be performed and more systems may be included in the survey in the future. The results may provide as a reference for digital mammography quality assurance program established in Taiwan.

TBS precision and accuracy comparison between the hologic and GE-lunar DXA systems

TBS precision and accuracy comparison between the hologic and GE-lunar DXA systems

Scatter radiation intensities around full-field digital mammography units.

The aim of this study was to investigate the scatter radiation intensity around digital mammography systems and apply these data to standard shielding calculations to reveal whether shielding design of existing breast screening rooms is adequate for the use of digital mammography systems. Three digital mammography systems from GE Healthcare, Hologic and Philips were employed in the study. A breast-equivalent phantom was imaged under clinical workload conditions and scatter radiation intensities around the digital mammography systems were measured for a range of angles in three planes using an ionisation chamber. The results were compared with those from previous studies of film-screen systems. It may be deduced from the results that scattering in the backward direction is significant for all three systems, while scattering in the forward direction can be significant for some planes around the GE and Hologic systems. Measurements at typical clinical settings on each system revealed the Philips system to have markedly lower scatter radiation intensities than the other systems. Substituting the measured scattered radiation intensity into shielding calculations yielded barrier requirements similar to those already in place at the screening centres operating these systems. Current radiation protection requirements based on film-screen technology remain sufficient when applied to rooms with digital mammography installations and no alteration is required to the structural shielding.

A multinational study to develop universal standardization of whole-body bone density and composition using GE Healthcare Lunar and Hologic DXA systems

Dual-energy x-ray absorptiometry (DXA) is used to assess bone mineral density (BMD) and body composition, but measurements vary among instruments from different manufacturers. We sought to develop cross-calibration equations for whole-body bone density and composition derived using GE Healthcare Lunar and Hologic DXA systems. This multinational study recruited 199 adult and pediatric participants from a site in the US (n = 40, ages 6 through 16 years) and one in China (n = 159, ages 5 through 81 years). The mean age of the participants was 44.2 years. Each participant was scanned on both GE Healthcare Lunar and Hologic Discovery or Delphi DXA systems on the same day (US) or within 1 week (China) and all scans were centrally analyzed by a single technologist using GE Healthcare Lunar Encore version 14.0 and Hologic Apex version 3.0. Paired t-tests were used to test the results differences between the systems. Multiple regression and Deming regressions were used to derive the cross-conversion equations between the GE Healthcare Lunar and Hologic whole-body scans. Bone and soft tissue measures were highly correlated between the GE Healthcare Lunar and Hologic and systems, with r ranging from 0.96 percent fat [PFAT] to 0.98 (BMC). Significant differences were found between the two systems, with average absolute differences for PFAT, BMC, and BMD of 1.4%, 176.8 g and 0.013 g/cm(2) , respectively. After cross-calibration, no significant differences remained between GE Healthcare Lunar measured results and the results converted from Hologic. The equations we derived reduce differences between BMD and body composition as determined by GE Healthcare Lunar and Hologic systems and will facilitate combining study results in clinical or epidemiological studies.

Cross Calibration of Whole Body Scans Between GE-Lunar and Hologic Systems: Bone and Body Composition

The trabecular bone score (TBS, Med-Imaps, Pessac, France) is an index of bone microarchitecture texture extracted from anteroposterior dual-energy X-ray absorptiometry images of the spine. Previous studies have documented the ability of TBS of the spine to differentiate between women with and without fractures among age- and areal bone mineral density (aBMD)-matched controls, as well as to predict future fractures. In this cross-sectional analysis of data collected from 3 geographically dispersed facilities in the United States, we investigated age-related changes in the microarchitecture of lumbar vertebrae as assessed by TBS in a cohort of non-Hispanic US white American women. All subjects were 30 yr of age and older and had an L1–L4aBMDZ-score within ±2 SD of the population mean. Individuals were excluded if they had fractures, were on any osteoporosis treatment, or had any illness that would be expected to impact bone metabolism. All data were extracted from Prodigy dual-energy X-ray absorptiometry devices (GE-Lunar, Madison, WI). Cross-calibrations between the 3 participating centers were performed for TBS and aBMD. aBMD and TBS were evaluated for spine L1–L4 but also for all other possible vertebral combinations. To validate the cohort, a comparison between the aBMD normative data of our cohort and US non-Hispanic white Lunar data provided by the manufacturer was performed. A database of 619 non-Hispanic US white women, ages 30–90 yr, was created. aBMD normative data obtained from this cohort were not statistically different from the non-Hispanic US white Lunar normative data provided by the manufacturer (p = 0.30). This outcome thereby indirectly validates our cohort. TBS values at L1–L4 were weakly inversely correlated with body mass index (r = −0.17) and weight (r = −0.16) and not correlated with height. TBS values for all lumbar vertebral combinations decreased significantly with age. There was a linear decrease of 16.0% (−2.47 T-score) in TBS at L1–L4 between 45 and 90 yr of age (vs. −2.34 for aBMD). Microarchitectural loss rate increased after age 65 by 50% (−0.004 to −0.006). Similar results were obtained for other combinations of lumbar vertebra. TBS, an index of bone microarchitectural texture, decreases with advancing age in non-Hispanic US white women. Little change in TBS is observed between ages 30 and 45. Thereafter, a progressive decrease is observed with advancing age. The changes we observed in these American women are similar to that previously reported for a French population of white women (r2 > 0.99). This reference database will facilitate the use of TBS to assess bone microarchitectural deterioration in clinical practice.

Evaluation of Standardization Equations as a Substitute for Scanner Specific In Vivo Measurements

We quantified confidence intervals (CIs) for T-scores for the lumbar spine and hip and determined the practical effect (impact on diagnosis) of variability around the T-score cutpoint of −2.5. Using precision data from the literature for GE Lunar Prodigy dual-energy X-ray absorptiometry (DXA) systems, the 95% CI for the T-score was ±0.23 at the lumbar spine (L1–L4), ± 0.20 at the total hip, and ±0.41 at the femoral neck. Thus, T-score variations of ±0.23 or less at the spine, ±0.20 at the total hip, and ±0.41 at the femoral neck are not statistically significant. When diagnosing osteoporosis, T-scores in the interval −2.3 to −2.7 for spine or total hip (after rounding to conform to guidelines from the International Society for Clinical Densitometry) and −2.1 to −2.9 for femoral neck are not statistically different from −2.5. Better precision values resulted in smaller 95% CIs. This concept was applied to actual clinical data using Hologic DXA systems. The study cohort comprised 2388 white women with either normal or osteopenic spines in whom the densitometric diagnosis of osteoporosis would be determined by hip T-scores. When evaluating actual patient T-scores in the range −2.5 ± 95% CI, we found that the diagnosis was indeterminate in approximately 12% of women when T-scores for femoral neck were used and in 4% of women when T-scores for total hip were used, with uncertainty as to whether the classification was osteopenia or osteoporosis. We conclude that precision influences the variability around T-scores and that this variability affects the reliability of diagnostic classification.

Does standardized BMD still remove differences between Hologic and GE-Lunar state-of-the-art DXA systems?

SummaryThe standardized bone mineral density (sBMD) values, derived using universal standardized equations, were shown to be equivalent within 1.0% for hip but significantly different for spine for state-of-art fan-beam dual X-ray absorptiometry (DXA) Hologic and GE-Lunar systems. Spine L1-L4 and L2-L4 sBMD mean differences between the two systems were 0.042 g/cm2 (4.1%) and 0.035 g/cm2 (3.2%), respectively.IntroductionThe objective of this study is to validate the 1994 pencil-beam DXA “universal standardization equations” for state-of-the-art fan-beam DXA systems.MethodsThe spine and bilateral femurs of 87 postmenopausal women were scanned on both Hologic Delphi and GE-Lunar Prodigy DXA systems at three different clinical centers. The scans were analyzed using Hologic Apex and GE-Lunar EnCore software. The BMD results were converted to sBMD using the equations previously developed. Linear regression analysis was used to describe the relationship of the two systems’ BMD results. Bland–Altman analysis was used to assess the differences in measures.ResultsThe Apex and Prodigy sBMD values were highly correlated (r ranged from 0.92 to 0.98). Spine L1-L4 and L2-L4 sBMD values had significant intercepts and slopes for Bland–Altman regression, with mean differences of 0.042 g/cm2 (4.1%) and 0.035 g/cm2 (3.2%), respectively. The total hip and neck sBMD showed no significant intercept and slope, except left total sBMD had a significant difference between the two systems of 0.009 g/cm2 (1.0%).ConclusionsThe sBMD values were shown to be equivalent within 1.0% for hip but were significantly different for spine on the two systems. Biases may persist in pooled sBMD data from different manufacturers, and further study is necessary to determine the cause.