Hologic Scanners Research Articles

Diagnosing (severe) Osteoporosis by Hologic vs. Lunar Measurements: A Single-Center Retrospective Study

Introduction: Although different dual-energy X-ray absorptiometry (DXA) scanners provide different bone mineral density (BMD) values, there is not a gold standard DXA scanner. T-score is used to facilitate the interpretation of BMD, and osteoporosis (OP) is diagnosed based on T-scores. In this retrospective study, we aimed to evaluate the BMD and T-score differences between Lunar Prodigy and Hologic Horizon DXA scanners.Methodology: Data were collected for patients with previous BMD measurement on Lunar Prodigy and Hologic Horizon DXA scanners within one year in the same medical center.Results: In a total of 55 patients, BMD values of femoral neck/total, and lumbar vertebrae were all lower at Hologic than Lunar (all p < 0.01). The mean T-score difference at the lumbar spine was 0.74 ± 0.42 (p < 0.001). Of the 49 patients diagnosed as OP (T-score ≤−2.5) with the Hologic, the diagnoses were changed for 25 individuals (51.0 %) with Lunar (p < 0.001). Herewith, although the diagnoses of OP did not change by the repeat technique in other 24 patients (49 %), 13 of them (26.5 %) were categorized as having “high fracture risk” instead of “very high fracture risk” group (i.e., T-score <−3.0). We observed moderate-to-good reliabilities (with an intraclass correlation coefficient [ICC] of 0.633–0.878 and 0.733–0.842 for BMD and T-scores, respectively) between measurements with the Lunar and Hologic scanners. Except for one measurement in L3, L4, L1–4 vertebrae, the Bland–Altman plot did not reveal any consistent bias between the measurements of the Lunar and Hologic scanners.Conclusions: The consistency between different DXA scanners (especially for Hologic vs. Lunar) is important for proper management, especially in patients with low T-scores and OP.

Reference ranges for body composition indices by dual energy X-ray absorptiometry from the Bone Mineral Density in Childhood Study Cohort

BackgroundBody composition assessment aids evaluation of energy stores and the impact of diseases and interventions on child growth. Current United States pediatric reference ranges from the National Health and Nutrition Examination Survey (NHANES) include 20% of children with obesity, body mass index of ≥95th percentile. ObjectivesThis study aimed to develop dual energy X-ray absorptiometry (DXA) based reference ranges in a diverse cohort with low-obesity prevalence from the Bone Mineral Density in Childhood Study (BMDCS). MethodsThis is a secondary analysis of a longitudinal, prospective, observational cohort. Healthy children (height and BMI within 3rd to 97th percentiles, ages 5–19 y at enrollment), from 5 United States centers were measured annually for ≤7 visits. Whole body scans were acquired using Hologic scanners. A subsample underwent repeat measurements to determine precision. We generated reference ranges for appendicular and total lean soft tissue mass index (LSTM Index), fat mass index (FMI), and other body composition measures. Resulting curves were compared to NHANES and across subgroups. Sex and age-specific equations were developed to adjust body composition Z-scores for height Z score. ResultsWe obtained 9846 scans of 2011 participants (51% female, 22% Black, 17% Hispanic, 48% White, 7% Asian/Pacific Islander, and 6% with obesity). Precision (percent coefficient of variation) ranged from 0.7% to 1.96%. Median and–2 standard deviation curves for BMDCS and NHANES were similar, but NHANES +2 standard deviation LSTM Index and FMI curves were distinctly greater than the respective BMDCS curves. Subgroup differences were more extreme for appendicular LSTM Index-Z (mean ± SD: Asian −0.52 ± 0.93 compared with Black 0.77 ± 0.87) than for FMI-Z (Hispanic 0.29 ± 0.98 compared with Black −0.14 ± 1.1) and were smaller for Z-scores adjusted for height Z-score. ConclusionsThese reference ranges add to sparse normative data regarding body composition in children and adolescents and are based on a cohort with an obesity prevalence similar to current BMI charts. Awareness of subgroup differences aids in interpreting results.

The EMory BrEast imaging Dataset (EMBED): A Racially Diverse, Granular Dataset of 3.4 Million Screening and Diagnostic Mammographic Images.

Supplemental material is available for this article. Keywords: Mammography, Breast, Machine Learning © RSNA, 2023.

Prevalence and causes of elevated bone mass.

Reports of elevated bone mass (EBM) on routine DXA scanning are not infrequent. However, epidemiological studies of EBM are few in number and definition thresholds variable. The purpose of this study was to assess the prevalence and causes of EBM in the general population referred to a single university hospital - catering for a population of 4 million inhabitants - for DXA scanning. DXA databases were initially searched for individuals with a bone mineral density (BMD) Z-score ≥+4 at any site in the lumbar spine or hip from April 1st, 2008 to April 30st, 2018. Two Hologic scanners were available at the Lille University Hospital (France). Prevalence of EBM was evaluated, as were causes associated with EBM. At the lumbar spine, 18,229 bone density tests were performed in women and 10,209 in men. At the hip, 17,390 tests were performed in women and 9857 in men. The total number of patients who had at least one bone density test was 14,745, of which 64.2% were female. Of these 14,745 patients, 211 had a Z-score ≥+4 at any site, i.e. a prevalence of 1.43% [1.25%-1.64%]. The DXA scans and medical records of 92 men and 119 women with elevated BMD were reviewed to assess causes. An artefactual cause was found in 164 patients (75%) with EBM (mostly degenerative disease of the spine), and an acquired cause of focal EBM was found in only 2 patients, both of whom had sclerotic bone metastases from prostate cancer. An acquired cause of generalized EBM was found in 32 patients (15%), the vast majority of whom had renal osteodystrophy (n=11), followed by hematological disorders (n=9; e.g. myeloproliferative syndromes and mastocytosis) and diffuse bone metastases from solid cancer (n=5). Of the remaining causes, rare hereditary diseases (e.g. osteopetrosis…) and unexplained EBM were found in 10 and 6 cases respectively. The prevalence of EBM (Z-score ≥+4 at any site) was 1.43% [1.25%-1.64%]. In nearly all instances (97.1%) the explanation for EBM could be found in the medical record and through conventional investigations. This study suggests that the main cause of EBM is degenerative disease of the spine. Further studies are needed to differentiate artefactual EBM from hereditary or acquired EBM, and to investigate unexplained EBM. Genetic testing may prove useful in elucidating rare unknown causes.

“Effect of very dense artifacts on Hologic and general electric bone densitometry results”

Very dense objects, such as lead bullets are described as "black hole" artifacts on Hologic densitometers. Whether similar results occur on GE scanners is not reported. We hypothesized that dense artifacts confound both brands of densitometers. Three lead bullets of varying size were placed overlying or adjacent to L3 on anthropomorphic and encapsulated aluminum spine phantoms. Three scans were acquired with and without projectiles on a Hologic Discovery W, GE iDXA, and Prodigy densitometer. Lead bullets are measured as having high bone mineral content (BMC); they appear black in dual-energy mode on Hologic scanners and are colored blue on GE scanners. On Hologic scanners, BMC of a dense artifact over bone is excluded, but the bone area is not altered. Consequently, bone mineral density (BMD) of the affected vertebra, and of L1-4, is decreased. For example, a .45 caliber bullet over L3 decreased BMD (p < 0.05) by 48.3% and L1-4 by 9.1%. GE scanners excluded associated BMC and area covered by the artifact, thereby minimizing impact on BMD. Dense artifacts over soft tissue on a phantom do not substantially affect BMD on either manufacturer's densitometer when scanned. Densitometer manufacturers handle very dense artifacts differently. GE software removes artifact BMC and area with resultant minimal impact on BMD, Hologic removes only BMC, not area, thereby decreasing BMD. Regardless of this difference, when dense artifacts overlay the spine, it is best to exclude the affected vertebral body. Finally, the BMD stability observed with artifacts over soft tissue may not be replicated in humans.

Added values of DXA-derived visceral adipose tissue to discriminate cardiometabolic risks in pre-pubertal children.

BackgroundThe new generation of dual energy X-ray absorptiometry (DXA) scanners provide visceral adipose tissue (VAT) estimates by applying different algorithms to the conventional DXA-derived fat parameters such as total fat, trunk fat and android fat for the same image data.ObjectiveThis cross-sectional study aimed to investigate whether VAT estimates from Hologic scanners are better predictors of VAT than conventional DXA parameters in pre-pubertal children, and to explore the discrimination ability of these VAT methods for cardiometabolic risks.MethodsHealthy pre-pubertal children aged 7–10 years were recruited for basic anthropometric, DXA and magnetic resonance imaging (MRI) measurements. Laboratory tests included lipid profile, glycaemic tests and blood pressure.ResultsAll VAT methods had acceptable to excellent performance for the diagnosis of dyslipidaemia (area under the curve [AUC] = 0.753–0.837) and hypertensive risk (AUC = 0.710–0.821) in boys, but suboptimal performance for these risks in girls, except for VAT by MRI in the diagnosis of dyslipidaemia. In both sexes, all VAT methods had no or poor discrimination ability for diabetes risk.ConclusionsDXA-derived VAT estimates are very highly correlated with standard methods but has equivalent discrimination abilities compared to the existing DXA-derived fat estimates.

Amalgamated Reference Data for Size-Adjusted Bone Densitometry Measurements in 3598 Children and Young Adults-the ALPHABET Study.

The increasing use of dual-energy X-ray absorptiometry (DXA) in children has led to the need for robust reference data for interpretation of scans in daily clinical practice. Such data need to be representative of the population being studied and be "future-proofed" to software and hardware upgrades. The aim was to combine all available pediatric DXA reference data from seven UK centers to create reference curves adjusted for age, sex, ethnicity, and body size to enable clinical application, using in vivo cross-calibration and making data back and forward compatible. Seven UK sites collected data on GE Lunar or Hologic Scanners between 1996 and 2012. Males and females aged 4 to 20 years were recruited (n = 3598). The split by ethnic group was white 2887; South Asian 385; black Afro-Caribbean 286; and mixed heritage 40. Scans of the total body and lumbar spine (L1 to L4 ) were obtained. The European Spine Phantom was used to cross-calibrate the 7 centers and 11 scanners. Reference curves were produced for L1 to L4 bone mineral apparent density (BMAD) and total body less head (TBLH) and L1 to L4 areal bone mineral density (aBMD) for GE Lunar Prodigy and iDXA (sex- and ethnic-specific) and for Hologic (sex-specific). Regression equations for TBLH BMC were produced using stepwise linear regression. Scans of 100 children were randomly selected to test backward and forward compatibility of software versions, up to version 15.0 for GE Lunar and Apex 4.1 for Hologic. For the first time, sex- and ethnic-specific reference curves for lumbar spine BMAD, aBMD, and TBLH aBMD are provided for both GE Lunar and Hologic scanners. These curves will facilitate interpretation of DXA data in children using methods recommended in ISCD guidelines. The databases have been created to allow future updates and analysis when more definitive evidence for the best method of fracture prediction in children is agreed. © 2016 American Society for Bone and Mineral Research.

Application of sub-regional analysis to bone mineral density of the lower limb from whole body DXA scans

Bone mineral density at spine and hip is widely used to diagnose osteoporosis. Certain conditions cause changes in bone density at other sites, particularly in the lower limb, with fractures occurring in non-classical locations. Bone density changes at these sites would be of interest for diagnosis and treatment. We describe an application, based on an existing software option for Hologic scanners, which allows reproducible measurement of bone density at six lower limb sites (upper femur, mid-femur, lower femur; upper leg, mid-leg, lower leg). In 30 unselected subjects, referred for bone density, precision (CV%) measured on 2 occasions, separated by repositioning, ranged from 1.7% (mid-femur) to 4.5% at the lowest leg site. Intra-operator precision, measured by three operators on ten subjects on three occasions, was between 1.0% and 2.9%, whilst inter-operator precision was between 1.0% and 3.6%, according to region. These values compare well with those at the spine and upper femur, and in the literature. There was no evidence that this operator agreement improved between occasions 1 and 3. This technique promises to be useful for assessing bone changes at vulnerable sites in the lower limb, in diverse pathological states and in assessing response to treatment.

A study of the long-term precision of dual-energy X-ray absorptiometry bone densitometers and implications for the validity of the least-significant-change calculation

Short-term precision is often quoted and used as the most important performance parameter of a dual-energy X-ray absorptiometry (DXA) scanner; however, long-term precision has a more profound impact on patient monitoring. Long-term precision refers to the combination of in-vivo precision errors and long-term equipment stability. To monitor long-term equipment stability, a phantom was designed with four inserts ranging in bone-mineral density from 0.5 to 3.3 g/cm(2). This phantom was used to monitor the equipment stability of four modern fan-beam densitometers, two each from Hologic and GE/Lunar, over a 4-year period. Manufacturer-recommended quality assurance (QA) procedures were performed, and the scanners stayed within manufacturer-specified tolerances throughout the study. During the 4-year period, the Hologic scanners were observed to cause clinically insignificant BMD shifts (maximum of 0.34%), whereas the GE/Lunar scanners revealed BMD shifts that were clinically significant (1.5% and 2.1%). As a result, using least-significant-change (LSC) calculations based only on short-term in-vivo precision studies for monitoring patients is not valid for the two GE/Lunar densitometers due to the poorer long-term stability they exhibited.

Cross-calibration of dual-energy X-ray densitometers for a large, multi-center genetic study of osteoporosis

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass and an increased risk of fragility fractures. Bone mineral density (BMD) is the most important determinant of osteoporotic fracture risk, but the genes responsible for BMD regulation and fracture are incompletely defined. To enable multi-center studies to examine the genetic influences on BMD there is a requirement to standardize measurements across different manufacturers of bone densitometers, different versions of machines and different normative ranges. This paper describes a method developed to allow near-identical subjects with low age-adjusted BMD (based on Z-scores) to be recruited in 17 centers using 27 different densitometers. Cross-calibration was based on measurements using a European spine phantom circulated to all centers and measured ten times on each individual machine. From theses values an individual exponential curve, based on nominal versus observed BMD, was derived for each machine. As expected, there were large and significant variations in nominal BMD values, not only between scanners from different manufacturers but also between different versions of scanners from the same manufacturer. Hologic scanners tended to underestimate the nominal BMD, while Lunar scanners overestimated the value. Norland scanners gave mixed values over estimating BMD at the lower nominal value (0.5 g/cm2) while underestimating the value at the higher value (1.5 g/cm2). The validity of the exponential equations was tested using hip and spine measurements on 991 non-proband women from a familial osteoporosis study (FAMOS). After cross-calibration there was a considerable reduction in variation between machines. This observation, coupled with the absence of a similar reduction in variation attributable to a linear regression on age, demonstrated the validity of the cross-calibration approach. Use of the cross-calibration curves along with a standard normative range (in the case of this study, the Hologic normative range) allowed age-specific Z-scores to be used as an inclusion criterion in this genetic study, a method that will be useful for other trials where age-specific BMD inclusion criteria are required.

Dual-Energy X-Ray Absorptiometry Measurements of Total-Body Bone Mineral During Weight Change

Bone mineral measurements were made using dual-energy X-ray absorptiometry during a multicenter diet trial. There were five centers, two using Hologic QDR4500 fan-beam scanners, two using Lunar Prodigy fan-beam scanners,and one using a pencil-beam Lunar DPX. Measurements were made at 0, 2.5, and 6 mo. The mean weight loss was 7.9 kg, but there was a wide range. With the Lunar instruments, the total-body bone mineral density reduced with weight loss, but with the Hologic scanners, it appeared to increase. This anomaly is similar to that observed previously with a Hologic QDR1000 pencil-beam scanner. It was shown that changes of fat distribution can lead to alterations in bone measurement without any real change in the skeleton. With all of the scanners, there was a strong correlation between the change in the bone mineral content and bone area, with some values of the latter being quite implausible. There was an associated worsening of long-term precision compared with that derived from short-term duplicated scans, more marked with the Lunar scanners. It is concluded that measurement artifacts preclude the valid assessment of total-body bone mineral during weight change.

Discordant normal ranges for proximal femur bone density in Australia.

The aim of the study was to investigate the reference ranges currently in use for femoral neck bone mineral density (BMD) in Australia. Representative scans were obtained of the proximal femur from 78 dual-energy X-ray absorptiometry centers across Australia. Femoral neck BMD was standardized using published conversion equations and corresponding T-scores calculated using an Australian reference range (ARR) and using the NHANES-III reference range (NH3RR). Reported T-scores (TR) from the DXA centers were compared with T-scores derived from the NH3RR (TNH) and from the ARR (TA). Examination of the regression lines comparing TR with TNH, and TR with TA, demonstrated that the reference ranges used by centers with Lunar, and some of the Norland and Hologic instruments, differed only slightly from both the NH3RR and the ARR. A number of centers, however, with Norland or Hologic scanners, were using reference ranges which differed from both the NH3RR and ARR. The reference ranges used with these latter Hologic or Norland scanners could result in T-score differences of up to I standard deviation in the clinically relevant T-score range. The NH3RR was compared with the ARR using a set of BMD values covering the clinical range. There was close agreement between TNH and corresponding TA, confirming close agreement between the NH3RR and ARR. There are thus clinically important differences in the reference ranges currently used within Australia for interpretation of femoral neck BMD. For consistency, and in view of its validation, the NH3RR is recommended as the most appropriate Caucasian normal range in Australia. The ARR for femoral neck BMD does not differ significantly from the NH3RR and is also acceptable. Problems relating to the use of discordant BMD reference ranges potentially may exist in other countries.