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PubMed2004

Comparison of Bod Pod and DXA in female collegiate athletes.

PURPOSE: This study was designed to evaluate the reliability and validity of air displacement plethysmography (ADP) compared with dual energy x-ray absorptiometry (DXA) Hologic QDR 4500A (Waltham, MA) in female collegiate athletes. METHODS: Forty-seven females representing various Division II collegiate sports and 24 controls participated in the current study. All women underwent both methods of testing within a 30-min period. RESULTS: Comparison of means indicated that the ADP and DXA are not different when measuring body fat (BF%) in the athletes (ADP = 22.5 +/- 5.5%, DXA = 22.0 +/- 4.7%P = 1.0). Furthermore, this study determined that ADP is a reliable measure of body fat (BF%; r = 0.96, P < 0.001; 0.97, P < 0.001) in collegiate female athletes and nonathletes, respectively. CONCLUSION: The results from this study indicate that ADP is a valid measure of body composition in female athletes and nonathletes when compared with DXA.

Absorptiometry, Photon↗
PubMed1997

Comparison of two Hologic DXA systems (QDR 1000 and QDR 4500/A).

Bone mineral content is reliably measured by dual energy X-ray absorptiometry (DXA), if manufacturers' recommendations and quality control (QC) procedures are followed. Several phantoms (Hologic anthropomorphic spine phantom, the Groupe de Recherche et d'Informations sur les Osteoporoses (GRIO) test objects and the European semi-anthropomorphic phantoms) were used to evaluate reproducibility, linearity, accuracy and spatial resolution of two DXA devices in vitro. These parameters were also evaluated in vivo from measurements performed on 120 volunteer patients. It was found that when one device (a single beam monodetector QDR 1000) is replaced by another (a fan beam multidetector QDR 4500/A), the novel combination of procedures described here, ensures that the accuracy of DXA study results is maintained when both devices are used in succession for the same patient. To study the possible responses in clinical situations, the influence of bone environment (soft and adipose tissues) was also evaluated. In both systems, similar performances (in vitro coefficients of variation of 0.5%) were established. At extreme bone density values, slight differences in linearity were found, as well as differences in accuracy and spatial resolution. Lumbar spine and femoral neck measurements were performed with both systems in 120 volunteers, both measurements being made on the same day. The corresponding bone mineral density (BMD) values were highly correlated (r2 = 0.985 for lumbar spine and 0.948 for the femoral neck), and the mean BMD differences were 0.68% and 0.37% for each anatomical site, respectively. Although small, these differences add to the precision error of the method, which is near 1%. A calibration curve has to be obtained in order that both devices can be equally used in regular clinical study. We concluded that when a DXA system is replaced by a new one, appropriate QC procedures must be strictly observed.

Absorptiometry, Photon↗
PubMed2000

Effect of Paget's disease of bone on areal lumbar spine bone mineral density measured by DXA, and density of cortical and trabecular bone measured by quantitative CT.

Although bone density may be increased in bone that is affected by Paget's disease, density changes in cortical and trabecular bone and the effect on bone that is apparently unaffected by Paget's disease are relatively unexplored. We have investigated 81 vertebrae (28 affected, 53 unaffected) in 27 patients with Paget's disease, by dual X-ray absorptiometry (DXA) and by quantitative CT (QCT) bone density measurements of trabecular and cortical bone. DXA bone density was high (mean z-score = 1.62, p < 0.001) in vertebrae affected by Paget's disease, but not significantly different from normal in unaffected vertebrae (mean z-score = 0.07, ns). Mean QCT z-score in Paget's vertebrae was 2.07 (p = 0.009) for cortical bone and 1.37 (p = 0.008) for trabecular bone. DXA correlated with QCT cortical values in affected and unaffected bone (r = 0.8 and 0.56, respectively), and with QCT trabecular values (r = 0.72 and 0.48, respectively). There was no significant difference in the slopes for the correlations in affected or unaffected bone. Cortical QCT values are underestimated in Paget's disease compared with physical measurements of density, owing to the computer algorithm used. High DXA values may alert to the possibility of Paget's disease, especially if the value deviates from the expected normal sequence in lumbar vertebrae. Osteoporotic vertebrae may be overlooked if the average value of bone mineral density is taken in the lumbar spine without reviewing each vertebra.

Absorptiometry, Photon↗
PubMed2007

Alterations of cortical and trabecular architecture are associated with fractures in postmenopausal women, partially independent of decreased BMD measured by DXA: the OFELY study.

UNLABELLED: We assessed the role of low aBMD and impaired architecture-assessed by an HR-pQCT system-in a case-control study of postmenopausal women with fractures. Vertebral and nonvertebral fractures are associated with low volumetric BMD and architectural alterations of trabecular and cortical bone, independent of aBMD assessed by DXA. INTRODUCTION: Alterations of bone architecture and low BMD both contribute to skeletal fragility, but the contribution of cortical and trabecular architecture, independently of areal BMD (aBMD), to the risk of fracture in postmenopausal women has not been thoroughly evaluated. We assessed the role of impaired architecture and low BMD in postmenopausal women with fractures. MATERIALS AND METHODS: A matched case-control study in women from the OFELY cohort was performed after 13 years of follow-up. One hundred one women (mean, 73.7+/-8 years) who sustained a fragility fracture during the follow-up of the study were age-matched with one control who never had a fracture. Density and architecture at the distal radius and tibia were measured with high-resolution pQCT (HR-pQCT) using an XTreme CT (Scanco Medical AG, Bassersdorf, Switzerland). aBMD at the total hip and ultradistal radius was measured by DXA. RESULTS: There were 80 peripheral fractures in 72 women, 44 vertebral fractures in 34 women, and both types of fractures in 5 women over the 14 years of follow-up. At the distal radius, women with fractures had lower volumetric total (D tot) and trabecular (D trab) BMDs, BV/TV, cortical thickness (Cort Th), trabecular number (TbN), and trabecular thickness (TbTh) and higher trabecular separation (TbSp) and distribution of trabecular separation (TbSpSd) than controls without fractures. In a logistic model, each SD decrease of volumetric total and trabecular densities was associated with a significantly increased risk of fracture at both sites (ORs ranged from 2.00 to 2.47). After adjusting for aBMD measured by DXA at the ultradistal radius, differences between cases and controls remained significant for D trab, and there was a similar trend for TbN, TbSp, and TbSpSd, with adjusted ORs ranging from 1.32 to 1.50. At the distal tibia, before and after adjusting for total hip aBMD, differences between cases and controls remained significant for D tot, D trab, Cort Th, and TbTh, with adjusted ORs ranging from 1.80 to 2.09. CONCLUSIONS: In postmenopausal women, vertebral and nonvertebral fractures are associated with low volumetric BMD and architectural alterations of trabecular and cortical bone that can be assessed noninvasively and that are partially independent of aBMD assessed by DXA.

Adult↗
PubMed2004

Patient preference for being informed of their DXA scan results.

Evidence suggests that patients diagnosed with osteoporosis are often undertreated. One potential solution to undertreatment is to enhance patient involvement in their osteoporosis care (a.k.a. patient activation) by having the dual-energy X-ray absorptiometry (DXA) center directly provide patients with their test results and educational material. However, little is known about patient interest in such an intervention. Consecutive patients presenting to an academic medical center DXA scanning unit were given a questionnaire to assess their preferences for being informed of their test results and interest in receiving their results plus educational material by mail from the testing center. Two hundred and two (202) of 206 (98%) of patients agreed to complete the survey. Fifty-one percent of participants preferred receiving their results by mail directly from the DXA center, followed by phone call (28%) and office visit (11%). Overall, 90% of patients reported interest in receiving results and educational material by mail. Younger patients were more interested in receiving their results by mail when compared with older patients, but this difference did not reach statistical significance (odds ratio [OR] = 2.40: 95% confidence interval [CI]: 0.91-6.31, p = 0.14). Patients undergoing DXA scanning were interested in receiving their scan results and educational material directly from the testing center. This might represent an effective intervention for improving care of patients with osteoporosis.

Absorptiometry, Photon↗
PubMed2004

Relationship among MRTA, DXA, and QUS.

Dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) are the accepted modalities for the evaluation of fracture risk in the clinical setting. However, neither method provides a direct measurement of bone mechanics. In this study, we investigated a prototype device, known as a mechanical response tissue analyzer (MRTA), which provides direct mechanical measurements of mechanical properties of bone. A total of 56 healthy volunteers (20 men and 36 women) between the ages of 18 and 83 were recruited. The MRTA was used to measure the cross-sectional bending stiffness (EI) of the ulna bone. Axial speed of sound (SOS) at the ulna bone was determined by QUS; bone mineral content (BMC) and bone mineral density (BMD) were determined by DXA. Correlations, regression analysis, and analyses of variance (ANOVAs) were used to compare the three modalities. These analyses revealed that although there are strong linear relationships among the data collected by the various technologies, the bone properties reflected by MRTA are not fully explained by DXA and QUS. We conclude that the total information conveyed by MRTA measurements is unique. Further research is needed to delineate the different qualities of bone strength that are captured by MRTA, but not by DXA or QUS.

Absorptiometry, Photon↗
PubMed2005

The precision of digital X-ray radiogrammetry compared with DXA in subjects with normal bone density or osteoporosis.

Digital X-ray radiogrammetry (DXR) is a technique to estimate bone mineral density (BMD) that can be available in any area able to take a standard radiograph of the hand. We aimed to establish the precision of this technique and compare this with that obtained by dual energy X-ray absorptiometry (DXA) at the hip and spine. We compared DXA and DXR in 28 women with osteoporosis defined by DXA at the femoral neck and in 28 women with normal BMD. We found that DXR has excellent precision of 0.004 g/cm(2) compared with 0.021 g/cm(2) and 0.015 g/cm(2) obtained by DXA at the hip and spine, respectively. We conclude that DXR measured by the automated Pronosco system has excellent precision.

Absorptiometry, Photon↗
PubMed1996

[Bone mineral density of the calcanei dissected from 30 cadavers--correlation of the values measured by the DXA, QCT and USD methods].

The bone mineral density (BMD) of calcanei dissected from 30 cadavers (14 males and 16 females; ages 61 to 100) was measured by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT), while the stiffness was measured by ultrasound bone densitometry (USD). There was high correlation between BMD by DXA and average bone density by QCT (R = 0.94), but poor correlation between BMD by DXA and stiffness by USD (R = 0.55). However, the correlation coefficient of stiffness to BMD was much higher in the female calcanei (R = 0.74) than in the male calcanei (R = 0.32). Analyzing the three elements, stiffness, speed of sound (SOS) and broad-band ultrasound attenuation (BUA), it was clear that SOS rather than stiffness correlated strongly to BMD by DXA and to bone density of trabeculated bones by QCT (R = 0.618; 0.699 respectively). The value of BUA shows more relationship to the width of the calcanei than the area of X-ray projection from the side (R = 0.561).

Absorptiometry, Photon↗
PubMedDate not supplied

Evaluating a nurse-led DXA scanning service.

AIM: To examine the feasibility of using a peripheral dual energy X-ray absorptiometry (DXA) scanning service in a nurse-led clinic and whether or not it would influence treatment and clinician satisfaction with the service. METHOD: A nurse-led clinic, using peripheral DXA scans to identify patients at risk of osteoporosis, was established in the rheumatology department of the hospital. Patients were referred from several sources. A questionnaire was sent to referring health professionals with each scan result. Returned questionnaires were statistically analysed. Of the sample size of 2000, 1024 questionnaires were returned, giving a response rate of 51 per cent. RESULTS: The results confirmed the hypothesis that a nurse-led peripheral DXA scanning service is feasible and beneficial to referring clinicians. Eighty nine per cent (n=912) of respondents stated that the scan results influenced treatment of patients. CONCLUSION: Further investigation of the extent that the DXA scanning service may have reduced unnecessary treatment is required.

Absorptiometry, Photon↗
PubMed1999

Simulation studies of optimum energies for DXA: dependence on tissue type, patient size and dose model.

Dual-energy x-ray absorptiometry (DXA) is a well established technique for measuring bone mineral density (BMD). However, in recent years DXA is increasingly being used to measure body composition in terms of fat and fat-free mass. DXA scanners must also determine the soft tissue baseline value from soft-tissue-only regions adjacent to bone. The aim of this work is to determine, using computer simulations, the optimum x-ray energies for: a number of dose models, different tissues, i.e. bone mineral, average soft tissue, lean soft tissue and fat; and a range of anatomical sites and patient sizes. Three models for patient dose were evaluated: total beam energy, entrance exposure and absorbed dose calculated by Monte Carlo modelling. A range of tissue compositions and thicknesses were chosen to cover typical patient variations for the three sites: femoral neck, PA spine and lateral spine. In this work, the optimisation of the energies is based on: (1) the uncertainty that arises from the quantum statistical nature of the number of x-rays recorded by the detector, and (2) the radiation dose received by the patient. This study has deliberately not considered other parameters such as detector response, electronic noise, x-ray tube heat load etc, because these are technology dependent parameters, not ones that are inherent to the measuring technique. Optimisation of the energies is achieved by minimisation of the product of variance of density measurement and dose which is independent of the absolute intensities of the x-ray beams. The results obtained indicate that if solving for bone density, then Elow in the range 34 to 42 keV, Ehigh in the range 100 to 200 keV and incident intensity ratio (low energy/high energy) in the range 3 to 10 is a reasonable compromise for the normal range of patient sizes. The choice of energies is complicated by the fact that the DXA unit must also solve for fat and lean soft tissue in soft-tissue-only regions adjacent to the bone. In this case the ranges of energies suggested above are acceptable only for the average phantom. In extreme cases the variance-dose product can be up to 50 times higher than for the ideal energies.

Absorptiometry, Photon↗
PubMed2003

[Manufacture and evaluation of a spine phantom used in the cross-calibration of DXA bone densitometry].

OBJECTIVE: To design and manufacture a reliable spine phantom used in the cross calibration and quality control of dual X-ray absorptiometry (DXA). METHODS: A hydroxyapatite quality control phantom was designed and made through three steps: solid water, bone phantom material and integration, then evaluated the phantom on four different types of DXA machines made by LUNAR company. RESULTS: Among the four DXA densitometers, the Expert fan beam densitometer had the biggest accuracy errors of bone mineral density (BMD), bone mineral content(BMC) and area values while the other three one narrow fan beam (Prodigy) and two pencil beam densitometers-had small errors. Of the three indexes measured by all the machines, BMD error was the smallest (-15.4%-11.5%), with the Prodigy's BMD was most outstanding. BMD errors at the higher density ends were small, tend to be positive values while the errors at the lower ends were big, tend to be negative. In cross calibration, giving consideration to the differences between the both ends, it is better to use the regression equation to correct. The base line of precision error derived by scanning the phantom once a day for consecutive 25 days was better than that derived by scanning the phantom 25 times consecutively on the same day. As to precision error, the coefficient of variation (CV) of scanning-25 times-a day was the smallest (0.0043) while the CV of 12 adults measurements was the biggest (0.0078). CONCLUSIONS: This phantom can be used in the quality control and cross-calibration of different types of DXA machines.

Absorptiometry, Photon↗
PubMed2004

Influence of anthropometric parameters on the body composition measured by bioelectrical impedance analysis or DXA in children.

AIM: To investigate the influence of anthropometric measures (skinfold thicknesses, girths, lengths and breadths/lengths) on (1) the whole body impedance and impedance index and (2) the body fat mass measured by means of DXA in children. METHODS: Nine skinfolds, 13 girths, eight lengths and eight breadths/lengths were measured in 26 boys and 27 girls, 11-12 y of age. The somatotype components-endomorphy, mesomorphy and ectomorphy--were assessed according to the method of Carter and Heath. Body impedance at 50 kHz was measured (Multiscan 5000, Bodystat Ltd, UK) and impedance index (height2 / impedance) was calculated. Four body components-total body fat mass and separate hands, legs and trunk fat mass--were determined using DXA. RESULTS: Skinfold thicknesses did not influence body impedance or impedance index according to stepwise multiple regression analysis. Impedance index was influenced more by the girth measures than was body impedance. The leg length measures highly influenced the impedance index (50-81%, R2 x 100). Different breadth/length parameters influenced body impedance and body impedance index (21-49%). Mesomorphy influenced body impedance only in boys (35%). Body fat mass measured by DXA was highly dependent on the measured skinfold thicknesses (59-92%). The influence of lengths and breadths/lengths on the total fat mass was significant (25-49%). Endomorphy characterized total fat mass as 86% and 52% in boys and girls, respectively. CONCLUSION: Variation in anthropometry highly determined the variance observed in impedance in children, and the girths were the best predictors of impedance. Selected skinfold thicknesses highly predicted fat mass measured by DXA for total body, trunk, arms and legs.

Absorptiometry, Photon↗
PubMed2005

Pediatric DXA bone measurements.

Dual-energy x-ray absorptiometry (DXA) has become the most commonly employed technique worldwide for assessment of bone mineral content in adults and children. DXA interpretation in children is more complex because bone dimensions are highly dynamic. Pediatric use of DXA can be used to identify risk of adult osteoporosis. This technology and the increasing knowledge of the genetics, mutations, and mutagens associated with the development of osteoporosis are tools to identify the phenotypes and genotypes in children at risk for osteoporosis later in life, and to design appropriate early interventions for this condition. This paper gives a brief overview of how DXA works, calibration issues, efficacy, safety, and test interpretation.

Absorptiometry, Photon↗
PubMed2006

Health care disparities in postmenopausal women referred for DXA screening.

BACKGROUND: Racial disparities have been identified in a number of areas in clinical medicine. Limited data are available on osteoporosis screening rates between races. We assessed the racial distribution in Dual Energy X-ray Absorptiometry (DXA) screening rates among African American and Caucasian women referred from our primary care clinics. METHODS: We obtained DXA results during the years 1998-2002 for all 546 women ages >50 years referred for bone mineral density (BMD) testing from a primary care population. We compared the DXA screening rates between African American and Caucasian women with the racial demographics of the referring primary care clinic population. RESULTS: African American women represented 45.9% and Caucasian women 51.7% of our primary care clinic population. Yet, only 14.5% (n=79) of the DXA screened women were African American, while 82.8% (n=452) were Caucasian. Age and recognized risk factors only explained a small portion of this difference. In women 65 years and older with universal screening recommendations, 19.4% (n=46) of the screened women were African American, and 80.6% (n=191) were Caucasian. The prevalence of osteoporosis was similar in both populations, 21.5% and 20.1% for African American and Caucasian women, respectively. CONCLUSIONS: Significantly fewer African American women had BMD screening even though national guidelines do not differentiate by race. The large disparity between the proportion of African American and Caucasian women screened calls for more equitable BMD screening among races.

Absorptiometry, Photon↗
PubMed1992

Bone mass measurement by DXA: influence of analysis procedures and interunit variation.

Interunit variability among bone densitometers is due to different factors, including different calibration procedures and algorithms and variability in photon source energies and/or intensities. Other factors, such as the choice of scan parameters or the analysis procedures, can also introduce variability. The new generation of dual-energy x-ray absorptiometry (DXA) has partially improved this situation. The aim of this study was to investigate the operator-dependent analysis procedures that can affect scan results and to evaluate the phantom and in vivo interunit variation of some DXA instruments. Four DXA instruments (QDR 1000 and 1000/W, Hologic, Inc.) were used. Potential sources of variability in the analysis procedures of anteroposterior lumbar spine and hip scans were considered: in most cases these procedures significantly influenced scan results. On lumbar spine, an enlargement of the scan window of less than 3 cm was responsible for an average increase in bone mineral density (BMD) of about 3%. On the hip, lowering the scan window by about 1 cm accounted for an increase in the whole-segment BMD of about 4%. After standardization of analysis procedures, interunit and intraunit coefficients of variation and percentage differences among instruments were less than 1% for all the parameters considered (area and bone mineral content and density) with both an anatomic and a geometric phantom, and in nine subjects scanned by two different devices the percentage difference in BMD was greater than 2%. This study shows that present interunit variability allows comparisons among laboratories, but only if highly standardized analysis procedures are used.

Absorptiometry, Photon↗
PubMed1994

Accuracy, precision, and utility of spine and whole-skeleton mineral measurements by DXA in rats.

We evaluated the precision and accuracy of dual-energy x-ray bone densitometry (DXA) in 38 male and female rats aged 1-10 months. The coefficients of variation (CV) estimated from same-day paired measurements of bone mineral content (BMC) were 1.26% at the lumbar spine and 0.69% at the whole skeleton, and the corresponding CV for BMC corrected for projected bone area (i.e., bone mineral density, BMD) were 0.57 and 0.66%. BMC, measured in vivo, correlated closely with the subsequently determined ash weights (spine r2 = 0.94, whole-skeleton r2 = 0.97). The long-term CV for BMC measurements, assessed by measuring a frozen animal daily for 4 weeks, were 1.28% for the spine and 1.03% for the whole skeleton; for BMD the corresponding CV were 0.88 and 1.15%. To examine the utility of serial DXA measurements we followed female rats subjected to ovariectomy (OVX) or sham operation at 10 months of age and male rats given daily subcutaneous injections of hPTH-(1-34) or vehicle starting at 10 months of age every 3 weeks for 15 weeks. In the OVX rats a progressive decrease in spine BMC was observed that was most rapid during the first 6 weeks. By 15 weeks the mean spine BMC decreased by 17% in the OVX rats (p < 0.007 versus sham operation). OVX did not affect the accuracy of DXA measurements as assessed by comparison with the ash weight at the end of the 15 week study. PTH treatment increased spine BMC by a mean of 32% and increased whole-skeleton BMC by a mean of 19% within 15 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1995

Assessment of spine bone mineral density in ovariectomized rats using DXA.

Measurements of lumbar spine (L1-L6) bone mineral density (BMD) and bone mineral content (BMC) of Wistar rats were obtained by dual energy X-ray absorptiometry (DXA) (QDR-1000W, Hologic Inc., Waltham, MA) to estimate reproducibility and investigate age-related changes. In addition we evaluated the accuracy of the technique in female rats. The coefficients of variation (CV) for spine BMD measurements were found to range from 0.73-1.04 in vivo and from 0.36-1.56 in vitro. The in vitro measurements were performed in a 3 cm deep water bath to stimulate an equivalent tissue thickness. Spine BMC, measured in vivo and in vitro correlated closely with the subsequently determined ash weights (r2 = 0.87 and 0.97, respectively). We examined age-related spine BMD by DXA. A relatively constant increase in spine BMD was observed from 6 weeks to 22 weeks; spine BMD remained stable between 22 and 58 weeks. No peak was observed in spine BMD. To evaluate the effect of estrogen deficiency on animals of different ages, we measured spine BMD weekly in female rats subjected to ovariectomy (OVX) or sham operation at 8 and 23 weeks of age. The spine BMDs in each OVX rat were significantly lower than that of the controls. In the 23-week-old rats, bone loss was quite rapid for the first 3 weeks of observation and stable afterward. The BMD of 8-week-old OVX rats increased with body size. We conclude that DXA allows the observation of age-related changes in the spine BMD of rats with great precision.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1997

DXA longitudinal quality control: a comparison of inbuilt quality assurance, visual inspection, multi-rule Shewhart charts and Cusum analysis.

The performance of dual-energy X-ray absorptiometry (DXA) instruments can be monitored using various quality control (QC) procedures. It has not been established which of these is most appropriate. The aim of this study was to determine which of four QC procedures is the best to use for longitudinal monitoring. Eighteen centres with DXA instruments scanned an aluminium spine phantom weekly for up to 16 months, and the bone mineral density data were used for the QC procedures. The methods investigated were the instrument's inbuilt quality assurance (QA) procedure, visual inspection, multi-rule Shewhart control charts, and Cusum analysis using a truncated-V mask. True and false positive fractions (TPF and FPF) of each method were calculated, including those for a range of action levels for the Shewhart charts and dimensions of the Cusum mask. For Shewhart, the action levels giving the most desirable TPF and FPF were whole multiples of the standard deviation (SD). For Cusum, the most desirable mask dimensions were 3.6 SD for the total height of the vertical section and 0.9 SD per data point for the gradient of the wings. Predictive power of each method as a means of fault detection was decided by the number of faults detected out of a total of 8 non-mechanical faults subsequently diagnosed. The inbuilt QA detected 2, visual inspection 7, Shewhart chart 7 and Cusum analysis 7. The FPFs were: visual inspection 0.09, Shewhart 0.04, Cusum 0.08. At these levels of FPF, the average time in days (range) from onset of a fault to detection was 39 (6-82) for visual inspection, 39 (4-116) for Shewhart and 21 (1-49) for Cusum. All three "phantom" methods are excellent for DXA QC, with modified Cusum analysis being the most effective. The inbuilt QA appears of little use on its own for longitudinal QC.

Absorptiometry, Photon↗