Dual Photon Absorptiometry Research Articles

Artificial neural network analysis of bone quality DXA parameters response to teriparatide in fractured osteoporotic patients.

Teriparatide is a bone-forming therapy for osteoporosis that increases bone quantity and texture, with uncertain action on bone geometry. No data are available regarding its influence on bone strain. To investigate teriparatide action on parameters of bone quantity and quality and on Bone Strain Index (BSI), also derived from DXA lumbar scan, based on the mathematical model finite element method. Forty osteoporotic patients with fractures were studied before and after two years of daily subcutaneous 20 mcg of teriparatide with dual X-ray photon absorptiometry to assess bone mineral density (BMD), hip structural analysis (HSA), trabecular bone score (TBS), BSI. Spine deformity index (SDI) was calculated from spine X-ray. Shapiro-Wilks, Wilcoxon and Student's t test were used for classical statistical analysis. Auto Contractive Map was used for Artificial Neural Network Analysis (ANNs). In the entire population, the ameliorations after therapy regarded BSI (-13.9%), TBS (5.08%), BMD (8.36%). HSA parameters of femoral shaft showed a worsening. Dividing patients into responders (BMD increase >10%) and non-responders, the first presented TBS and BSI ameliorations (11.87% and -25.46%, respectively). Non-responders presented an amelioration of BSI only, but less than in the other subgroup (-6.57%). ANNs maps reflect the mentioned bone quality improvements. Teriparatide appears to ameliorate not only BMD and TBS, but also BSI, suggesting an increase of bone strength that may explain the known reduction in fracture risk, not simply justified by BMD increase. BSI appears to be a sensitive index of TPD effect. ANNs appears to be a valid tool to investigate complex clinical systems.

Assessment of BMD and Statistical Analysis for Osteoporosis Detection

Biomedical engineering is one of the promising disciplines in engineering that deals with technology advancement in human health. Osteoporosis is a common metabolic disease categorized by decreased bone mass and increased liability to fractures. Bone densitometry is a broad term comprising the art and science of measuring the bone mineral content (BMC) and bone mineral density (BMD) of particular skeletal sites or the whole body. There are various methods to measure bone mineral density which differs based on the differential absorption of ionizing radiation or the sound waves. The methods are SPA (Single Photon Absorptiometry), DPA (Dual Photon Absorptiometry), SEXA (Single Energy X ray Absorptiometry), DEXA (Dual Energy X ray Absorptiometry), QCT (Quantitative Computed Tomography), QUS (Quantitative Ultra Sound) and RA (Radiographic absorptiometry). The DEXA test can measure the whole body but usually the lower spine and hips. A major disadvantage of DEXA is that currently there is a lack of standardization in bone and soft tissue measurements. Furthermore, for a given manufacturer, results may vary by the model of the instrument, the mode of operation or the version of the software used to analyze the data. In addition to that, DEXA scan images are only for the confirmation of correct positioning of the patient and correct placement of the regions of interest (ROI). Motivated by the above issues, this paper can pave a way for analysis in the measurement of BMD, measurement of T-score, and Z-score from the DEXA scan images. This proposed methodology includes segmentation algorithms such as k means clustering & mean –shift algorithm and comparison of the accuracy of algorithms. Also in addition, a novel mathematical analysis is also proposed to measure the T–score values in DEXA images with a new parameter ‘S’ from BMD values in order to detect the osteoporosis condition accurately.

Association Between Hormone Therapy and Muscle Mass in Postmenopausal Women

Hormone therapy (HT) has been suggested for protection against age-related muscle weakness in women. However, the potential for HT-associated health risks necessitates a better understanding of the direction and magnitude of the association between HT and health outcomes, such as lean body mass (LBM). To determine whether HT was associated with reduced LBM loss compared with not receiving HT among postmenopausal women aged 50 years and older. MEDLINE, Embase, AgeLine, CINAHL, and SportDiscus (searched from inception until April 25, 2018). For this systematic review and meta-analysis, randomized clinical trials including postmenopausal women undergoing HT and control groups of women not receiving HT were selected by 2 reviewers. Studies were included if LBM or fat-free mass were measured as an outcome. Studies with participants from hospitals, long-term care facilities, or with specific diseases were excluded. Information regarding study characteristics and outcome measures were extracted by 1 reviewer and verified by another. Risk of bias was evaluated. Quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used to abstract data and assess data quality/validity. Data were pooled using a fixed-effects model. The primary study outcome was the overall absolute change in LBM (measured in kilograms), captured by dual-energy x-ray absorptiometry, dual-photon absorptiometry, or bioelectrical impedance analysis imaging. Of 8961 studies that met selection criteria, 12 were included, with a total of 4474 recruited participants. Of the participants, mean (SD) age was 59.0 (6.1) years. Data on ethnicity were collected by 2 of the studies. Of the 22 HT intervention arms, 15 used estrogen-progesterone combination HT and 7 used estrogen-only HT. Control participants were women who received no HT at all or who received placebo. The median follow-up duration was 2 years (range, 6 months to 6 years). Seven treatment arms showed a loss of LBM, and 14 were protective. Overall, HT users lost 0.06 kg (95% CI, -0.05 to 0.18) less LBM compared with control participants, but the difference was not statistically significant (P = .26). The results were unchanged when stratified based on treatment type and dosage, duration of follow-up, time since menopause, study quality, and type of LBM measurement, with HT users losing between 0.06 kg more to 0.20 kg less LBM compared with control participants for all strata. The quality of evidence based on GRADE was low. This systematic review and meta-analysis did not show a significant beneficial or detrimental association of HT with muscle mass. Although muscle retention in aging women is of crucial importance, these findings suggest that interventions other than HT should be explored.

Bone strain index reproducibility and soft tissue thickness influence: a dual x-ray photon absorptiometry phantom study

BackgroundBone strain index (BSI) is a tool measuring bone strain, derived from dual x-ray photon absorptiometry. It is able to characterise an aspect of bone quality that, joined to the quantity and quality parameters of bone mineral density (BMD) and trabecular bone score (TBS), permits an accurate definition of fracture risk. As no data are available about BSI precision, our aim was to assess its in vitro reproducibility.MethodsA Hologic spine phantom was used to perform BSI scans with three different scan modes: fast array (FA), array (A), and high definition (HD). Different soft tissue thicknesses (1, 3, 6 cm) of fresh pork rind layers as a surrogate of abdominal fat were interposed. For each scan mode, the phantom was consecutively scanned 25 times without repositioning.ResultsIn all scan modes (FA, A, HD) and at every fat thickness, BSI reproducibility was lower than that of BMD. The highest reproducibility was found using HD-mode with 1 cm of pork rind and the lowest one using HD-mode with 6 cm of pork rind. Increasing fat thickness, BSI reproducibility tended to decrease. BSI least significant change appeared to be about three times that of BMD in all modalities and fat thicknesses. Without pork rind superimposition and with 1-cm fat layer, BSI reproducibility was highest with HD-mode; with 3 or 6 cm fat thickness, it was higher with A-mode.ConclusionsBSI reproducibility was worse than that of BMD, but it is less sensitive to fat thickness increase, similarly to TBS.

Assessment of Bone Quality in Osteoporosis Treatment with Bone Anabolic Agents: Really Something New?

Osteoporosis is a chronic pathologic condition, particularly of the elderly, in which a reduction of bone mineral density (BMD) weakens bone, leading to the so-called fragility fractures, most often of spine and femur. The gold standard exam for the quantitative measurement of BMD is the dual X-ray photon absorptiometry (DXA), a radiological method. However, a relevant number of fragility fractures occurs in the range of normal BMD values, meaning that also qualitative aspects of bone play a role, namely bone architecture and bone geometry. Bone structure is investigated by microCT and histomorphometry, which necessitate an invasive approach with a biopsy, usually taken at the iliac crest, not the typical site of fragility fractures. New tools, trabecular bone score (TBS) and hip structural analysis (HSA), obtained during DXA, can supply informations about bone structure of spine and femur, respectively, in a not invasive way. Therapy of osteoporosis is based on two types of drugs leading to an increase of BMD: antiresorptive and anabolic treatments. The antiresorptive drugs inhibit the osteoclasts, whereas teriparatide and, in part, strontium ranelate ameliorate bone structure. The present review deals with the relation between the anabolic drugs for osteoporosis and the cited new tools which investigate bone architecture and geometry, in order to clarify if they represent a real advantage in monitoring efficacy of osteoporosis' treatment. Data from the studies show that increases of TBS and HSA values after anabolic therapy are small and very close to their least significant change at the end of the usual period of treatment. Therefore, it is questionable if TBS and HSA are really helpful in monitoring bone quality and in defining reduction of individual fragility fracture risk during osteoporosis treatment with bone anabolic agents.

30 years of DXA technology innovations

As the successor of Dual Photon Absorptiometry (DPA), Dual X-ray Absorptiometry (DXA) has seen 30years of continuous technological innovations. Implementation of measures for standardization and quality assurance made DXA a reliable and clinically useful approach. Its use in clinical multicenter drug studies in osteoporosis lead to general acceptance as the standard technique of bone densitometry. The limitations of DXA are well established. As a measure of areal bone mineral density (aBMD) it depends on bone size and is biased by overlaying soft tissue and calcified structures. To some extent these errors can be reduced by estimation of bone depth and/or lateral imaging. DXA based aBMD can be supplemented by additional information obtainable from DXA scans: geometric indices such as hip axis length or complex models like 2-D finite element analysis have been developed and tested. Given the drastic improvement in image quality current DXA scans can be used for Vertebral Fracture Analysis (VFA) or grading of Abdominal Aortic Calcifications. A textural measure, Trabecular Bone Score (TBS) provides independent information on fracture risk. DXA devices can also be used for assessments beyond bone density. Periprosthetic aBMD changes can be monitored to study the mechanical fitting of bone implants. Total body composition measurements are increasingly being used in studies on nutrition, obesity, and sarcopenia.30years after its inception DXA is the undisputed standard imaging technique for the assessment of osteoporotic fracture risk with new applications beyond bone densitometry adding to its value.

Association between low bone mineral density and fibromyalgia: a meta-analysis.

We aimed to evaluate the relationship between bone mineral density (BMD) and fibromyalgia (FM). Meta-analyses were performed comparing BMD in FM patients and healthy controls, and in FM patients in subgroups based on ethnicity, BMD site, age, sex, and measurement method. Twelve studies including 695 FM patients and 784 controls were selected. Meta-analysis by ethnicity revealed a significantly lower BMD in the FM group in Caucasian populations [standardized mean difference (SMD)=-0.144, 95% CI=-0.271-(-0.017), p=0.026], but not in Turkish populations. Subgroup analysis by BMD site showed that BMD was significantly lower in the FM group than in the control group in the lumbar spine [SMD=-0.588 (medium), 95% CI=-1.142-(-0.033), p=0.038], but not in the femur neck and hip. Stratification by measurement method revealed a significantly lower BMD in the FM group by dual X-ray absorptiometry and dual-photon absorptiometry [SMD=-0.531 (medium), 95% CI=-1.040-(-0.023), p=0.041; SMD=-0.315 (small), 95% CI=-0.544-(-0.085), p=0.007, respectively], but not by quantitative ultrasound, but not by quantitative ultrasound. Subgroup analysis by sex, menopause status, and age revealed a significantly lower BMD in the female FM group [SMD=-0.588 (medium), 95% CI=-1.142-(-0.033), p=0.038], but not in the pre-menopausal group and the group greater than mean age 50years old. Our meta-analysis demonstrated that BMD was significantly lower in FM patients in Caucasian and female populations.

The Effect of Surrounding Fat on Measurment of Bone Mineral Density (BMD) by Dual Energy Photon Absorptiometry (DXA) a High Resolution Peripheral Quatitative Computerized Tomography (HR-pQCT)

The Effect of Surrounding Fat on Measurment of Bone Mineral Density (BMD) by Dual Energy Photon Absorptiometry (DXA) a High Resolution Peripheral Quatitative Computerized Tomography (HR-pQCT)

PP14.7 – 2997: Screening osteoporosis in patients with antiepileptic drug using urine N-telopeptide of collagen type I

Objective Antiepileptic drug (AED) can affect bone metabolism. But pediatric neurologists ignore the fact because of shorter use of AED in children than in adults. We tried to find out results of reduced bone mineral density (BMD) after use of AED and appropriate screening methods for osteoporosis. Methods This retrospective study was conducted in total 63 patients with epilepsy who visit the Department of Pediatrics of Catholic University Bucheon Saint Mary's Hospital from January 2013 to December 2014. We measure BMD by dual photon absorptiometry and check urine N-telopeptide of collagen type I (NTx) level for bone turnover marker. Results In whole study population, 37 urine NTx level elevated higher than normal range. Among positive urine NTx group, 17 patients had results of reduced BMD after use of AED. Patients with valproic acid (VPA) were 18, oxcarbazepine (OCZ) 28, levetiracetam (LEV) 26, topiramate (TPM) 9 and lamotrigine (LTG) 8. Due to preceding number including multidrug therapy cases, patients with single VPA were 9, single OCZ 19, single LEV 8, single TPM 0 and single LTG 0. Positive urine NTx number of VPA, OCZ, LEV, TPM and LTG group was 9, 21 (P=0.02), 12, 5 and 4 respectively. Positive urine NTx number single VPA, single OCZ and single LEV group was 4, 16 (P=0.01) and 3 respectively. Conclusion Some patient had reduced BMD after use of AED. The incidence of positive urine NTx was significantly different between the patients with OCZ and those with other AEDs in both monotherapy and multitherapy. We suggest using urine NTx for bone turnover marker in pediatric patients with AED.

Thalassemic osteopathy: A new marker of bone deposition

Osteopathy represents a prominent cause of morbidity in patients with beta-thalassemia major (TM) and manifests as osteopenia/osteoporosis. Biochemical turnover markers (BTMs) are considered a useful, non-invasive tool for the clinical follow-up of osteoporotic patients; they can provide a dynamic view of the remodeling process and give information on the metabolic activity of bone tissue as well as on the pathogenesis of bone loss. The amino-terminal pro-peptide of type I procollagen (P1NP) is a recently introduced marker that is considered the most sensitive index of bone formation. Although demonstrated in several categories of patients with bone disease, there is little information on the clinical usefulness of this bone formation index in thalassemic patients. We evaluated the P1NP levels of 53 adult patients with b-thalassemia major (21 males and 32 females, mean age 34.5 ± 5.7, range 22-46 years) and associated osteopathy. We investigated the correlation between P1NP and bone condition as examined by dual X-ray photon absorptiometry and with BTMs expressing bone resorption and bone mineralization (carboxyterminal collagen cross-linked (CTX) terminal regions of type I collagen and osteocalcin, respectively). P1NP serum levels were correlated with CTX levels (r=0.545, p<0.001); the results were unchanged when males and females, as well as osteoporotic and osteopenic subgroups, were considered separately. No correlation was demonstrated neither between OC and CTX (r=0.17, p=ns), nor between P1NP and OC levels (r=0.11, p=ns). No correlation was demonstrated among the P1NP/CTX ratio and age, OC or densitometric values and no difference was found in the same ratio between osteopenic (0.19 ± 0.16) and osteoporotic (0.15 ± 0.14) patients. Similar results were obtained for the OC/CTX ratio, as it was not correlated with age, P1NP or densitometric values. This is the first report of circulating P1NP in patients with TM-associated osteoporosis. P1NP and CTX assays show good precision and low analytical CV, and, compared to other markers, they can acceptably reflect bone metabolic processes and promptly respond to antiosteoporotic treatments. We trust that this sensitive marker can be useful in the assessment of treatment efficacy and can overcome the pitfalls due to wide variability in the normal values of most BTMs that create difficulty in pinpointing the individual patient's response.

Frailty and osteoporosis in older women—a prospective study

Despite sharing common risk factors and biological pathways, the relationship between frailty and osteoporosis (OP) is not clear. This prospective study has shown that frailty defined by the Vulnerable Elders Survey can predict a decrease in bone mineral density after 1 year. Thus, frail older women should be assessed for osteoporosis. Frailty and OP share common risk factors such as age, sarcopenia, lack of physical activity, low body weight, and smoking. Despite shared risk factors and biological pathways, the relationship between frailty and OP is not clear. The purpose of our prospective study was to examine this relationship in a community sample of older women. A sample of 235 community-dwelling women was assessed for demographic, medical, frailty and OP status at baseline, and after at least 1 year. Frailty was assessed using the Cardiovascular Health study (CHS) frailty phenotype and using the Vulnerable Elders Survey (VES-13). OP was measured using dual photon absorptiometry bone mineral density (BMD). Descriptive statistics and regression models were used. At baseline, 235 women with a mean age of 77.6 (SD = 5.4), body mass index (BMI) of 28.3 (SD = 5.2) kg/m(2), and BMD of 0.7 (SD = 0.2) g/cm(2)were assessed. No correlation was found between BMD and the CHS (BMD spine, r = 0.009, p = 0.889; BMD hips, r = 0.050, p = 0.473) or the VES-13 (BMD spine, r = 0.034, p = 0.605; BMD hips, r = -0.042, p = 0.537) frailty scales. One hundred fifty-two (63.9 %) women were assessed after 1 year. In a regression model, women who were frail at baseline (VES-13) were found to have a statistically significantly lower hip and spine BMD at follow-up (controlling for BMI) than women who were non-frail at baseline (p = 0.0393, hip; p = 0.0069, spine). Frailty status as defined by the VES-13 predicts a decrease in BMD after 1 year.

Better tools for assessing osteoporosis

Some 30 years ago, we applied the newly described method of dual photon absorptiometry (DPA) to demonstrate that osteoporotic women with vertebral fractures had lost substantially more bone from the vertebrae than controls. This opened a whole new field of research into the determinants of bone loss and fractures in the axial skeleton and set the stage for subsequent development of dual-energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT), which are now the standard methods for assessing osteoporosis severity and treatment efficacy.

Vertebral fracture prevalence in a referral population of 750 Canadian men and women

To establish the prevalence of vertebral fracture (VF) in a representative sample of 750 Canadians and to examine the relationships between VF prevalence and bone mineral density (BMD) at the spine and proximal femur. X-ray-based dual-photon absorptiometry (DXA) was used to perform measurements of lumbar spine BMD, proximal femur BMD, and VF assessment (VFA). Two hundred and fifty-nine VFs were identified in 156 patients and the prevalence of unknown or unsuspected VF was 18.7%. For premenopausal women and for men, there was no difference in BMD at either the spine or the hip whether or not there was at least one VF. For postmenopausal women, BMD of the total region of the proximal femur was statistically lower (p < 0.001) in women with at least one VF whereas spine BMD only tended to be less (0.10 > p > 0.05). Proximal femur BMD was lower for postmenopausal women with more VF, while spine BMD was virtually unchanged as the number of VF increased. Neither spine nor hip BMD was lower for men with more VF. A strong association was observed in postmenopausal women between an age-dependent increase in VF prevalence and a reduction in femoral BMD. Such an association was not present in men. VFs are common, are often independent of either spine or hip BMD, and frequently go unnoticed. Therefore, VFA should be part of a routine assessment of fracture risk.

Age‐ and gender‐dependent values of skeletal muscle mass in healthy children and adolescents

BackgroundSkeletal muscle mass (SMM) can be extracted from whole-body scans obtained by X-ray-based dual-photon absorptiometry (DXA). There is a need to establish expected age-dependent values for children and adolescents.MethodsAppendicular lean tissue mass (ALM) was extracted from whole-body DXA scans in 140 healthy children and adolescents (68 females and 72 males). Whole-body SMM was calculated from ALM using equations developed by Kim et al. (Am J Clin Nutr 84:1014–1020, 2006). Age-dependent patterns of increase in SMM were derived by fitting SMM values to equations that consisted of the sum of two logistic expressions, one accounting for SMM changes during growth and the other for SMM changes during puberty. Normal ranges were defined so that 95% of the SMM values were included. The reproducibility of SMM measurements was obtained from whole-body DXA scans repeated on three occasions in each of a separate group of 32 normal children with repositioning between scans.ResultsNormal ranges are presented as equations describing the age-dependent pattern of increase in SMM as well as population standard deviations that increased steadily with age. For 15 children below age 10, SMM reproducibility (95% CI) was 149 g (119–199 g) while for 17 children and adolescents over age 10, reproducibility was 170 g (138–223 g).ConclusionDXA-based measurements of SMM in children and adolescents are reproducible and can be expressed in terms of age-dependent Z scores.

Identification par l’analyse des facteurs cliniques de risque et la densitométrie osseuse des hommes à risque d’ostéoporose

Male osteoporosis is often secondary to other conditions. However the causes of osteoporosis in men are dramatically variable according to the authors. The aim of this observational multicenter study was to assess the main risk factors and causes for male patients with low bone mineral density (LBM). The study was performed in a cohort of rheumatologists who usually prescribe bone mineral density assessment according to HAS criteria (one or more criteria) for bone mineral density (BMD) measurement as defined by: (a): vertebral fracture; (b): non traumatic non vertebral fracture; (c): corticosteroid therapy; (d): hypogonadism or GnRH agonist therapy; (e): endocrine disorders; (f): osteogenesis imperfecta (OI). BMD was measured by dual photon absorptiometry (DXA) at lumbar spine, femoral or total neck sites. Osteoporosis was defined as a T-score value less or equal to 2.5 at one of those region of interest (ROI); LBM as a T-score value between -1 and -2.5. A total of 431 rheumatologists included 1198 male patients (66.6 ± 12.2 years). According to DXA results, 888 patients (74.1 %) had osteoporosis and 231 (19.3 %) had osteopenia. BMD was considered as normal for 79 patients (6.6 %). A total of 1146 patients (95.7 %) satisfied to the criteria of reimbursement of DXA measurement. Six hundred and eighty-six patients (57.3 %) had suffered from vertebral fractures and 349 patients (29.2 %) from non vertebral fractures. Corticosteroids had been prescribed in 28.7 % of patients and 6.6 % were treated with GnRH agonists for prostate cancer. Hypogonadism was diagnosed in 27 %. Five patients suffered from OI. Other risk factors were detected: alcoholism and smoking in 28.1 % and 42.9 % respectively; rheumatoid arthritis or spondylarthropathy in 12.5 % of patients; chronic pulmonary disorders in 16.1 %. By contrast endocrinopathies were rare (2.5 %). Several risk factors were more frequently encountered for patients with osteoporosis as compared with osteopenia, i.e., smoking, alcohol abuse, low calcium intake, vitamin D insufficiency and maternal history of hip fracture. A diagnosis of osteoporosis (BMD ≤ 2.5) was established by rheumatologists in 74.1 % of patients with clinical risk factors: LBM was found in 93.4 %. In 95.7 % the criteria for reimbursement of DXA measurement were satisfied. DXA is useful in male patients with classical risk factors of osteoporosis to confirm the diagnosis of the disease and start a treatment.

Effect of Strength Training and the Practice of Alpine Skiing on Bone Mass Density, Growth, Body Composition, and the Strength and Power of the Legs of Adolescent Skiers

This work examines the influence of practicing strength training and Alpine skiing over 2 years on bone mineral density (BMD), growth, body composition, and the strength and power of the legs of adolescent skiers. The study subjects were 20 adolescent skiers (10 girls and 10 boys) and 19 sedentary adolescents (9 girls and 10 boys), all 13-16 years of age. The BMDs of the lumbar column (L2-L4) and hip (neck of the femur, trochanter, and Ward's triangle) were determined by dual x-ray photon absorptiometry at the beginning and end of the experimental period. The increase in height and the percentage fat and muscular masses of the subjects were also recorded, as was their ability to jump (countermovement jump [CMJ]), their leg strength and power (squat test), and their leg anaerobic power (continuous jump test [CMJ15″]). No significant differences were seen in the increase in height, body weight, or percentage fat mass between the skiers and sedentary subjects, although the boy skiers showed a significant increase in percentage muscular mass (p < 0.05) compared to the sedentary boys. The improvement in the values of the different CMJ variables was significantly greater among the boy skiers than among the sedentary boys (p < 0.001-0.01). The same was true for the girls (p < 0.001), except for CMJ15″. The skiers experienced a significantly greater increase in L2-L4 BMD than the sedentary subjects (boys p < 0.05; girls p < 0.01). These results suggest that Alpine skiing combined with rational strength training involves no special risk for the physical development of young people, has a positive effect on the power and the percentage of muscle mass in the legs, and helps to have a higher bone density in the lumbar spine (L2-L4).

Dual-Energy X-Ray Absorptiometry Analysis for the Determination of Moisture Content in Biomass

The aim of the present study was to describe and validate a novel method able to fast, accurately and with a high precision determine the moisture content of biological materials ranging 10% to 70%. A calibrated Dual X-ray photon absorptiometry technique is validated against moisture content in wood chips. Conventional criteria such as the Pearson correlation coefficient, the root mean square errors of calibration and coefficient of variation were used for the evaluation of the method. The method is independent of the thickness and density of the object but dependent of the effective atomic number of the material. The results shows that this photon absorptiometric method gives accurate (<2%) and precise (<1%) results for moisture content determination in wood chips.

Methods for quantitative measurement of bone mineral densityand their performance comparison

Along with the population aging,osteoporosis has been a focused issue of concern of public health around the world.Up to date,the best method for osteoporosis diagnosis is the quantitative measurement of bone mineral density (BMD),which has been paid much attention to in clinic.In this paper,manifold methods applied in clinic for quantitative BMD measurement,including X-ray radiography,density measurement of Xphotograph,single photon absorptiometry or single-energy X-ray absorptiometry,dual photon absorptiometry or dual-energy X-ray absorptiometry,quantitative computed tomography or quantitative ultrasound or quantitative magnetic resonance imaging (MRI),are reviewed by principles and compared by their features. Key words: Osteoporosis; Bone mass; Bone density; Bone mineral density; Bone quality; Quantitative measurement

Bone mineral density and calcium regulating hormones in patients with inflammatory bowel disease (Crohn's disease and ulcerative colitis).

Inflammatory bowel disease (Crohn's disease and ulcerative colitis) is associated with decreased bone mineral density and increased risk of osteoporosis. However, the pathogenesis of this bone loss is not yet fully understood. In the present study we measured lumbar bone mineral density (by dual photon absorptiometry), serum levels of parathyroid hormone (PTH) and vitamin D metabolites, and serum markers of bone turnover (alkaline phosphatase and osteocalcin) in 15 patients with Crohn's disease and in 4 patients with ulcerative colitis. The median duration of the disease was 4 years and the median lifetime steroid dose was 10g of prednisone. We compared our results to a control group of 19 normal persons, who were matched for age and sex to the patients. We found that lumbar bone density was reduced by 11% in patients compared with control persons (Z-score -0.6 +/- 0.6 versus -0.1 +/- 0.8; p < 0.05). In patients, the serum levels of PTH, 25-hydroxyvitamin D3, and calcitriol (1,25(OH)2D3) were significantly reduced compared with control persons. Serum alkaline phosphatase activity (AP) was significantly higher in the patients and was inversely related to lumbar bone density. Osteocalcin values were not different between patients and control persons. There was also no difference in serum levels of calcium between the two groups, whereas phosphorus levels were higher in patients. We conclude that malabsorption of calcium was not a primary cause of bone loss in our patients, because we did not find secondary hyperparathyroidism. Accordingly, we did not find a severe vitamin D deficiency, since 25-hydroxyvitamin D3 levels were within the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Composition in Humans: Advances in the Development of Multicompartment Chemical Models

Until recently it was practical to divide body weight into only two or three chemical compartments in living subjects due to an inability to quantify directly total body mineral, protein, and fat in vivo. The six-compartment chemical model is now the cornerstone of research in human body composition. Advanced technologies, including neutron activation analysis systems and dual photon absorptiometry, now enable investigators to extend body composition estimates and to construct near-complete chemical models in vivo. These new or refined approaches will advance our knowledge of human body composition and will also improve our accuracy in calibrating simpler epidemiologic and bedside body-composition techniques.