Olivia Louis

Fat fraction of lumbar bone marrow using in vivo proton nuclear magnetic resonance spectroscopy

Localized proton spectra of the human lumbar vertebral body were recorded in vivo at 1.5 T, using the STEAM (stimulated echo acquisition mode) pulse sequence. Thirty-seven patients (18 men, 19 women) were examined, ranging in age from 21 to 68 years (mean = 40, SD = 13). The fat fraction of the bone marrow was calculated from the areas of the fat and water peaks in the spectrum. The results demonstrate that, in the course of aging, there is a systematic increase in measured fat percentage of about 7% per decade of age. No sex difference could be established on the basis of our results.

Bone metabolism and mineralisation after cytotoxic chemotherapy including ifosfamide.

Lumbar spine bone mineral density and bone mineral metabolism were studied in 13 children three months or more after completion of cytotoxic chemotherapy that included ifosfamide given for different malignancies. Blood and urine were analysed for calcium, phosphorus, and magnesium and blood for alkaline phosphatase activity, parathyroid hormone, and 1,25(OH)2 vitamin D3. Bone mineral density (BMD) was measured at the lumbar spine (L1-L4) using a commercial dual x ray absorptiometer. Serum concentrations of calcium, phosphorus, and magnesium and alkaline phosphatase activity, as well as plasma 1,25(OH)2 vitamin D3 concentrations were normal in all children. Slightly raised parathyroid hormone concentrations were seen in two children. An increased urinary excretion of calcium was found in five children. Mean (SD) BMD of the children was -0.88 (1.44). Three children had osteopenia, as defined by a BMD lower than -2 SD for age and sex related standards. No significant relation was found between the BMD and the biochemical parameters. In conclusion, a normal BMD was found in most patients who had received ifosfamide, even in those with persisting hypercalciuria.

Trabecular Bone Mineral Density and Bone Geometry of the Distal Radius at Completion of Pubertal Growth in Childhood Type 1 Diabetes

Aim: To identify disease-related risk factors for an altered bone mineral density (BMD) and geometry at young adulthood in patients with diabetes mellitus type 1 (DM1). Methods: Fifty-six DM1 patients (23 females, 33 males) with prepubertal onset of diabetes were studied after completion of skeletal growth. Bone parameters at the distal radius were investigated by peripheral quantitative computed tomography. Disease-related parameters, in particular average HbA1c during the 2 years around peak height velocity, were analyzed. Forty-seven healthy controls (32 females, 15 males) were studied. Results: Trabecular BMD was similar between DM1 patients and controls. The mean (±SD) cross-sectional bone area (CSA) was smaller in DM1 patients compared to controls (282.5 ± 45.4 vs. 326.7 ± 52.2 mm2, p = 0.002 and males 391.0 ± 61.3 vs. 423.4 ± 81.9 mm2, p = 0.1). In female DM1 patients, the CSA z-score correlated negatively with the body mass index z-score (r = -0.52, p = 0.01) and positively with the height z-score (r = 0.49, p = 0.02). Conclusions: DM1 patients are at risk for smaller bone sizes at the distal radius at the end of pubertal growth, especially females with increased adiposity. Diabetes-specific parameters seem to have a low impact on forearm volumetric apparent mineral density.

Comparative bone status assessment by dual energy X-ray absorptiometry, peripheral quantitative computed tomography and quantitative ultrasound in adolescents and young adults with cystic fibrosis

PURPOSE Quantitative ultrasound bone sonometry (QUS) might be a promising screening method for cystic fibrosis (CF)-related bone disease, given its absence of radiation exposure, portability of the equipment and low cost.The value of axial transmission forearm QUS in detecting osteopenia in CF was therefore studied. METHODS We investigated the application of QUS in the evaluation of bone status in a group of 64 adolescents (>12 years) and young adults (<40 years) with CF in a comparison with a dual X-ray absorptiometry (DXA) of the whole body and peripheral quantitative computed tomography (pQCT) of the radius at 4% and 66% sites. RESULTS Mean (SD) Z-scores of speed of sound (SOS), whole body bone mineral content (BMC), radial trabecular bone mineral density (BMD), and radial cortical BMD were respectively -0.31 (0.78), -0.09 (1.28), 0.10 (1.16) and -0.62 (2.88). The pQCT determined bone geometry values (cortical bone area and cortical thickness) were more depressed than the BMD data. QUS had a sensitivity and specificity of respectively 0% and 96% for diagnosing osteopenia (based on a whole body BMC Z-score<-2). CONCLUSIONS QUS cannot replace DXA, but can screen out patients with normal bone mass. Further and larger studies are needed to examine if QUS may reflect other aspects than bone mass, or if it is possible to improve its sensitivity by supplementing the SOS results with clinical risk factors.

STUDY OF SERUM LEPTIN IN CAFETERIA-DIET-OVERFED RATS : INFLUENCE OF DIET, INSULIN AND CORTICOSTERONE

In a group of 15 male Wistar rats overfed with cafeteria foods (delivering a mean fat percentage of 60%) during 5 months from the age of 8 weeks and in a control group of 15 rats fed with a standard chow for the same period, serum leptin, insulin and corticosterone were measured by RIA and body composition was determined by dual-energy X-ray absorptiometry. Significantly higher fasting serum concentrations of leptin, insulin and corticosterone were found in the cafeteria-diet group. Fasting leptin concentrations were significantly higher in rats with a body fat percentage of more than 25% compared to the others, irrespective of the type of feeding. The log serum leptin correlated positively with body fat percentage and fasting insulin concentration but not with corticosterone concentration. Leptin concentration corrected for body fat mass was, however, comparable between the two diet groups, while the leptin/insulin ratio was lower in the cafeteria-diet group. In conclusion, chronic overfeeding resulting in an increased body fat percentage in rats is associated with hyperleptinemia, hyperinsulinemia and hypercorticism. Serum leptin levels appear to primarily track total body fat percentage and are unaffected by dietary fat manipulation in cafeteria-diet-induced obese rats.

Whole body bone mineral content is similar at discharge from the hospital in premature infants receiving fortified breast milk or preterm formula

Background: Prematurely born infants, especially those with very low birth weight (<1500 g) are at risk for metabolic bone disease. Objectives: The influence of the type of oral feeding regimen and of other potential determinants of whole bone mineral content in prematurely born infants, when they approached full gestation, were evaluated. Previous studies have mainly examined effects at the level of regional bone. Methods: 34 infants (21males and 13 females), all born between 25.4 and 33.7 weeks of gestation, were studied before discharge. Whole body bone mineral content measurements were made just before hospital discharge using a commercial densitometer (Hologic QDR 4500, Hologic Inc, Waltham, MA) at a median age of 40 days (range, 10 to 115 days) after birth. Results: Expressed as a percentage of whole body mass, bone mass ranged between 0.86% and 1.99%, was similar between girls and boys and correlated positively with birth weight SD (r = 0.42; P < 0.05) and body weight SD (r = 0.35; P < 0.05). No difference in bone mass percentage was found between the different types of oral feedings (fortified human milk and preterm formula) or medications studied (corticoids and diuretics). Conclusions: Whereas prenatal and postnatal weight gain determines the degree of bone mineralization of premature infants, it appears that the type of oral feeding does not affect differently the postnatal bone mineralization of premature infants, when assessed at the moment of discharge.

MR phase imaging to quantify bone volume fraction: Computer simulations and in vivo measurements

Magnetic resonance phase images can be used to assess trabecular bone by measuring the standard deviation of the phases in a region of interest. The standard deviation of regional phase measurements reflects the degree of magnetic field inhomogeneity caused by susceptibility differences between bone and marrow. A 3D computer model of trabecular bone was developed and then used to explore the influence of bone volume fraction and imaging parameters such as pixel size and slice width on the standard deviation of regional phase measurements. The results from these tests show that with appropriate selection of these parameters, phase spread strongly reflects variations in trabecular bone density (a correlation of R(2) = 0.98 with bone volume fraction between 0 and 10%). The technique was then applied in vivo on the radius of 25 patients who already had a bone density scan with peripheral quantitative tomography and a correlation between phase standard deviation and trabecular bone density was found (R(2) = 0.46).

Quantitative ultrasound of the calcaneus with parametric imaging : correlation with bone mineral density at different sites and with anthropometric data in menopausal women

OBJECTIVE To prospectively study the relationship of quantitative ultrasound of the calcaneus with anthromopometric variables and with bone mineral density (BMD) assessed at the level of the calcaneus as well as at other sites. METHOD Osteosonography of the non-dominant calcaneus was performed in 135 menopausal women, using a DTU-one device with parametric imaging. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were assessed. BMD of the calcaneus (BMDcal) was measured using dual energy X-ray absorptiometry (DXA), in a subregion matched with the region of interest for osteosonography. BMD of the lumbar trabecular bone was measured using quantitative computed tomography (BMD QCT) while the non-dominant hip was studied using DXA, which provided the total bone mineral density (BMDhip) and that of the Ward triangle (BMDWard). RESULTS The Pearson correlation coefficients between BUA, SOS and the various measurements of BMD ranged from 0.305 (SOS versus BMDhip) to 0.717 (BUA versus BMDcal). BMD QCT and BMDWard were found to depend on age, but not on weight or height, while BUA, SOS, BMDcal, BMDhip were unrelated to age, but correlated with weight (SOS, BMDhip) or with weight and height (BUA, BMDcal). In a multiple stepwise regression analysis, age was a significant predictor for BMD QCT, BMD hip and BMDWard; BMD QCT, BMDWard and BMDhip admitted BUA as sole predictor, while BMDcal was significantly related to both BUA and SOS. CONCLUSION BUA and SOS of the calcaneus, assessed in 135 menopausal women using a parametric imaging device, reflected BMDcal, measured with DXA at a matched region of interest, and did not decline significantly with age.

Whole Body Composition by Hologic QDR 4500/A DXA: System Reliability versus User Accuracy and Precision

Accurate and precise measurement of human tissue composition is both important and imperative in individual health assessment. Although body composition (BC) data acquisition and analysis are both popular and important, selecting an appropriate method or technique for accurate and/or precise assessment of individuals and/or groups remains a challenging task within various sectors of public health. Since 1950s and 1960s, with the pioneer work of Keys & Brozek (1953), Forbes et al. (1956), Siri (1956), Brozek et al. (1963), Behnke (1963), Durnin & Rahaman (1967), BC almost became a scientific discipline profiling itself with the development of many methods, techniques, and equipments. Popular approaches have been criticized over the years because they are subject to measurement errors and/or violation of basic assumptions underlying their use such as hydrodensitometry (Clarys et al., 2010c; Clasey et al., 1999; Elowsson et al., 1998; Heyward, 1996; Johansson et al., 1993; Prior et al., 1997) or anthropometry, e.g., skinfolds (Beddoe, 1998; Clarys et al., 1987, 2005, 2010a; Martin et al., 1985, 1992; Scafoglieri et al., 2010a) and the universally accepted new method of choice, the dual energy X-ray absorptiometry (DXA) (Bolotin, 1998, 2007; Bolotin & Sievanen, 2001; Bolotin et al., 2001; Clarys et al., 2010b; Provyn et al., 2008; Scafoglieri et al., 2010c).

Quantitative Ultrasound of the Calcaneus: An In Vivo Comparison with Dual-Energy X-ray Absorptiometry and Magnetic Resonance Imaging

The current study was performed in a clinical setting and aimed to evaluate the relationship between quantitative ultrasound (QUS) of the calcaneus with bone mineral density (BMD) assessed with dual-energy X-ray absorptiometry (DXA) and with variables derived from magnetic resonance imaging (MRI). Thirty-two postmenopausal women (mean age 61 years) were studied at the level of the nondominant calcaneus. QUS was performed using a DTU-one device including parametric imaging and yielded speed of sound (SOS) and broadband ultrasound attenuation (BUA) data. DXA was performed at a matched region of interest (ROI) in the calcaneus, using a Hologic QDR 4500 device. MRI, also performed at a matched ROI, yielded, using a Siemens Magnetom Vision device, the inverse of the transverse relaxation time (1/T(2)(*)) and the phase standard deviation (PSD). The strongest relationship between QUS and the other variables involved BUA and BMD (r &equals: 0.677, p < 0.001); 1/T(2)(*) showed a trend to correlation with SOS (r = 0.359, p = 0. 044) and with BMD (r = 0.364, p = 0.040), while the relationship between 1/T(2)(*) and BUA, PSD and BUA, PSD and SOS, PSD and BMD remained far from significance. Regression analysis of QUS, DXA, and MRI variables against age showed a trend to significant decline only for 1/T(2)(*) (r = -0.409, p = 0.020). In conclusion, this study shows that BUA of the calcaneus has the best correlation with BMD, and that, at least in a clinical setting, the ability of QUS to give information about bone structure is limited.