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Vicente Gilsanz

Publications and source records attributed to Vicente Gilsanz.

16 recordsLinked to original sources
PubMed2006

Timing of peak bone mass: discrepancies between CT and DXA.

CONTEXT: The time of life in which peak bone mass in the axial skeleton is attained has been the subject of considerable controversy, with estimates ranging from the time of sexual and skeletal maturity to the fifth decade of life. OBJECTIVE: The objective was to examine whether dual energy x-ray absorptiometry (DXA) and computed tomography (CT) values for bone mass and bone density (BD) in the axial skeleton increase after sexual and skeletal maturity. DESIGN/PARTICIPANTS: Measurements of vertebral bone mineral density and bone mineral content (BMC) by DXA and vertebral BD and BMC by CT were obtained in 50 sexually and skeletally mature white females at baseline and 3 yr later. CT BMC values were calculated through analysis of vertebral volume in relation to density (BMC = vertebral volume x BD). RESULTS: Although neither CT BD nor BMC measures changed with time, DXA bone mineral density and BMC values were significantly higher at follow-up (P < 0.0001). Despite strong correlations between DXA and CT bone measures, DXA yielded greater changes in bone values in 47 of 50 subjects. CONCLUSIONS: Bone acquisition in the lumbar spine as measured by CT reaches its peak by sexual and skeletal maturity. In contrast, bone values by DXA continue to increase after puberty and cessation of longitudinal growth. Increases in DXA measures are likely a reflection of inhomogeneous changes in soft tissues around the spine or of disproportionate increases in the posterior elements of the vertebrae rather than of changes within the vertebral body.

Absorptiometry, Photon↗
PubMed2006

Fat mass is not beneficial to bone in adolescents and young adults.

CONTEXT: Although muscle mass is beneficial to bone, studies on the effect of fat mass on bone have yielded conflicting results. OBJECTIVE: The aim of this study was to assess the relations between lean and fat mass and bone structure. DESIGN: This study was cross-sectional. SETTING: The study was conducted in a general community. SUBJECTS: Subjects included 300 healthy sexually mature adolescents and young adults (150 males and 150 females) between the ages of 13 and 21 yr. MAIN OUTCOME MEASURE: We investigated the relation between dual-energy x-ray absorptiometry (DXA) measures of total body fat and lean mass and bone values obtained with DXA (legs and lumbar spine bone mineral density and bone mineral content) and computed tomography (CT) (cross-sectional and cortical bone areas of the femurs and cross-sectional area and cancellous bone density of the vertebrae). RESULTS: Simple and multiple linear regression analyses showed significant positive relations between DXA lean mass and all CT and DXA measures of bone in the axial and appendicular skeletons (all P < 0.005). In contrast, whereas Pearson correlations between DXA measures of fat mass and bone parameters were generally positive, multiple regression analyses showed that fat mass, after accounting for lean mass, trunk height/leg length, had a negative, or no, correlation with CT and DXA values for bone. CONCLUSIONS: Our findings provide compelling evidence that, despite increased mechanical loading and independent of lean mass, adipose tissue is not beneficial to bone structure.

Absorptiometry, Photon↗
PubMed2006

Assessing bone mass in children and adolescents.

Growing awareness that osteoporosis may have its antecedents in childhood has led to increasing interest in assessing bone mass in children and adolescents. Several noninvasive imaging techniques are currently available to measure properties of the growing skeleton, including bone mass, density, cross-sectional area, and microarchitecture. Dual-energy x-ray absorptiometry (DXA) is the most widely used technique, but it has several major limitations associated with its dependence on two-dimensional projections. Quantitative CT and peripheral quantitative CT allow three-dimensional imaging but are more costly and have higher radiation exposure. Quantitative ultrasound is simple and inexpensive but can measure bone "quality" only at a single peripheral site. MRI techniques for measuring bone are still under development and not yet ready for clinical use. For all of these techniques, clinical interpretation of the bone measures obtained remains a significant challenge. Further research is needed to relate these measures to osteoporosis in the elderly and to short-term and long-term fracture risk.

Absorptiometry, Photon↗
PubMed2006

Low-level, high-frequency mechanical signals enhance musculoskeletal development of young women with low BMD.

UNLABELLED: The potential for brief periods of low-magnitude, high-frequency mechanical signals to enhance the musculoskeletal system was evaluated in young women with low BMD. Twelve months of this noninvasive signal, induced as whole body vibration for at least 2 minutes each day, increased bone and muscle mass in the axial skeleton and lower extremities compared with controls. INTRODUCTION: The incidence of osteoporosis, a disease that manifests in the elderly, may be reduced by increasing peak bone mass in the young. Preliminary data indicate that extremely low-level mechanical signals are anabolic to bone tissue, and their ability to enhance bone and muscle mass in young women was investigated in this study. MATERIALS AND METHODS: A 12-month trial was conducted in 48 young women (15-20 years) with low BMD and a history of at least one skeletal fracture. One half of the subjects underwent brief (10 minutes requested), daily, low-level whole body vibration (30 Hz, 0.3g); the remaining women served as controls. Quantitative CT performed at baseline and at the end of study was used to establish changes in muscle and bone mass in the weight-bearing skeleton. RESULTS: Using an intention-to-treat (ITT) analysis, cancellous bone in the lumbar vertebrae and cortical bone in the femoral midshaft of the experimental group increased by 2.1% (p = 0.025) and 3.4% (p < 0.001), respectively, compared with 0.1% (p = 0.74) and 1.1% (p = 0.14), in controls. Increases in cancellous and cortical bone were 2.0% (p = 0.06) and 2.3% (p = 0.04) greater, respectively, in the experimental group compared with controls. Cross-sectional area of paraspinous musculature was 4.9% greater (p = 0.002) in the experimental group versus controls. When a per protocol analysis was considered, gains in both muscle and bone were strongly correlated to a threshold in compliance, where the benefit of the mechanical intervention compared with controls was realized once subjects used the device for at least 2 minute/day (n = 18), as reflected by a 3.9% increase in cancellous bone of the spine (p = 0.007), 2.9% increase in cortical bone of the femur (p = 0.009), and 7.2% increase in musculature of the spine (p = 0.001) compared with controls and low compliers (n = 30). CONCLUSIONS: Short bouts of extremely low-level mechanical signals, several orders of magnitude below that associated with vigorous exercise, increased bone and muscle mass in the weight-bearing skeleton of young adult females with low BMD. Should these musculoskeletal enhancements be preserved through adulthood, this intervention may prove to be a deterrent to osteoporosis in the elderly.

Adolescent↗
PubMed2005

Obesity and fat quantification in lean tissues using three-point Dixon MR imaging.

BACKGROUND: It has been suggested that increased hepatic and intramuscular fat is associated with insulin resistance, and that increased pancreatic fat is related to impaired insulin secretion. OBJECTIVE: We postulated that in obese nondiabetic teenagers insulin levels would be directly related to increases in intramuscular and hepatic fat and inversely related to increases in pancreatic fat. MATERIALS AND METHODS: MRI was used to assess the percentage of fat in the liver, muscle and pancreas in 15 healthy Mexican-American girls, 14-17 years old, with body mass indexes (BMIs) ranging from 17.7 kg/m(2) to 46 kg/m(2). RESULTS: Strong correlations were observed between BMI and fat content in the liver, muscle, and pancreas (r(2)s between 0.50 and 0.89; P<0.003). Serum insulin levels were closely associated with fat measures in the muscle and liver (r(2s)=0.63 and 0.29, and P=0.001 and P=0.023, respectively). In contrast to our hypothesis, fat content in the pancreas was also directly related to insulin secretion (r(2)=0.74; P=0.001). SUMMARY: We conclude that in nondiabetic teenagers, obesity is associated with an increased accumulation of fat in the pancreas without impairment of insulin secretion.

Adipose Tissue↗
PubMed2005

Bone measures in HIV-1 infected children and adolescents: disparity between quantitative computed tomography and dual-energy X-ray absorptiometry measurements.

Investigators have found that dual-energy X-ray absorptiometry (DXA) of areal bone mineral density (BMD) values in HIV-1 infected children and adolescents are reduced. Volumetric bone density (BD) measured by quantitative computed tomography (CT) in this population has not been studied. This study was designed to evaluate bone measurements in HIV-1 infected children and adolescents using DXA and CT. Fifty-eight children and adolescents (32 females and 26 males with a mean age +/- SD of 12.0+/-3.9 years, age range 5.0-19.4 years) with perinatally acquired HIV-1 infection underwent simultaneous bone area and density evaluation by DXA and CT. Height and weight measurements as well as pubertal assessment were performed on the same day. All but four subjects were receiving highly active antiretroviral therapy (HAART). Subjects were matched with healthy children and adolescents for age, gender, and ethnicity. HIV-1 infected children were significantly shorter (P <0.001), lighter (P <0.005), and had delayed puberty (P <0.001) compared to controls. Using DXA, HIV-1 infected subjects had significantly less bone area (P <0.001), bone mineral content (BMC) (P <0.005), and BMD (P <0.05) at the vertebral level compared to controls. In addition, bone area (P <0.001), BMC (P <0.001), and BMD (P <0.005) of the whole body were also reduced relative to controls. In contrast, using CT, HIV-1 infected subjects had similar vertebral BD compared to controls, but smaller vertebral height and cross-sectional area (CSA) (P =0.01 and P <0.005, respectively). DXA Z-scores provided values significantly lower than CT Z-scores in the HIV-1 infected population (P <0.01). After accounting for weight and vertebral height, stepwise multiple regression demonstrated that the prediction of CT BD values of L1 to L3 from DXA values of these vertebrae was significantly improved. HIV-1 infected children and adolescents have lower vertebral and whole body BMC and BMD DXA measures. In contrast, vertebral BD measurements by CT are normal. The lower bone measurements were primarily due to the decreased bone and body size of the HIV-1 subjects.

Absorptiometry, Photon↗
PubMed2005

Bone acquisition in healthy children and adolescents: comparisons of dual-energy x-ray absorptiometry and computed tomography measures.

The effect that growth has on dual-energy x-ray absorptiometry (DXA) bone measurements is yet to be fully defined. The purpose of this study was to determine the best method for optimizing pediatric bone measurements using DXA. Height, weight, body mass index, skeletal age, and Tanner stage of sexual development were determined for 64 healthy boys and 60 healthy girls ages 6-17 yr. DXA of the lumbar vertebrae was performed to measure bone mineral content (BMC, grams) and areal bone mineral density (aBMD, grams per square centimeter), and geometric corrections were used to calculate volumetric bone mineral densities (vBMD): vBMD1 = aBMD/ radical(DXA-area) and vBMD2 = aBMD/bone height. Computed tomography (CT) imaging was performed to measure volumetric bone density (vBD) and vertebral volume (Vol) and to calculate CT-BMC = vBD * Vol. Linear regression was used to compare DXA-BMC vs. CT-BMC and CT vBD vs. DXA aBMD, vBMD1, and vBMD2. Multiple regression including the anthropometric and developmental parameters was also performed. DXA and CT BMC were highly correlated (r2= 0.94). However, DXA aBMD correlated more strongly with CT Vol (r2= 0.68) than with CT density (r2= 0.39), and calculation of DXA volumetric densities only slightly improved the density correlations (r2= 0.49 for vBMD1; r2= 0.55 for BMD2). The correlations for density were particularly poor for subjects in Tanner stages 1-3 (r2= 0.02 for aBMD; r2= 0.13 for vBMD1; r2= 0.27 for vBMD2). In contrast, multiple regression accounting for the anthropometric and developmental parameters greatly improved the agreement between the DXA and CT densities (r2= 0.91). These results suggest that DXA BMC is a more accurate and reliable measure than DXA BMD for assessing bone acquisition, particularly for prepubertal children and those in the early stages of sexual development. Use of DXA BMD would be reasonable if adjustments for body size, pubertal status, and skeletal maturity are made, but these additional assessments add significant complexity to the studies.

Absorptiometry, Photon↗
PubMed2005

Fat quantification using three-point dixon technique: in vitro validation.

RATIONALE AND OBJECTIVES: To test the repeatability, reproducibility and accuracy of the three-point Dixon (3PD) sequence for estimating true fat volume ratios using a fat/water phantom. MATERIALS AND METHODS: A phantom, constructed from test tubes of varying fat content, was imaged using the 3PD sequence on a 1.5T MRI scanner by two operators four times each. Fat volume ratios were calculated from these images and compared with true fat volumes. RESULTS: Measures of fat volume ratios calculated from the 3PD MR images correlated strongly with values for true fat volumes (r = 0.96). CONCLUSION: The 3PD technique was found to be highly reproducible and accurate, and may be useful for in vivo quantification of fat in lean tissues, such as the liver, pancreas or skeletal muscle.

Adipose Tissue↗
PubMed2005

Bone densitometry in pediatric populations: discrepancies in the diagnosis of osteoporosis by DXA and CT.

OBJECTIVES: To test the hypothesis that because of errors associated with growth and development, osteoporosis is frequently overdiagnosed in children when using dual-energy x-ray absorptiometry (DXA). This study compared bone density values obtained by DXA with those from computed tomography (CT), which is not influenced by body or skeletal size. STUDY DESIGN: Vertebral bone density was measured by using both DXA and CT in 400 children (100 each, healthy and sick boys and girls). Regression analysis was used to compare DXA and CT Z scores, and the agreement between DXA and CT classifications of Z scores below -2.0 was examined. RESULTS: DXA and CT Z scores were moderately related (r2 = 0.55 after accounting for age and anthropometric measures). DXA Z scores predicted CT Z scores below -2.0 with reasonable sensitivity (72%), specificity (85%), and negative predictive value (98%), but positive predictive value was low (24%). Many more subjects were classified as having bone density lower by DXA (76/400) than by CT (25/400), particularly subjects below the 5 th percentile of height and/or weight for age. CONCLUSIONS: The inability of DXA to account for the large variability in skeletal size and body composition in growing children greatly diminishes the accuracy of this projection technique for assessing bone acquisition and diagnosing osteoporosis in pediatric populations.

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↗
PubMed2004

Aortic calcification and the risk of osteoporosis and fractures.

We investigated the relation between computed tomography measures of aortic calcification and values for bone density and the number of fragility fractures in 2348 healthy, postmenopausal women. To determine whether increases in vascular calcification and bone loss progress in parallel, baseline values were compared with measurements obtained 9 months to 8 yr later in a subgroup of 228 women. Of the 2348 subjects studied, 70% had osteoporosis, 30% had at least one vertebral fracture, and 9% had at least one hip fracture. Aortic calcifications were inversely related to bone density and directly related to fractures. After adjusting for age and potential confounders, measures for aortic calcification predicted 26.1% of the variance in bone density (P < 0.001). Compared with women without calcification, the odds ratios for vertebral and hip fractures in those with calcification were estimated to be 4.8 (95% confidence interval, 3.6-6.5) and 2.9 (95% confidence interval, 1.8-4.8), respectively. The subgroup analysis of 228 women longitudinally studied showed that the percentage of yearly increase in aortic calcification accounted for 47% of the variance in the percentage rate of bone loss (P < 0.001). Moreover, a strong graded association was observed between the progression of vascular calcification and bone loss for each quartile. Women in the highest quartile for gains in aortic calcification had four times greater yearly bone loss (5.3 vs.1.3% yearly; P < 0.001) than women of similar age in the lowest quartile. Smaller, but highly significant differences were also found between all other quartiles. We conclude that aortic calcifications are a strong predictor for low bone density and fragility fractures.

Aged↗
PubMed2004

Quantitative computed tomography measurements of bone mineral density in prepubertal children with congenital hypothyroidism treated with L-thyroxine.

Low bone density (BD) has been reported in patients with hyperthyroidism. Whether or not levothyroxine (LT4) therapy in children with congenital hypothyroidism (CH) affects BD is unclear. Medical records of 45 patients with various etiologies of CH who had at least one BD measurement (32 female, mean age 7.6 +/- 2.6 years) were reviewed. The mean LT4 dose was 3.6 +/- 0.88 microg/kg/day. Cancellous bone density (CaBD) was measured by quantitative computed tomography (CT) in all 45 patients and 20 had measurements of cortical bone density (CoBD), cross-sectional area (CSA) and cortical bone area (CBA) of the femur. TSH levels were considered partially or completely suppressed when values were <1.0 or <0.5 microIU/ml, respectively. The control group consisted of age- and gender-matched healthy children. No significant differences were found in CaBD, CoBD, CSA, or CBA between patients with CH and controls. There were no significant differences between initial and subsequent BD measurements. No correlations were found between CaBD and etiology of CH, dose or duration of LT4 therapy, or serum TSH. In pre-pubertal children with CH, LT4 appears to have no significant effect on BD. Moreover, absence or hypoplasia of the thyroid parenchyma appears to have no significant impact on bone formation within the first 10 years of life.

Bone Density↗
PubMed2003

Establishment of peak bone mass.

Among the main areas of progress in osteoporosis research during the last decade or so are the general recognition that this condition, which is the cause of so much pain in the elderly population, has its antecedents in childhood and the identification of the structural basis accounting for much of the differences in bone strength among humans. Nevertheless, current understanding of the bone mineral accrual process is far from complete. The search for genes that regulate bone mass acquisition is ongoing, and current results are not sufficient to identify subjects at risk. However, there is solid evidence that BMD measurements can be helpful for the selection of subjects that presumably would benefit from preventive interventions. The questions regarding the type of preventive interventions, their magnitude, and duration remain unanswered. Carefully designed controlled trials are needed. Nevertheless, previous experience indicates that weight-bearing activity and possibly calcium supplements are beneficial if they are begun during childhood and preferably before the onset of puberty. Modification of unhealthy lifestyles and increments in exercise or calcium assumption are logical interventions that should be implemented to improve bone mass gains in all children and adolescents who are at risk of failing to achieve an optimal peak bone mass.

Adolescent↗
PubMed2002

Bone, muscle, and fat: sex-related differences in prepubertal children.

PURPOSE: To determine whether there are sex-related differences in vertebral cross-sectional dimensions, in paraspinous muscle area, and in the amount of fat in the subcutaneous and visceral compartments of prepubertal boys and girls. MATERIALS AND METHODS: Subcutaneous fat, visceral fat, paraspinous musculature, and vertebral cross-sectional dimensions were studied in 31 pairs of prepubertal healthy white girls and boys 5-10 years of age, rigorously matched for age, height, and weight. Data were analyzed with the Student t test and multiple regression analysis. RESULTS: Sex had a differential effect on fat accumulation and musculoskeletal development. Compared with boys, girls had, on average, 28% greater total fat and 30% higher subcutaneous fat (P <.001 for both), but 10% less paraspinous musculature (P =.002) and 15% smaller vertebral cross-sectional dimensions (P <.001). In contrast, the sexes were monomorphic for visceral fat (P =.24). Stepwise regression analysis indicated that only 22% of the difference in vertebral cross-sectional area could be explained by sex-related differences in paraspinous musculature. CONCLUSION: Together, these data indicate that sex is an important determinant of the morphology in humans well before the beginning of puberty.

Adipose Tissue↗