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PubMed1978

Photon absorptiometry of soft tissue and fluid content: the method and its precision and accuracy.

Dichromatic absorptiometry (DA) is a new, non-invasive method for determining soft tissue (STC) and fluid content (FC), and their changes. The technique uses linear transmission scans made across the limbs with a congruent 125I and 241Am dual-photon source and a NaI(TI)--PMT detector. Patient measurements could be made at the bedside with the mobile system. Factors affecting the precision and accuracy were evaluated theoretically and experimentally. Repositioning and subject motion were the greatest sources of variation and limited the precision to 2--3% in normals and 3--7% in patients; instrumental variation was 0.5%. The accuracy was 4% for typical (p10%) fluid changes observed in vivo. The ease, simplicity and small errors of the technique suggest its utility in monitoring the time course and degree of fluid changes in patients.

Americium↗
PubMed1984

Non-invasive measurement of long bone cross-sectional moment of inertia by photon absorptiometry.

The use of the Norland-Cameron Bone Mineral Analyzer (BMA) to measure the cross-sectional moment of inertia of the mineral in a long bone is described and data regarding the usefulness and precision of the method are presented. The correlation coefficients between BMA-measured CSMI and that obtained from cross-sectional geometry were 0.99 both for a series of aluminum tubes and five bones of different sizes. The BMA-measured CSMI was linearly correlated with the CSMI digitized from cross-sections of a series of human ulnas at the r = 0.92 and 0.95 level in the AP and ML directions, respectively. The BMA-measured CSMI also correlated well with the torsional and bending behavior of ulnar specimens. Finally, a method for estimation the CSMI of a long bone section from BMA readings of mineral content and bone width is described. A linear correlation of r = 0.98 with the CSMI digitized from sections of human radii is demonstrated.

Biomechanical Phenomena↗
PubMed1989

Dual-photon absorptiometry: comparison of bone mineral and soft tissue mass measurements in vivo with established methods.

This study extended initial observations that indicated the potential of dualphoton absorptiometry (DPA) to measure total-body bone mineral (TBBM) and fat in vivo. DPA-derived TBBM and fat were compared with established methods in 13 subjects (aged 24-94 y) who underwent measurement of body density (Db), total-body water (TBW), potassium (TBK), calcium (TBCa, delayed-gamma neutron activation), and nitrogen (prompt-gamma neutron activation). TBBM was highly correlated with TBCa (r = 0.95, p less than 0.001) and the slope of TBCa vs TBBM (0.34) was similar to Ca content of ashed skeleton (0.34-0.38). DPA-measured fat (means +/- SD, 16.7 +/- 4.9 kg) correlated significantly (r = 0.79-0.94; p less than 0.01-0.001) with fat established by Db (16.3 +/- 5.4 kg), TBW (16.0 +/- 4.3 kg), TBK (17.7 +/- 4.6 kg), combined TBW-neutron activation (17.6 +/- 5.9 kg), and means of all four methods (16.9 +/- 4.8 kg). DPA thus offers a new opportunity to study human skeleton in vivo and to quantify fat by a method independent from the classical assumption that bone represents a fixed fraction of fat-free body mass.

Adipose Tissue↗
PubMed1988

Value of single photon absorptiometry in osteoporosis screening.

Radial bone mineral content and bone mineral density were measured in 1515 women referred for osteoporosis screening. A detailed questionnaire allowed the selection of 1069 normal white women for further analysis who had no historical evidence of bone disease or predisposing factors for bone disease. The nondominant radius was measured at two locations: the midradial bone density (MRBD) composed of predominantly cortical bone and the distal radial bone density at the 5 mm site (DRBD) composed of a mixture of cortical and trabecular bone. Women considered at risk were defined as those whose bone density values fell below fracture risk levels (0.550 g/cm2 for the MRBD and 0.325 g/cm2 for the DRBD). Between the ages of 20 and 70 years, the DRBD showed significantly greater sensitivity in defining subjects at risk (N = 223) than than MRBD (N = 80); P less than 0.001. Analysis of all ages showed that 684 women were above the fracture risk value (FRV) at both sites (64.0%), 260 were below the FRV at the DRBD 5 mm site (24.3%), 14 were below the FRV at the MRBD site (1.3%), and 111 were below the FRV at both sites (10.4%). Postmenopausal women age 50 to 70 years receiving estrogen replacement therapy (N = 221) had significantly higher values at both sites (P less than 0.001) than age-matched postmenopausal women not receiving replacement therapy (N = 239). Hereditary factors significantly correlated with both sites but neither site showed that calcium intake, activity level, or cigarette smoking were significant variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone and Bones↗
PubMed1986

Bone mineral content of the spine with dual photon absorptiometry: normalization of the values.

A Novo Industry BMC-LAB 22a densitometer equipped with a 153Gd source was recently implemented for the measurement of bone mineral content (BMC). 70 females (aged 16 to 86 years) and 67 males (aged 20 to 79 years) were selected to form a reference population. Care was taken to exclude patients with an illness or taking a drug that could influence the measurements, made at the lumbar spine level (L2-L4). Normalization procedures using several parameters (age, length, weight, span, lean body mass, an index of obesity, accepted scans) were developed to try and reduce the large interindividual coefficient of variation (CV). Total BMC values were found to yield a larger CV than when expressed as BMC cm-1. The relation of BMC with age showed a significant linear decrease of 0.3% year-1 for the male population. In the female population the BMC was not correlated with age up to the age of 50 years. Thereafter a linear bone loss of 0.76% year-1 was noted. Correcting for length decreased the CV in males and in females younger than 50 years. The use of the other parameters resulted in no or a very slight improvement. Combining parameters in a multiple regression analysis resulted in a significant decrease of the CV in females older than 50 years only.

Adolescent↗
PubMed1975

The reflex sympathetic dystrophy syndrome. A comprehensive analysis using fine-detail radiography, photon absorptiometry, and bone and joint scintigraphy.

Nine patients with reflex sympathetic dystrophy were examined. Clinical manifestations suggesting arthropathy were supported by radiographic demonstration of juxta-articular and subchondral bone erosions and by radionuclide demonstration of increased activity localized in the joint regions. Aggressive demineralization was demonstrated by fine-detail radiography and consisted of endosteal and intracortical excavation and subperiosteal and trabecular bone resorption. A one-third reduction in bone mineral was confirmed by quantitative analyses. Newer modalities of study have aided in the documentation of arthropathy in reflex sympathetic dystrophy and have helped in defining the patterns of aggressive bone resorption.

Adult↗