A Method for Determining Skeletal Lengths from DXA Images

Background  

Skeletal ratios and bone lengths are widely used in anthropology and forensic pathology and hip axis length is a useful predictor of fracture. The aim of this study was to show that skeletal ratios, such as length of femur to height, could be accurately measured from a DXA (dual energy X-ray absorptiometry) image.     

Long-term precision of 18F-fluoride PET skeletal kinetic studies in the assessment of bone metabolism.

(18)F-Fluoride PET allows noninvasive evaluation of regional bone metabolism and has the potential to become a useful tool for assessing patients with metabolic bone disease and evaluating novel drugs being developed for these diseases. The main PET parameter of interest, termed K(i), reflects regional bone metabolism. The aim of this study was to compare the long-term precision of (18)F-fluoride PET with that of biochemical markers of bone turnover assessed over 6 mo. METHODS: Sixteen postmenopausal women with osteoporosis or significant osteopenia and a mean age of 64 y underwent (18)F-fluoride PET of the lumbar spine and measurements of biochemical markers of bone formation (bone-specific alkaline phosphatase and osteocalcin) and bone resorption (urinary deoxypyridinoline) at baseline and 6 mo later. Four different methods for analyzing the (18)F-fluoride PET data were compared: a 4k 3-compartmental model using nonlinear regression analysis (K(i-4k)), a 3k 3-compartmental model using nonlinear regression analysis (K(i-3k)), Patlak analysis (K(i-PAT)), and standardized uptake values. RESULTS: With the exception of a small but significant decrease in K(i-3k) at 6 mo, there were no significant differences between the baseline and 6-mo values for the PET parameters or biochemical markers. The long-term precision, expressed as the coefficient of variation (with 95% confidence interval in parentheses), was 12.2% (9%-19%), 13.8% (10%-22%), 14.4% (11%-22%), and 26.6% (19%-40%) for K(i-3k), K(i-PAT), mean standardized uptake value, and K(i-4k), respectively. For comparison, the precision of the biochemical markers was 10% (7%-15%), 18% (13%-27%), and 14% (10%-21%) for bone-specific alkaline phosphatase, osteocalcin, and urinary deoxypyridinoline, respectively. Intraclass correlation between the baseline and 6-mo values ranged from 0.44 for K(i-4k) to 0.85 for K(i-3k). No significant correlation was found between the repeated mean standardized uptake value measurements. CONCLUSION: The precision and intraclass correlation observed for K(i-3k) and K(i-PAT) was equivalent to that observed for biochemical markers. This study provided initial data on the long-term precision of (18)F-fluoride PET measured at the lumbar spine, which will aid in the accurate interpretation of changes in regional bone metabolism in response to treatment.     

Eyelid movements during blinking in patients with Parkinson's disease.

We examined eyelid movements during spontaneous, voluntary, and trigeminal reflex blinks in 16 patients with mild to moderate Parkinson's disease (PD) off medication and 14 controls. Voluntary and reflex blink amplitudes tended to be smaller than normal for PD patients, whereas eyelid kinematics (amplitude-maximum velocity relationship) for all three blink types were normal. Spontaneous blink rate was less than normal for 10 patients and abnormally high for 6 patients. A significant positive correlation between spontaneous blink amplitude and blink rate was found. These observations suggest that PD modifies the gain of a premotor blink circuit shared by spontaneous, voluntary, and reflex blinks.     

The correction of BMD measurements for bone strontium content.

Strontium ranelate (SR) is a new oral treatment for osteoporosis associated with large increases in bone mineral density (BMD) compared with alternative therapies such as bisphosphonates. Much of the BMD increase during SR treatment is a physical effect caused by the increased attenuation of X-rays due to the accumulation of strontium in bone tissue. The aim of this study was to assess the contribution made by bone strontium content (BSC) to the overall BMD increase by evaluating the percentage F of the BMD change explained by the physical presence of strontium in bone. A value of F less than 100% would provide evidence of the anabolic effect of SR as an additional factor contributing to the overall BMD increase. Studies of mixtures of strontium hydroxyapatite (SrHA) and calcium hydroxyapatite (CaHA) scanned on a variety of dual-energy X-ray absorptiometry (DXA) systems show that a 1% molar ratio of SrHA/(CaHA+SrHA) causes a 10% overestimation of BMD. The correction of spine BMD measurements for the physical effects of strontium depends on knowledge of 2 further factors: (1) bone biopsy measurements of iliac crest BSC and (2) the ratio R of BSC at the DXA site to BSC at the iliac crest measured in animal studies. We used clinical trial data and values of R(spine) measured in studies of monkeys and beagle dogs to determine values of F(spine) for 1, 2, and 3 yr treatment with SR. Based on the average value of R(spine) approximately 0.7 for male and female monkeys, we found values for F(spine) approximately 75-80% for 1, 2, and 3 yr of treatment. Using the value of R(spine) approximately 1.0 from the beagle study gave values of F(spine) approximately 100%. Although values of F(spine) as low as 40% are possible, we conclude that the most likely figure is 75% or greater. However, it is apparent that there are large uncertainties in the correction of BMD results for the effect of bone strontium and that the most important of these is the inference of BSC values at DXA scan sites from measurements of iliac crest bone biopsy specimens.     

Emulsion copolymerization of acrylonitrile and butyl acrylate, 10. Effect of 1,1-diphenyl-2-picrylhydrazyl on the polymerization process

The emulsion copolymerization of acrylonitrile with butyl acrylate, initiated by ammonium persulfate in the presence of disodium dodecylphenoxybenzenedisulfonate and 1,1-diphenyl-2-picrylhydrazyl (DPPH), was kinetically investigated at 70°C by conventional GLC and gravimetric methods. The copolymerization under batch conditions was conducted to both low and high conversion. In the presence of a small amount of DPPH the molecular weight of the copolymer is little decreased when compared with that prepared without DPPH. In addition, the rate of copolymerization unexpectedly decreases with increasing emulsifier concentration. The radical scavenger was found to decrease the average particle size. In the interval 2 the rate of polymerization is approximately proportional to the 0,35th power of the emulsifier concentration and to the 0,5th power of the initiator concentration (without DPPH). The dependence of the rate of polymerization on the final particle number and of the final particle number on the emulsifier concentration also deviates from the simple micellar theory predictions. The results can be explained by a coagulative nucleation mechanism.     

Polymerization of vinyl monomers photoinitiated by benzoylated polystyrene

The rate of the polymerization of vinyl monomers photoinitiated (at λ = 365 nm) by benzoylated polystyrene in N,N-dimethylformamide (DMF) decreases in the sequence vinyl acetate>acrylonitrile>methyl methacrylate ? styrene ≈ 0 and is related to the rate constant of propagation of the mentioned monomers. In addition to DMF, aromatic hydrocarbons (benzene, toluene, p-xylene), cyclohexane and tetrahydrofuran were employed as hydrogen donors. The maximum polymerization rate was achieved in the system containing p-xylene; the system with benzene turned out inefficient for the initiation of acrylonitrile polymerization. Turbidimetric titration of a soluble fraction of the acrylonitrile polymerization in DMF in presence of benzoylated polystyrene showed that the soluble fraction does not contain graft copolymers of benzoylated polystyrene with acrylonitrile. It is assumed, however, that the polyacrylonitrile in the insoluble fraction is bound to benzoylated polystyrene in the form of graft copolymers.     

Improved lesion detection with dimethyl-amino-diphosphonate: A report of two cases

In two patients with metastatic disease more lesions were detected on scintigraphs obtained with the low uptake bone-scanning agent dimethyl-amino-diphosphonate than on images produced using methylene diphosphonate. The results in these two patients provide practical support for the suggestion that bone-scanning agents with low uptake in normal bone, but high tumour-to-normal bone ratios, will allow better delineation of local bone abnormalities.     

Non-invasive assessment of skeletal kinetics using fluorine-18 fluoride positron emission tomography: evaluation of image and population-derived arterial input functions

To measure regional skeletal kinetics using fluorine-18 fluoride positron emission tomography (PET) it is necessary to know the concentration of radioactive tracer being delivered to bone by arterial plasma with relation to time, the arterial input function (IFa). Methods by which IFa can be derived without arterial sampling are attractive because of their relative technical simplicity and the reduction in possible morbidity to the subject. We have compared the use of a scaled population input function (IFp) and a corrected image-derived input function from the aorta (IFi) with an IFa directly measured from a radial artery line in ten normal postmenopausal women. Both of the aforementioned methods rely only on a small number of discrete venous samples. Each subject had a dynamic PET acquisition of the lumbar spine performed after the intravenous injection of 180 MBq ¹⁸F-fluoride. Both the IFp and the IFi were compared with the IFa in terms of the accuracy of determination of six parameters. These were: plasma clearance of fluoride to bone mineral (K _i), unidirectional plasma clearance to total bone tissue (K ₁) and individual rate constants k ₂, k ₃ and k ₄, calculated using non-linear regression with a three-compartment model, and the plasma clearance to bone mineral calculated using the Patlak method (K _pat). For both the IFp and the IFi method the root mean square errors for K _pat and K _i were similar and small (<8.2%). The errors in determining K ₁ and the rate constants k ₂ to k ₄ are larger by either method, but with a small advantage using the IFp method. It is concluded that the use of either non-invasive method for determining the arterial plasma input function is suitable for the measurement of the most important parameters, K _i and K _pat, in these subjects. Received 8 April and in revised form 11 July 1999     

Environmental justice, regulation, and the local community.

This article examines the sociological significance of the concept of "environmental justice" for grassroots groups responding to toxic contamination in their local communities. Taking into account nationwide mobilization patterns in such communities, the author documents a precedent-setting episode in the city of Jacksonville, Arkansas, where citizen protests and support from national environmental groups led the Environmental Protection Agency to withdraw three Technical Assistance Grants inappropriately awarded to a group with links to a polluting industry, and subsequently to rewrite the rules for participation in such grants. As the first such challenge nationally, the Jacksonville scenario is an important "test case" and permits a theoretical and practical evaluation of the relationship between social groups, technology, and the governmental regulatory process. More particularly, it gives insight into the Technical Assistance Grants program, which was set up to enable citizens living close to contaminated sites to interpret and evaluate technical information relating to such sites, but which has been undercut by a weak EPA and cooptation efforts by industries. The article concludes with an exploration of the concept of community in relation to the new construction of environmental justice engaged in by grassroots groups fighting contamination locally and nationally.