Effects of providing personalized feedback of child's obesity risk on mothers' food choices using a virtual reality buffet.

BACKGROUND: Providing personalized genetic-risk feedback of a child's susceptibility to adult-onset health conditions is a topic of considerable debate. Family health history (FHH), specifically parental overweight/obesity status, is a useful assessment for evaluating a child's genetic and environmental risk of becoming obese. It is unclear whether such risk information may influence parents' efforts to reduce their child's risk of obesity. PURPOSE: To evaluate whether telling mothers the magnitude of their child's risk of becoming obese based on personal FHH influenced food choices for their young child from a virtual reality-based buffet restaurant. METHODS: Overweight/obese mothers of a child aged 4-5 years who met eligibility criteria (N=221) were randomly assigned to one of three experimental arms, which emphasized different health information: arm 1, food safety control (Control); arm 2, behavioral-risk information (BRI) alone or arm 3, behavioral-risk information plus personal FHH-based risk assessment (BRI+FHH). Mothers donned a head-mounted display to be immersed in a virtual restaurant buffet, where they selected virtual food and beverages as a lunch for their child. RESULTS: Mothers who were randomized to BRI+FHH filled the index child's plate with an average of 45 fewer calories than those in the Control arm (P<0.05); those in the BRI arm filled the plate with 35 fewer calories than the Control arm, a non-significant difference. Calorie restriction was greatest among mothers in the BRI+FHH arm who received the weaker-risk message (that is, only one overweight parent). CONCLUSIONS: The influence of communicating a child's inherited risk of obesity on mothers' feeding practices may vary by the risk level conveyed. High-risk messages may best be coupled with strategies to increase mother's perceptions that efforts can be undertaken to reduce risk and build requisite behavioral skills to reduce risk.

Growth regulation by peroxisome proliferators: opposing activities in early and late G1.

Peroxisome proliferators (PPs) are a diverse group of nongenotoxic rodent liver carcinogens. One potential mechanism for the carcinogenicity of PPs is epigenetic modulation of growth-regulatory signal transduction pathways. We investigated the effects of PPs on growth-regulatory gene expression and cell proliferation in immortalized mouse liver cells, comparing PPs with other growth regulators and tumor promoters of known activity. The PPs Wy-14643, mono-ethylhexyl phthalate, clofibrate, and ciprofibrate ethyl-ester were found to be potent inducers of immediate-early gene expression (including c-fos, c-jun, junB, egr-1, NUP475, and to a lesser extent fosB, JE, and KC, with maximal expression seen 1 h after treatment of serum-deprived quiescent cells. The gene induction was potently inhibited by protein kinase inhibitor H7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride] but not by H8 [N-¿2-(methyl-amino)ethyl¿-5-isoquinolinesulfonamide dihydrochloride], indomethacin, or nordihydroguaiaretic acid. Compared with other growth regulators, the profile of PP-induced gene expression was most similar to that induced by arachidonic acid and eicosatetraynoic acid. The induction of immediate-early gene expression by PPs was followed by enhanced progression into S phase (DNA synthesis) when quiescent cells were treated with the PPs for only 1 h, washed, and then incubated without PPs. However, no stimulation of DNA synthesis was seen when the PPs were continually present. Furthermore, the PPs inhibited serum-induced DNA synthesis, even when they were added 6 h after serum stimulation (in late G1). Dehydroepiandrosterone-sulfate, a unique PP in being a steroid, had no detectable effect on immediate-early gene expression, did not stimulate DNA synthesis when applied for only 1 h, but did inhibit serum-induced DNA synthesis. Thapsigargin and A23187 mimicked this mitoinhibitory activity of PPs, suggesting that calcium mobilization by PPs might be involved. Our results demonstrate that PPs can modulate cell proliferation either by a stimulatory activity that functions in early G1, associated with activation of immediate-early gene expression, or by an inhibitory activity that functions in late G1; both activities could potentially play a role in tumor promotion by PPs.

Radiation-induced micrencephaly in guinea pigs.

The effect of X rays on brain weight of guinea pig pups at birth was studied in 21-day-old embryos exposed in utero to doses of 75 and 100 mGy. When compared to controls and when corrected for body weight, gestation time, litter size, sex, and examiner differences, the brains of irradiated pups weighed approximately 46 mg less than those of controls (P < 0.001) for the 75-mGy group and about 55 mg less for the 100-mGy group. Brains of females weighed 51 mg less than those of males of the same body weight. Dam weight and caging conditions had no observed effect on brain weight.

Determination of diagnostic x-ray spectra with characteristic radiation using attenuation analysis.

An analytical method to compute x-ray spectra from attenuation data utilizing the Laplace transformation has been extended to include characteristic radiation. It is based on an a priori technique of determining the ratio of characteristic radiation exposure to the total radiation exposure in diagnostic spectra. The technique is shown to produce characteristic intensities in good agreement with experimentally determined values.

A Laplace transform pair model for spectral reconstruction.

A four-parameter Laplace transform pair model, which accurately reconstructs an experimental bremsstrahlung spectrum from attenuation data, is presented. Computed spectral values with both aluminum and copper attenuators generally agree with experimental 70-kVp data to better than 2%. Reconstructed spectra at other kVp's also show good agreement with published data.

Scatter in 240-kVp mobile chest radiography.

The effects of scatter radiation on signal-to-noise ratio and optical density contrast are quantitatively compared for three tissue interfaces at 85, 110, and 240 kVp in mobile chest techniques. It is shown that scatter in the mediastinal portion of the radiograph is virtually independent of energy, while it substantially increases with energy in the lung fields.

Analysis of variations in contrast-detail experiments.

Three sources of variability in a contrast-detail (CD) experiment have been quantitated: within-observer variance, between-observer variance, and sample variance. It is concluded that (1) it is more efficient to increase the numbers of replicated images and observers than to increase the number of readings; (2) sampling and between-observer variations are approximately equal; (3) one can expect approximately 10% standard errors in the measured value of threshold detail or threshold contrast in a CD experiment which employs four observers, four replicate image samples, and one reading per observer.

On the measurement of half-value layer in film-screen mammography.

Sources of variations in the measurement of half-value layer (HVL) in film-screen mammography are evaluated. Two principal sources are the energy responses of ionization chambers and the elemental compositions of the 1100 aluminum-alloy attenuation materials. Methods in measuring the thickness of attenuation materials are also an important potential source of error. These factors as well as the influence of geometry of measurement, position of measurement in the field, and precision of radiation output are examined. Recommendations for consistency in measurement are provided.

Laplace reconstruction of experimental diagnostic x-ray spectra.

This paper displays the results of a blind study used to determine the capability of a Laplace transform pair model to accurately reconstruct diagnostic x-ray spectra from experimental attenuation data. Spectra reconstructed from attenuation measurements are compared to experimental spectra obtained on the same unit using an intrinsic germanium spectrometer system. The results show that when pure attenuation materials are used, good agreement is obtained between the experimental and computed spectra. If an alloy attenuator like 1100 aluminum is used, the proportion of contaminants must be included in the Laplace formulation for accurate reconstruction.

Relative dose efficiencies of antiscatter grids and air gaps in pediatric radiography.

The relative dose efficiencies (RDE) of various antiscatter grids and air gaps were determined for conditions simulating those found in pediatric radiography, using phantoms representing a newborn child, a 5-yr-old and a 10-yr-old child. Our data indicate than an air gap is best for the newborn, due to the low levels of scatter. The 8:1 fiber grid or 15.2-cm air gap without a grid can improve dose efficiency (DE) for the 5-yr-old child by 20%-25% relative to the 3.3-cm air gap and no-grid technique, while for the 10-yr-old child, DE can be improved by 40% with an 8:1 fiber grid.

Resolution in radiographic magnification.

Radiographic resolution and image sharpness are analyzed as a function of magnification for a few screen/film systems and a microfocal spot x-ray tube. Resolution and sharpness are described in terms of both MTF and effective aperture. The analysis demonstrates advantages of magnification for any combination of radiographic screen/film system and x-ray focal spot, and, in addition, allows one to compare different screen/film systems each used at different magnifications. Such an analysis is applicable to any radiographic system and may serve as a guide in selecting screen/film systems for use in magnification procedures.

Dose efficiency and the effects of resolution and noise on detail perceptibility in radiographic magnification.

The detail signal-to-noise ratio model of radiographic imaging is quantitatively analyzed in terms of its accuracy in describing observer threshold perceptibility of radiographic detail. The model is found to adequately describe the effects of magnification, scatter radiation, and system resolution on observer threshold perceptibility. However, it is shown that the model does not apply in screen/film radiography for very low contrasts and high scatter conditions due to insufficient optical density contrast. The dose-to-information conversion efficiency of a radiographic imaging system is defined and the effects of magnification, scatter, resolution, image processing, detector efficiency, grids, patient table support, field size, and geometry on the dose efficiency of the imaging system are investigated.

Application of a Laplace transform pair model for high-energy x-ray spectral reconstruction.

A Laplace transform pair model, previously shown to accurately reconstruct x-ray spectra at diagnostic energies, has been applied to megavoltage energy beams. The inverse Laplace transforms of 2-, 6-, and 25-MV attenuation curves were evaluated to determine the energy spectra of these beams. The 2-MV data indicate that the model can reliably reconstruct spectra in the low megavoltage range. Experimental limitations in acquiring the 6-MV transmission data demonstrate the sensitivity of the model to systematic experimental error. The 25-MV data result in a physically realistic approximation of the present spectrum.

Energy and rate dependence of diagnostic x-ray exposure meters.

Variations in x-ray exposure measurements among a variety of contemporary diagnostic exposure meters are investigated. Variations may result from systematic errors due to calibration, beam-quality dependence and exposure-rate dependence. It is concluded that the majority of general purpose diagnostic meters will agree to within 10% of each other if exposure rates are below 1.3 mC kg-1S-1 of air (5 R s-1) and beam qualities are typical for general purpose radiology, excluding mammography. For exposure rates comparable to those in barium enema radiography the variations can range up to 25% or more. Variations up to 40% were observed among general purpose exposure meters at mammographic beam qualities. In the mammographic range, mammographic (thin window) exposure meters varied by no more than 2%.

Probability of causation for cancers potentially induced by ionizing radiation.

Prompted by increasing litigation claiming cancer induction from exposure to radiation from nuclear weapons tests, the United States Congress enacted an amendment to the Orphan Drug Act (Public Law 97-414, January 4, 1983), through which the National Institutes of Health was directed to and did produce Probability of Causation (PC) Tables. This review defines PC and discusses the data, limitations, and uses of the concept.

An examination of errors in characteristic curve measurements of radiographic screen/film systems.

The precision and accuracy achieved in the measurement of characteristic curves for radiographic screen/film systems is quantitatively investigated for three techniques: inverse square, kVp bootstrap, and step-wedge bootstrap. Precision of all techniques is generally better than +/- 1.5% while the agreement among all intensity-scale techniques is better than 2% over the useful exposure latitude. However, the accuracy of the sensitometry will depend on several factors, including linearity and energy dependence of the calibration instrument, that may introduce larger errors. Comparisons of time-scale and intensity-scale methods are made and a means of measuring reciprocity law failure is demonstrated.

Contrast-detail-dose and dose efficiency analysis of a scanning digital and a screen-film-grid radiographic system.

The purpose of this study is to examine the diagnostic potential of a scanning digital radiography (SDR) system currently used clinically as a CT localization device. The technique of contrast-detail-dose analysis is used to compare the low-contrast sensitivity and dose efficiency of an SDR unit with standard radiography (SR). The theory of threshold perceptibility in both digital radiography and SR is described, including the effects of scattered radiation and antiscatter devices, object attenuation, geometry, system image processing, and recorder quantum efficiency. The concept of dose efficiency is defined and derived from the contrast-detail-dose data. The SDR system is shown to operate with a threshold signal-to-noise ratio of 7.3 +/- 1.2 for large area detection (d greater than or equal to 2 mm); to be relatively scatter-free; and to be as much a 100x more dose efficient than SR for visualization of large low contrast objects (C less than or equal to 0.04, d greater than or equal to 2 mm).

Fetal dose from radiotherapy with photon beams: report of AAPM Radiation Therapy Committee Task Group No. 36.

Approximately 4000 women per year in the United States require radiotherapy during pregnancy. This report presents data and techniques that allow the medical physicist to estimate the radiation dose the fetus will receive and to reduce this dose with appropriate shielding. Out-of-beam data are presented for a variety of photon beams, including cobalt-60 gamma rays and x rays from 4 to 18 MV. Designs for simple and inexpensive to more complex and expensive types of shielding equipment are described. Clinical examples show that proper shielding can reduce the radiation dose to the fetus by 50%. In addition, a review of the biological aspects of irradiation enables estimates of the risks of lethality, growth retardation, mental retardation, malformation, sterility, cancer induction, and genetic defects to the fetus.

Recommendations on performance characteristics of diagnostic exposure meters: report of AAPM Diagnostic X-Ray Imaging Task Group No. 6.

Task Group 6 of the Diagnostic X-Ray Imaging Committee of the American Association of Physicists in Medicine (AAPM) was appointed to develop performance standards for diagnostic x-ray exposure meters. The recommendations as approved by the Diagnostic X-Ray Imaging Committee and the Science Council of the AAPM are delineated in this report and provide specifications on meter precision, calibration accuracy, calibration reference points, linearity, energy dependence, exposure rate dependence, leakage, amplification gain settings, directional dependence, the stem effect, constancy checks, and calibration intervals. The report summarizes recommendations for meters used in mammography, general purpose radiography including special procedures, computed tomography, and radiation safety surveys for x-ray radiography.

Reproducibility and accuracy of measurements with a hand held autorefractor in children.

AIM: To determine reproducibility and accuracy of the Nikon Retinomax autorefractor when used with children who were made cycloplegic. METHODS: Autorefraction and retinoscopy or subjectively refined retinoscopy (where, under the patient's direction, the refraction was varied until the best visual acuity was achieved) were performed on the right eye of 47 children, age 11-93 months. Autorefraction was performed using the Nikon Retinomax, which provides up to eight measured values of refractive error and one representative measurement of refractive error. RESULTS: Autorefractor measurements were successfully obtained from 7/9 children age 3 years or younger, and from all older children. Vector methods were used to calculate differences. Retinomax reproducibility averaged 0.43 D. Unbiased Retinomax and retinoscopy measurements differed by an average of 0.82 D. Unbiased Retinomax and subjectively refined retinoscopy differed by an average of 1.03 D. CONCLUSIONS: Reproducibility of Retinomax measured values in children is comparable with reproducibility of retinoscopy, subjective refraction, and autorefraction measurements in adults. Agreement between Retinomax and retinoscopy and agreement between Retinomax and subjective refinement in children is comparable with agreement between autorefraction and subjective refraction in adults. The study indicates that the Retinomax is a useful instrument for measuring refractive errors in young children.