Anomalous diffraction of light with geometrical path statistics of rays and a Gaussian ray approximation.

The anomalous-diffraction theory (ADT) of extinction of light by soft particles is shown to be determined by a statistical distribution of the geometrical paths of individual rays inside the particles. Light extinction depends on the mean and the mean-squared geometrical paths of the rays. Analytical formulas for optical efficiencies from a Gaussian distribution of the geometrical paths of rays are derived. This Gaussian ray approximation reduces to the exact ADT in the intermediate case of light scattering for an arbitrary soft particle and describes well the extinction of light from a system of randomly oriented and (or) polydisperse particles. The implications for probing of the sizes and shapes of particles by light extinction are discussed.

Photon migration in turbid media using a cumulant approximation to radiative transfer.

A photon transport model for light migration in turbid media based on a cumulant approximation to radiative transfer is presented for image reconstruction inside an infinite medium or a bounded medium with a planar geometry. This model treats weak inhomogeneities through a Born approximation of the Boltzmann radiative transfer equation and uses the second-order cumulant solution of photon density to the Boltzmann equation as the Green's function for the uniform background. It provides the correct behavior of photon migration at early times and reduces at long times to the center-moved diffusion approximation. At early times, it agrees much better with the result from the Monte Carlo simulation than the diffusion approximation. Both approximations agree well with the Monte Carlo simulation at later times. The weight function for image reconstruction under this proposed model is shown to have a strong dependence at both early and later times on absorption and/or scattering inhomogeneities located in the propagation direction of and close to the source, or in the field of view of and close to the detector. This effect originates from the initial ballistic motion of incident photons, which is substantially underestimated by the diffusion approximation.

Time-resolved Fourier optical diffuse tomography.

Time-resolved Fourier optical diffuse tomography is a novel approach for imaging of objects in a highly scattering turbid medium with use of an incident (near) plane wave. The theory of the propagation of spatial Fourier components of the scattered wave field is presented, along with a fast algorithm for three-dimensional reconstruction in a parallel planar geometry. Examples of successful reconstructions of simulated hidden absorptive or scattering objects embedded inside a human-tissue-like semi-infinite turbid medium are provided.

Clinical and imaging correlates of response to treatment with infliximab in patients with ankylosing spondylitis.

OBJECTIVES: Ankylosing spondylitis (AS) is a chronic disease leading to progressive spinal ankylosis and deformity. The aims of this study were to (1) determine whether infliximab is an effective treatment for AS patients who have failed conventional treatment; (2) identify any baseline clinical variables that can be associated with responsiveness to treatment; and (3) resolve whether the clinical response correlated with changes from baseline inflammatory changes on magnetic resonance imaging (MRI). METHODS: Twenty-one patients who met the modified New York criteria for AS (M:F 18:3) were enrolled in this open labeled study. The mean age was 37.9+/-7.9 years and mean disease duration was 8.69+/-6.58 years. Patients received infliximab at a dose of 5 mg/kg by intravenous infusion over 2 hours at 0, 2, 6, weeks. Nine functional variables were measured [i.e., Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI) etc.], 6 clinimetrics (chest expansion, finger to floor, etc.), and inflammatory markers in the peripheral blood at baseline and each subsequent visit. Primary response to treatment was defined as a > 20% response in 5/9 functional variables. A subset of 9 consecutive patients was selected for MRI scans before and after infusions. RESULTS: Eighteen patients were available for assessment at week 14 having received 3 infusions (wks 0, 2, 6). There was > 60% improvement in functional variables, i.e., BASDAI, BASFI, Health Assessment Questionnaire, fatigue, and spinal and total body pain. Clinimetric scores selectively improved, e.g., chest expansion (p < 0.021) by 14 weeks. ESR, CRP and haptoglobin all showed significant improvement at 6 weeks and were maintained to the 14 week assessment point. Imaging studies showed improvement in all patients studied including those with advanced disease. Three patients developed headache during the infusions. Infliximab was effective in all, but degree of response varied. Very good responders were distinguished from good responders by shorter duration of disease and better baseline clinimetric scores. CONCLUSIONS: Infliximab was an effective treatment for AS in a short term trial. Longterm control of symptoms and potential alteration in clinical course of disease will require longterm assessment.

Analytical solution of the polarized photon transport equation in an infinite uniform medium using cumulant expansion.

An analytical solution for time-dependent polarized photon transport equation in an infinite uniform isotropic medium is studied using a circular representation of the polarized light and expansion in the generalized spherical functions. We extend our cumulant approach for solving the scalar (unpolarized) photon transport equation to the vector (polarized) case. As before, an exact angular distribution is obtained and a cumulant expansion is derived for the polarized photon distribution function. By a cutoff at the second cumulant order, a Gaussian analytical approximate expression of the polarized photon spatial distribution is obtained as a function of the direction of light and time, whose average center position and half-width are always exact. The central limit theorem claims that this spatial distribution approaches accuracy in detail when the number of collisions or time becomes large. The analytical expression of cumulants up to an arbitrary high order is also derived, which can be used for calculating a more accurate polarized photon distribution through a numerical Fourier transform. Contrary to what occurs in other approximation techniques, truncation of the cumulant expansion at order n is exact at that order and cumulants up to and including order n remain unchanged when higher orders are added, at least as applied in our photon transport equation.

Photon-transport forward model for imaging in turbid media.

A photon-transport forward model for image reconstruction in turbid media is derived that treats weak inhomogeneities through a Born approximation of the Boltzmann radiative transfer equation. This model can conveniently replace the commonly used diffusion approximation in optical tomography. An analytical expression of the background Green's function is obtained from the cumulant solution of the Boltzmann equation. Our model provides the correct behavior of photon migration at early times and reduces at long times to the center-moved diffusion approximation. Numerical comparisons between this model and the standard and center-moved diffusion models are presented.

Access to medical care for individuals with workers' compensation claims.

Experience at a publically funded occupational health clinical center in New York State suggests that patients with work-related illnesses often have great difficulty accessing diagnostic and treatment services. A study was designed to more quantitatively investigate the extent and nature of barriers to medical services for patients with Workers' Compensation claims. Medical practices from 13 selected medical specialties were identified from telephone directories. The directories covered six areas encompassing almost all of a 15-county region. All practices from each selected specialty were contacted by phone and asked a set of standardized questions regarding patient acceptance policies. A number of barriers were identified by the survey including practices closed to new patients and practices closed specifically to patients with Workers' Compensation claims. Barriers also were found to be widespread among practices that did accept Workers' Compensation claims, primarily related to requiring a guarantee of payment prior to seeing the patient. The results were compared by medical specialty and geographic area. While the study showed some of the difficulties patients with occupational illnesses face attempting to access medical services, it most likely underestimated the extent of the problem. Attitudes and practices that impede access, but were not measurable, create additional barriers. Our study strongly suggests that policies that improve access to medical care for individuals with Workers' Compensation claims are necessary to better serve the needs of workers with occupational illnesses.

Cumulant solution of the elastic boltzmann transport equation in an infinite uniform medium

We consider an analytical solution of the time-dependent elastic Boltzmann transport equation in an infinite uniform isotropic medium with an arbitrary phase function. We obtain (1) the exact distribution in angle, (2) the exact first and second spatial cumulants at any angle, and (3) an approximate combined distribution in position and angle and a spatial distribution whose central position and half-width of spread are always exact. The resulting Gaussian distribution has a center that advances in time, and an ellipsoidal contour that grows and changes shape providing a clear picture of the time evolution of the particle migration from near ballistic, through snakelike and into the final diffusive regime.

The fetish of the objective finding.

Pressure is mounting for clinicians to rely solely on objective measures when evaluating workers with possible work-related disease. These measures are intended to largely supplant the worker's history as sources of information regarding diagnosis, work relatedness, and extent of disability. While seeming to promote more accurate and neutral evaluation methods, the underlying agenda is to reduce business costs by denying work-related illness and disability. Promoting the view of occupational health as the province of technical experts, the campaign for the objective finding silences workers as unqualified to comment. The methods proposed to enhance objectivity also suffer from significant specific shortcomings. To resist efforts to fetishize the objective finding, clinicians need to recognize the subjective elements of objective methods as well as the objective value of subjective data. This requires recognition of the central role of workers and histories in the clinical evaluation process.

Medical examination for asbestos-related disease.

There are millions of workers whose exposure to asbestos dust prior to the implementation of asbestos regulation and improved control measures places them at risk of asbestos-related disease today. In addition, workers are still being exposed to significant amounts of asbestos, when asbestos materials in place are disturbed during renovation, repair, or demolition. Given the continued presence of asbestos-containing materials in industrial, commercial, and residential settings throughout the U.S., a sizeable population remains at risk of asbestos-related disease. This article reviews the health effects associated with exposure to asbestos and delineates the steps necessary for the comprehensive screening and clinical assessment for asbestos-related disease, in order to assist physicians in identifying and preventing illness associated with exposure to asbestos among their patients.

Optical tomographic image reconstruction from ultrafast time-sliced transmission measurements.

Optical imaging and localization of objects inside a highly scattering medium, such as a tumor in the breast, is a challenging problem with many practical applications. Conventional imaging methods generally provide only two-dimensional (2-D) images of limited spatial resolution with little diagnostic ability. Here we present an inversion algorithm that uses time-resolved transillumination measurements in the form of a sequence of picosecond-duration intensity patterns of transmitted ultrashort light pulses to reconstruct three-dimensional (3-D) images of an absorbing object located inside a slab of a highly scattering medium. The experimental arrangement used a 3-mm-diameter collimated beam of 800-nm, 150-fs, 1-kHz repetition rate light pulses from a Ti:sapphire laser and amplifier system to illuminate one side of the slab sample. An ultrafast gated intensified camera system that provides a minimum FWHM gate width of 80 ps recorded the 2-D intensity patterns of the light transmitted through the opposite side of the slab. The gate position was varied in steps of 100 ps over a 5-ns range to obtain a sequence of 2-D transmitted light intensity patterns of both less-scattered and multiple-scattered light for image reconstruction. The inversion algorithm is based on the diffusion approximation of the radiative transfer theory for photon transport in a turbid medium. It uses a Green s function perturbative approach under the Rytov approximation and combines a 2-D matrix inversion with a one-dimensional Fourier-transform inversion to achieve speedy 3-D image reconstruction. In addition to the lateral position, the method provides information about the axial position of the object as well, whereas the 2-D reconstruction methods yield only lateral position.

Multiple chemical sensitivities: the social construction of an illness.

Multiple chemical sensitivities (MCS) has emerged as an important and highly controversial issue in occupational health. Debate centers on whether the illness is "physical" or "psychological." A strong corporate-backed campaign has framed the debate and has pushed MCS advocates into a strategy of "proving the physical" nature of MCS. Proponents of both positions, however, share key assumptions that impede long-term efforts to benefit MCS sufferers, including acceptance of the physical/psychological dichotomy as a paradigm for the illness, a desire to rid the debate of "politics" to allow "objective scientific" data to be amassed, and a view of MCS as unique without links to other occupational illnesses. While a grassroots movement has benefited MCS sufferers in a number of important ways, the shared assumptions have impeded development of a more complex model for the illness that is reflective of a complex reality, reproduced mainstream expert/non-expert relationships, and failed to connect with the broader occupational health and safety movement. The author outlines an alternative theory and practice to begin addressing these issues, beginning with a recognition of MCS as a problem of developing knowledge within a context of class power.

Recognizing occupational disease--taking an effective occupational history.

Occupational exposures contribute to the morbidity and mortality of many diseases. However, occupational diseases continue to be underrecognized even though they are responsible for an estimated 860,000 illnesses and 60,300 deaths each year. Family physicians can play an important role in improving the recognition of occupational disease, preventing progressive illness and disability in their own patients, and contributing to the protection of other workers similarly exposed. This role can be maximized if physicians raise their level of suspicion for workplace disease, develop skills in taking occupational histories and establish routine access to occupational health resources.

Lead exposure in a developmentally disabled workforce.

Over-exposure to lead was identified among developmentally disabled workers engage in furniture refinishing at two separate sites. The index case was identified at the first site by a public health nurse assigned to provide care to some of the workers. Referral to a regional occupational health clinic initiated an exposure assessment and medical consultation at both work sites. Blood lead levels (BLLs) among sanders and helpers at site A averaged 60 micrograms per deciliter of blood (mcg/dl). At site B, BLLs were lower, but 6 individuals had BLLs greater than mcg/dl. Hand sanding of chemically stripped wood previously coated with lead-based paint was determined to be the exposure source. These incidents document potential lead overexposure in an underecognized setting. They also emphasize the importance of incorporating a workplace health risk assessment in the process of placing and protecting the developmentally disabled on the job.

Lung cancer mortality in a cohort of older pulp and paper workers.

The occurrence of deaths due to lung cancer was studied among 883 white male workers from a pulp and paper company in northern New Hampshire. All subjects had participated in a longitudinal study of respiratory morbidity, and data from interviews were used to construct lifetime cigarette smoking and occupational histories. Most of the subjects had entered follow-up in the 1960s and, at that time, their mean age was 51 years and they had worked for the pulp and paper company a mean of 25 years. By the end of follow-up in 1992, the 512 deceased subjects included 35 whose underlying cause of death had been lung cancer. With an internal comparison using the Cox proportional-hazards model, the hazard ratio for sulfite pulp mill work was 2.5 (95% CI 1.3-4.9), while controlling for the effects of age, cigarette smoking, and work in other parts of the pulping operation. In addition, the hazard ratio for the combination of >35 pack-years of smoking and >10 years sulfite mill work was greater than the product of the hazard ratios for each factor alone. While these findings are consistent with past asbestos exposure in the sulfite pulp mill environment, the absence of mesothelioma cases is inconsistent with this type of exposure.

Time-resolved optical backscattering model in highly scattering media.

A time-resolved backscattering model, which combines a single large-angle scattering with multiple small-angle scatterings, is used to produce a scattered-light profile about a medium. Inhomogeneity of the medium is included in the model. Some multidimensional integrals can be evaluated analytically.

Relationship between prenatal anxiety and perinatal outcome in nulliparous women: a prospective study.

Nulliparous women with singleton gestation were assessed prospectively for anxiety levels with the State-Trait Anxiety Inventory, which measured state (situational and transitional) and trait (dispositional and stable) anxiety, with high scores indicating high anxiety. Bivariate and multivariate methods were used for data analysis. Anxiety assessments (n = 239) were obtained in 88 women at different stages of gestation. Mean anxiety scores were lowest at 22 to 26 weeks. A woman's successive scores were highly correlated. The trait anxiety (A-T) scores were higher for married women. A positive correlation was present between anxiety scores and gestational age at delivery. Low A-T scores correlated with low birthweight, preterm delivery, and chorioamnionitis. High state anxiety (A-S) levels correlated with the presence of meconium in the amniotic fluid and neonatal congenital abnormalities. Postdate delivery also was associated with higher although statistically insignificant anxiety scores. Women who presented to the labor and delivery room for various complaints had higher A-S and A-T levels. Maternal anxiety level was associated with adverse perinatal outcome; specifically, prematurity and low birthweight correlated with low A-T levels.

Time-resolved optical diffusion tomographic image reconstruction in highly scattering turbid media.

The image of an object hidden in highly scattering media was reconstructed using a fast, noise-resistant algorithm newly applied to diffusion tomography. A pulsed light source producing scattered and transmitted light is examined at multiple times. Multiple source detector pairs around the medium are used to obtain data in many different directions. An inverse scattering algorithm with nonuniform regularization achieves rapid inversion convergence.