Spatially variant regularization improves diffuse optical tomography

Diffuse tomography with near-infrared light has biomedical application for imaging hemoglobin, water, lipids, cytochromes, or exogenous contrast agents and is being investigated for breast cancer diagnosis. A Newton-Raphson inversion algorithm is used for image reconstruction of tissue optical absorption and transport scattering coefficients from frequency-domain measurements of modulated phase shift and light intensity. A variant of Tikhonov regularization is examined in which radial variation is allowed in the value of the regularization parameter. This method minimizes high-frequency noise in the reconstructed image near the source-detector locations and can produce constant image resolution and contrast across the image field.     

Three-dimensional optical tomography: resolution in small-object imaging

Near-infrared (NIR) optical tomography provide estimates of the internal distribution of optical absorption and transport scattering from boundary measurement of light propagation within biological tissue. Although this is a truly three-dimensional (3D) imaging problem, most research to date has concentrated on two-dimensional modeling and image reconstruction. More recently, 3D imaging algorithms are demonstrating better estimation of the light propagation within the imaging region and are providing the basis of more accurate image construction algorithms. As 3D methods emerge, it will become increasingly important to evaluate their resolution, contrast, and localization of optical property heterogeneity. We present a concise study of 3D reconstructed resolution of a small, low-contrast, absorbing and scattering anomaly as it is placed in different locations within a cylindrical phantom. The object is an 8-mm-diameter cylinder, which represents a typical small target that needs to be resolved in NIR mammographic imaging. The best resolution and contrast is observed when the object is located near the periphery of the imaging region (12-22 mm from the edge) and is also positioned within the multiple measurement planes, with the most accurate results seen for the scatter image when the anomaly is at 17 mm from the edge. Furthermore, the accuracy of quantitative imaging is increased to almost 100% of the target values when a priori information regarding the internal structure of imaging domain is utilized.     

Metrics for small projects: Experiences at the SED

An organized, comprehensive metrics program can bring order to the chaos of small-project management and form the foundation for a concerted process improvement effort. The authors describe their experience in applying metrics to one such US Army organization     

TFF1 gene expression in human medullary thyroid carcinoma

This epidemiological study investigated the reasons why children in Northern Ireland who need orthodontic treatment do not receive treatment even when it is provided free by the state. A total of 1584 15- and 16-year-olds were examined in 23 high schools with the Index of Orthodontic Treatment Need. The characteristics of the adolescents who had received orthodontic treatment were compared with those who had a definite need for treatment and yet did not receive treatment or advice. One in 10 of the adolescents examined had an unmet need for orthodontic treatment. Logistic regression analysis was used to assess the influence of 11 variables including socioeconomic status, religion, and standard of dental health on the uptake of orthodontic care. This analysis revealed that the only significant predictors of whether an adolescent received orthodontic treatment was the dental attendance pattern of the adolescent, the adolescent's dental health, and the dental attendance pattern of the adolescent's mother. Those adolescents who had good dental health, who regularly attended a dentist, and whose mother regularly attended a dentist were more likely to receive orthodontic treatment.     

Characterization of stability of performance in patients with traumatic brain injury: Variability and consistency on reaction time tests.

The stability of performance of reaction times (RTs) on 3 visual discrimination tasks was assessed in patients with varying severity of traumatic brain injury (TBI) and in matched control Ss. Results were analyzed for group and individual variability and consistency of performance over time. There was significantly greater intersubject (group) variability in the TBI group. Individual patients (intrasubject) tended to be more variable in performance and less consistent over time than control Ss, but this occurred only with specific measures, which suggests that increased lack of stability in performance is not a general impairment after brain damage but requires specific analyses for identification of performance differences. This intrasubject variability was indepedent of test–retest and split-half test reliability. No obvious factors such as severity of brain injury were related to the variability and inconsistency of performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organizational strategies with unilateral or bilateral frontal lobe injury in word learning tasks.

To define the capacity to organize verbal learning after frontal lobe injury, 32 patients with stable frontal lesions were evaluated with list learning tasks. Lesion size and site were determined from CAT or magnetic resonance imaging (MRI) scans. The lists were contructed to assess several potential organizational processes. A mild deficit in recognition performance was observed in patients with left frontal lesions accompanied by residual minor language impairments or in patients with septal lesions. Patients with frontal lesions also had a verbal recall deficit that was related to several factors: poor higher order organization of learning, independent of lesion size or site; a selective secondary memory impairment, associated with a language deficit and size of the lesion in the left frontal region; and excess intralist repetitions in patients with right frontal lesions. Impaired list learning after frontal lesions involves several independent psychological processes. This functional heterogeneity is based on regional anatomical specialization and dissociation of task processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Magnetic-resonance-imaging-coupled broadband near-infrared tomography system for small animal brain studies

A novel magnetic-resonance-coupled broadband near-infrared (NIR) tomography system for small animal brain studies is described. Several features of the image formation approach are new in NIR tomography and represent major advances in the path to recovering high-resolution hemoglobin and oxygen saturation images of tissue. The NIR data were broadband and continuous wave and were used along with a second-derivative-based estimation of the path length from water absorption. The path length estimation from water was then used along with the attenuation spectrum to recover absorption and reduced scattering coefficient images at multiple wavelengths and then to recover images of total hemoglobin and oxygen saturation. Going beyond these basics of NIR tomography, software has been developed to allow inclusion of structures derived from MR imaging (MRI) for the external and internal tissue boundaries, thereby improving the accuracy and spatial resolution of the properties in each tissue type. The system has been validated in both tissue-simulating phantoms, with 10% accuracy observed, and in a rat cranium imaging experiment. The latter experiment used variation in inspired oxygen (FiO2) to vary the observed hemoglobin and oxygen saturation images. Quantitative agreement was observed between the changes in deoxyhemoglobin values derived from NIR and the changes predicted with blood-oxygen-level-dependent (BOLD) MRI. This system represents the initial stage in what will likely be a larger role for NIR tomography, coupled to MRI, and illustrates that the technological challenges of using continuous-wave broadband data and inclusion of a priori structural information can be met with careful phantom studies.     

Effects of refractive index on near-infrared tomography of the breast

Near infrared (NIR) optical tomography is an imaging technique in which internal images of optical properties are reconstructed with the boundary measurements of light propagation through the medium. Recent advances in instrumentation and theory have led to the use of this method for the detection and characterization of tumors within the female breast tissue. Most image reconstruction approaches have used the diffusion approximation and have assumed that the refractive index of the breast is constant, with a bulk value of approximately 1.4. We have applied a previously reported modified diffusion approximation, in which the refractive index for different tissues can be modeled. The model was used to generate NIR data from a realistic breast geometry containing a localized anomaly. Using this simulated data, we have reconstructed optical images, both with and without correct knowledge of the refractive-index distribution to show that the modified diffusion approximation can accurately recover the anomaly given a priori knowledge of refractive index. But using a reconstruction algorithm without the use of correct a priori information regarding the refractive-index distribution is shown as recovering the anomaly but with a degraded quality, depending on the degree of refractive index mismatch. The results suggest that provided the refractive index of breast tissue is approximately 1.3-1.4, their exclusion will have minimal effect on the reconstructed images.     

Evaporative tunnel cooling of dairy cows in the southeast. I: effect on body temperature and respiration rate

The techniques used to mitigate the effects of heat stress on lactating dairy cows are often overwhelmed in the southeastern United States, where elevated heat and humidity often persist for extended periods. A model free-stall barn located at the North Mississippi Branch Experiment Station in Holly Springs was used to evaluate the potential of tunnel ventilation with evaporative cooling to alleviate heat stress in lactating dairy cows. Two studies were conducted using 2 groups of 10 lactating Holsteins housed in the tunnel barn (inside) and 2 groups of matched herdmates housed in an adjacent covered free-stall barn (outside), which was cooled by fans and sprinklers during 2001 or by shade and fans alone in 2003. Peak daytime temperatures inside were 5.2 ± 0.18°C below that outside in 2001 and 3.1 ± 0.20°C lower in 2003. Although evaporative cooling increased humidity by 22%, cows housed in the tunnel barn received 84% less exposure to moderate heat stress (temperature-humidity index >80) in both years. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 15.5 ± 0.56 breaths/min and rectal temperatures by 0.6 ± 0.02°C compared with shade and fans alone in 2003. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 13.1 ± 0.78 breaths/min and rectal temperatures by 0.4 ± 0.03°C compared with fans and sprinklers in 2001. Thus, tunnel ventilation cooling dramatically reduced the exposure to heat stress and improved the comfort of lactating dairy cows when compared with traditional cooling technologies under the conditions present in the southeastern United States.     

Metal-Sulfate Induced Generation of ROS in Human Brain Cells: Detection Using an Isomeric Mixture of 5- and 6-Carboxy-2',7'-Dichlorofluorescein Diacetate (Carboxy-DCFDA) as a Cell Permeant Tracer

Evolution of reactive oxygen species (ROS), generated during the patho-physiological stress of nervous tissue, has been implicated in the etiology of several progressive human neurological disorders including Alzheimer's disease (AD) and amylotrophic lateral sclerosis (ALS). In this brief communication we used mixed isomers of 5-(and-6)-carboxy-2',7'-dichlorofluorescein diacetate (carboxy-DCFDA; C(25)H(14)C(l2)O(9); MW 529.3), a novel fluorescent indicator, to assess ROS generation within human neuronal-glial (HNG) cells in primary co-culture. We introduced pathological stress using the sulfates of 12 environmentally-, industrially- and agriculturally-relevant divalent and trivalent metals including Al, Cd, Cu, Fe, Hg, Ga, Mg, Mn, Ni, Pb, Sn and Zn. In this experimental test system, of all the metal sulfates analyzed, aluminum sulfate showed by far the greatest ability to induce intracellular ROS. These studies indicate the utility of using isomeric mixtures of carboxy-H(2)DCFDA diacetates as novel and highly sensitive, long-lasting, cell-permeant, fluorescein-based tracers for quantifying ROS generation in intact, metabolizing human brain cells, and in analyzing the potential epigenetic contribution of different metal sulfates to ROS-generation and ROS-mediated neurological dysfunction.