Timing of the intervention for intracranial hematomas is critical for its success, specifically since expansion of the hemorrhage can result in debilitating and sometimes fatal outcomes. Led by Britton Chance, we and an extended team from University of Pennsylvania, Baylor and Drexel universities developed a handheld brain hematoma detector for early triage and diagnosis of head trauma victims. After obtaining de novo Food and Drug Administration clearance, over 200 systems are deployed in all Marine battalion aid stations around the world. Infrascanner, a handheld brain hematoma detection system, is based on the differential near-infrared light absorption of the injured versus the noninjured part of brain. About 12 independent studies have been conducted in the USA, Canada, Spain, Italy, the Netherlands, Germany, Russia, Poland, Afghanistan, India, China, and Turkey. Here, we outline the background and design of the device as well as clinical studies with a total of 1293 patients and 203 hematomas. Infrascanner demonstrates high sensitivity (adults: 92.5% and children: 93%) and specificity (adults: 82.9% and children: 86.5%) in detecting intracranial hematomas >3.5 mL in volume and <2.5 cm from the surface of the brain. Infrascanner is a clinically effective screening solution for head trauma patients in prehospital settings where timely triage is critical.
Detection of cerebral hypoxia-ischemia in infants remains problematic, as current monitors in clinical practice are impractical, insensitive, or nonspecific. Our study develops a multiwavelength spatial domain construct for near-infrared spectroscopy (NIRS) to detect cerebral hypoxia-ischemia and evaluates the construct in several models. The NIRS probe contains photodiode detectors 2, 3, and 4 cm from a three-wavelength, light-emitting diode. A construct determines cerebral O2 saturation based on spatial domain principles. Device performance and construct validity are examined in in-vitro models simulating the brain, and in piglets subjected to hypoxia, hypoxia-ischemia, and hyperoxic conditions using a weighted average of arterial and cerebral venous O2 saturation measured by CO-oximetry. The results in the brain models verify key equations in the construct and demonstrate reliable performance of the device. In piglets, the device measures cerebral O2 saturation with bias ±4% and precision ±8%. In conclusion, this NIRS device accurately detects cerebral hypoxia-ischemia and is of a design that is practical for clinical application.
The atmosphere is the optical medium between the imaging system and the observed object. The effect of this optical turbulent, absorbing and scattering element on the quality of an image is difficult to predict. Since the beginning of the sixties there were several attempts to build a model that will describe the degrading effect of the atmosphere on spatial resolution of imaging systems. In the field of atmospheric turbulence there is a common agreement on its relative contribution to the degradation of the spatial resolution of an image. On the other hand in the field of atmospheric scattering there is a disagreement on its degrading effects and an international scientific discussion has been developed in the past five years in this scientific field. A model, that was suggested several years ago by Sadot and Kopeika, claimed that the effect of the atmospheric scattering on the spatial resolution of imaging systems is a function of the properties of the imaging system, apart from the inherent properties of the atmosphere. The results of their model were in contrast with the results of the work of other scientists and therefore, caused a scientific debate. The purpose is to propose an alternative theoretical model which describes the effects of atmospheric scattering by focusing on the point spread function of the imaging system.
KEYWORDS: Atmospheric modeling, Point spread functions, Imaging systems, Data modeling, Aerosols, Scattering, Modulation transfer functions, Radiometry, Monte Carlo methods, Atmospheric physics
This paper presents the results of a field experiment that was carried out in order to verify a physical model which describes the relationship between the optical properties of the atmosphere and the characteristics of an imaging system. The model depicts how different components of the light that are reaching the imaging system, after passing through the atmosphere, are detected by it. The measurements were done using a scanning point radiometer, while a local meteorological station measured the properties of the atmosphere. Theoretical predictions, which were achieved using a Monte-Carlo simulation of atmospheric scattering effects, are compared with the experimental data acquired in the field test. Comparison of theoretical predictions, using the above model, with the experimental data of other researchers is included. Both our data and the results of Luc Bissonnette of Canada supports the suggested model.
In this paper a physical model that describes the relationship between the optical properties of the atmosphere and the characteristics of an imaging system is suggested. The model describes how different components of the light reaching the imaging system, after passing through the atmosphere, are detected by it. The model includes the effects of the final size of the detector elements of the imaging system and the dynamic range and the final field of view limits of the imager. It is found that for common imaging systems (with resolution of 8 bit or 12 bit) working in general atmosphere conditions (VIS >= 5 km), the processes of atmospheric scattering and absorption hardly contribute to spatial blurring of the recorded images. A field experiment was carried out in order to verify the predictions of the suggested model. The measurements were performed using a scanning point radiometer, while a local meteorological station and a visibility meter measured the properties of the atmosphere. Theoretical predictions, which were accomplished by using a Monte-Carlo simulation of atmospheric scattering effects, are compared with the experimental data acquired in the field tests. A good agreement was obtained between the measured data and the theoretical predictions.
A numerical code is used to examine the features of the effect of atmospheric turbidity on the modulation transfer function of an optical system operating on ground, on an airplane or a satellite. Models of size distributions and optical properties of particulate suspended in the atmosphere are considered. The relevant scattering phase functions are calculated by Mie theory and are later used by a code using both Monte Carlo and geometrical optics procedures to evaluate the contribution of atmospheric turbidity to the augmentation of the point spread function. Comparison of ours with other researchers procedures is shown. The effect of atmospheric turbidity is evaluated as due to the presence of scatterers (the secondary sources) whose defocused images are distributed on the plane of the image of the primary source. The positions of the scatterers are determined by a Monte Carlo procedure, while the contribution of each secondary source to the irradiance on the image plane is evaluated by means of geometrical optics. Cases of different aerosols types, geometry aspects of viewing through the atmosphere and atmospheric absorption effects on the MTF are shown.
A field measurement program was initiated to determine the utility of the 4.6- to 4.9-μm spectral region as a remote temperature sensing channel. A spectroradiometer (covering the 1.3- to 14-μm region) was used to determine effective surface temperatures of various natural objects both in the 4.6- to 4.9-μm and the commonly used 10.5- to 12.5-μm regions. Comparisons of the effective temperatures obtained from both short-range (30 to 300 m) and long-range (3 to 10 km) measurements are presented. For measurements at short ranges, the deduced effective temperature for each region wascompared with contact temperature measurement of the surface. For measurements over long ranges, the effective temperatures were compared after having accounted for path radiance effects. Accurate path radiance corrections were made from measurements over the tail region of the 4.3-μm CO2 absorption band.
Modern infrared (IR) imaging systems are sensitive enough to detect weak targets, but background clutter makes the detection difficult. The introduction of an IR polarizer into thermal imaging systems is one of the techniques to improve this low target-to-clutter ratio. The use of polarized IR energy helps to detect man-made objects in complex natural backgrounds. Over the past 4 years, we have investigated the polarization properties of thermal IR radiation (8 - 12 micrometers ). In the course of our work, we have built an infrared imaging polarimeter and participated in field and laboratory experiments. This paper summarizes the results of our work. It includes a brief theoretical background, description of the equipment, and a comparison of our empirical findings with a theoretical model and with results of other researchers.
Spectral radiance of various background elements (e.g., vegetation, rocks, snow and concrete) were measured in the 4.5 - 5 micrometers atmospheric window, both during the day and night. Effective temperatures of these surfaces were calculated and an attempt was made to evaluate true temperatures as well. The results are quite satisfactory, probably due to the following reasons: (1) The emissivity of most natural surfaces in this spectral region is high. Therefore the non-thermal (reflected solar component of the radiance) is small. (2) The spectral variation of the emissivity of most natural surfaces in this spectral region is very small, thus facilitating the evaluation of contact surface temperature. The results suggest the feasibility of using the 4.5 - 5 micrometers atmospheric window for background temperature evaluation.
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