1257 results about "Attenuation coefficient" patented technology

The present invention pertains to a method and an apparatus to generate a density image of an object using fan or cone beams of radiation and collimated detectors on one side of the object. The method consists of irradiating an object with a plurality of pairs of non-parallel radiation beams wherein the beams in each pair intersect a same segment along the axis of the detector. Compton-scattering radiation from the beams are then measured, and corrected attenuation coefficients along each beam are obtained. This latter step is effected by taking a first ratio of detector measurements for the beams in each pair; comparing the first ratio with a second ratio of corresponding calculated detector measurements and balancing discrepancies between the first and second ratios in a forward-inverse numerical analysis algorithm. Taking ratios of attenuation coefficients along related incident beams eliminates non-linearity problems whereby the aforesaid algorithm can be solved.

Imaging apparatus, is provided, comprising a first device, for obtaining a first image, by a first modality, selected from the group consisting of SPECT, PET, CT, an extracorporeal gamma scan, an extracorporeal beta scan, x-rays, an intracorporeal gamma scan, an intracorporeal beta scan, an intravascular gamma scan, an intravascular beta scan, and a combination thereof, and a second device, for obtaining a second, structural image, by a second modality, selected from the group consisting of a three-dimensional ultrasound, an MRI operative by an internal magnetic field, an extracorporeal ultrasound, an extracorporeal MRI operative by an external magnetic field, an intracorporeal ultrasound, an intracorporeal MRI operative by an external magnetic field, an intravascular ultrasound, and a combination thereof, and wherein the apparatus further includes a computerized system, configured to construct an attenuation map, for the first image, based on the second, structural image. Additionally, the computerized system is configured to display an attenuation-corrected first image as well as a superposition of the attenuation-corrected first image and the second, structural image. Furthermore, the apparatus is operative to guide an in-vivo instrument based on the superposition.

Cone beam volume CT breast imaging is performed with a gantry frame on which a cone-beam radiation source and a digital area detector are mounted. The patient rests on an ergonomically designed table with a hole or two holes to allow one breast or two breasts to extend through the table such that the gantry frame surrounds that breast. The breast hole is surrounded by a bowl so that the entire breast can be exposed to the cone beam. Spectral and compensation filters are used to improve the characteristics of the beam. A materials library is used to provide x-ray linear attenuation coefficients for various breast tissues and lesions.

A method is provided for conducting an electromagnetic induction survey of a geological formation penetrated by a borehole lined with a conductive casing. The method includes positioning a transmitter in the borehole, whereby the transmitter generates a transmitter magnetic moment, and positioning a distant receiver external of the borehole to detect a magnetic field induced by the transmitter, whereby the distant receiver is disposed across part of the formation from the borehole. Furthermore, an auxiliary receiver is positioned in the borehole proximate the transmitter to detect a magnetic field induced by the transmitter and attenuated by the conductive casing. Subsequently, a first casing attenuation factor that is applicable to the magnetic field measured by the auxiliary receiver is determined from a ratio of the measured magnetic field at the auxiliary receiver and the transmitter magnetic moment. A second casing attenuation factor applicable to the measurement of the magnetic field at the distant receiver is determined from a non-linear relationship (e.g., a power law relationship) between the first casing attenuation factor and the second attenuation factor, wherein the second attenuation factor is less than the first attenuation factor. Then, a formation attenuation factor applicable to the measured magnetic field at the distant receiver is determined from a relationship between the magnetic moment of the transmitter, the second casing attenuation factor, and the measured magnetic field at the distant receiver. Finally, the method correlates the determined value of the formation attenuation factor to a resistivity characteristic of the formation between the distant receiver and the transmitter.

A photographic flash unit comprises a direct flash unit and a bounce flash unit rotatably connected to the direct flash unit. Status and control lines coupled between a hot shoe and each flash unit enable independent triggering and control of each flash unit. The direct and bounce flash units may be a part of a digital camera adapted to make a first test exposure using direct flash illumination and second test exposure using bounce flash illumination, then computing an attenuation factor for compensating a selected flash exposure parameter by dividing the selected parameter by the attenuation factor. Steps in a method embodiment include making a first test image, making a second test image, selecting regions in the first and second test images, computing an attenuation factor from luminosity values for the first and second test images, and compensating settings for a final bounce flash image by the attenuation factor.