X-ray or gamma ray systems or devices – Specific application – Absorption
Patent
1992-06-02
1995-11-07
Epps, Georgia Y.
X-ray or gamma ray systems or devices
Specific application
Absorption
378 54, 378 19, 378 989, 378207, 2502521, 250368, 25037009, 2503851, 250580, G01N 2304
Patent
active
054652847
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In recent years the use of radiological examining equipment to make measurements of bone density in patients has continually increased. In particular, the use of such equipment in diagnosing and analyzing osteoporosis has become prevalent in the medical community. Osteoporosis is characterized by the gradual loss of bone mineral content or atrophy of skeletal tissue, resulting in a corresponding overall decrease in average bone density. Such a condition is common in elderly women and greatly increases the risk of fracture or similar bone related injury.
The presently available techniques for the radiological measurement of bone density utilize a rectilinear scanning approach. In such an approach, a radiation source, such as a radionuclide source or an x-ray tube, and a point detector are scanned over a patient in a raster fashion. This scan results in an image which has been derived from the point-by-point transmission of the radiation beam through the bone and soft tissue of a patient. The calculation of the bone-mineral concentration (the "bone density") is usually performed by a dual energy approach.
The current rectilinear scanning approach is generally limited by its long scanning time and its lack of good spatial resolution. The poor spatial resolution results in an inability to provide an image displaying high anatomical detail and which will permit accurate determination of the area in the scan occupied by bone. Moreover, the output of the x-ray source and the response of the detector must be closely monitored in order to assure high accuracy and precision.
SUMMARY OF THE INVENTION
In accordance with the present invention, a stationary bone densitometry apparatus is provided for examining a subject's body. A dual energy x-ray source directs a beam of x-ray radiation toward the subject's body. The radiation is applied to the entire region of the body being examined. A scintillation screen receives the x-ray radiation passing through the body of the subject, and emits radiation in the visible spectrum with a spatial intensity pattern proportional to the spatial intensity pattern of the received x-ray radiation.
A charge coupled device (CCD) then receives radiation from the scintillation screen. This CCD sensor generates a discrete electronic representation of the spatial intensity pattern of the radiation emitted from the scintillation screen. A focusing element between the screen and the CCD sensor focuses the scintillation screen radiation onto the CCD sensor. To prevent ambient radiation from reaching the CCD sensor, the present embodiment employs a shade or hood surrounding a region between the scintillation screen and the CCD sensor. A CCD controller then processes the electronic representation generated by the CCD sensor, and outputs corresponding image data.
A dual photon x-ray source is used to allow the examination to be performed with x-rays at two different energy levels. This source can be an x-ray tube, or a radionuclide source with a filter element to remove one of the energy levels when desired. Correlation of the image data retrieved using each of the two x-ray energy levels provides quantitative bone density information.
A focusing element between the scintillation screen and the CCD sensor can take the form of a lens or a fiber optic reducer. An image intensifier can be used in conjunction with the CCD sensor. The image intensifier can be a "proximity type" image diode or a microchannel based device. It can also be directly attached to the CCD. An image store used with the CCD controller allows manipulation of the CCD sensor output signals by a data processor. This includes the correlation of measurements utilizing x-ray beams of two different energy levels. The system can also be adapted to operate at higher shutter speeds enabling the counting of x-ray transmissions. This provides energy measurements of x-ray transmissions that are useful in certain applications.
An additional preferred embodiment is directed to systems and methods of imaging spectr
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Chu Kim-Kwok
Epps Georgia Y.
University of Massachusetts Medical Center
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