X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
1999-06-14
2001-02-27
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S057000
Reexamination Certificate
active
06195413
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims the right of foreign priority with respect to Application No. DE 19826062.8 filed in Germany on Jun. 12, 1998, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a method for detecting X-rays where the individual energy ranges are simultaneously radiated onto an object to be X-rayed and are thereby weakened and, the weakened X-ray beams are separated into a low-energy range and a high-energy range. The invention additionally relates to an arrangement for implementing this method.
It is known to use a detection device, configured with several detector pairs, for the detection and determination of materials with the aid of X-rays. Each detector pair consists of one 0.1-0.5 mm thin and one 0.5-20 mm thick radiation detector. The radiation detectors are arranged one after another and are therefore penetrated successively by the X-rays or the roentgen quanta from a radiation source. The X-ray beam consequently is separated into individual energy ranges, which is necessary to determine the material types of a good examined with the aid of X-rays. The fact that photons with higher energy show little interaction in the thin detector, in the following called a low-detector, and are thus absorbed in the subsequent thick detector, in the following called a high detector, is used for the separation of the radiation into different energy ranges. In contrast, photons with low energy are absorbed almost completely in the low detector. The radiation impinging on the detector pairs changes as a result of the good or material to be tested, which is located between the radiation source and the detection device. Based on the change in the signals of each detector pair, it is then possible to draw conclusions as to the materials inserted into the ray path.
Since a certain interaction of the high-energetic photons in the low detector cannot be prevented, high-energy shares of the impinging radiation are also absorbed. As a result, an overlapping of the energy ranges occurs. Consequently, these traditional arrangements are not suitable for an exact material determination.
British patent reference GB-1154973 discloses a detector arrangement for taking an X-ray of a human body. In that case, a respective one filter is arranged between three X-ray films. Bones, muscles and fatty tissues are shown on the first X-ray film. The following first filter is dimensioned such that it filters out the energy shares of the bones so that only the energy shares of the muscles and the fatty tissue are shown on the second X-ray film. Subsequently, the energy shares for the fat or fatty tissue are filtered out in the second filter, so that only the energy shares for the muscles are captured on the third X-ray film. The X-ray picture is then composed of the image on the first X-ray film less the images from both the second and third X-ray films. For this, the first X-ray film is a film positive and the other two films are respectively film negatives. The resulting X-ray image represents the bone information.
U.S. Pat. No. 4,626,688 discloses a separated energy radiation detection with varied energy levels, which are generated and transmitted with a time displacement. Thus, a low frequency radiation is initially produced and is beamed through the body of a patient. A first detector absorbs this radiation and transmits the signals, resulting from the energy spectra, to a digital processor circuit. Subsequently, a higher frequency is generated and is beamed as radiation with higher energy through the patient and is then transmitted to the processor via a second detector. In the processor, the low frequency is subtracted from the high frequency, so that the low energy shares no longer form a component of the higher frequency. The higher frequency represents the bone information, as is known, so that the low energy shares of the soft body tissues are computed out of the high-energy shares through this measure. The image on a luminous screen again represents only the information on the X-rayed bones.
The disadvantage of the aforementioned arrangements and methods is that the energy ranges are reduced to an energy range that corresponds to the searched for material, so that the arrangements and methods can be used only if the materials and energy spectra to be detected are known ahead of time.
U.S. Pat. No. 4,029,963 discloses an arrangement and a method for detecting and identifying various materials. In this case, the transmitted X-rays are from the start separated into low-energy ranges and high-energy ranges, which are thus free of spectral displacements. A radiation depending on the atomic number Z, as well as a density-dependent radiation are determined from the separately transmitted rays through mathematical correlation. The radiation depending on the atomic number Z is proportional to the photoelectric component while the density-dependent radiation is proportional to the electrode density. The material is determined on the basis of this correlation.
It is the object of the invention to provide a method and an arrangement, which allow a clearer separation of low-energy shares and high-energy shares of a single X-ray beam. As a result, the X-rayed materials can be identified easier with only a single X-ray beam.
SUMMARY OF THE INVENTION
The above object generally is achieved according to one aspect of the present invention by a method for detecting X-rays where the individual energy ranges are simultaneously radiated onto an object to be X-rayed and are thereby weakened and, the weakened X-ray beams are separated into a low-energy range and a high-energy range, and wherein the high-energy shares absorbed in the low energy range are once more computed out of the low-energy range signal using an additional signal determined from another low-energy range signal that also represents the low-energy range of the weakened X-ray beam.
The above object generally is achieved according to a further aspect of the invention by an arrangement for implementing the above method with the arrangement comprising: an X-ray beam generator for directing an X-ray beam toward an object to be X-rayed: a detection device including several pairs of detectors with respectively one low detector and one high detector, and a subsequently installed computation unit and an image evaluation unit, and wherein each detector pair is provided with an additional low detector that provides the additional signal and is spatially integrated in the beam path between the first low detector and the high detector so that these detectors form a detector group.
The invention is based on the idea of creating the highest possible signal differences following penetration of an object, so that this will result in the best possible, meaning a high-contrast, separation of a X-ray beam into low-energy range and high-energy range. In addition to identifying the material, the method according to the invention is also used to determine the type of material, which occurs with the aid of the separated low-energy and high-energy ranges of this one X-ray beam. The polychromatic X-ray beam and thus all quanta up to the limit energy are radiated at the same time and are captured in the detectors at the same time, spatially one after another. For an improved separation, a signal is generated that corresponds to a high-energy share absorbed in a first detector. With this signal, the undesirable high-energy shares are computed out of the energy spectrum of the first detector. Several identical detector pairs, respectively consisting of a detector for low-energy shares and a detector for high-energy shares, are provided for this with an additional detector. This detector also absorbs the low-energy shares and is located between the low-detector and the high-detector, so that these detectors are successively penetrated by an X-ray beam that is weakened by the object. The second low detector is used to generate the signal with the undesirable high-ene
Geus George
Hartick Martin
Schall Patricia
Dunn Drew A.
Heimann Systems GmbH
Kunitz Norman N.
Porta David P.
Venable
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