Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
1999-03-26
2001-10-30
Epps, Georgia (Department: 2873)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S483100
Reexamination Certificate
active
06310352
ABSTRACT:
The invention relates to a device for the detection of incident radiation, e.g. X-rays, &ggr;-rays, ionizing radiation and fluorescence or low-level light, having at least one detecting element which has a sensor section (scintillator, wavelength shifter, and the like) for converting the incident radiation into photons in the UV, visible, or IR portions of the electromagnetic spectrum (e.g., scintillation light) and an optical amplifier section that receives the converted light from the detector section, transmits it for further processing, and amplifies it in the process.
Devices and detectors for detection of incident radiation from the wavelength spectrum of X-rays and &ggr;-rays are known in many embodiments. These devices have achieved great importance in the field of medicine, particularly in connection with imaging processes such as PET (positron emission tomography), SPECT (single photon emission computed tomography), scintigraphy (Anger camera), and X-ray CT (computed tomography).
Among the various imaging processes in medicine, MR (magnetic resonance or nuclear magnetic resonance) tomography has great diagnostic importance based on superior image quality and three-dimensional image information. This is based on the measurement of the three-dimensional distribution of hydrogen atoms. It is orders of magnitude better than other radiation or nuclear medicine processes such as scintigraphy and PET in terms of resolution. For these reasons MR tomography is particularly suitable for diagnostic localization. In contrast, the strengths of scintigraphy or PET are in the areas of detection of physiological parameters.
There thus exists a need for a medical instrument that appropriately combines the advantages of imaging processes based on physiological parameters, e.g. scintigraphy/PET, with those of imaging processes based on structural information, as for example MR tomography.
Attempts to combine information from the two systems after the fact have been made at the Deutsche Krebsforschungszentrum [German Cancer Research Center] among other places (L. R. Schad, “Three Dimensional Image Correlation of CT, MR and PET: Studies in Radiotherapy Treatment Planning of Brain Tumors”, Journal of Computer assisted Tomography, 1987, II (6), p. 948-954).
However, a difficulty in the later combination of information from multiple different imaging systems is that the human body is not rigid. Conversion problems thus arise among the various imaging systems. Attempts are made to compensate for these problems through digital image processing, an effort which succeeds for tumors in the cranial region through stereotactic methods.
A combination device that permits the simultaneous acquisition of structural information and the three-dimensional distribution of radioactivity would be desirable. This is not achievable through a combination of currently available devices. The primary obstacles in this regard are the high static magnetic field, the time-switched strong magnetic field gradients, the pulsed incident electromagnetic waves in the MHz region and the scarcity of available space for additional detection devices in the central area of an MR tomograph. For this reason, electronic detectors cannot be used inside an MR tomograph. This means that the crystals currently used in PET devices (BGO, BaF
2
and the like) that are directly coupled to a photomultiplier are unsuitable for the desired combination device.
These problems can be at least partially overcome by the use of bundles of scintillating optical waveguides instead of crystals. Initial tests of bundled scintillating optical waveguides have already been published (R. C. Chaney et al, “Testing the Spatial Resolution and Efficiency of Scintillating Fiber PET Modules”, IEEE Transactions of Nuclear Science, Vol. 39 No. 5, October 1992). In a seminar presentation given at the German Cancer Research Center in the summer of 1995, Professor P. P. Antich reported on the first tests of a combination device (PET/MR tomography). Scintillating plastic optical waveguides were used in these instruments. The scintillation light exiting the end of the fiber bundle was converted into an electrical signal with photomultipliers (the distance between the scintillation light and photomultiplier was approximately 5 m here). In these experiments, great problems were presented by the not to be neglected optical attenuation of the scintillating plastic fibers as well as the small number of photons generated in the scintillating optical waveguides. The invention solves precisely these problems in an elegant fashion, as is described in detail below.
As an alternative to photomultipliers, MCPs (multichannel plates, multichannel plate amplifiers) are used to detect weak optical signals. A disadvantage of both systems is that high voltages in the range of several hundred volts are required for their operation. This increases the cost of devices equipped with such detectors.
Electronic components are also used for detection of X-rays and &ggr;-quanta. These are primarily PIN and avalanche diodes, which exhibit a pronounced thermal noise characteristic and for this reason alone are inherently inferior to optical amplifiers.
Optical amplifiers are inherently superior to electronic amplifiers for physical reasons because they have a better signal-to-noise ratio.
In summary, it can be said with regard to the above-described state of the art that the amplifier sections of known radiation detectors are only conditionally suited for amplifying very weak signals and transmitting these signals over large distances. A further disadvantage of the known devices is that very weak scintillation or fluorescence light is only detectable with difficulty, especially in hard-to-reach experimental or investigative arrangements. Moreover, a spatial separation between the place of detection and the place of analysis is achievable only with difficulty on account of the weak signals.
Reference is made to the following publications regarding the general state of the art:
DE-OS 23 51 450; this publication relates to a scintigraphic collimator that serves to focus the &ggr;-rays emerging from a &ggr;-ray-emitting experimental object.
DE-OS 24 46 226; this publication relates to a scintillator that consists of metal-ion-doped alkali halogenide material.
DE 39 18 843; this publication relates to an X-ray detector that consists of a series of small rods of scintillator material.
DE 33 27 031 A1; this publication relates to an X-ray device in which a slot-shaped X-ray image is converted into a visible image and delivered via an optical waveguide arrangement to an image intensifier whose output image is translated into an electrical signal by a converter.
DE 43 34 594; this publication relates to a detector for high-energy radiation for computer tomography, wherein is provided a series of scintillators which are associated with corresponding optical waveguides that are separated from one another by slits.
EP 0 471 926 A2; this publication relates to a fast, radiation-stable CT-scintillation system in which a special garnet material is used.
The objective of the present invention is to create a radiation detector which can be used for imaging processes that have high spatial resolution even for weak incident radiation and especially in combination with difficult-to-reach arrangements.
Advantageous further refinements of the invention are presented in the subsidiary claims. Advantageous applications of the device in accordance with the invention are named in the application claims.
Thus in other words, the invention creates a radiation detector with a detecting element whose amplifier section ensures optical amplification of scintillation light in the manner of a laser by means of an optical waveguide whose material is optically pumped. Through the optical pumping, the photons obtained by the sensor section from the incident radiation are amplified several thousand times. A crucial advantage of the device in accordance with the invention is that the optical waveguide, and thus the amplif
Gross Karlheinz
Klaus Michael
Maier-Borst Wolfgang
Schrenk Hans-Hermann
Sinn Hannsjorg
Deutsches Krebsforschungszentrum Stiftung Des Offentlichen Recht
Epps Georgia
Fuierer Marianne
Hanig Richard
Hultquist Steven J.
LandOfFree
Radiation detection device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiation detection device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation detection device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561070