BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure will become more clearly understood from the following detailed description in connection with the accompanying drawings, in which:
FIG. 1 is a schematic illustration of a prior art radiation detector;
FIG. 2 is a schematic illustration showing gamma ray interactions with a scintillation crystal of a prior art radiation detector;
FIG. 3 is a schematic illustration of an optic taper according to the prior art;
FIG. 4 is a side, schematic illustration of a radiation detector in accordance with an embodiment of the present disclosure;
FIG. 5 is a perspective view of a light guide illustrating a plurality of light pipes in accordance with the present disclosure;
FIG. 6 is a schematic bottom view of the light guide shown by FIG. 5 illustrating the plurality of light pipes;
FIG. 7 is a schematic top view of the light guide shown by FIG. 5 illustrating the plurality of light pipes;
FIGS. 8
a and 8b are schematic side views of the light guide shown by FIG. 5 showing respective distance and angular measurements; and
FIGS. 9
a, 9b and 9c are enlarged views of the area of details shown by FIGS. 6 and 7.
DETAILED DESCRIPTION
The following description is presented to enable one of ordinary skill in the art to make and use the disclosure and is provided in the context of a patent application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present disclosure is not intended to be limited to the embodiments shown but is to be accorded the broadest scope consistent with the principles and features described herein.
Referring now to the drawings, and initially to FIG. 4, there is shown a side, schematic illustration of a radiation detector in accordance with the present disclosure and generally referenced by numeral 100. The radiation detector 100 can be a positron emission tomography (PET) camera and includes a scintillator array 102 having a plurality of scintillator crystals or elements 102a, a light guide 104 (see FIGS. 5-9c) having a plurality of optical elements or light pipes 105, and a position-sensitive photodetector assembly 106 having components as known in the art (such as the components described above with reference to FIGS. 1 and 2). The light guide 104 does not include fused optical elements or light pipes and increases the detection surface area of the radiation detector 100 relative to the surface area of the position-sensitive photodetector assembly 106.
The scintillator array 102, as known in the art, is at least partially used for detecting and absorbing gamma photon radiation emissions 108 emanating from the body and directing the photons from one end 102′ of the array 102 to an opposite end 102″ of the array 102. Types of scintillator elements 102a that can be used in the scintillator array 102 include inorganic crystals, organic plastics, organic liquids and organic crystals. Preferably, the elements 102a of the scintillation array 102 are made from high light yield scintillators, such as lutetium oxyorthosilicate (LSO) or lanthanum bromide (LaBr).
End 102″ of the scintillator array 102 is positioned in proximity to and preferably in contact with bottom square surface 104a of the light guide 104. A top square surface 104b of the light guide 104 is positioned in proximity to and preferably in contact with the photodetector assembly 106 for transferring photons from the scintillator array 102 to the photodetector assembly 106. Top square surface 104b is preferably in contact with a glass entrance window 107 of the photodetector assembly 106.
As shown by FIGS. 5-8, the light guide 104 includes a plurality of glass, plastic and/or silica light pipes 105. The light pipes 105 can also be made from other optical materials, besides glass, plastic and silica. The light pipes 105 transfer light photons from the bottom square surface 104a to the top square surface 104b of the light guide 104. A group of light pipes 105 can be bundled together to form a light pipe bundle, such that the light guide 104 includes a plurality of light pipe bundles packed together to form a particular geometrical configuration of the light guide 104.
In particular, the light guide 104 has a tapered geometrical configuration and a trapezoidal geometric shape. The trapezoidal geometric shape includes the bottom square surface 104a and the top square surface 104b adjoined to each other by four trapezoid sides 104c-f defining four equidistant, angled edges 110a-d.
Each of the plurality of light pipes 105 includes a first end 105a flush with the bottom square surface 104a (FIG. 6) and a second end 105b flush with the top square surface 104b (FIG. 7). The first end 105a of each optical light pipe 105 is configured for being optically coupled with a plurality of scintillator elements or crystals 102a of the scintillator array 102. The second end 105b of each optical light pipe 105 is configured for being optically coupled with the photodetector assembly 106.
In a preferred embodiment as shown by FIGS. 6-9c (the measurements shown are in millimeters and degrees (FIG. 8a only)), each of the second ends 105b flush with the top square surface 104b has a square-shaped cross-section (see FIG. 9a which is an enlarged view of area B in FIG. 7). A majority of the first ends 105a flush with the bottom square surface 104a have a square-shaped cross-section (see FIG. 9c which is an enlarged view of area C in FIG. 6). Several of the first ends 105a flush with the bottom square surface 104a and located along the periphery of the bottom square surface 104a have a rectangular-shaped cross-section (see FIG. 9b which is an enlarged view of area A in FIG. 6). In the preferred embodiment, the top square surface 104b has a surface area of 368.87351 square millimeters and the bottom square surface 104a has a surface area of 999.10357 square millimeters.
The light guide 104 is symmetrical with respect to at least one axis thereof, such as along the X-axis and Y-axis shown by FIG. 7, as well as with respect to each of its diagonal axes. Accordingly, the measurements shown by FIG. 9a are representative of each corner of the top square surface 104b; and the measurements shown by FIG. 9b are representative of each corner of the bottom square surface 104a.
FIG. 8
a illustrates the angular measurements of the sixteen light pipes 105 flush with a side (e.g., side 104c) of the light guide 104. All the sides 104c-f are identical with respect to the layout of the light pipes 105 thereat, such that the side shown by FIG. 8a is representative of all the sides 104c-f. FIG. 8b illustrates the distance measurements from the center of the bottom square surface 104a and the top square surface 104b to each of the first and second ends 105a, 105b of the light pipes 105.
When the light guide 104 is positioned in the radiation detector 100 as shown by FIG. 4, the first end 105a of each optical light pipe 105 is optically coupled to a plurality of scintillator elements 102a for enabling the light guide 104 to read out of more scintillator elements or crystals per photodetector surface area. The second end 105b of each optical light pipe 105 is optically coupled to the photodetector assembly 106. In particular, during operation of the radiation detector 100, gamma photon radiation emissions 108 propagate through the scintillator crystals 102a and individual light pipes 105 of the light guide 104 before being directed to the photodetector assembly 106. In the radiation detector embodiment illustrated by FIG. 4, the light guide 104 allows the detection of the scintillator array 102 that is significantly larger than the active surface area 107′ of the photodetector assembly 106.
The tapering down from the scintillator array surface area to a smaller photodetector surface area using the light guide 104 enables the tiling of photodectors into larger detecting surfaces. For example, the light guide 104 can be used to read out 400 pixels (20×20) on a single photosensor. Labeling such a device as a “detector”, one may subsequently tile four of these detectors into a 1×4 array to form a pixel surface composed of 20×80 elements of common pitch, or into a 2×2 array for 40×40 elements of common pitch.
In particular, a preferred embodiment of the light guide 104 optically couples in a 9:4 manner. This means that a 3×3 array of scintillator elements or crystals 102a are coupled to a 2×2 array of light guide elements or light pipes 105.
As described above, the light guide 104 according to the present disclosure does not include fused light pipes, has a tapered geometrical configuration and improves light collection in a radiation detector for reading out a scintillator array having a significantly larger surface area than the active surface area of a photodetector assembly.
Although the present disclosure has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiment and these variations would be within the spirit and scope of the present disclosure. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.
Patent Application
20080073542
