TECHNIQUE FOR CONSTRUCTING A RADIATION DETECTOR HAVING OPTIMIZED LIGHT OUTPUT
Publication Date: 2015-Nov-27
The IP.com Prior Art Database
A technique for constructing a radiation detector with optimized light output response at the detector is disclosed The technique allows minimizing tube heel effect by assembling parts with the highest light output in those regions of the detector with the most tube heel effect degradation According to the proposed technique chiclets in a lower intensity X ray region are made with lower amounts of chromium concentration in the reflector to enhance light output response of the chiclets Plurality of chiclets in Z direction of the detector can be optimized to match desired chromium levels of the detector reflector
The present invention relates generally to a volume computed tomography (CT) technique and more particularly to a technique for constructing a detector having optimized light output response at the detector.
Volume computed tomography (CT) provides CT images with improved spatial resolution and wide coverage of area of body of a patient. Generally, volume CT utilizes large volume detectors to cover an organ in one rotation. The large volume CT scanners require X-ray tubes with large apertures to provide a desired coverage. However, X-ray detection technique faces challenges in that when X-ray tubes with a single focal spot are used, the intensity of radiation from the X-ray beam decreases in direction of a patient. In general, as X-ray tube aperture grows in size, intensity of the X-ray beam decreases in X and Z directions of a detector due to self-absorption and the tube heel effect.
An example of a conventional method to reduce the tube heel effect for X-ray tubes using large tangles angles includes an X ray CT unit designed with a copper or aluminum wedge or step filter between an anode and a detector array. The filter is formed such that direction dependent intensity changes in X-ray radiation can be compensated perpendicular to Z direction. However, such conventional method reduces overall available radiation for imaging and in cases of low signal imaging (i.e. large patients), this creates more dose to the patient..
It would be desirable to have a technique to construct a detector such that decrease in intensity of radiation is minimized.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts a trend of useful X-ray region intensity as function of a target angle, θ.
A technique for constructing a radiation detector with optimized light output response at the detector is disclosed. Generally, a tile-able scalable design has been used for constructing volume detectors. A unit block, called chiclet, is assembled in groups in either of the X or Z directions of the detector. Further, a detector scintillator requires lower concentration of chromium in a reflector scintillator for a larger light output. The disclosed technique optimizes the chromium concentration in the reflector scintillator, such that, light output degradation due to tube heel effect in the Z-direction is minimized.
Furthermore, zero chromium content in the reflector scintillator produces the most output of light. Also, half the chromium concentration of that present in a conventional chromium content formula produces enhanced light output. The technique allows minimizing the tube heel effect by assembling parts with the highest light output in th...