X-ray and gamma ray detector readout system
Inventors
Tumer, Tumay O • Clajus, Martin • Visser, Gerard
Assignees
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Publication Number
US-7818047-B2
Publication Date
2010-10-19
Expiration Date
Abstract
A readout electronics scheme is under development for high resolution, compact PET (positron emission tomography) imagers based on LSO (lutetium ortho-oxysilicate, Lu2SiO5) scintillator and avalanche photodiode (APD) arrays. The key is to obtain sufficient timing and energy resolution at a low power level, less than about 30 mW per channel, including all required functions. To this end, a simple leading edge level crossing discriminator is used, in combination with a transimpedance preamplifier. The APD used has a gain of order 1,000, and an output noise current of several pA/√Hz, allowing bipolar technology to be used instead of CMOS, for increased speed and power efficiency. A prototype of the preamplifier and discriminator has been constructed, achieving timing resolution of 1.5 ns FWHM, 2.7 ns full width at one tenth maximum, relative to an LSO/PMT detector, and an energy resolution of 13.6% FWHM at 511 keV, while operating at a power level of 22 mW per channel. Work is in progress towards integration of this preamplifier and discriminator with appropriate coincidence logic and amplitude measurement circuits in an ASIC suitable for a high resolution compact PET instrument. The detector system and/or ASIC can also be used for many other applications for medical to industrial imaging.
Core Innovation
The invention is a medical imaging system and corresponding method that image at least one portion of at least one living organism treated with at least one radiopharmaceutical. The radiopharmaceutical emits a plurality of positrons that annihilate and produce a plurality of photons, and the detector system includes a plurality of position sensitive photon detectors with at least one entrance aperture external to the living organism and proximate to the portion being imaged.
The detector system comprises at least one scintillator having a first side connected to at least one first scintillation light detector and a second side connected to at least one second scintillation light detector. The system includes at least one multi-channel integrated circuit coupled to the plurality of position sensitive photon detectors, at least one processor coupled to the multi-channel integrated circuit, and at least one display system coupled to the processor for displaying at least one image.
The invention further provides interaction determination by processing photon interaction information to produce images, including determining depth of interaction and using front/back pulse-height ratios for DOI. It also extracts timing and energy information from the detected signals and uses the interaction information to refine reconstructed imaging, including energy cuts and reduction of radial elongation error associated with DOI blurring.
The disclosed approach includes a multi-channel readout architecture for an APD-array readout electronics/ASIC concept in which front and back APD readout is used to obtain DOI. DOI, energy, and timing extraction is performed from pulse-height ratios and leading-edge level-crossing discriminator concepts, with coincidence/sample-hold logic and sparse readout concepts for large channel counts.
Claims Coverage
The partial content provides two independent claims: clm-00001 (system) and clm-00017 (method). Across these independent claims, the main inventive features include a specific detector architecture using position sensitive photon detectors with scintillators coupled to scintillation light detectors on different sides, integration with a multi-channel integrated circuit, and direction-based imaging with photon direction determination.
Medical imaging system with position sensitive photon detectors
A medical imaging system for imaging at least one portion of at least one living organism treated with at least one radiopharmaceutical, where positrons annihilate to produce photons; a detector system comprises a plurality of position sensitive photon detectors with at least one entrance aperture external to the living organism and proximate to the portion, such that photons pass into the position sensitive detectors and the detectors comprise at least one scintillator with a first side connected to at least one first scintillation light detector and a second side connected to at least one second scintillation light detector.
Multi-channel integrated circuit coupled to position sensitive photon detectors with processor and display
At least one multi-channel integrated circuit coupled to the plurality of position sensitive photon detectors; at least one processor coupled to the at least one multi-channel integrated circuit; and at least one display system coupled to the at least one processor, displaying at least one image of the at least one portion of the at least one living organism.
Imaging method using scintillator with at least two scintillator light detectors on different sides
A method of imaging at least one portion of at least one living organism comprising treating the portion with at least one radiopharmaceutical producing a plurality of photons; providing at least one detection system comprising at least one scintillator and at least two scintillator light detectors; connecting at least a first scintillator light detector to at least a first side of the scintillator and at least a second scintillator light detector to at least a second side of the scintillator; positioning the detection system to receive at least a portion of the plurality of photons.
Determining photon direction, processing direction to produce and display an image
Determining a direction of at least one portion of the plurality of photons entering the detection system; processing the direction for a portion of the plurality of photons to produce at least one image of the at least one portion of the living organism; and displaying the at least one image.
The independent claims define an imaging architecture that detects photons with position sensitive photon detectors that use scintillators coupled to scintillation light detectors on different sides, and that integrates multi-channel integrated circuitry with a processor and display to form images. The independent method claim complements this by specifying photon direction determination and direction-based image processing using a scintillator with at least two light detectors, followed by displaying the image.
Stated Advantages
The document reports timing and energy resolution performance at 511 keV.
The document reports DOI position resolution on the order of a few millimeters FWHM.
The interaction information is used to refine reconstructed imaging, including energy cuts and reduction of radial elongation error associated with DOI blurring.
Low-power readout electronics and ASIC multi-channel architecture concepts are intended for high-resolution, low-power PET.
Documented Applications
Medical imaging of at least one portion of at least one living organism treated with at least one radiopharmaceutical.
High-resolution PET.
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