Development of a novel depth of interaction PET detector using highly multiplexed G-APD cross-strip encoding

Purpose: The aim of this study was to develop a prototype PET detector module for a combined small animal positron emission tomography and magnetic resonance imaging (PET/MRI) system. The most important factor for small animal imaging applications is the detection sensitivity of the PET camera, whic...

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Published in:	Medical physics (Lancaster) Vol. 41; no. 8; pp. 081916 - n/a
Main Authors:	Kolb, A., Parl, C., Mantlik, F., Liu, C. C., Lorenz, E., Renker, D., Pichler, B. J.
Format:	Journal Article
Language:	English
Published:	United States American Association of Physicists in Medicine 01.08.2014
Subjects:	Animals avalanche photodiodes Biological material, e.g. blood, urine; Haemocytometers biomedical MRI Clinical applications Digital computing or data processing equipment or methods, specially adapted for specific applications DoI Electrical Equipment and Supplies Encoding ENERGY RESOLUTION Equipment Design Floods FLUORINE 18 Geiger counters Geiger‐Muller counter tubes G‐APD image coding Image coding, e.g. from bit‐mapped to non bit‐mapped Image data processing or generation, in general image resolution Including semiconductor components sensitive to infra‐red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY Involving electronic [emr] or nuclear [nmr] magnetic resonance, e.g. magnetic resonance imaging LUTETIUM Magnetic field sensors Magnetic resonance imaging Magnetic Resonance Imaging - instrumentation Magnetic Resonance Imaging - methods Measurement of nuclear or x‐radiation Measuring half‐life of a radioactive substance medical image processing Multimodal Imaging - instrumentation Multimodal Imaging - methods NMR IMAGING PET PET/MRI Photodiodes; phototransistors; photoresistors Photomultipliers Plates or blocks in which tracks of nuclear particles are made visible by after‐treatment, e.g. using photographic emulsion, using mica Position sensitive detectors POSITRON COMPUTED TOMOGRAPHY positron emission tomography Positron emission tomography (PET) Positron-Emission Tomography - instrumentation Positron-Emission Tomography - methods readout electronics READOUT SYSTEMS Scintigraphy Scintillation detectors Semiconductor devices sensitive to infra‐red radiation, light, electromagnetic radiation of shorter wavelength, or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof SiPM solid scintillation detectors SPATIAL RESOLUTION the detector being a crystal the detector being a liquid the detector being made of plastics the potential barrier working in avalanche mode, e.g. avalanche photodiode Time Tubes for determining the presence, intensity, density or energy of radiation or particles with ionisation‐chamber arrangements with semiconductor detectors G-APD PET/MRI SiPM PET DoI
ISSN:	0094-2405, 2473-4209, 2473-4209
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Summary:	Purpose: The aim of this study was to develop a prototype PET detector module for a combined small animal positron emission tomography and magnetic resonance imaging (PET/MRI) system. The most important factor for small animal imaging applications is the detection sensitivity of the PET camera, which can be optimized by utilizing longer scintillation crystals. At the same time, small animal PET systems must yield a high spatial resolution. The measured object is very close to the PET detector because the bore diameter of a high field animal MR scanner is limited. When used in combination with long scintillation crystals, these small-bore PET systems generate parallax errors that ultimately lead to a decreased spatial resolution. Thus, we developed a depth of interaction (DoI) encoding PET detector module that has a uniform spatial resolution across the whole field of view (FOV), high detection sensitivity, compactness, and insensitivity to magnetic fields. Methods: The approach was based on Geiger mode avalanche photodiode (G-APD) detectors with cross-strip encoding. The number of readout channels was reduced by a factor of 36 for the chosen block elements. Two 12 × 2 G-APD strip arrays (25μm cells) were placed perpendicular on each face of a 12 × 12 lutetium oxyorthosilicate crystal block with a crystal size of 1.55 × 1.55 × 20 mm. The strip arrays were multiplexed into two channels and used to calculate the x, y coordinates for each array and the deposited energy. The DoI was measured in step sizes of 1.8 mm by a collimated 18F source. The coincident resolved time (CRT) was analyzed at all DoI positions by acquiring the waveform for each event and applying a digital leading edge discriminator. Results: All 144 crystals were well resolved in the crystal flood map. The average full width half maximum (FWHM) energy resolution of the detector was 12.8% ± 1.5% with a FWHM CRT of 1.14 ± 0.02 ns. The average FWHM DoI resolution over 12 crystals was 2.90 ± 0.15 mm. Conclusions: The novel DoI PET detector, which is based on strip G-APD arrays, yielded a DoI resolution of 2.9 mm and excellent timing and energy resolution. Its high multiplexing factor reduces the number of electronic channels. Thus, this cross-strip approach enables low-cost, high-performance PET detectors for dedicated small animal PET and PET/MRI and potentially clinical PET/MRI systems.
Bibliography:	armin.kolb@med.uni‐tuebingen.de Author to whom correspondence should be addressed. Electronic mail ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Undefined-1 ObjectType-Feature-3 content type line 23
ISSN:	0094-2405 2473-4209 2473-4209
DOI:	10.1118/1.4890609