Parallax correction in PET using depth of interaction information

MacDonald, L.R.; Dahlbom, M.

doi:10.1109/nssmic.1997.670625

Cited by 11 publications

(13 citation statements)

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“…On the other hand, there are numerous detector designs in research systems aimed at optimizing one or more of the aforementioned characteristics. For example, utilizing semiconductor detector like cadmium zinc telluride (CZT) that can achieve excellent spatial and energy resolutions; 4 detector configurations that provides depth-of-interaction (DOI) information; 5 detectors utilizing monolithic scintillator that provides good spatial resolution and manufacturability; [6][7][8][9] and nonconventional radiation detectors such as resistive plate chamber (RPC)-PET with superior spatial information, 10 etc. Among the various possible detector types for PET, scintillation crystal based detectors are by far the most prevalent due to established technologies and trade-off of the characteristics mentioned above.…”

Section: Introductionmentioning

confidence: 99%

Side readout of long scintillation crystal elements with digital SiPM for TOF‐DOI PET

2014

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Purpose: Side readout of scintillation light from crystal elements in positron emission tomography (PET) is an alternative to conventional end-readout configurations, with the benefit of being able to provide accurate depth-of-interaction (DOI) information and good energy resolution while achieving excellent timing resolution required for time-of-flight PET. This paper explores different readout geometries of scintillation crystal elements with the goal of achieving a detector that simultaneously achieves excellent timing resolution, energy resolution, spatial resolution, and photon sensitivity. Methods: The performance of discrete LYSO scintillation elements of different lengths read out from the end/side with digital silicon photomultipliers (dSiPMs) has been assessed. Results: Compared to 3 × 3 × 20 mm 3 LYSO crystals read out from their ends with a coincidence resolving time (CRT) of 162 ± 6 ps FWHM and saturated energy spectra, a side-readout configuration achieved an excellent CRT of 144 ± 2 ps FWHM after correcting for timing skews within the dSiPM and an energy resolution of 11.8% ± 0.2% without requiring energy saturation correction. Using a maximum likelihood estimation method on individual dSiPM pixel response that corresponds to different 511 keV photon interaction positions, the DOI resolution of this 3 × 3 × 20 mm 3 crystal side-readout configuration was computed to be 0.8 mm FWHM with negligible artifacts at the crystal ends. On the other hand, with smaller 3 × 3 × 5 mm 3 LYSO crystals that can also be tiled/stacked to provide DOI information, a timing resolution of 134 ± 6 ps was attained but produced highly saturated energy spectra. Conclusions: The energy, timing, and DOI resolution information extracted from the side of long scintillation crystal elements coupled to dSiPM have been acquired for the first time. The authors conclude in this proof of concept study that such detector configuration has the potential to enable outstanding detector performance in terms of timing, energy, and DOI resolution. C 2014 American Association of Physicists in Medicine. [http://dx

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Section: Introductionmentioning

confidence: 99%

Side readout of long scintillation crystal elements with digital SiPM for TOF‐DOI PET

2014

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“…1c [7]. Consequently, DOI-encoding PET detectors allow small ring scanners with long crystals to have uniform spatial resolution in all directions without the degradation due to the parallax error [8].…”

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confidence: 99%

Positron emission tomography (PET) detectors with depth-of- interaction (DOI) capability

2011

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Because positron emission tomography (PET) provides biochemical information in vivo with the sensitivity at the sub-pico-molar level, pre-clinical research using PET plays an important role in biological and pharmaceutical sciences. However, small animal imaging by PET has been challenging with respect to spatial resolution and sensitivity due to the small volume of the imaging objects. A DOI-encoding technique allows for pre-clinical PET to simultaneously achieve high spatial resolution and high sensitivity. Thus many DOI-encoding methods have been proposed. In this paper we describe why DOI measurements are important, what is required in DOI-encoding designs, and how to extract DOI information in scintillator-based DOI detectors. Recently, there has been a growing interest in DOI measurements for TOF PET detectors to correct time walk as a function of DOI position. Thus, the DOI-encoding method with a high time performance suitable for TOF detectors is now required. The requirements to improve the time resolution in DOI detectors are discussed as well.Keywords Positron emission tomography (PET), Depth of interaction (DOI), Multi-layer detector, Dual-ended readout, Single-ended readout THE IMPORTANCE OF DOI MEASUREMENT Simultaneous improvement in spatial resolution and sensitivityThe PET is an important pre-clinical imaging technique because PET provides biochemical information down to the sub-pico-molar level in vivo [1]. Thus, the development of pre-clinical PET scanners has been actively promoted. The major focus of the development is to obtain a similar quality in small animal images as human images, while the size of the imaging subject decreases and the amount of radiopharmaceutical injected into the small animals is limitedTo obtain a similar level of detail and SNR in mouse images as human images, spatial resolution and sensitivity should be increased. That is why many PET instrument researchers have been attempting for the pre-clinical PET to simultaneously achieve high spatial resolution and high sensitivity. The pre-clinical PET systems therefore have been designed by using very long and narrow crystals with small diameter ring geometry. However, such system structures cause the parallax error to become lager when providing no depth-of-interaction (DOI) information within crystals (general PETs can measure no DOI information), and bring the degradation of the radial resolution in the peripheral field of view (FOV). That is because the reconstruction algorithm, when drawing a line of response (LOR) without DOI information, usually assigns the interaction positions over all depths within a crystal to a single position (i.e. the center position on the front of the interacted crystals).

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“…Figure 7 and Table 1 show that the possible spatial frequencies (in cycles/mm) that can be resolved are gradually reduced from the center toward the edge of the FOV. This is due to the streak artifacts and the parallax effect that are present in the images [32,33]. Using the plane source method, spatial resolution was assessed by examining MTF in a large part of the FOV.…”

Section: Resultsmentioning

confidence: 99%