Time-of-Flight PET Detector Based on Multi-Pixel Photon Counter and Its Challenges

Kim, Chang Lyong; McDaniel, David L.; Ganin, Alexander

doi:10.1109/tns.2010.2100085

Cited by 34 publications

(14 citation statements)

References 17 publications

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“…As well, the peak detection efficiency is compared to for the M-series [13] and for the Philips DPC [14]. The measured energy resolution is comparable to what has been measured by Kim et al [15]. This group measured an average energy resolution of 12% with an LYSO array coupled to an array of Hamamatsu SiPMs.…”

Section: Discussionsupporting

confidence: 62%

Characterization of a Small Animal PET Detector Block Incorporating a Digital Photon Counter Array

Stortz

Thompson

Retière

et al. 2015

IEEE Trans. Nucl. Sci.

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A Small Animal PET detector block made with a Dual Layer Offset crystal array with 1.27 mm wide LYSO crystals on a Philips PDC3200-22-44 Digital Photon Counter (DPC) array was characterized while operating near room temperature. Crystal map peak to valley ratio, energy resolution, and timing resolution were characterized as a function of various device settings of the DPC and temperature. In addition, rates of count loss due to the phenomena of incomplete neighbor logic and dark-readout deadtime were measured. Device settings of interest were: Trigger scheme-defining the threshold of when a DPC will generate a timestamp and enter a readout cycle, inhibit fraction-the fraction of noisy cells which are disabled, and RTL-refresh-a setting which reduces the probability of the DPC being triggered from dark noise. At 15 , peak to valley ratios were measured to be around 11, and energy resolution around 11.5% regardless of device settings. Timing resolution ranged from near 300 ps to 1.5 ns. Count loss from dark readout deadtime was insignificant compared to incomplete neighbor logic, which ranged from as high as 95% to 5% of coincidences. It was found that trade-offs had to be made between timing resolution and count loss. With the most optimal device settings for small animal PET, a timing resolution of 1.4 ns and coincidence losses of 5% were achieved. At these settings, the detector block had little sensitivity to a 5 temperature fluctuation.Index Terms-Digital photon counter, dual layer offset crystal block, small animal PET.

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Section: Discussionsupporting

confidence: 62%

Characterization of a Small Animal PET Detector Block Incorporating a Digital Photon Counter Array

Stortz

Thompson

Retière

et al. 2015

IEEE Trans. Nucl. Sci.

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“…It is likely to be even flatter using a lower energy threshold. To get better timing resolution without time-walk correction, a lower threshold should be used and a narrow energy window should be applied to select data, as has been previously presented in many publications [13], [17], [25]–[27]. …”

Section: Resultsmentioning

confidence: 99%

A Time-Walk Correction Method for PET Detectors Based on Leading Edge Discriminators

Schmall

Judenhofer

et al. 2017

IEEE Trans. Radiat. Plasma Med. Sci.

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The leading edge timing pick-off technique is the simplest timing extraction method for PET detectors. Due to the inherent time-walk of the leading edge technique, corrections should be made to improve timing resolution, especially for time-of-flight PET. Time-walk correction can be done by utilizing the relationship between the threshold crossing time and the event energy on an event by event basis. In this paper, a time-walk correction method is proposed and evaluated using timing information from two identical detectors both using leading edge discriminators. This differs from other techniques that use an external dedicated reference detector, such as a fast PMT-based detector using constant fraction techniques to pick-off timing information. In our proposed method, one detector was used as reference detector to correct the time-walk of the other detector. Time-walk in the reference detector was minimized by using events within a small energy window (508.5 – 513.5 keV). To validate this method, a coincidence detector pair was assembled using two SensL MicroFB SiPMs and two 2.5 mm × 2.5 mm × 20 mm polished LYSO crystals. Coincidence timing resolutions using different time pick-off techniques were obtained at a bias voltage of 27.5 V and a fixed temperature of 20 °C. The coincidence timing resolution without time-walk correction were 389.0 ± 12.0 ps (425 –650 keV energy window) and 670.2 ± 16.2 ps (250–750 keV energy window). The timing resolution with time-walk correction improved to 367.3 ± 0.5 ps (425 – 650 keV) and 413.7 ± 0.9 ps (250 – 750 keV). For comparison, timing resolutions were 442.8 ± 12.8 ps (425 – 650 keV) and 476.0 ± 13.0 ps (250 – 750 keV) using constant fraction techniques, and 367.3 ± 0.4 ps (425 – 650 keV) and 413.4 ± 0.9 ps (250 – 750 keV) using a reference detector based on the constant fraction technique. These results show that the proposed leading edge based time-walk correction method works well. Timing resolution obtained using this method was equivalent to that obtained using a reference detector and was better than that obtained using constant fraction discriminators.

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“…Commercial LSO and LYSO scanners that use light sharing detector design with large PMTs achieve timing resolution values in the range of 550–600ps (Surti et al, 2007, Jakoby et al, 2011, Bettinardi et al, 2011). New detector designs using 1-1 coupling of thinner LYSO scintillators to new photo-detectors such as the silicon photomultipliers (SiPMs) (Kim et al, 2011, Gola et al, 2012) show a timing resolution in the range of 300ps. Hence, we chose timing resolution of 300ps and 600ps for the simulated LSO scanners.…”

Section: Methodsmentioning

confidence: 99%

Study of PET scanner designs using clinical metrics to optimize the scanner axial FOV and crystal thickness

2013

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The aim of this study is to understand the trade-off between crystal thickness and scanner axial FOV (AFOV) for clinical PET imaging. Clinical scanner design has evolved towards 20–25 mm thick crystals and 16–22 cm long scanner AFOV, as well as time-of-flight (TOF) imaging. While Monte Carlo studies demonstrate that longer AFOV and thicker crystals will lead to higher scanner sensitivity, cost has prohibited the building of commercial scanners with > 22 cm AFOV. In this study, we performed a series of system simulations to optimize the use of a given amount of crystal material by evaluating the impact on system sensitivity and NEC, as well image quality in terms of lesion detectability. We evaluated two crystal types (LSO and LaBr3) and fixed the total crystal volume used for each type (8.2 liters of LSO and 17.1 liters of LaBr3) while varying the crystal thickness and scanner AFOV. In addition, all imaging times were normalized so that the total scan time needed to scan a 100 cm long object with multiple bed positions was kept constant. Our results show that the highest NEC/cm in a 35 cm diameter×70 cm long line source cylinder is achieved for an LSO scanner with 10 mm long crystals and AFOV of 36 cm while for LaBr3 scanners, the highest NEC/cm is obtained with 20 mm long crystals and an AFOV of 38 cm. Lesion phantom simulations show best lesion detection performance is achieved in scanners with long AFOV (≥ 36 cm) and using thin crystals (≤ 10 mm of LSO and ≤ 20 mm of LaBr3). This is due to a combination of improved NEC, as well as improved lesion contrast estimation due to better spatial resolution in thinner crystals. Alternatively, for lesion detection performance similar to that achieved in standard clinical scanner designs, the long AFOV scanners can be used to reduce the total scan time without increasing the amount of crystal used in the scanner. In addition, for LaBr3 based scanners, the reduced lesion contrast relative to LSO based scanners requires improved timing resolution and longer scan times in order to achieve lesion detectability similar to that achieved in an LSO scanner with similar NEC/cm.

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Time-of-Flight PET Detector Based on Multi-Pixel Photon Counter and Its Challenges

Cited by 34 publications

References 17 publications

Characterization of a Small Animal PET Detector Block Incorporating a Digital Photon Counter Array

Characterization of a Small Animal PET Detector Block Incorporating a Digital Photon Counter Array

A Time-Walk Correction Method for PET Detectors Based on Leading Edge Discriminators

Study of PET scanner designs using clinical metrics to optimize the scanner axial FOV and crystal thickness

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