Measuring Photon Time Spread Distribution of Scintillators on the Picosecond Time Scale

Haas, J.T.M. de; Kolk, Erik van der; Dorenbos, P.

doi:10.1109/tns.2013.2288693

Cited by 7 publications

(5 citation statements)

References 10 publications

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“…In previous publications we presented Monte Carlo calculations of the optical photon time dispersion and its characterization as a distribution with a sharp rise (<10 ps) at the time of arrival of the earliest possible photon followed by an exponential decay (Derenzo et al 2014) for both rough and polished surfaces (Moses et al 2014) followed by a similar pulse of photons reflected from the opposite end. This is consistent with previously published calculations (Yeom et al 2013, Gundacker et al 2014, Vinke et al 2014 and experimental measurements of rectangular LSO crystals (de Haas et al 2014).…”

Section: Monte Carlo Calculations Of the Optical Photon Time Dispersi...supporting

confidence: 93%

“…Single-ended readout has the complication that the photons arrive at the photodetector in two swarms, the first from those that travel directly from the interaction point to the photodetector and a delayed swarm from the opposite reflective surface. This is shown in figure 1 of Moses et al (2014) , figure 11 of Yeom et al (2013) , figure 4 of de Haas et al (2014) , figure 18 of Gundacker et al (2014) , and figure 9 of Vinke et al (2014) .…”

Section: Monte Carlo Calculations Of the Optical Photon Time Dispementioning

confidence: 94%

“…Note 2: To perform step 4.4.12 it was necessary to first do a preliminary run of steps 4.4.1 to 4.4.8 and tabulate the variances of E A kn and E B kn in bands of Z j and trigger fraction F n . This could be done for a PET system by scanning an ultra-fast laser along the length of a component scintillator (as in ( de Haas et al 2014 )), where the laser intensity was adjusted to produce the same number of fluorescent photons as the scintillation photons from an annihilation photon interaction.…”

Section: Monte Carlo Calculationsmentioning

confidence: 99%

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Monte Carlo calculations of PET coincidence timing: single and double-ended readout

2015

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We present Monte Carlo computational methods for estimating the coincidence resolving time (CRT) of scintillator detector pairs in positron emission tomography (PET) and present results for Lu2SiO5 : Ce (LSO), LaBr3 : Ce, and a hypothetical ultra-fast scintillator with a 1 ns decay time. The calculations were applied to both single-ended and double-ended photodetector readout with constant-fraction triggering. They explicitly include (1) the intrinsic scintillator properties (luminosity, rise time, decay time, and index of refraction), (2) the exponentially distributed depths of interaction, (3) the optical photon transport efficiency, delay, and time dispersion, (4) the photodetector properties (fill factor, quantum efficiency, transit time jitter, and single electron response), and (5) the determination of the constant fraction trigger level that minimizes the CRT. The calculations for single-ended readout include the delayed photons from the opposite reflective surface. The calculations for double-ended readout include (1) the simple average of the two photodetector trigger times, (2) more accurate estimators of the annihilation photon entrance time using the pulse height ratio to estimate the depth of interaction and correct for annihilation photon, optical photon, and trigger delays, and (3) the statistical lower bound for interactions at the center of the crystal. For time-of-flight (TOF) PET we combine stopping power and TOF information in a figure of merit equal to the sensitivity gain relative to whole-body non-TOF PET using LSO. For LSO crystals 3 mm × 3 mm × 30 mm, a decay time of 37 ns, a total photoelectron count of 4000, and a photodetector with 0.2 ns full-width at half-maximum (fwhm) timing jitter, single-ended readout has a CRT of 0.16 ns fwhm and double-ended readout has a CRT of 0.111 ns fwhm. For LaBr3 : Ce crystals 3 mm × 3 mm × 30 mm, a rise time of 0.2 ns, a decay time of 18 ns, and a total of 7600 photoelectrons the CRT numbers are 0.14 ns and 0.072 ns fwhm, respectively. For a hypothetical ultra-fast scintillator 3 mm × 3 mm × 30 mm, a decay time of 1 ns, and a total of 4000 photoelectrons, the CRT numbers are 0.070 and 0.020 ns fwhm, respectively. Over a range of examples, values for double-ended readout are about 10% larger than the statistical lower bound.

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Section: Monte Carlo Calculations Of the Optical Photon Time Dispersi...supporting

confidence: 93%

Section: Monte Carlo Calculations Of the Optical Photon Time Dispementioning

confidence: 94%

Section: Monte Carlo Calculationsmentioning

confidence: 99%

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Monte Carlo calculations of PET coincidence timing: single and double-ended readout

2015

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“…Published Monte Carlo calculations of the optical photon time dispersion in long scintillators show that the time distribution at the photodetector has a sharp rise (<10 ps) at the time of arrival of a direct path (earliest possible) photon followed by an exponential decay for both rough and polished surfaces (Yeom et al 2013, Gundacker et al 2014, Vinke et al 2014. This is consistent with experimental measurements of LSO crystals (de Haas et al 2014).…”

Section: Optical Photon Time Delay and Dispersion As A Function Of Th...supporting

confidence: 82%

Monte Carlo simulations of time-of-flight PET with double-ended readout: calibration, coincidence resolving times and statistical lower bounds

Derenzo

2017

Phys. Med. Biol.

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This paper demonstrates through Monte Carlo simulations that a practical positron emission tomograph with (1) deep scintillators for efficient detection, (2) double-ended readout for depth-of-interaction information, (3) fixed-level analog triggering, and (4) accurate calibration and timing data corrections can achieve a coincidence resolving time (CRT) that is not far above the statistical lower bound. One Monte Carlo algorithm simulates a calibration procedure that uses data from a positron point source. Annihilation events with an interaction near the entrance surface of one scintillator are selected, and data from the two photodetectors on the other scintillator provide depth-dependent timing corrections. Another Monte Carlo algorithm simulates normal operation using these corrections and determines the CRT. A third Monte Carlo algorithm determines the CRT statistical lower bound by generating a series of random interaction depths, and for each interaction a set of random photoelectron times for each of the two photodetectors. The most likely interaction times are determined by shifting the depth-dependent probability density function to maximize the joint likelihood for all the photoelectron times in each set. Example calculations are tabulated for different numbers of photoelectrons and photodetector time jitters for three 3 × 3 × 30 mm3 scintillators: Lu2SiO5:Ce,Ca (LSO), LaBr3:Ce, and a hypothetical ultra-fast scintillator. To isolate the factors that depend on the scintillator length and the ability to estimate the DOI, CRT values are tabulated for perfect scintillator-photodetectors. For LSO with 4000 photoelectrons and single photoelectron time jitter of the photodetector J = 0.2 ns (FWHM), the CRT value using the statistically weighted average of corrected trigger times is 0.098 ns FWHM and the statistical lower bound is 0.091 ns FWHM. For LaBr3:Ce with 8000 photoelectrons and J = 0.2 ns FWHM, the CRT values are 0.070 and 0.063 ns FWHM, respectively. For the ultra-fast scintillator with 1 ns decay time, 4000 photoelectrons, and J = 0.2 ns FWHM, the CRT values are 0.021 and 0.017 ns FWHM, respectively. The examples also show that calibration and correction for depth-dependent variations in pulse height and in annihilation and optical photon transit times are necessary to achieve these CRT values.

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“…This results in an additional time-spread, in [16] known as the photon time-spread distribution, and it can increase the observed rise time significantly, depending on the dimensions of the crystal, surface polish, and wrapping material [17]. The benefit of using x-ray excitation instead of gamma excitation is that x-rays are absorbed within a layer of a few hundred microns below the surface, whereas gammas are absorbed over the entire bulk of the crystal.…”

Section: Discussionmentioning

confidence: 99%

Comparative Study of Co-Doped and Non Co-Doped LSO:Ce and LYSO:Ce Scintillators for TOF-PET

Weele

Schaart

Dorenbos

2015

IEEE Trans. Nucl. Sci.

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Scintillation properties of LSO:Ce, LSO:Ce,0.2%Ca, LYSO:Ce, LYSO:0.11%Ce,0.2%Mg, and LYSO:0.2%Ce,0.2%Ca were studied for application in time-of-flight positron emission tomography. To find the scintillation material with the best timing performance among those, we measured intrinsic scintillation pulse shapes-defined as the number of photons emitted per unit time at the ionization track as a function of time -by means of 100 ps x-ray excitation in the temperature range from 193 K to 373 K, from which intrinsic rise and decay time constants were derived. Photoelectron yields were measured by 662 keV gamma excitation. From these scintillation properties we calculated the corresponding lower bound on the timing resolution for each material.

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Measuring Photon Time Spread Distribution of Scintillators on the Picosecond Time Scale

Cited by 7 publications

References 10 publications

Monte Carlo calculations of PET coincidence timing: single and double-ended readout

Monte Carlo calculations of PET coincidence timing: single and double-ended readout

Monte Carlo simulations of time-of-flight PET with double-ended readout: calibration, coincidence resolving times and statistical lower bounds

Comparative Study of Co-Doped and Non Co-Doped LSO:Ce and LYSO:Ce Scintillators for TOF-PET

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