Using neural networks, spatial characteristics of the prototype module of the positron-emission tomograph (PET) based on scintillation crystalline plates LSO(Y) and a silicon photomultiplier array ...were calculated. The average spatial resolution of the Z-coordinate of the interaction point of gamma-rays with an energy of 511 keV over the entire area of the scintillation plate was 1.76 mm. The proposed algorithm for calculating the determination accuracy of the interaction point can be used in positron-emission tomography.
•Neural network application for event reconstruction can approach the best physically possible precision.•A neural network reconstruction algorithm gives a good estimation of expected ...performance.•Comparing two realistic detector models with neural network reconstruction allows to evaluate the potential benefits with an unbiased algorithm.•Larger thinner crystal plates provide the best overall resolution, smaller plates reduce the maximal possible error.
We use neural networks to evaluate and compare the spatial resolution of two different simulated monolithic PET detector elements. The effects of mixing events with single photoeffect interactions and multiple Compton scatterings are also studied.
Two PET detector models were used in this study. The first one consisted of a LYSO crystal plate with 19.25 × 19.25 × 12 mm3 dimensions and 256-channel photomultiplier with parameters modeled after a Hamamatsu S-13615-1050N-16 SiPM. The second model used a larger LYSO crystal (57.6 × 57.6 × 12 mm3) and a 64-channel Sensl ARRAYC-60035-64P-PCB photomultiplier.
A feed-forward neural network was used to reconstruct the point of 511 keV gamma interaction. The number of layers and the number of neurons per layer were varied.
The best resolution was achieved with the 57.6 × 57.6 mm2 detector model, with an average of 0.74 ± 0.01 mm for the XY plane and an average 1.01 ± 0.01 mm for the Z coordinate (depth of interaction).
Neural networks can be a powerful tool that can help to determine the optimal parameters for a design of an experimental device. This study demonstrates how neural networks can be used to evaluate the performance of two detector variants while not being dependent on specific signal and noise functions.
We report simulation and resolution evaluation of monolithic position sensitive detectors with different surfaces. The best result was obtained using a combination of rough polishing of the crystal ...surface and a Teflon wrapper with a resolution in the interaction depth of
dZ
= 0.89 ± 0.01 mm. The best planar resolution
dX
= 0.53 ± 0.01 mm is obtained for a finely polished plate with an ESR film. The diffuse reflector also demonstrates an increase in light collection by 33% compared to the specular one.
It is found that the emission intensity of the 2
+
band system of the N
2
molecule (C
3
Π
u
→ B
3
Π
g
transition) under electron bombardment of pyrolytic aerogel SiO
2
in air at atmospheric pressure ...is 40–70% higher than that in the case of bombardment of aluminum under the same conditions. The dependences of the emission intensity at 337 nm (0-0 vibrational transition in the 2+ band system of the N
2
molecule) on the target temperature in the range of 30–60°C are different for the aluminum and SiO
2
targets, which indicates different excitation mechanisms of the N
2
(C
3
Π
u
) state. It is suggested that when the SiO
2
target is bombarded, the N
2
(C
3
Π
u
) state is excited not only by direct collisions with the electrons of the primary beam and secondary electrons, but also by the energy transfer from SiO
2
excitons and conduction electrons to N
2
molecules upon their contact with the SiO
2
surface.
Optical and luminescence characteristics of a scintillating fluoride glass sample (module) based on hafnium fluoride are studied with the purpose of using it in homogeneous electromagnetic and ...hadronic calorimeters. The module light yield is 290 photon/meV, the scintillation decay time is 21 ns. The calculated energy resolution of the electromagnetic calorimeter prototype based on fluoride glasses is 0.4% for an energy of 100 GeV. The possibility of recording Cherenkov and scintillation light on opposite end faces of a glass module is shown, which allows improving the energy resolution of the hadronic calorimeter.
Scintillation properties of a single-crystal Lu
2 –
x
Y
x
SiO
5
:Ce
3+
:Ca
2+
plate are compared with properties of a fine powder and a composite based on this powder, produced from the second part ...of this plate. A significant decrease in the decay time of the scintillation pulse in the powder sample is explained by the effect of the increased air—crystal side surface in comparison with the single crystal. In the Lu
2 –
x
Y
x
SiO
5
:Ce
3+
:Ca
2+
composite scintillator, the side surface of each particle contacts on all sides to polystyrene; therefore, the energy transfer of electron-hole pairs occurs without significant loss along the microcrystal surface without decreasing the luminescence time of cerium Ce
3+
ions.
The scintillation parameters of lutetium oxyorthosilicate doped with Ce
3+
, Y
3+
, and Ca
2+
ions are studied. The new material is described by the chemical formula Lu
(2–
y
)
Y
(
y
–
z
–
x
)
Ce
x
...Ca
z
SiO
5–
z
. A 65 mm in diameter with a cylindrical part length of 160 mm is grown by the Czochralski method. The crystal composition varies from top to bottom of the crystalline boule, causing scintillation time variation in the range of 38.5–37.9 ns. The promising application of this crystalline material in experimental setups of modern accelerator facilities is considered.
Scintillation Properties of New LuScSiO5 Crystals Belov, M. V.; Zavartsev, Yu. D.; Zavertyaev, M. V. ...
Bulletin of the Lebedev Physics Institute,
04/2021, Letnik:
48, Številka:
4
Journal Article
Recenzirano
New LuScSiO
5
crystals with intrinsic luminescence are grown by the Czochralski method. Pulsed cathodoluminescence spectra of new scintillators and their scintillation decay times are studied for the ...first time. Using 662-keV γ-rays from the
137
Cs source, amplitude distributions of the number of luminescence counts (so-called photopeaks) are measured for new crystals. It is shown that the light yield of LuScSiO
5
crystals is 13 500 photons/MeV.
For the first time, new YAG:Yb:Ca and YAG:Yb:Ca:Si crystals with ultrafast scintillation time are grown. The crystals are grown by the Czochralski method. The spectra of pulsed cathodoluminescence of ...new scintillators, light yield, and their scintillation time are studied. It was shown that the time constant of scintillation pulse decay of YAG:Yb:Ca and YAG:Yb:Ca:Si crystals is 1.48 ns and 1.15 ns, respectively.
Monte Carlo simulation is applied to a detector element for a positron-emission tomograph (PET) prototype based on multipixel silicon photomultipliers and new LFS-3 crystal scintillators to optimize ...its characteristics such as the light yield and energy resolution. These characteristics were calculated for various configurations of crystal surface treatment and cover material parameters. The highest light yield was achieved for a detector module with a Lumirror reflector as a cover material for the chemically treated scintillation crystal surface. For the above-mentioned configuration, one of the best energy resolution was achieved.
