Sharma S, Chhokar J, Curceanu C, Czerwiński E, Dadgar M, Dulski K, Gajewski J, Gajos A, Gorgol M, Gupta-Sharma N, Del Grande R, Hiesmayr B C, Jasińska B, Kacprzak K, Kapłon Ł, Karimi H, Kisielewska D, Klimaszewski K, Korcyl G, Kowalski P, Kozik T, Krawczyk N, Krzemień W, Kubicz E, Mohammed M, Niedzwiecki Sz, Pałka M, Pawlik-Niedźwiecka M, Raczyński L, Raj J, Ruciński A, Shivani S, Shopa R Y, Silarski M, Skurzok M, Stępień E Ł, Wiślicki W, Zgardzińska B, Moskal P
Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, prof. Stanisława Łojasiewicza 11, Cracow, 30-348, Poland.
INFN, Laboratori Nazionali di Frascati, Frascati, 00044, Italy.
EJNMMI Phys. 2020 Jun 5;7(1):39. doi: 10.1186/s40658-020-00306-x.
The time-over-threshold (TOT) technique is being used widely due to itsimplications in developing the multi-channel readouts, mainly when fast signal processing is required. Using the TOT technique, as a measure of energy loss instead of charge integration methods, significantly reduces the signal readout costs by combining the time and energy information. Therefore, this approach can potentially be utilized in J-PET tomograph which is built from plastic scintillators characterized by fast light signals. The drawback in adopting this technique lies in the non-linear correlation between input energy loss and TOT of the signal. The main motivation behind this work is to develop the relationship between TOT and energy loss and validate it by the J-PET tomograph setup.
The experiment was performed using a Na beta emitter source placed in the center of the J-PET tomograph. This isotope produces photons of two different energies: 511 keV photons from the positron annihilation (direct annihilation or through the formation of a para-positronium atom or pick-off process of ortho-positronium atoms) and a 1275 keV prompt photon. This allows the study of the correlation between TOT values and energy loss for energy ranges up to 1000 keV. Since the photon interacts predominantly via Compton scattering inside the plastic scintillator, there is no direct information of the energy deposition. However, using the J-PET geometry, one can measure the scattering angle of the interacting photon. Since the Na source emits photons of two different energies, it is necessary to know unambiguously the energy of incident photons and their corresponding scattering angles in order to estimate energy deposition. In summary, this work presents a dedicated algorithm developed to tag photons of different energies and studying their scattering angles to calculate the energy deposition by the interacting photons.
A new method was elaborated to measure the energy loss by photons interacting with plastic scintillators used in the J-PET tomograph. We find the relationship between the energy loss and TOT is non-linear and can be described by the functions TOT = A0 + A1 * ln(E + A2) + A3 * (ln(E + A2)) and TOT = A0 - A1 * A2[Formula: see text]. In addition, we also introduced a theoretical model to calculate the TOT as a function of energy loss in plastic scintillators.
A relationship between TOT and energy loss by photons interacting inside the plastic scintillators used in J-PET scanner is established for a deposited energy range of 100-1000 keV.
过阈值时间（TOT）技术因其在开发多通道读出方面的应用而被广泛使用，主要是在需要快速信号处理时。使用TOT技术作为能量损失的一种度量方法，而不是电荷积分方法，通过结合时间和能量信息显著降低了信号读出成本。因此，这种方法有可能应用于由具有快速光信号特性的塑料闪烁体制成的J-PET断层扫描仪。采用该技术的缺点在于信号的输入能量损失与TOT之间存在非线性相关性。这项工作的主要动机是建立TOT与能量损失之间的关系，并通过J-PET断层扫描仪设置对其进行验证。
实验使用放置在J-PET断层扫描仪中心的钠β发射源进行。这种同位素产生两种不同能量的光子：来自正电子湮灭（直接湮灭或通过形成仲正电子素原子或邻正电子素原子的拾取过程）的511keV光子和1275keV的瞬发光子。这使得能够研究高达1000keV能量范围内TOT值与能量损失之间的相关性。由于光子主要通过塑料闪烁体内的康普顿散射相互作用，因此没有能量沉积的直接信息。然而，利用J-PET的几何结构，可以测量相互作用光子的散射角。由于钠源发射两种不同能量的光子，为了估计能量沉积，必须明确知道入射光子的能量及其相应的散射角。总之，这项工作提出了一种专门开发的算法，用于标记不同能量的光子并研究它们的散射角，以计算相互作用光子的能量沉积。
阐述了一种测量光子与J-PET断层扫描仪中使用的塑料闪烁体相互作用时能量损失的新方法。我们发现能量损失与TOT之间的关系是非线性的，可以用函数TOT = A0 + A1 * ln(E + A2) + A3 * (ln(E + A2))和TOT = A0 - A1 * A2[公式：见正文]来描述。此外，我们还引入了一个理论模型来计算作为塑料闪烁体中能量损失函数的TOT。
在100 - 1000keV的沉积能量范围内，建立了J-PET扫描仪中使用的塑料闪烁体内光子相互作用的TOT与能量损失之间的关系。
