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. 2026 Sep 23;13:99. doi: 10.1186/s40658-026-00941-w

Evaluation of a lead-loaded plastic scintillator for next-generation positron emission tomography detectors using Geant4 simulation

Makoto Yamazaki 1,✉, Masahiro Sato 2
PMCID: PMC13620012  PMID: 42804052

Abstract

Purpose

Lead-loaded plastic scintillators are promising candidates for next-generation positron emission tomography (PET) detectors owing to their short fluorescence decay times, high machinability and low production cost. However, their γ-ray detection performance has not been fully quantified. This study evaluated the detection efficiency and energy-resolution characteristics of a 5 wt% lead-loaded plastic scintillator (EJ-256) and compared its performance with that of a conventional polyvinyltoluene (PVT) scintillator.

Methods

Monte Carlo simulations were performed using Geant4. Monoenergetic 511 keV gamma rays (100 000 events) were irradiated onto scintillator blocks with thicknesses varied from 20 mm to 200 mm in 5 mm increments. The resulting absorbed-energy spectra were analysed using ROOT to determine detection efficiency and the simulated full width at half maximum (FWHM) of the 511-keV photopeak. To identify the thickness region at which detection efficiency saturated, a non-parametric Kruskal–Wallis test was conducted to consecutive thickness groups to determine the point beyond which differences were no longer statistically significant (p > 0.05).

Results

EJ-256 exhibited a distinct 511 keV photopeak, whereas PVT showed only a broad Compton continuum. The detection efficiency increased from 0.9% at 20 mm to 2.9% at 200 mm and saturated above approximately 135 mm, consistent with the Kruskal–Wallis analysis. The simulated 511-keV photopeak width remained stable at approximately 10% FWHM across all thicknesses.

Conclusion

These results indicate that EJ-256 demonstrates photon-absorption performance comparable to that of conventional inorganic PET scintillators, while offering substantially faster temporal response and reduced fabrication cost. This combination suggests strong potential for application in future time-of-flight PET detector modules.

Keywords: Full width at half maximum, Positron emission tomography, Time-of-flight, EJ-256

Background

Positron emission tomography (PET) generates functional images by detecting pairs of 511 keV annihilation photons in coincidence [1]. The detection performance of PET systems, particularly sensitivity and timing accuracy, is fundamentally governed by the scintillator material employed in the detector [2]. Inorganic scintillators such as Bi4Ge3O₁2 (bismuth germanate, BGO), Lu2SiO5:Ce (lutetium oxyorthosilicate, LSO) and Lu2−xYxSiO5:Ce (lutetium yttrium oxyorthosilicate, LYSO) provide high stopping power and good energy resolution. However, their relatively long fluorescence decay times (40–44 ns) limit coincidence timing performance and contribute to higher system cost [3, 4]. As a result, improving timing resolution while maintaining sufficient γ-ray sensitivity has become a key challenge in the development of next-generation PET detectors, particularly for time-of-flight (TOF) imaging.

Plastic scintillators have attracted increasing interest as fast alternatives to conventional inorganic materials because of their nanosecond-scale decay times, mechanical robustness and low production cost [5, 6]. The development of plastic scintillators dates back to the early 1950s, when fluorescent aromatic molecules such as anthracene and stilbene were incorporated into polymer matrices including (C8H8)n (polystyrene, PS) and [CH2CH(C6H4CH3)]n (polyvinyltoluene, PVT). In these materials, deposited radiation energy is converted into visible light through molecular excitation and de-excitation processes. Their suitability for large-volume fabrication led to widespread use in high-energy physics, cosmic-ray experiments and radiation-monitoring systems [5]. More recently, their application space has expanded through nanocomposite design and heavy-element loading strategies aimed at enhancing γ-ray interaction probability while retaining fast optical response.

Despite these developments, the low effective atomic number of common polymer scintillators results in limited γ-ray stopping power, which constrains their applicability in PET systems. To overcome this limitation, heavy-element-doped plastics, including lead-loaded scintillators, have been developed. EJ-256 is a commercially available plastic scintillator containing 5 wt% Pb and has recently been explored for radiation detection, fast timing measurements and hybrid imaging applications [6].

The aim of this study is to quantitatively evaluate the γ-ray detection efficiency and energy-resolution characteristics of EJ-256 using Geant4 Monte Carlo simulations and to compare its performance with that of a conventional PVT scintillator. We hypothesise that moderate Pb loading enhances photon-absorption probability sufficiently to enable formation of a measurable 511 keV photopeak, while preserving the inherently fast scintillation response of organic materials. Confirmation of this behaviour would support the feasibility of lead-loaded plastic scintillators as cost-effective candidates for next-generation TOF-PET detector systems.

Methods

Lead-loaded plastic scintillator EJ256 applying to PET

PET detects functional information by recording pairs of 511 keV annihilation photons in coincidence. System sensitivity and timing accuracy are strongly influenced by the scintillator material employed in the detector. Inorganic scintillators such as BGO, LSO and LYSO provide high stopping power and good energy resolution; however, their relatively long fluorescence decay times result in limited timing performance.

Plastic scintillators, composed primarily of hydrocarbons such as polyvinyltoluene (PVT), exhibit much faster decay times, typically on the order of a few nanoseconds, as well as excellent machinability. To compensate for their intrinsically low γ-ray sensitivity, heavy-element-doped plastic scintillators have been proposed [7]. EJ-256 [8], a commercially available plastic scintillator containing 5 wt% Pb, combines a fast decay time of approximately 2.1 ns with improved photon-stopping capability. In this study, the detection efficiency and energy-resolution characteristics of EJ-256 were quantitatively evaluated using Geant4 Monte Carlo simulations and compared with those of a standard PVT scintillator.

Geant4 simulation toolkit

Geant4 (GEometry ANd Tracking, version 11.1.1) is an open-source Monte Carlo simulation toolkit developed at CERN for modelling particle–matter interactions [9, 10]. It provides a comprehensive set of electromagnetic, hadronic and optical physics models over an energy range extending from a few eV to several TeV. Although originally developed for high-energy physics applications, Geant4 is now widely used in medical imaging, radiation dosimetry and detector development [11, 12].

In this study, Geant4 was employed to simulate 511 keV γ-ray interactions in EJ-256 and PVT scintillators using the G4EmStandardPhysics_option4 physics list [13], which includes photoelectric absorption, Compton scattering and pair production with optimised low-energy transport. Material parameters, including density, elemental composition, mean excitation energy and optical constants, were obtained from Eljen Technology datasheets, NIST photon cross-section tables and the Geant4 G4MaterialPropertiesTable database.

Simulation setup

The detector geometry consisted of a scintillator block with a 4 × 4 mm2 cross section optically coupled to a silicon photomultiplier, while the scintillator thickness was varied from 20 mm to 200 mm in 5 mm increments (Fig. 1). The SiPM was not modelled as an active optical or electronic readout device. Instead, a simplified 0.3-mm-thick silicon layer was included behind the scintillator to represent the sensor material and to account for possible photon and secondary-electron interactions at the scintillator–sensor boundary, including Compton scattering and backscattering from silicon [14]. Energy deposited in the silicon layer was not included in the photopeak analysis. Optical photon detection, photon-detection efficiency, gain, dark noise and electronic response of the SiPM were not included in the present simulation. Two scintillator materials were modelled: EJ-256, with a density of 1.081 g/cm3 and a reference PVT scintillator with a density of 1.03 g/cm3. The relevant physical properties of both materials are summarised in Table 1. A monoenergetic 511 keV γ-ray source was implemented using the G4Gamma class. Primary particles were emitted as a pencil beam incident normal to the scintillator surface, ensuring uniform irradiation over the entire 4 × 4 mm2 entrance area. Additional simulations incorporating small angular spreads of up to ± 5° confirmed that angular divergence did not produce a measurable effect on the results within the statistical uncertainties of this study.

Fig. 1.

Fig. 1

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Geant4 detector geometry schematic. Schematic illustration of the simulated detector geometry consisting of a lead-loaded plastic scintillator (EJ-256) coupled to a silicon photomultiplier (SiPM). The scintillator block has a 4 × 4 mm2 cross section with a variable thickness of t = 20–200 mm. A monoenergetic 511 keV gamma-ray beam is incident from the left

Table 1.

Physical and optical properties of the lead-loaded plastic scintillator (EJ-256) and the reference plastic scintillator (polyvinyltoluene, PVT)

Property EJ-256 (Pb-loaded) PVT (reference) Unit/Note
Base polymer

Polyvinyltoluene

+ 5 wt% Pb

 Polyvinyltoluene –
Density 1.081 1.03 g cm−3
Refractive index 1.58 1.58 –
Light yield ≈ 5200 ≈ 10,000 Photons MeV−1
Emission peak 425 423 nm
Decay time 2.1 2.4 ns
Optical attenuation length Not specified ≈ 160 cm
Machinability Excellent Excellent Qualitative
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Each simulation comprised 100 000 primary γ-ray events, with random-number seeds varied between runs to verify reproducibility. Fully absorbed events were defined as those with total deposited energy between 505 and 515 keV. Detection efficiency was calculated as the ratio of fully absorbed events to the total number of incident photons. Absorbed-energy spectra were exported in ROOT [14] format and analysed using Gaussian fitting to determine the peak centroid and full width at half maximum required of the 511-keV photopeak. Statistical uncertainties were evaluated using binomial errors for detection efficiency and fitting uncertainties for the photopeak. Repeated simulations confirmed that observed variations remained within expected statistical limits. The overall simulation parameters and analysis procedures are summarised in Table 2.

Table 2.

Main parameters and physics settings used in the Geant4 Monte Carlo simulation to ensure reproducibility

Parameter Value/setting Note
Geant4 version 11.1.1 –
Physics list G4EmStandardPhysics_option4 Includes photoelectric, Compton, pair production
Source energy 511 keV γ-rays Monoenergetic
Number of events 100 000 per thickness Ten repetitions averaged
Geometry 4 × 4 mm2 cross section Thickness 20–200 mm
Material EJ-256 (5 wt% Pb) Density 1.081 g cm− 3
Detector coupling SiPM (4 × 4 mm2, 0.3 mm thick) Perfect optical coupling assumed
Output data Deposited energy per event Analysed in Python + ROOT
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Results

To facilitate interpretation of the results presented in this section, the overall structure of the findings is outlined first. The simulations were designed to evaluate three principal performance metrics of EJ-256: absorbed-energy behaviour, detection efficiency and energy resolution. These characteristics were directly compared with those of a conventional PVT scintillator. Each subsection focuses on one metric by presenting the relevant figures and discussing the physical mechanisms responsible for the observed trends. By relating the present results to previously reported properties of heavy-element-loaded plastic scintillators and conventional inorganic detectors, the advantages and limitations of EJ-256 for PET applications can be more clearly evaluated.

Absorbed-energy spectra

Representative absorbed-energy spectra obtained for the EJ-256 and PVT scintillators are shown in Fig. 2. For the lead-loaded scintillator, a distinct photopeak was observed at approximately 511 keV, corresponding to full-energy-absorption events primarily arising from photoelectric interactions within the Pb-doped polymer matrix [15]. For the representative EJ-256 spectrum, the integral of the 505–515 keV photopeak window corresponded to the number of full-energy-absorption events used for the detection-efficiency calculation. At a thickness of 200 mm, this fraction was approximately 2.9% of all incident photons. The appearance of this photopeak is consistent with earlier studies on Bi- or Hf-loaded plastic scintillators, in which the incorporation of high-Z constituents significantly increased the probability of photoelectric absorption compared with standard PVT-based materials [16, 17].

Fig. 2.

Fig. 2

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Representative absorbed-energy spectra obtained from the Geant4 simulation for 511 keV γ-rays: A EJ-256 and B PVT. The EJ-256 scintillator exhibits a distinct photopeak at 511 keV, whereas the reference PVT scintillator shows a broad Compton continuum

In contrast, the reference PVT scintillator exhibited only a broad Compton continuum with no discernible photopeak, confirming that the low-Z polymer matrix provides very limited stopping power for 511 keV γ-rays. These observations are in line with expectations and indicate that heavy-element loading can substantially enhance γ-ray interaction probability while maintaining sufficient optical transparency, thereby improving energy-absorption characteristics.

Detection efficiency

The dependence of detection efficiency on scintillator thickness is summarised in Fig. 3. Detection efficiency was defined as the ratio of fully absorbed events to the total number of incident photons. For EJ-256, the efficiency increased monotonically from 0.9% ± 0.1% at 20 mm to 2.9% ± 0.2% at 200 mm and approached saturation beyond approximately 135 mm. This trend reflects the increased probability of successive Compton scatterings followed by final photoelectric absorption within the Pb-loaded scintillator volume. In contrast, the reference PVT scintillator exhibited negligible efficiency (≤ 0.01%) across all thicknesses, underscoring the necessity of high-Z loading for effective γ-ray detection [16, 17] and confirming the well-known limitations of undoped organic scintillators.

Fig. 3.

Fig. 3

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Detection efficiency as a function of scintillator thickness for the lead-loaded plastic scintillator (EJ-256) and the reference plastic scintillator (PVT). The detection efficiency of EJ-256 increases with thickness and saturates beyond approximately 135 mm, while that of PVT remains nearly constant over the investigated range

To assess the statistical significance of efficiency variations with thickness, a Kruskal–Wallis test [18] was applied to consecutive thickness groups (20–60 mm, 65–100 mm, 105–140 mm and so forth). Statistically significant differences (p < 0.05) were observed for thicknesses below 135 mm, whereas no significant differences (p > 0.05) were found beyond this range, indicating the onset of an efficiency saturation plateau. These results, summarised in Fig. 4; Table 3, support the interpretation that Pb loading enhances absorption efficiency up to a thickness at which photon interactions reach a balance between scattering and absorption processes.

Fig. 4.

Fig. 4

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Results of the Kruskal–Wallis statistical test applied to consecutive scintillator-thickness groups (three adjacent data points). The p-value falls below 0.05 for thinner regions and becomes non-significant (p > 0.05) beyond approximately 135 mm

Table 3.

Detection efficiency and simulated photopeak of EJ-256 for representative scintillator thicknesses (20–200 mm). The detection efficiency saturates beyond approximately 135 mm, whereas the simulated photopeak remains constant at about 10% FWHM

Thickness (mm) Detection efficiency (%) Simulated photopeak (FWHM%) Remarks
20 0.9 ± 0.1 10.1 ± 0.4 –
60 1.7 ± 0.2 9.9 ± 0.3 –
100 2.4 ± 0.2 10.0 ± 0.3 –
135 2.8 ± 0.2 9.8 ± 0.4 Efficiency plateau
200 2.9 ± 0.2 10.0 ± 0.3 –
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Simulated photopeak

The absorbed-energy spectra were fitted with Gaussian functions to determine the mean energy (µ) and standard deviation (σ) of the 511 keV photopeak, from which the simulated FWHM of the photopeak was calculated. Over the investigated thickness range of 20–200 mm, the simulated photopeak FWHM remained essentially constant at approximately 10% ± 0.3% FWHM (Fig. 5). This thickness-independent behaviour indicates a uniform scintillation-light yield and effective photon transport throughout the detector volume. The stability of the simulated photopeak FWHM suggests that the deposited-energy spectra were not strongly affected by scintillator thickness in the present geometry. However, since optical photon transport and SiPM response were not included, this result should not be used to infer experimental light-collection uniformity directly.

Fig. 5.

Fig. 5

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Simulated photopeak FWHM of EJ-256 as a function of scintillator thickness. The photopeak FWHM remains close to 10% across the entire thickness range, indicating uniform scintillation-light collection

The simulated photopeak FWHM of approximately 10% obtained for EJ-256 is comparable to that of conventional inorganic scintillators used in PET systems, which typically exhibit values in the range of 8%–12% for LYSO and BGO [3, 4]. This is achieved while retaining a substantially faster scintillation decay time (≈ 2 ns compared with ≈ 40 ns). The combination of moderate energy resolution and ultrafast temporal response supports the suitability of EJ-256 for TOF-PET applications and is consistent with performance trends reported for Bi2O3- or HfO2-loaded plastic scintillators.

Interaction and track visualisation

Figure 6 presents a Geant4 visualisation snapshot of representative particle tracks in the EJ-256 scintillator. The incident 511-keV γ-rays are shown as normally incident primary photon tracks, and secondary-electron tracks generated by Compton scattering or photoelectric absorption are indicated separately [9, 11]. Most incident photons undergo one or more Compton scatterings before final photoelectric absorption within the EJ-256 scintillator. The presence of Pb atoms increases the probability of such terminal photoelectric interactions, thereby improving overall photon-absorption efficiency.

Fig. 6.

Fig. 6

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Geant4 visualisation of representative particle tracks in the lead-loaded plastic scintillator (EJ-256). Normally incident 511-keV primary γ-rays and secondary electron tracks generated by Compton scattering or photoelectric absorption are indicated with separate colours and labels

Discussion

The results of this study demonstrate that Pb loading substantially enhances the γ-ray detection capability of plastic scintillators. The increase in detection efficiency from 0.9% at 20 mm to 2.9% at 200 mm, together with saturation beyond approximately 135 mm, reflects the combined contributions of multiple Compton scatterings and final photoelectric absorption within the Pb-doped matrix [15]. These findings are consistent with previous Monte Carlo and experimental studies on other heavy-metal-loaded polymers, such as EJ-254 (Bi-loaded) and Bi2O3-nanocomposite plastics [6, 16, 17]. In those reports, incorporation of high-Z elements increased the linear attenuation coefficient by factors of 3–5 relative to conventional polyvinyltoluene (PVT), while maintaining scintillation decay times below 3 ns.

The present results further elucidate how Pb incorporation modifies γ-ray interaction probabilities as a function of scintillator thickness. At smaller thicknesses, the limited interaction length reduces the probability that a 511 keV photon undergoes multiple Compton scatterings, resulting in a low likelihood of full-energy absorption. With increasing thickness, the extended photon path length allows repeated scattering events, and the higher atomic number of Pb significantly enhances the photoelectric cross section, increasing the probability of complete energy deposition. The observed depth-dependent evolution of scattering and absorption processes is consistent with standard γ-ray interaction theory and tabulated mass attenuation coefficients [19, 20]. Once the scintillator thickness exceeds approximately 135 mm, further increases in material depth do not substantially alter the balance between Compton and photoelectric interactions, leading to the observed saturation in detection efficiency. The percentage of photopeak events in the whole spectrum was therefore small but clearly enhanced by Pb loading. This indicates that EJ-256 does not simply increase the total interaction probability, but also enables a measurable fraction of full-energy-absorption events at 511 keV.

The simulated photopeak FWHM of approximately 10% FWHM obtained in this study falls numerically within the range often reported for PET scintillators; however, it should not be directly compared with experimentally measured detector energy resolution because optical photon transport, SiPM photon-detection efficiency, gain fluctuation, dark noise and electronic response were not included. This indicates that the intrinsic energy-transfer processes and light yield in EJ-256 are stable and that Pb loading at the 5 wt% level does not introduce significant optical self-absorption. The thickness-independent stability of the simulated photopeak FWHM indicates that the deposited-energy spectra were stable over the investigated thickness range. However, because optical photon transport was not explicitly simulated, optical attenuation and scintillation-light collection should be evaluated experimentally in future work. This behaviour implies that Pb incorporation does not substantially disturb the internal optical structure of the polymer, which is critical for maintaining signal quality in thick or monolithic detector geometries.

The detection efficiency obtained in the present single-block simulation should also be distinguished from the system sensitivity reported for recent long-axial-field-of-view crystal-based PET systems. Systems such as uEXPLORER and Biograph Vision Quadra achieve high sensitivity through the use of high-stopping-power crystal scintillators and extended axial coverage. In contrast, the present work evaluates the full-energy absorption probability of a small EJ-256 scintillator element under pencil-beam irradiation. Therefore, the absolute efficiency values reported here should not be directly compared with whole-system NEMA sensitivities but rather interpreted as material-level indicators of the effect of Pb loading.

The present approach is also different from plastic-scintillator-based J-PET systems. J-PET scanners use long plastic scintillator strips and primarily exploit Compton interactions of 511-keV photons, whereas the present study focuses on the formation of a full-energy photopeak in a Pb-loaded plastic scintillator. The efficiency defined in this study, namely the fraction of events depositing 505–515 keV in the scintillator, is therefore stricter than a Compton-based detection criterion. This difference in detection principle should be considered when comparing EJ-256 with J-PET-type plastic scintillator detectors.

In particular, if a Compton-based threshold such as an energy loss greater than 200 keV is used, the apparent detection efficiency would be expected to be higher than the full-energy-absorption efficiency reported in the present study. This is because the present definition counts only events in the 505–515 keV full-energy window. Therefore, the efficiency values reported here should be regarded as conservative values for photopeak-based detection, not as direct estimates of Compton-threshold-based J-PET detection efficiency.

Compared with inorganic scintillators, the principal advantages of lead-loaded plastics lie in their ultrafast timing response and ease of fabrication. The decay time of EJ-256 (approximately 2 ns) is around 20 times shorter than that of LYSO (approximately 40 ns), enabling coincidence-timing resolutions below 200 ps when coupled with modern silicon photomultipliers [21–23]. These timing characteristics are consistent with established analyses of scintillator response and SiPM timing models [23, 24], reinforcing the potential of Pb-loaded polymers for TOF-PET applications. In addition, their fast response and mechanical flexibility make such materials attractive for large-area detector modules and detector geometries where reduced mass and machining versatility are advantageous.

Despite these strengths, several limitations must be addressed before Pb-loaded plastic scintillators can be considered viable replacements for inorganic crystals in clinical PET systems. First, the absolute light yield of EJ-256 (approximately 5 200 photons MeV− 1) is only about 14% of that of NaI(Tl), and its emission peak at 425 nm may not optimally match the spectral sensitivity of standard SiPMs, necessitating careful optimisation of optical coupling and wavelength-matching materials [25–27]. Second, the radiation hardness of polymer-based scintillators is generally inferior to that of oxide crystals, with long-term irradiation studies reporting gradual degradation of light output at doses exceeding 10 kGy [28]. Finally, maintaining optical uniformity in multilayer or large monolithic detector configurations remains a significant challenge [29]. Another important limitation is the possible increase in optical photon absorption caused by Pb loading. Although Pb increases the interaction probability of 511-keV γ-rays, it may also enhance attenuation of scintillation photons in the plastic matrix. This can reduce the number of photoelectrons detected by the photosensor and consequently degrade experimentally measured energy and timing resolution. Because optical photon transport was not explicitly simulated in the present work, direct measurements of light output, optical attenuation length and coincidence timing resolution will be necessary.

These constraints highlight the need for continued optimisation of material composition, optical interfaces and detector geometry. For instance, maximising timing performance may favour thinner scintillator elements, whereas higher detection efficiency generally requires increased thickness, implying an inherent trade-off that must be carefully balanced in TOF-PET system design. Integration with SiPMs also requires optimisation of surface treatments, reflector configurations and scintillator–sensor coupling to minimise optical losses.

Nevertheless, ongoing advances in polymer nanocomposites and additive manufacturing are actively addressing many of these challenges. Recent investigations of hafnium-oxide (HfO2) nanoparticle-doped plastics and hybrid perovskite–polymer scintillators have demonstrated improved optical transparency and radiation tolerance while retaining sub-nanosecond decay times [30–33]. Similar trends have been reported for other high-Z-doped polymer systems developed in recent years [6, 18, 33–35], suggesting that material-engineering strategies may further enhance both γ-ray sensitivity and timing performance. Together, these developments point towards a feasible pathway for next-generation PET detectors based on cost-effective, fast and mechanically robust organic scintillators.

The present simulation study therefore supports the feasibility of moderately Pb-loaded plastic scintillators as promising candidates for TOF-PET applications. Further experimental validation, particularly direct measurements of coincidence-timing resolution, optical attenuation length and radiation durability, will be essential to confirm their practical suitability for clinical and preclinical PET systems.

Conclusions

This study presented a Monte Carlo evaluation of the γ-ray detection characteristics of a 5 wt% lead-loaded plastic scintillator (EJ-256) in comparison with a conventional polyvinyltoluene (PVT) scintillator. The simulations showed that incorporation of Pb substantially enhances photon-absorption probability and detection efficiency, with efficiency increasing from 0.9% at 20 mm to 2.9% at 200 mm and reaching a plateau at approximately 135 mm, where Compton scattering and photoelectric absorption become effectively balanced. EJ-256 exhibited a distinct 511 keV photopeak, whereas PVT produced only a broad Compton continuum, confirming the critical role of high-Z loading in enabling effective γ-ray absorption. The simulated 511-keV photopeak FWHM remained nearly constant at around 10% FWHM across all investigated thicknesses, indicating stable deposited-energy spectra in the present simulation geometry.

Beyond improved absorption performance, the simulations highlight several practical advantages of Pb-loaded plastic scintillators, including ultrafast decay time, mechanical flexibility and low fabrication cost. These attributes suggest strong potential for application in TOF-PET and other large-area detector configurations. Nevertheless, further work is required to translate these simulation results into functional detector modules. Experimental validation of light yield, energy resolution and coincidence-timing performance will be essential, together with systematic investigations of optical coupling optimisation, long-term radiation stability and the scalability of thick or multilayer geometries. Future development may also benefit from exploring alternative heavy-element additives or hybrid nanocomposite formulations to further enhance 511-keV gamma-ray stopping power while preserving fast timing and material robustness. Overall, the present findings provide a solid basis for advancing Pb-loaded plastic scintillators towards practical implementation in next-generation PET systems.

Acknowledgements

Not applicable.

Abbreviations

FWHM

Full width at half maximum

PET

Positron emission tomography

TOF

Time-of-flight

Author contributions

Makoto Yamazaki assumed overall responsibility for the management of the study, including determining the direction of the research, validating the results, and writing the manuscript. Masahiro Sato performed data generation and statistical analysis.

Funding

We gratefully acknowledge financial support from the Gunma Prefectural College of Health Sciences (Individual Research Fund) for the publication of this paper.

Data availability

The datasets generated during and/or analyzed during the current study are available upon reasonable request to the corresponding author. The data are not publicly available because of copyright protection.

Declarations

Ethics approval and consent to participate

Not applicable. All analyses were performed on computer simulation–generated data only; no human.

Consent for publication

Not applicable (no individual person’s data, images, or videos are included).

Competing interests

the authors declares that there is no conflict of interests to disclose.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available upon reasonable request to the corresponding author. The data are not publicly available because of copyright protection.

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