Speaker
Description
Background: The development of Total-Body PET (TB-PET) based on plastic scintillators, such as J-PET [1,2], offers a longer axial field-of-view and cost-effective framework for whole-body imaging. This technology also enables advanced applications like positronium imaging of the human brain [3]. The necessity of an external CT scanner for attenuation correction (AC) limits the benefits of TB-PET by adding the cost, mechanical complexity & radiation exposure. In high-sensitivity TB-PET systems, the reduction in required tracer dose means the CT component now accounts for the majority of the patient's radiation exposure [4, 5]. We propose Detector-Scattered Attenuation Correction (DSAC) [6], which is a hardware-less method for CT-less AC. This framework converts inter-detector scattering, traditionally treated as noise, into a signal. The core idea is that as detector-scattered photons traverse the patient's body, they carry tissue information that can be used to construct an attenuation map.
Methods: We developed custom Monte Carlo simulations for a plastic scintillator-based total-body J-PET geometry to track photon transport through biological tissue models. Our analysis focused on triple-hit coincidence events, where an annihilation photon interacts with one detector module, undergoes Compton scattering, and is subsequently detected in a second module. At the same time, the second annihilation photon from the pair travels in the opposite direction and hits a third module. Due to the low atomic number of plastic scintillators, these scattering events occur frequently [1, 2]. For each event, the system recorded spatial coordinates and Time-of-Flight (TOF) data, which were then processed by a reconstruction algorithm. This algorithm utilized the spatial information to estimate the line-integral of the linear attenuation coefficient, enabling the mapping of material density without external anatomical data.
Results: The simulation results demonstrate the technical feasibility of the proposed approach. The algorithm successfully reconstructed tissue density maps independent of external CT datasets. A strong linear correlation was observed between the calculated density values and the ground-truth densities of the simulated test objects. These findings validate that the high probability of Compton scattering within plastic scintillators provides a viable signal for attenuation estimation. Furthermore, the extended axial field-of-view (AFOV) characteristic of total-body scanners significantly enhances the geometric sensitivity and capture rate of these inter-detector scattering events.
Conclusion: DSAC offers a viable, hardware-less method for plastic-scintillator based TB-PET systems. By eliminating the necessity for integrated CT hardware, this method reduces overall system complexity, lowers manufacturing costs, and minimizes patient radiation burden. Future research will focus on the optimization of image quality and the implementation of advanced denoising techniques to manage the statistical variance inherent in scatter-based data due to limited statistics.
References:
1. Moskal P, et al. Nucl Instrum Methods Phys Res A. 2014;764:317-321. doi:10.1016/j.nima.2014.07.010
2. Moskal P, et al. PET Clin. 2020;15:439-452. doi:10.1016/j.cpet.2020.06.012
3. Moskal P, et al. Sci Adv. 2024;10:adp2840. doi:10.1126/sciadv.adp2840
4. Badawi RD, et al. J Nucl Med. 2019;60:299-303. doi:10.2967/jnumed.118.221226
5. Cherry SR, et al. J Nucl Med. 2018;59:3-12. doi:10.2967/jnumed.116.184028
6. Tiwari S, et al. Bio-Algorithms Med-Syst. 2025;21:13-20. doi:10.1515/bams-2024-0010
Acknowledgement: We acknowledge support from the National Science Centre (NCN), grant nos. 2021/42/A/ST2/00423, 2021/43/B/ST2/02150, 2022/47/I/NZ7/03112, and 2023/50/E/ST2/00574; the Polish Ministry of Science and Higher Education (MNiSW), grants no. IAL/SP/596235/2023 and SPUB/SP/627733/2025; the SciMat and qLife Priority Research Areas; and the ERC Advanced Grant POSITRONIUM (no. 101199807).
| Track | TBPET |
|---|---|
| Presentation type | Oral |