EJNMMI Physics最新文献

{"title":"Evaluation of a lead-loaded plastic scintillator for next-generation positron emission tomography detectors using Geant4 simulation.","authors":"Makoto Yamazaki, Masahiro Sato","doi":"10.1186/s40658-026-00941-w","DOIUrl":"10.1186/s40658-026-00941-w","url":null,"abstract":"<p><strong>Purpose: </strong>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.</p><p><strong>Methods: </strong>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).</p><p><strong>Results: </strong>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.</p><p><strong>Conclusion: </strong>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.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13620012/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149074031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of increased injected activities up 9.0 GBq [¹⁷⁷Lu]Lu-PSMA-I&T on absorbed doses to lesions and kidneys.","authors":"Zachary Ells, Linus Hempel, Julia Ells, Muyu Wu, Maximilian Scheifele, Magdalena Schoell, Sophie C Siegmund, Mathias Zacherl, Rudolf A Werner, Jeremie Calais, Magnus Dahlbom, Guido Böning, Adrien Holzgreve, Astrid Delker, Lena M Unterrainer","doi":"10.1186/s40658-026-00932-x","DOIUrl":"10.1186/s40658-026-00932-x","url":null,"abstract":"<p><strong>Introduction: </strong>Administration activities of ¹⁷⁷Lu-PSMA were chosen cautiously in the treatment of advanced prostate cancer. The primary aim was to investigate the association between increased injected activities, and the calculated absorbed doses (AD).</p><p><strong>Methods: </strong>In this single center, retrospective analysis, patients with PSMA-avid metastatic castration-resistant prostate cancer treated with [¹⁷⁷Lu]Lu-PSMA-I&T were included. Patients underwent multiple timepoint SPECT/CT imaging at 24, 48, and 72 h post-injection. Patients included were injected with 7.4, or 9.1 GBq. Segmentations were completed manually for the kidneys (CT-based), while a 3.0 SUV threshold-based approach was used for lesions. Dosimetry calculations were then performed using a multiple-timepoint protocol. Manual verification of the individual segmentations coregistered between timepoints was completed. All time activity data was fit using a mono-exponential function. Time-integrated activity was then convolved with voxel-s-value using a predefined ¹⁷⁷Lu kernel resulting the AD in Gy. No further partial volume corrections were made.</p><p><strong>Results: </strong>76 patients treated were included: 22 and 54 were injected with 9.1 ± 0.3 and 7.4 ± 0.3 GBq respectively. The AD/GBq to the kidney was comparable, 0.29 ± 0.08 vs. 0.33 ± 0.13 Gy/GBq [p=0.193] (9.1 vs. 7.4 GBq). The tumor AD/GBq was comparable between 9.1 and 7.4 GBq cohorts: total tumor burden (0.95 ± 0.42 vs. 0.92 ± 0.52 Gy/GBq) [p=0.302]; bone lesions 0.78 ± 0.42 vs. 0.74 ± 0.46 Gy/GBq [p=<0.001]; hottest lesion in each patient 1.37 ± 0.61 vs. 1.30 ± 0.74 [p=0.421]; coldest lesion in each patient 0.40 ± 0.16 vs. 0.50 ± 0.32 Gy/GBq [p=0.930].</p><p><strong>Conclusion: </strong>The AD/GBq across the disease burden, individual lesions, and kidney remained comparable even with increased injected activity. No evidence of the tumor sink effect was found. No evidence of a clinically relevant tumor sink effect in patients with <2000 mL tumor volume was found but patients with substantially high TTV (> 2 L) lacks.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13569807/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148944551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction: Scan duration for dopamine transporter neuroimaging with[123I]FP-CIT and a high-sensitivity multiple-pinhole SPECT/CT.","authors":"Gerda Thomsen, Karine Madsen, Cecilie A Poulsen, Claus Svarer, Lars H Pinborg, Gitte M Knudsen, Robin de Nijs","doi":"10.1186/s40658-026-00937-6","DOIUrl":"10.1186/s40658-026-00937-6","url":null,"abstract":"","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13545183/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148891398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Virtual-patient nonlinear mixed-effects modelling for data-driven optimisation of single-time-point dosimetry: a proof-of-concept study in [¹⁷⁷Lu]Lu-PSMA-617 therapy.","authors":"Yeni Pertiwi, Indra Budiansah, Jaja Muhamad Jabar, Muchtaridi Muchtaridi, Freddy Haryanto, Idam Arif, Deni Hardiansyah, Gerhard Glatting","doi":"10.1186/s40658-026-00933-w","DOIUrl":"10.1186/s40658-026-00933-w","url":null,"abstract":"<p><strong>Background: </strong>Robust single-time-point (STP) dosimetry critically depends on selecting an imaging time that yields reliable estimates of the time-integrated activity coefficient (TIAC). This study developed and evaluated a virtual-patient nonlinear mixed-effects modelling (NLMEM) framework to optimise STP imaging schedules for renal TIAC estimation, using [¹⁷⁷Lu]Lu-PSMA-617 therapy as a proof of concept.</p><p><strong>Methods: </strong>A previously published NLMEM (sum-of-exponentials structure and parameter distributions) describing renal [¹⁷⁷Lu]Lu-PSMA-617 biokinetics in 63 patients served as the generative model [1]. Based on fixed- and random-effects parameters, 500 virtual patients (VPs) were sampled, and reference TIAC values were computed analytically (rTIAC). For each candidate imaging time, renal activity measurements were simulated by applying proportional noise (7.9%). Estimated STP TIAC values (sTIAC) were obtained via leave-one-out cross-validation and compared with rTIAC to quantify population-level error metrics using mean absolute percentage error (MAPE) and root-mean-square error (RMSE). Time-dependent MAPE-time and RMSE-time profiles were modelled using polynomial fits selected by predefined goodness-of-fit criteria to identify time windows with low and stable errors. Individual-level robustness was assessed by quantifying extreme patient-specific relative deviations (RD) using thresholds of 10%, 20%, and 30%.</p><p><strong>Results: </strong>MAPE- and RMSE-versus-time profiles were concordant and showed a pronounced minimum around 50 h post-injection. Among the investigated imaging time points, the lowest observed population-level error metrics occurred at 48 h, whereas polynomial modelling predicted an optimum centred at approximately 50 h (about 33-67 h). An additional VP-NLMEM evaluation at 50 h demonstrated comparable population-level performance and the lowest frequency of |RD| >30%, while the minima for the 10% and 20% thresholds occurred at nearby imaging times.</p><p><strong>Conclusion: </strong>The proposed virtual-patient NLMEM framework enables data-driven optimisation of STP imaging by identifying robust time windows that minimise both population-level error and extreme individual deviations in renal TIAC estimation for [¹⁷⁷Lu]Lu-PSMA-617 therapy. The approach appears transferable to STP dosimetry optimisation for other radiopharmaceuticals.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13529636/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148863886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monte Carlo simulation and experimental validation of SPECT systems via energy spectrum decomposition and image profile analysis.","authors":"Zhiqiang Peng, Muhammad Abdul Wasaye, Irfan Siddique, Faiz Wali, Mohsin Saeed","doi":"10.1186/s40658-026-00929-6","DOIUrl":"10.1186/s40658-026-00929-6","url":null,"abstract":"<p><strong>Background: </strong>Accurate modelling and performance evaluation of gamma-ray scintillation detectors are required in single photon emission computed tomography (SPECT) systems to ensure reliable nuclear medicine diagnostics. Monte Carlo simulation is therefore a powerful computational technique used to accurately model the gamma-ray scintillation detectors and photon transport in medical imaging systems. Therefore, the objective of this study is to validate the SIMIND Monte Carlo simulation code using a self-developed peak-detection algorithm for clinical SPECT gamma cameras (Siemens E.Cam and GE Infinia), with a focus on energy-spectrum decomposition and image-profile analysis.</p><p><strong>Methods: </strong>This study presents a dual-system evaluation of clinical SPECT gamma cameras-the Siemens E.Cam and GE Infinia systems using the SIMIND Monte Carlo simulation code. We assessed collimator and detector-specific SPECT performance metrics, including energy resolution, sensitivity, image evaluation, spatial resolutions, and spectral fidelity for a ^99mTc point source and spatial resolution with Co-57 flood source. A custom algorithm was then developed to automatically decompose energy spectra and identify key spectral components, including the photopeak, Compton edge, iodine escape, and lead X-ray peaks. Quantitative methods, such as 2D and 3D image profile analysis and FWHM comparisons, were integrated to validate the simulation against experimental data.</p><p><strong>Results: </strong>Energy resolution differences ≤ 4% and sensitivity variations < 1.2% were observed between simulated and experimental measurements. Spatial resolution analysis revealed a range of 3.5-4.8 mm for Siemens E.Cam (bar and pie phantoms) and ~ 1 cm for GE Infinia, highlighting system-specific imaging capabilities. A custom algorithm successfully identified key spectral components, including photopeaks, Compton edges, and lead X-ray peaks, with deviations < 3%. Image profile analysis revealed FWHM values of 4-4.5 pixels for both systems.</p><p><strong>Conclusion: </strong>This work shows that SIMIND accurately reproduces the fundamental photon interaction characteristics including energy spectra, energy resolution, and sensitivity for both Siemens E.Cam and GE Infinia SPECT systems. However, for image-profile evaluation, good agreement was obtained for Siemens E.Cam, whereas the GE Infinia results revealed a system-specific discrepancy associated with the actual clinical condition of the installed camera. Nevertheless, when used appropriately, SIMIND provides a robust framework for optimizing quantitative SPECT protocols and guiding system design improvements, particularly for well-calibrated systems.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13554010/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148911153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Toward an optimized PET reconstruction protocol for spinal cord: superiority of OSEM with TOF and PSF.","authors":"Jiyuan Wang, Jing Huang, Bixiao Cui, Hongwei Yang, Defeng Tian, Jie Ma, Wanru Duan, Zan Chen, Jie Lu","doi":"10.1186/s40658-026-00922-z","DOIUrl":"10.1186/s40658-026-00922-z","url":null,"abstract":"<p><strong>Background: </strong>Although multiple PET reconstruction approaches have been successfully applied in brain and oncologic imaging, their performance in the context of spinal cord imaging remains unverified. This study aims to identify the optimal reconstruction method for spinal cord PET image analysis based on assessments of image quality and quantitative uptake.</p><p><strong>Methods: </strong>We retrospectively analyzed ¹⁸F-fluorodeoxyglucose (FDG) PET/MR data from 22 patients with cervical spinal cord tumors. PET images were reconstructed using Ordered Subset Expectation Maximization (OSEM), OSEM + Point Spread Function (PSF), OSEM + Time-of-Flight (TOF), and OSEM + TOF + PSF algorithms. Image quality was assessed by noise, signal-to-noise ratio (SNR), and signal-to-background ratio (SBR), both overall and within equally sized small (n = 11) and large (n = 11) tumor subgroups. Tumor uptake metrics, including SUV_mean, SUV_max, SUVR_mean, and SUVR_max of the lesions, were quantified for each method. The differences among reconstruction methods were assessed using the Friedman test.</p><p><strong>Results: </strong>There were no significant differences in image noise among reconstruction methods (P > 0.05). Compared to OSEM reconstruction, the OSEM + PSF + TOF method significantly improved SNR (Z = 3.62, P < 0.01) and SBR (Z = 2.80, P = 0.03); the SBR of OSEM + PSF + TOF was also significantly higher than that of OSEM + PSF (Z = 3.04, P = 0.01). In large tumors, while image noise remained unaffected by the reconstruction method (P > 0.05), both SNR and SBR were significantly impacted (both P < 0.05). Specifically, OSEM + TOF + PSF achieved significantly higher SNR compared to OSEM (Z = 3.30, P < 0.01), and higher SBR compared to OSEM + PSF (Z = 3.14, P = 0.01). Quantitative lesion uptake metrics (SUV_max, SUV_mean, SUVR_max, and SUVR_mean) were significantly higher for OSEM + TOF + PSF compared to both OSEM and OSEM + PSF reconstructions (all P < 0.05). Additionally, SUV_mean (Z = 2.92, P = 0.02) and SUVR_mean (Z = 2.83, P = 0.03) values from OSEM + TOF + PSF reconstruction were significantly higher than those from OSEM + TOF.</p><p><strong>Conclusion: </strong>The OSEM + PSF + TOF reconstruction method demonstrated significant advantages in both image quality and quantitative assessment of FDG uptake, making it the recommended choice for spinal cord PET image reconstruction.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13554005/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148911189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monte Carlo microdosimetry of ²¹¹at in multi-species thyroid follicle models: AlfaMC versus MCNPX and Geant4.","authors":"Arman Romiani, Anders Josefsson, Roumiana Chakarova, Eva Forssell-Aronsson","doi":"10.1186/s40658-026-00925-w","DOIUrl":"10.1186/s40658-026-00925-w","url":null,"abstract":"<p><strong>Background: </strong>Radionuclide therapy is an increasingly used treatment modality for patients with disseminated cancer diseases. Tumor-binding radiopharmaceuticals labelled with the alpha-particle emitter astatine-211 (²¹¹At) are of interest to enable high radiation absorbed doses to small tumors. The alpha particles emitted by ²¹¹At will deposit all their energy in a short-range including neighboring cells, causing localized irradiation. Due to being part of group 17 the halogen family with iodine, free ²¹¹At accumulates in the thyroid gland, which is the main normal organ at risk. It is therefore of great importance to estimate the radiation absorbed dose accurately to the thyroid gland for free ²¹¹At. The aims of the work were to determine microdosimetric quantities for uniform and non-uniform 211At distributions within different models of the thyroid gland using the Monte Carlo (MC) codes AlfaMC and GEometry ANd Tracking (Geant4), and to compare the results with previously published data using Monte Carlo N-Particle eXtended (MCNPX). AlfaMC is customized for calculating microdosimetric quantities for alpha-particles.</p><p><strong>Results: </strong>Both a single and a multiple thyroid follicle model designed for man, rat and mouse were used from previously published studies. Monte Carlo simulations and absorbed dose-calculations were performed for different distributions of 211At within the thyroid models. The mean specific energy, single-hit mean specific energy and single-hit specific energy distribution were calculated for follicle cell nuclei in models for each species.</p><p><strong>Conclusion: </strong>The overall agreement between AlfaMC and MCNPX results, and between AlfaMC and Geant4 results, was found to be within 5% and 2%, respectively. The intercomparison suggested an effective way for validation of microdosimetry results; of AlfaMC validation, a code designed with a focus on reducing the calculation time.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13481933/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148789649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantification of image quality and partial volume effect along the axial field-of-view of uMI Panorama GS PET/CT system for multiple radionuclides.","authors":"Haiqiong Zhang, Guangjie Yang, Linfeng Li, Meixi Liu, Tong Wang, Xueqian Yang, Ziwei Liang, Mengshi Yan, Hongli Jing, Haiqun Xing, Li Huo","doi":"10.1186/s40658-026-00915-y","DOIUrl":"10.1186/s40658-026-00915-y","url":null,"abstract":"<p><strong>Purpose: </strong>The comprehensive knowledge of how the distinct physical decay characteristics of each radionuclide shape their image quality performance is essential for tailoring acquisition protocols and ensuring optimal clinical applications. Understanding the spatial dependence of the contrast recovery coefficient (CRC) is a prerequisite for robust quantitative image analyses and accurate clinical interpretations, since the partial volume effect (PVE) and the count rate vary along the axial field of view (AFOV). Image quality assessments with various radionuclides were performed on the uMI Panorama GS PET/CT system, with the CRC profile across its extended AFOV also evaluated.</p><p><strong>Methods: </strong>Following the NEMA NU 2-2018 standard, the image quality was assessed using the NEMA IEC (NEC) Body Phantom with ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁸⁹Zr, ¹²⁴I, and ⁹⁰Y. The CRC, the background variability (BV), and the lung residual error were measured to quantify the image quality. CRCs were sequentially measured at four axial offsets: 1/2, 1/4, 1/8, and 1/16 of the AFOV. The impact of the radionuclide-specific PSF (point spread function) modeling on the CRC was evaluated by comparing PET images reconstructed with and without PSF modeling.</p><p><strong>Results: </strong>The assessment demonstrated comparable image qualities for ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁸⁹Zr, ¹²⁴I, while ⁹⁰Y showed a similar CRC but a higher BV and a higher lung residual error, attributable to its low positron branching ratio. The BV and lung residual error increased with increasing axial distance from the AFOV center, whereas CRCs for larger spheres remained stable across AFOV positions; small-sphere CRC measurements exhibited increased dispersion toward the periphery due to reduced count statistics. The PSF modeling significantly improved CRCs for ⁶⁸Ga and ¹²⁴I, consistent with their long positron ranges.</p><p><strong>Conclusions: </strong>All investigated radionuclides were effectively imaged on the uMI Panorama GS PET/CT system. The AFOV uniformity was quantitatively evaluated based on CRC measurements obtained at multiple positions along the AFOV.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13661889/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148520173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Feasibility simulation study of positronium lifetime imaging with the Biograph Vision Quadra and J-PET tomographs.","authors":"Szymon Parzych, Szymon Niedźwiecki, Ermias Yitayew Beyene, Neha Chug, Maurizio Conti, Catalina Curceanu, Eryk Czerwiński, Manish Das, Kavya Valsan Eliyan, Jakub Hajduga, Sharareh Jalali, Krzysztof Kacprzak, Tevfik Kaplanoglu, Łukasz Kapłon, Kamila Kasperska, Aleksander Khreptak, Grzegorz Korcyl, Tomasz Kozik, Deepak Kumar, Anoop Kunimmal Venadan, Karol Kubat, Edward Lisowski, Filip Lisowski, Justyna Medrala-Sowa, Wiktor Mryka, Simbarashe Moyo, Piyush Pandey, Elena Perez Del Rio, Alessio Porcelli, Bartłomiej Rachwał, Martin Rädler, Axel Rominger, Sushil Sharma, Kuangyu Shi, Magdalena Skurzok, William M Steinberger, Tomasz Szumlak, Pooja Tanty, Keyvan Tayefi Ardebili, Satyam Tiwari, Ewa Ł Stepień, Paweł Moskal","doi":"10.1186/s40658-026-00920-1","DOIUrl":"10.1186/s40658-026-00920-1","url":null,"abstract":"<p><strong>Background: </strong>After its first ex-vivo and in-vivo demonstration, Positronium Lifetime Imaging (PLI) has received considerable interest as a potential new diagnostic biomarker. High sensitivity Positron Emission Tomography (PET) systems are needed for PLI since it requires simultaneous registration of annihilation photons and prompt gamma. In this simulation-based study, a feasibility of PLI with the long axial field-of-view Biograph Vision Quadra (Quadra) and the Total Body J-PET scanner was investigated.</p><p><strong>Methods: </strong>The study was performed using the GATE software. Background radiation, present within the Quadra tomograph, was added to the simulation. First, the optimal placement of the energy window for the registration of the prompt gamma was investigated. Next, the organ-wise sensitivity of Quadra was calculated for the [Formula: see text]Ga, [Formula: see text]Sc, [Formula: see text]Na and [Formula: see text]I radioisotopes. Finally, the sensitivity for the scandium isotope was compared to the sensitivities obtainable with the Total Body J-PET scanner, as well as with the modular J-PET prototype.</p><p><strong>Results: </strong>The PLI sensitivities for the Quadra with the background radiation are estimated to 9.22(3), 10.46(4), 5.91(3), and 15.39(4) cps/kBq for the [Formula: see text]Sc, [Formula: see text]Ga, [Formula: see text]Na and [Formula: see text]I radioisotopes, respectively. The highest sensitivity was obtained when the energy window for the deexcitation photon is adjacent to the energy window for the annihilation photons. In case of J-PET, the sensitivities for the [Formula: see text]Sc were estimated to 0.062(08) and 1.714(40) cps/kBq for the modular and Total Body J-PET scanners, respectively. The determined PLI sensitivities with Quadra and the Total Body J-PET are in the order of sensitivities of metabolic PET imaging with the short axial field-of-view (∼20 cm) PET scanners based on pure positron emitter isotopes.</p><p><strong>Conclusions: </strong>The PLI sensitivity of Quadra has been computed for the [Formula: see text]Ga, [Formula: see text]Sc, [Formula: see text]Na and [Formula: see text]I radioisotopes. A sensitivity gain by a factor of 150 was estimated relative to the modular J-PET system previously used for the first in-vivo PLI. Additionally, the sensitivity for Total Body J-PET is expected to be about 30 times higher than for modular J-PET.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13661834/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148497470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MLPET: a localized neural network approach for probabilistic post-reconstruction PET image analysis using informed priors.","authors":"Thomas Mejer Hansen, Nana Louise Christensen, Mikkel Holm Vendelbo","doi":"10.1186/s40658-026-00917-w","DOIUrl":"10.1186/s40658-026-00917-w","url":null,"abstract":"<p><strong>Purpose: </strong>PET images often make small lesions difficult to identify because of noise and system blur. We address this by developing and evaluating MLPET , a fast localized machine-learning method that approximates a computationally expensive probabilistic sampling approach while reducing noise and increasing spatial resolution.</p><p><strong>Methods: </strong>Building on a probabilistic deconvolution framework with informed priors, MLPET replaces computationally demanding Markov chain Monte Carlo sampling with a localized neural network trained to directly estimate the posterior mean of voxel activity from small image neighborhoods. The method incorporates scanner-specific point spread functions (PSF), spatially correlated noise modeling, and flexible prior information. Performance was evaluated on NEMA phantom data acquired on three PET systems (GE Discovery MI, Siemens Biograph Vision 600, and Siemens Biograph Vision Quadra Edge) under varying reconstruction settings and acquisition times.</p><p><strong>Results: </strong>On NEMA IEC phantom data, MLPET produced contrast-recovery coefficients consistently higher than PET and frequently close to 1.0 (including the 10 mm sphere in several settings), while simultaneously reducing background noise and improving spatial definition. The effective point-spread function (PSF) full width at half maximum (FWHM) was on average reduced from about 2 mm in PET to below 1 mm with MLPET , corresponding to roughly a 2.5× decrease in effective blur. Comparable image quality was obtained at 40-80 s acquisition time using MLPET versus 900 s with conventional PET. A clinical example in a breast cancer patient illustrates potential clinical applicability.</p><p><strong>Conclusions: </strong>MLPET provides a computationally efficient approach for quantitative probabilistic post-reconstruction PET image analysis. By combining informed priors with the speed of a neural network, it achieves both noise suppression and resolution enhancement. The method shows promise for improved small-lesion detectability and quantitative reliability in clinical PET imaging. Future clinical studies will evaluate its performance on patient data and quantify effects under realistic prior uncertainty.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148445088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}