EJNMMI Physics最新文献

{"title":"IDAC-Dose 2.2, an internal dosimetry software for diagnostic nuclear medicine based on the latest ICRP adult and paediatric reference computational phantoms.","authors":"Martin Andersson, Keith Eckerman, Sören Mattsson","doi":"10.1186/s40658-025-00774-z","DOIUrl":"10.1186/s40658-025-00774-z","url":null,"abstract":"<p><strong>Background: </strong>For patients investigated with radiopharmaceuticals, it is important to be able to perform valid calculations of the absorbed dose in organs and tissues. An internal dosimetry computer program, IDAC-Dose2.1, has been updated to be based on the ICRP specific absorbed fractions and computational framework of internal dose assessment for 12 adult and paediatric reference individuals given in ICRP Publication 133 and 155. The updated dosimetry software intended for nuclear medicine is named IDAC-Dose2.2. The calculations are based on radionuclide decay scheme of ICRP Publication 107. Biokinetic models can be based on up to 83 different source regions irradiating 48 target tissues, defining the effective dose as presented in ICRP Publications 60 and 103. The computer program was validated against another ICRP dosimetry software, DCAL ver. 2022, that employs the same computational framework and is used for occupational and environmental intakes of radionuclides. IDAC-Dose2.2 calculates absorbed doses to the 2 adult and 10 paediatric,15-yrs, 10-yrs, 5-yrs, 1-yr, 100 days (infant) and 0 day (new-born), sex specific ICRP reference phantoms. It has an additional sub-module which can interpolate the calculated absorbed dose and effective dose to an arbitrary age between 0 and 20 years (20 years = adult) or an arbitrary weight of 3.5-73 kg for male and 3.5-64 kg for female instead of only using the 6 fixed phantoms ages.</p><p><strong>Results: </strong>IDAC-Dose2.2 was applied on three frequently used radiopharmaceuticals: intravenously administered 2-[<sup>18</sup>F]FDG, orally administered <sup>99m</sup>Tc-pertechnetate and <sup>131</sup>I-iodide. Using the tissue weighting factors from ICRP Publication 103, the effective dose per administered activity was estimated for 2-[<sup>18</sup>F]FDG: 0.017mSv/MBq, 0.020 mSv/MBq, 0.029 mSv/MBq, 0.044 mSv/MBq, 0.075 mSv/MBq, 0.16 mSv/MBq 0.16 mSv/MBq for adult, 15-, 10-, 5-, 1-year old, 100 days (infant) and 0 day (newborn), respectively. Effective dose of 0.034 mSv/MBq was also calculated for 2-[<sup>18</sup>F]FDG to a reference person of 8-years old. For the same three radiopharmaceuticals, S-values were generated for all phantoms in IDAC-Dose2.2 and validated against the dosimetry program DCAL, showing identical results.</p><p><strong>Conclusions: </strong>The internal dosimetry program IDAC-Dose was updated to include all 12 specific sets of absorbed fractions of the ICRP adult and paediatric reference phantoms and applied to three radiopharmaceuticals for validation against DCAL and to generate improved absorbed dose estimations for preadults in diagnostic nuclear medicine. The sub-module for age or weight interpolation of absorbed doses follows the ICRP computational framework used for members of the public. IDAC-Dose2.2 will used by the ICRP for absorbed and effective dose calculations in diagnostic nuclear medicine. The results from other software, which uses the same primer d","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"56"},"PeriodicalIF":3.0,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12165913/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144283002","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":"Brain tau PET-based identification and characterization of subpopulations in patients with Alzheimer's disease using deep learning-derived saliency maps.","authors":"Yanxiao Li, Xiuying Wang, Qi Ge, Manuel B Graeber, Shaozhen Yan, Jian Li, Shuyu Li, Wenjian Gu, Shuo Hu, Tammie L S Benzinger, Jie Lu, Yun Zhou","doi":"10.1186/s40658-025-00761-4","DOIUrl":"10.1186/s40658-025-00761-4","url":null,"abstract":"<p><strong>Background: </strong>Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder in which tau neurofibrillary tangles are a pathological hallmark closely associated with cognitive dysfunction and neurodegeneration. In this study, we used brain tau data to investigate AD heterogeneity by identifying and characterizing the subpopulations among patients. We included 615 cognitively normal and 159 AD brain ¹⁸F-flortaucipr PET scans, along with T1-weighted MRI from the Alzheimer Disease Neuroimaging Initiative database. A three dimensional-convolutional neural network model was employed for AD detection using standardized uptake value ratio (SUVR) images. The model-derived saliency maps were generated and employed as informative image features for clustering AD participants. Among the identified subpopulations, statistical analysis of demographics, neuropsychological measures, and SUVR were compared. Correlations between neuropsychological measures and regional SUVRs were assessed. A generalized linear model was utilized to investigate the sex and APOE ε4 interaction effect on regional SUVRs.</p><p><strong>Results: </strong>Two distinct subpopulations of AD patients were revealed, denoted as S_Hi and S_Lo. Compared to the S_Lo group, the S_Hi group exhibited a significantly higher global tau burden in the brain, but both groups showed similar cognition distribution levels. In the S_Hi group, the associations between the neuropsychological measurements and regional tau deposition were weakened. Moreover, a significant interaction effect of sex and APOE ε4 on tau deposition was observed in the S_Lo group, but no such effect was found in the S_Hi group.</p><p><strong>Conclusion: </strong>Our results suggest that tau tangles, as shown by SUVR, continue to accumulate even when cognitive function plateaus in AD patients, highlighting the advantages of PET in later disease stages. The differing relationships between cognition and tau deposition, and between gender, APOE4, and tau deposition, provide potential for subtype-specific treatments. Targeting gender-specific and genetic factors influencing tau deposition, as well as interventions aimed at tau's impact on cognition, may be effective.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"55"},"PeriodicalIF":3.0,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12149067/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144247008","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":"Impact of image reconstruction on cerebral blood flow measured with ¹⁵O-water positron emission tomography.","authors":"Elin Bäck, My Jonasson, Elin Lindström, Andreas Tolf, Joachim Burman, Lieuwe Appel, Mark Lubberink","doi":"10.1186/s40658-025-00760-5","DOIUrl":"10.1186/s40658-025-00760-5","url":null,"abstract":"<p><strong>Background: </strong>¹⁵O-water positron emission tomography (PET) is considered the gold standard method for non-invasive measurement of cerebral blood flow (CBF). However, previously published average CBF values in healthy subjects have varied greatly and the cause of these variations remains unclear. This study investigates how image reconstruction methods and spatial resolution affect CBF measurements with ¹⁵O-water PET.</p><p><strong>Methods: </strong>Eight healthy subjects each underwent dynamic ¹⁵O-water PET scans with continuous arterial blood sampling. Images were reconstructed using two different algorithms; ordered subset expectation maximisation and block sequential regularised expectation maximalisation with varying reconstruction parameters. CBF was estimated for the whole brain, grey matter, and central white matter. Reconstruction-specific effective spatial resolution was estimated using phantom measurements and simulations.</p><p><strong>Results: </strong>The mean whole brain CBF was 0.48 mL/cm³/min and showed little dependence on the image reconstruction method. Grey matter CBF varied between 0.52 and 0.57 mL/cm³/min, and central white matter CBF between 0.20 and 0.28 mL/cm³/min. Regional CBF showed great dependence on effective spatial resolution with a negative correlation between grey matter CBF and resolution (r = -0.96) and a positive correlation between central white matter and resolution (r = 0.93).</p><p><strong>Conclusion: </strong>This study concludes that grey matter and central white matter CBF, but not whole brain CBF measured with quantitative ¹⁵O-water PET is reconstruction method dependent, mainly due to varying spatial resolution with consequent partial volume effects. Variations in published CBF values cannot be explained solely by reconstruction methods or spatial resolution.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"52"},"PeriodicalIF":3.0,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12144024/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144233533","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":"Interobserver ground-truth variability limits performance of automated glioblastoma segmentation on [¹⁸F]FET PET.","authors":"Selene De Sutter, Ine Dirks, Laurens Raes, Wietse Geens, Hendrik Everaert, Sophie Bourgeois, Johnny Duerinck, Jef Vandemeulebroucke","doi":"10.1186/s40658-025-00767-y","DOIUrl":"10.1186/s40658-025-00767-y","url":null,"abstract":"<p><strong>Background: </strong>Positron emission tomography (PET) with a [¹⁸F]fluoroethyl)-L-tyrosine ([¹⁸F]FET) tracer is of growing importance in the management of glioblastoma for the estimation of tumor extent and extraction of diagnostic and prognostic parameters. Robust and accurate glioblastoma segmentation methods are essential to maximize the benefits of this imaging modality. Given the importance of setting the foreground threshold during manual tumor delineation, this study investigates the added value of incorporating such prior knowledge to guide the automated segmentation and improve performance. Two segmentation networks were trained based on the nnU-Net guidelines: one with the [¹⁸F]FET PET image as sole input, and one with an additional input channel for the threshold map. For the latter, we investigate the benefit of manually obtained thresholds and explore automated prediction and generation of such maps. A fully automated pipeline was constructed by selecting the best performing threshold prediction approach and cascading this with the tumor segmentation model.</p><p><strong>Results: </strong>The proposed two-channel network shows increased performance with guidance of threshold maps originating from the same reader whose ground-truth tumor label the prediction is compared to (DSC = 0.901). When threshold maps were generated by a different reader, performance reverted to levels comparable to the one-channel network and inter-reader variability. The proposed full pipeline achieves results on par with current state of the art (DSC = 0.807).</p><p><strong>Conclusions: </strong>Incorporating a threshold map can significantly improve tumor segmentation performance when it aligns well with the ground-truth label. However, the current inability to reliably reproduce these maps-both manually and automatically-or the ground-truth tumor labels, restricts the achievable accuracy for automated glioblastoma segmentation on [¹⁸F]FET PET, highlighting the need for more consistent definitions of such ground-truth delineations.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"54"},"PeriodicalIF":3.0,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12144010/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144233534","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":"3D printing of radioactive wall-less PET phantoms improves threshold-based target delineation and quantification.","authors":"Adrian Jun Zounek, Nico Maximilian Joerg, Felix Lindheimer, Artem Zatcepin, Giovanna Palumbo, Rosel Oos, Astrid Delker, Franz Josef Gildehaus, Andreas Bollenbacher, Guido Boening, Peter Bartenstein, Matthias Brendel, Nathalie Lisa Albert, Sibylle Ziegler, Lena Kaiser","doi":"10.1186/s40658-025-00768-x","DOIUrl":"10.1186/s40658-025-00768-x","url":null,"abstract":"<p><strong>Background: </strong>Validation of threshold-based PET segmentation and PET quantification is typically performed with fillable phantoms. Theoretical considerations show that the inactive walls of the phantom cavities introduce a contrast dependence of the volume-reproducing threshold (VRT), potentially leading to segmentation errors and therefore miscalculations of target volumes. The goal of this study was to experimentally show the contrast independence of the VRT when using wall-less phantoms.</p><p><strong>Results: </strong>Radioactive spheres were produced according to NEMA specifications (D = 10/13/17/22/28/37 mm) using a stereolithographic (SLA) 3D printer. For comparison, hollow spheres were filled with a similar activity concentration. Image data from both sphere types were acquired with five different signal-to-background ratios (SBR = 2/4/6/8/10) using a Siemens mCT 20 and a Biograph 64 TruePoint PET/CT system. Results from wall-less and fillable spheres were compared to evaluate contrast dependence and segmentation accuracy based on VRT and intensity profiles. Wall-less phantoms demonstrated consistent VRT values, with a coefficient of variation of 2% over all SBRs, indicating independence from contrast. Conversely, fillable phantoms exhibited significant VRT variability, with a coefficient of variation (CV) of 9% over all SBRs and up to 40% volume overestimation at low contrast. Additionally, activity distribution in the printed spheres was evaluated using PET-based statistical analysis and autoradiography. The PET intensity distribution in the printed material was highly uniform (CV = 4.2%), with a Kullback-Leibler divergence near zero and no statistically significant difference to the fillable spheres. Autoradiography revealed microscopic regions with elevated counts, showing a CV of 11.7%, which was effectively reduced to 2.4% after Gaussian filtering.</p><p><strong>Conclusions: </strong>The theoretical predictions of a significant influence of inactive walls in low-contrast images and contrast-independent VRT in wall-less phantoms were successfully confirmed. SLA 3D printing of phantoms is a promising method for the reliable evaluation of PET quantification methods, particularly in low-contrast scenarios commonly encountered in clinical settings.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"53"},"PeriodicalIF":3.0,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12144006/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144233532","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":"Dual-ended readout TOF-DOI PET detectors based on 3.2 mm and 1.6 mm pitch LYSO arrays.","authors":"Haibo Wang, Jiahao Xie, Jinyi Qi, Simon R Cherry, Junwei Du","doi":"10.1186/s40658-025-00759-y","DOIUrl":"10.1186/s40658-025-00759-y","url":null,"abstract":"<p><strong>Background: </strong>The image quality of positron emission tomography (PET) can be significantly enhanced by using time-of-flight (TOF) and depth-of-interaction (DOI) information. PET detectors are pivotal in determining the TOF and DOI capabilities of PET scanners.</p><p><strong>Methods: </strong>This study developed and evaluated TOF-DOI PET detectors based on the dual-ended readout method and lutetium-yttrium oxyorthosilicate (LYSO) arrays with two different pitches and reflector configurations. Specifically, the performance of detectors based on three types of LYSO arrays with 20 mm thickness, 8 × 8 arrays with a 3.2 mm pitch, 16 × 16 arrays with a 1.6 mm pitch and normal reflectors, and 16 × 16 arrays with a 1.6 mm pitch and partial short reflectors, were assessed. Hamamatsu S14161-3050-08 silicon photomultiplier arrays were used as the photodetectors, and PETsys TOFPET2 was used as the readout electronics.</p><p><strong>Results: </strong>The flood histograms showed that all crystals in the three types of LYSO arrays were clearly resolved. The detectors based on the 8 × 8 LYSO arrays provided a coincidence timing resolution (CTR) of 207 ± 5 ps and a DOI resolution of 3.9 ± 0.6 mm. The detectors based on the 16 × 16 LYSO arrays with normal reflectors provided a CTR of 218 ± 7 ps and a DOI resolution of 2.6 ± 0.2 mm. In comparison, the detector based on the 16 × 16 LYSO arrays with partial short reflectors provided a CTR of 228 ± 11 ps and a DOI resolution of 2.9 ± 0.3 mm, and superior crystal resolvability compared to the detectors based on the 16 × 16 LYSO arrays with normal reflectors.</p><p><strong>Conclusion: </strong>These detectors are promising candidates for developing whole-body and brain PET scanners, offering effective sensitivity and uniform spatial resolution improvements across the field-of-view.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"51"},"PeriodicalIF":3.0,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12116964/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144157327","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":"Gamma camera imaging characteristics of ^203/212Pb as a theragnostic pair for targeted alpha therapy: a feasibility study.","authors":"David Kästner, Holger Hartmann, Robert Freudenberg, Marc Pretze, Claudia Brogsitter, Michael K Schultz, Jörg Kotzerke, Enrico Michler","doi":"10.1186/s40658-025-00763-2","DOIUrl":"10.1186/s40658-025-00763-2","url":null,"abstract":"<p><strong>Background: </strong>²⁰³Pb and ²¹²Pb show promise as theragnostic agents for targeted alpha therapy (TAT) because two chemically identical isotopes can be used for diagnostic imaging and treatment. In the ²¹²Pb decay chain, in addition to alpha and beta particles, a large number of photons are emitted, those with an energy of 239 keV and the characteristic X-rays of ²¹²Pb could be used for imaging. ²⁰³Pb decays by photon emission with an energy of 279 keV, which appears suitable for gamma camera imaging. The aim of this study was to investigate suitable imaging protocols and to characterize the scintigraphic imaging properties and their implications for the clinical feasibility as theragnostic isotopes.</p><p><strong>Methods: </strong>Planar and SPECT/CT images were obtained with medium- and high-energy collimators on a Siemens Symbia Intevo 6 using a NEMA image quality phantom in various phantom setups and another body-shaped phantom with several inserts. Different energy windows were investigated and measurements were evaluated in terms of sensitivity, count rate performance, spatial resolution, contrast recovery, lesion detectability, and image quantification.</p><p><strong>Results: </strong>Evaluation of image quality showed superior imaging characteristics for ²⁰³Pb compared to ²¹²Pb regarding spatial resolution, contrast recovery, image noise, and quantification accuracy. Both medium- and high- energy collimators were suitable for ²⁰³Pb imaging, with the medium energy collimators showed slightly better imaging properties. Images obtained with the HE collimators in the 79 keV energy window showed the best visual image quality for ²¹²Pb. Due to high-energy photon emissions from ²¹²Pb daughter nuclides (e.g., 2.6 MeV from ²⁰⁸Tl), dead time related count losses occurred even at low activities (20% count loss at 20 MBq for MELP collimators).</p><p><strong>Conclusions: </strong>According to our results and first-in-human imaging studies, SPECT/CT imaging with the ^203/212Pb theragnostic pair is clinically feasible. ²⁰³Pb is an appropriate imaging surrogate to investigate pharmacokinetics and perform predictive dosimetry. The less favorable imaging characteristics of ²¹²Pb make image quantification and post-treatment dosimetry challenging and require further research.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"50"},"PeriodicalIF":3.0,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12106261/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144149858","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":"First performance evaluation of easyPET.3D, a high-resolution and cost-effective benchtop preclinical PET scanner.","authors":"Fabiana M Ribeiro, Pedro M C C Encarnação, Ana L M Silva, Pedro M M Correia, Afonso X Pinto, Regina G Oliveira, José Sereno, Mariana Lapo Pais, Antero Abrunhosa, Ismael F Castro, Ana C Santos, João F C A Veloso","doi":"10.1186/s40658-025-00757-0","DOIUrl":"10.1186/s40658-025-00757-0","url":null,"abstract":"<p><strong>Purpose: </strong>EasyPET.3D is a preclinical positron emission tomography (PET) scanner with a unique scanning method based on two face-to-face detector modules with two axes of motion. Its performance evaluation is presented using the NEMA NU-4 standards and an animal model.</p><p><strong>Methods: </strong>Each detector module consists of a 32 × 2 pixelated cerium-doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator array with individual crystals of 2.0 × 2.0 × 30 mm³. The crystal arrays are coupled to 1.3 × 1.3 mm² silicon photomultipliers (SiPMs). The transaxial field-of-view (FoV) is adjustable up to 48 mm in diameter, and the axial length is 73 mm. The performance characterization includes spatial resolution, sensitivity, count rate, scatter fraction (SF), and image quality (IQ) measurements. Furthermore, mice experiments were conducted to evaluate the in vivo imaging capability.</p><p><strong>Results: </strong>Spatial resolution at the FoV centre (CFoV) in radial, tangential, and axial directions was 0.98±0.08, 0.97±0.06 and 0.94±0.08 mm, respectively. An absolute sensitivity of 0.23% was measured at CFoV. The mouse-like phantom SF was 16% (913 cps at 18 MBq). Recovery coefficients in the IQ phantom varied from 21±34% to 85±50% (1 to 5 mm diameter rods, accordingly). The uniformity was 17.6%, and spill-over ratios for water-filled and air-filled chambers were 0.49 and 0.40, respectively.</p><p><strong>Conclusion: </strong>EasyPET.3D geometry favours the reduction of parallax error, despite its low sensitivity. The system linearity is suitable for the low range of activities (7-8 MBq) used for mice imaging. The overall performance showed that easyPET.3D has potential for entry-level preclinical applications.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"48"},"PeriodicalIF":3.0,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12106262/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144141810","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":"Performance evaluation of a medium axial field-of-view sparse PET system based on flat panels of monolithic LYSO detectors: a simulation study.","authors":"Maya Abi-Akl, Jens Maebe, Boris Vervenne, Othmane Bouhali, Christian Vanhove, Stefaan Vandenberghe","doi":"10.1186/s40658-025-00766-z","DOIUrl":"10.1186/s40658-025-00766-z","url":null,"abstract":"<p><strong>Background: </strong>The combination of longer axial field-of-view (AFOV) and time-of-flight positron emission tomography (PET) has significantly improved system sensitivity and, as a result, image quality. This study investigates a cost-effective extended AFOV PET system design using monolithic LYSO detectors with depth-of-interaction capabilities. These detectors, arranged in a vertical flat-panel geometry and positioned closer to the patient, enable superior spatial resolution while maintaining a compact and affordable system design. We simulate the performance of two flat-panel PET configurations: one with a fully populated 106 cm AFOV and another cost-efficient design featuring a reduced AFOV with axial gaps and vertical panel motion optimized for head and torso imaging.</p><p><strong>Methods: </strong>Both configurations consist of two monolithic LYSO-based flat panels placed 50 cm apart. The panels are 71 cm wide, with the Long Flat Panel (L-FP) design extending to a length of 106 cm while the Sparse Medium Flat Panel (SpM-FP) design measures 60 cm in length. Monte Carlo simulations evaluated the two designs using the NEMA protocol and additional tests for a more thorough assessment. Sensitivity, spatial resolution, axial noise variability, and image quality were analyzed, and an XCAT phantom at standard dose was used to demonstrate the achievable clinical image quality.</p><p><strong>Results: </strong>The SpM-FP showed 4-5 times lower sensitivity than the L-FP, requiring an acquisition time of 2-3 min to match the image quality achieved by the L-FP in 30 s. This finding is supported by the contrast-to-noise ratio of the image quality phantom and the standard deviation values obtained from the liver and lung regions of the XCAT phantom. Both configurations achieved uniform spatial resolution below 2 mm in the two directions parallel to the panels and an average of 3-3.5 mm in the direction towards the panels, with slight degradation observed away from the center of the AFOV. Additionally, the axial noise profile of the SpM-FP revealed minimal variability.</p><p><strong>Conclusions: </strong>The SpM-FP design shows potential as a cost-effective system, combining the benefits of extended AFOV, superior spatial resolution and high patient throughput.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"49"},"PeriodicalIF":3.0,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12106179/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144141811","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":"Shorter SPECT scans using self-supervised coordinate learning to synthesize skipped projection views.","authors":"Zongyu Li, Yixuan Jia, Xiaojian Xu, Jason Hu, Jeffrey A Fessler, Yuni K Dewaraja","doi":"10.1186/s40658-025-00762-3","DOIUrl":"10.1186/s40658-025-00762-3","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Purpose: &lt;/strong&gt;This study addresses the challenge of extended SPECT imaging duration under low-count conditions, as encountered in Lu-177 SPECT imaging, by developing a self-supervised learning approach to synthesize skipped SPECT projection views, thus shortening scan times in clinical settings.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;We developed SpeRF, a SPECT reconstruction pipeline that integrates synthesized and measured projections, using a self-supervised coordinate-based learning framework inspired by Neural Radiance Fields (NeRF). For each single scan, SpeRF independently trains a multi-layer perceptron (MLP) to estimate skipped SPECT projection views. SpeRF was tested with various down-sampling factors (DFs = 2, 4, 8) on both Lu-177 phantom SPECT/CT measurements and clinical SPECT/CT datasets, from 11 patients undergoing [177Lu]Lu-DOTATATE and 6 patients undergoing [177Lu]Lu-PSMA-617 radiopharmaceutical therapy. Performance was evaluated both in projection space and by comparing reconstructed images using (1) all measured views (\"Full\"), (2) down-sampled measured views only (\"Partial\"), and partially measured views combined with skipped views (3) generated by linear interpolation (\"LinInt\") and (4) synthesized by our method (\"SpeRF\").&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;SpeRF projections demonstrated lower Normalized Root Mean Squared Difference (NRMSD) compared to the measured projections, than LinInt projections. Across various DFs, the NRMSD for SpeRF projections averaged 7% vs. 10% in phantom studies, 18% vs. 26% in DOTATATE patient studies, and 20% vs. 21% in PSMA-617 patient studies, compared to LinInt projections. For SPECT reconstructions, DF = 4 is recommended as the best trade-off between acquisition time and image quality. At DF = 4, in terms of Contrast-to-Noise Ratio relative to Full, SpeRF outperformed LinInt and Partial: (1) DOTATATE: 88% vs. 69% vs. 69% for lesions and 88% vs. 73% vs. 67% for kidney, (2) PSMA-617: 78% vs. 71% vs. 69% for lesions and 78% vs. 57% vs. 67% for organs, including kidneys, lacrimal glands, parotid glands, and submandibular glands. SpeRF slightly underestimated count recovery relative to Full, compared to Partial but still outperformed LinInt: (1) DOTATATE: 98% vs. 100% vs. 88% for lesions and 98% vs. 100% vs. 94% for kidney, (2) PSMA-617: 98% vs. 101% vs. 94% for lesions and 96% vs. 101% vs. 78% for organs.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;The proposed method, SpeRF, shows potential for significant reduction in acquisition time (up to a factor of 4) while maintaining quantitative accuracy in clinical SPECT protocols by allowing for the collection of fewer projections. The self-supervised nature of SpeRF, with data processed independently on each patient's projection data, eliminates the need for extensive training datasets. The reduction in acquisition time is particularly relevant for imaging under low-count conditions and for protocols that require multiple-bed positions such as whole-bo","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"47"},"PeriodicalIF":3.0,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12092854/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144109948","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}