EJNMMI Physics最新文献

{"title":"A novel method for harmonization of PET image spatial resolution without phantoms.","authors":"Felix Carbonell, Alex P Zijdenbos, Evan Hempel, Mihály Hajós, Barry J Bedell","doi":"10.1186/s40658-025-00740-9","DOIUrl":"10.1186/s40658-025-00740-9","url":null,"abstract":"<p><strong>Background: </strong>Estimation of the spatial resolution in real images is extremely important in several fields, including crystallography, optics, microscopy, and tomography. In human PET imaging, estimating spatial resolution typically involves the acquisition of images from a physical phantom, typically a Hoffman phantom, which poses a logistical burden, especially in large multi-center studies. Indeed, phantom images may not always be readily available, and this method requires constant monitoring of scanner updates or replacements, scanning protocol changes, and image reconstruction guidelines to establish a equivalence with scans acquired from human subjects.</p><p><strong>Methods: </strong>We propose a new computational approach that allows estimation of spatial resolution directly from human subject PET images. The proposed technique is based on the generalization of the logarithmic intensity plots in the 2D Fourier domain to the 3D case. The spatial resolution of the image is obtained through the estimated coefficients of a multiple linear regression problem having the logarithm of the squared norm of the Fourier transform as dependent variable and the squared 3D frequencies as multiple predictors.</p><p><strong>Results: </strong>The proposed approach was applied to a cohort of subjects consisting of [18F]florbetapir amyloid PET images and matching phantoms from a Phase II clinical trial, and a second cohort including β-amyloid, FDG, and tau PET images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study. The resulting in-plane and axial resolution estimators varied between 3.5 mm and 8.5 mm for both PET and matching phantom images. They also yielded less than one voxel size across-subjects variability in groups of images sharing the same PET scanner model and reconstruction parameters. For human PET images, we also proved that the spatial resolution estimators showed: (1) a very high reproducibility, as measured by intraclass correlation coefficients (ICC > 0.985), (2) a strong cross-tracer linear correlations, and (3) a high within-subject longitudinal consistency, as measured by the maximum difference value between pairs of visits from the same subject.</p><p><strong>Conclusions: </strong>Our novel approach does not only eliminate the need for surrogate phantom data, but also provides a general framework that can be applied to a wide range of tracers and other imaging modalities, such as SPECT.</p><p><strong>Clinical trial data: </strong>Cognito Therapeutics' OVERTURE clinical trial (NCT03556280, 2021-08-24), https://clinicaltrials.gov/study/NCT03556280 .</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"23"},"PeriodicalIF":3.0,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11906943/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143623994","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":"Machine-learning based quantification of lung shunt fraction from 99mTc-MAA SPECT/CT for selective internal radiation therapy of liver tumors using TriDFusion (3DF).","authors":"Daniel Lafontaine, Finn Augensen, Adam Kesner, Raoul Vincent, Assen Kirov, Simone Krebs, Heiko Schöder, John L Humm","doi":"10.1186/s40658-025-00732-9","DOIUrl":"10.1186/s40658-025-00732-9","url":null,"abstract":"<p><strong>Background: </strong>Prior to selective internal radiotherapy of liver tumors, a determination of the lung shunt fraction (LSF) is performed using 99mTc- macroaggregated albumin (99mTc-MAA) injected into the hepatic artery. Most commonly planar but sometimes SPECT/CT images are acquired upon which regions of interests are drawn manually to define the liver and the lung. The LSF is then calculated by taking the count ratios between these two organs. An accurate estimation of the LSF is necessary to avoid an excessive pulmonary irradiation dose.</p><p><strong>Methods: </strong>In this study, we propose a computational, semi-automatic approach for LSF calculation from SPECT/CT scans, based on machine learning 3D segmentation, implemented within TriDFusion (3DF). We retrospectively compared this approach with the LSF calculated using the standard planar approach on 150 patients. Using CT images (from the SPECT/CT) as a blueprint, the TotalSegmentor machine learning algorithm automatically computes masks for the liver and lungs. Then, the SPECT attenuation-corrected images are fused with the CT and, based on the CT segmentation mask, TriDFusion (3DF) generates volume-of- interest (VOI) regions on the SPECT images. The liver and lung VOIs are further augmented to compensate for breathing motion. Finally, the LSF is calculated using the number of counts in the respective VOIs. Measurements using an anthropomorphic 3D-printed phantom with variable 99mTc activity concentrations for the liver and lungs were performed to validate the accuracy of the algorithm.</p><p><strong>Results: </strong>On average, LSF determined from 2D planar images were between 21 and 70% higher than those determined from SPECT/CT data. Semi-automated determination of the LSF using TriDFusion (3DF) analysis of SPECT-CT acquisitions was within 4-12% of the phantom-determined ratio measurements (ground truth).</p><p><strong>Conclusions: </strong>The utilization of TriDFusion (3DF) AI 3D Lung Shunt is a precise method for quantifying lung shunt fraction (LSF) and is more accurate than planar 2D image-based estimates. By incorporating machine learning segmentation and compensating for breathing motion, the approach underscores the potential of artificial intelligence (AI)-driven techniques to revolutionize pulmonary imaging, providing clinicians with efficient and reliable tools for treatment planning and patient management.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"22"},"PeriodicalIF":3.0,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11893963/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143596592","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":"Automated segmentation of the sacro-iliac joints, posterior spinal joints and discovertebral units on low-dose computed tomography for Na[¹⁸F]F PET lesion detection in spondyloarthritis patients.","authors":"Wouter R P van der Heijden, Floris H P van Velden, Robert Hemke, Tom C Doorschodt, Ronald Boellaard, Conny J van der Laken, Gerben J C Zwezerijnen","doi":"10.1186/s40658-025-00734-7","DOIUrl":"10.1186/s40658-025-00734-7","url":null,"abstract":"<p><strong>Purpose: </strong>Spondyloarthritis (SpA) is a chronic inflammatory rheumatic disease which involves the axial skeleton. Quantitative sodium fluoride-18 (Na[¹⁸F]F) PET/CT is a new imaging approach promising for accurate diagnosis and treatment monitoring by assessment of molecular bone pathology in SpA. Detection of Na[¹⁸F]F PET positive lesions is time-consuming and subjective, and can be replaced by automatic methods. This study aims to develop and validate an algorithm for automated segmentation of the posterior spinal joints, sacro-iliac joints (SIJs) and discovertebral units (DVUs) on low-dose computed tomography (LDCT), and to employ these segmentations for threshold-based lesion detection.</p><p><strong>Methods: </strong>Two segmentation methods were developed using Na[¹⁸F]F PET/LDCT images from SpA patients. The first method employed morphological operations to delineate the joints and DVUs, while the second used a multi-atlas-based approach. The performance and reproducibility of these methods were assessed on ten manually segmented LDCTs using average Hausdorff distance (HD) and dice similarity coefficient (DSC) for DVUs and SIJs, and mean error distance for the posterior joints. Various quantitative PET metrics and background corrections were compared to determine optimal lesion detection performance relative to visual assessment.</p><p><strong>Results: </strong>The morphological method achieved significantly better DSC (0.82 (0.73-0.88) vs. 0.74 (0.68-0.79); p < 0.001) for all DVUs combined compared to the atlas-based method. The atlas-based method outperformed the morphological method for the posterior joints with a median error distance of 4.00 mm (4.00-5.66) vs. 5.66 mm (4.00-8.00) (p < 0.001). For lesion detection, the atlas-based segmentations were more successful than the morphological method, with the most accurate metric being the maximum standardized uptake value (SUVmax) of the lesional Na[¹⁸F]F uptake, corrected for the median SUV (SUVmedian) of the spine, with an area under the curve of 0.90.</p><p><strong>Conclusion: </strong>We present the first methods for detailed automatic segmentation of the posterior spinal joints, DVUs and SIJs on LDCT. The atlas-based method is the most appropriate, reaching high segmentation performance and lesion detection accuracy. More research on the PET-based lesion segmentation is required, to develop a pipeline for fully automated lesional Na[¹⁸F]F uptake quantification.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"20"},"PeriodicalIF":3.0,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11891110/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143585194","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":"Myocardial perfusion imaging SPECT left ventricle segmentation with graphs.","authors":"Ádám István Szűcs, Béla Kári, Oszkár Pártos","doi":"10.1186/s40658-025-00728-5","DOIUrl":"10.1186/s40658-025-00728-5","url":null,"abstract":"<p><strong>Purpose: </strong>Various specialized and general collimators are used for myocardial perfusion imaging (MPI) with single-photon emission computed tomography (SPECT) to assess different types of coronary artery disease (CAD). Alongside the wide variability in imaging characteristics, the apriori \"learnt\" information of left ventricular (LV) shape can affect the final diagnosis of the imaging protocol. This study evaluates the effect of prior information incorporation into the segmentation process, compared to deep learning (DL) approaches, as well as the differences of 4 collimation techniques on 5 different datasets.</p><p><strong>Methods: </strong>This study was implemented on 80 patients database. 40 patients were coming from mixed black-box collimators, 10 each, from multi-pinhole (MPH), low energy high resolution (LEHR), CardioC and CardioD collimators. The testing was evaluated on a new continuous graph-based approach, which automatically segments the left ventricular volume with prior information on the cardiac geometry. The technique is based on the continuous max-flow (CMF) min-cut algorithm, which performance was evaluated in precision, recall, IoU and Dice score metrics.</p><p><strong>Results: </strong>In the testing it was shown that, the developed method showed a good improvement over deep learning reaching higher scores in most of the evaluation metrics. Further investigating the different collimation techniques, the evaluation of receiver operating characterstic (ROC) curves showed different stabilities on the various collimators. Running Wilcoxon signed-rank test on the outlines of the LVs showed differentiability between the collimation procedures. To further investigate these phenomena the model parameters of the LVs were reconstructed and evaluated by the uniform manifold approximation and projection (UMAP) method, which further proved that collimators can be differentiated based on the projected LV shapes alone.</p><p><strong>Conclusions: </strong>The results show that prior information incorporation can enhance the performance of segmentation methods and collimation strategies have a high effect on the projected cardiac geometry.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"21"},"PeriodicalIF":3.0,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11893936/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143596596","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":"The first human study of add-on PET: A PET-integrated RF coil for 3 T MRI.","authors":"Miwako Takahashi, Fumihiko Nishikido, Go Akamatsu, Hideaki Tashima, Yuma Iwao, Mikio Suga, Taiga Yamaya","doi":"10.1186/s40658-025-00731-w","DOIUrl":"10.1186/s40658-025-00731-w","url":null,"abstract":"<p><strong>Background: </strong>Combined PET and MRI scanners allow for simultaneous image acquisition, simplifying the interpretation of both PET and MRI images. We prototyped an insert-type PET that can convert a standalone MRI to a PET-MRI system, named Add-on PET. In Add-on PET, we fully integrated the PET modules into a head radiofrequency (RF) coil so that PET detectors can be close to the brain and avoid placing the RF coil in the field of view of PET. This study aimed at confirming the feasibility of human brain simultaneous PET and MRI imaging using a prototype of add-on PET.</p><p><strong>Results: </strong>The PET images obtained with and without simultaneous MRI sequences were identical (Pearson's correlation coefficient, r = 0.953). Background noise was observed in the MRI images acquired during the PET scan; however, the noise decreased when the count rates of PET declined. The MRI obtained simultaneously was used for attenuation correction, providing well-correlated voxel values with those using the CT-based attenuation correction method (r = 0.989).</p><p><strong>Conclusions: </strong>The simultaneous PET and MRI images were performed without noticeable artifacts. There was no significant interference in PET images caused by the simultaneous MRI sequence; however, some background noise was observed in the MRI, likely due to the electric current from PET modules used for counting a clinically used radioactivity concentration.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"19"},"PeriodicalIF":3.0,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11885769/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143566298","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":"¹³N-NH₃ myocardial perfusion imaging with reduced scan duration: a feasibility study in the era of total-body PET/CT.","authors":"Xiaochun Zhang, Zeyin Xiang, Fanghu Wang, Xiaoqiang Pan, Qing Zhang, Peng Wang, Lei Jiang, Hui Yuan","doi":"10.1186/s40658-025-00729-4","DOIUrl":"10.1186/s40658-025-00729-4","url":null,"abstract":"<p><strong>Purpose: </strong>To explore the feasibility of reducing scan duration of ¹³N-NH₃ myocardial perfusion imaging (MPI) using a total-body PET/CT scanner.</p><p><strong>Methods: </strong>Forty-five patients with known or suspected coronary artery disease (CAD) performing rest ¹³N-NH₃ MPI with total-body PET/CT were retrospectively included. PET data were acquired in list mode for 10 min, and reconstructed into sequence images of different scan duration: 10-min, 7-min, 5-min, 3-min, and 2-min (G10 to G2). Subjective visual evaluation including overall impression, image noise and lesion visibility was evaluated using 5-point Likert scale. Quantitative parameters including perfusion defect extent (Extent), total perfusion defect (TPD), summed rest score (SRS), end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and myocardial blood flow (MBF) were analyzed. The full-time images (G10) were served as the reference.</p><p><strong>Results: </strong>There were no significant differences in subjective visual scores between G7-G5 and G10 groups (p > 0.05). A significant decrease in overall impression and image noise of G3-G2 was observed when compared to G10 (p < 0.05). However, no significant difference in lesion visibility was noted between G3 and G10 (p > 0.05). All G3 image quality was clinically acceptable (≥ 3 points). Except for EDV and ESV, other quantitative parameters showed no significant difference between G7-G3 and G10 (p > 0.05) and agreements were good (ICC = 0.974-0.998). For G2, only TPD exhibited no significant difference when compared to G10 (p > 0.05).</p><p><strong>Conclusion: </strong>Regarding imaging quality and parametric quantification accuracy of ¹³N-NH₃ MPI, a 3-min scan is clinically acceptable, while a 5-min scan is sufficiently reliable.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"18"},"PeriodicalIF":3.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11876496/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143540593","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":"openSSS: an open-source implementation of scatter estimation for 3D TOF-PET.","authors":"Rodrigo José Santo, André Salomon, Hugo W A M de Jong, Simon Stute, Thibaut Merlin, Casper Beijst","doi":"10.1186/s40658-025-00730-x","DOIUrl":"10.1186/s40658-025-00730-x","url":null,"abstract":"<p><strong>Background: </strong>Scatter correction is essential for quantitative and accurate time-of-flight (TOF) PET imaging. It is implemented by an accurate scatter estimation algorithm, to calculate the statistical distribution of scattered photons among the measured coincidences. However, to our knowledge, scatter estimation algorithms that account for TOF and that are compatible with custom geometries are not available in open-source reconstruction libraries, such as CASToR and STIR. To this end, we have developed an open-source implementation of the TOF-aware single-scatter-simulation (SSS) algorithm: openSSS.</p><p><strong>Results: </strong>openSSS is validated on NEMA phantoms and patient data, for three PET geometries, compared to Monte-Carlo simulations and two proprietary vendor-specific reconstruction platforms. The reconstructed images have similar contrast recovery and background variability, deviating by up to 3.7%-point on contrast recovery and 1.8 on background variability and looking visually similar.</p><p><strong>Conclusion: </strong>We have developed and validated an open-source scatter estimation library to complement reconstruction frameworks. By enabling vendor-independent clinical-grade reconstructions on custom scanner geometries, openSSS represents a crucial step in transparent research on quantitative PET and novel PET scanner designs.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"17"},"PeriodicalIF":3.0,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11868006/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143522916","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":"ASICs in PET: what we have and what we need.","authors":"Vanessa Nadig, Stefan Gundacker, Katrin Herweg, Stephan Naunheim, David Schug, Bjoern Weissler, Volkmar Schulz","doi":"10.1186/s40658-025-00717-8","DOIUrl":"10.1186/s40658-025-00717-8","url":null,"abstract":"<p><strong>Background: </strong>Designing positron emission tomography (PET) scanners involves several significant challenges. These include the precise measurement of the time of arrival of signals, accurate integration of the pulse shape, maintaining low power consumption, and supporting the readout of thousands of channels. To address these challenges, researchers and engineers frequently develop application-specific integrated circuits (ASICs), which are custom-designed readout electronics optimized for specific tasks. As a result, a wide range of ASIC solutions has emerged in PET applications. However, there is currently no comprehensive or standardized comparison of these ASIC designs across the field.</p><p><strong>Methods: </strong>In this paper, we evaluate the requirements posed to readout electronics in the field of PET, give an overview of the most important ASICs available for PET applications and discuss how to characterize their essential features and performance parameters. We thoroughly review the hardware characteristics of the different circuits, such as the number of readout channels provided, their power consumption, input and output design. Furthermore, we summarize their performance as characterized in literature.</p><p><strong>Results: </strong>While the ASICs described show common trends towards lower power consumption or a higher number of readout channels over the past two decades, their characteristics and also their performance assessment by the developers, producers and vendors differ in many aspects. To cope with the challenge of selecting a suitable ASIC for a given purpose and PET application from the varying information available, this article suggests a protocol to assess an ASIC's performance parameters and characteristics.</p><p><strong>Conclusion: </strong>ASICs developed for PET applications are versatile. With novel benchmarks set for the impact of scintillator and photosensor on the time-of-flight performance, the pressure on ASICs to deliver higher timing resolution and cope with an even higher data rate is enormous. Latest developments promise new circuits and improvements in time-of-flight performance. This article provides an overview on existing and emerging readout solutions in PET over the past 20 years, which is currently lacking in literature.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"16"},"PeriodicalIF":3.0,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11822191/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143406405","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":"A generative whole-brain segmentation model for positron emission tomography images.","authors":"Wenbo Li, Zhenxing Huang, Hongyan Tang, Yaping Wu, Yunlong Gao, Jing Qin, Jianmin Yuan, Yang Yang, Yan Zhang, Na Zhang, Hairong Zheng, Dong Liang, Meiyun Wang, Zhanli Hu","doi":"10.1186/s40658-025-00716-9","DOIUrl":"10.1186/s40658-025-00716-9","url":null,"abstract":"<p><strong>Purpose: </strong>Whole-brain segmentation via positron emission tomography (PET) imaging is crucial for advancing neuroscience research and clinical medicine, providing essential insights into biological metabolism and activity within different brain regions. However, the low resolution of PET images may have limited the segmentation accuracy of multiple brain structures. Therefore, we propose a generative multi-object segmentation model for brain PET images to achieve automatic and accurate segmentation.</p><p><strong>Methods: </strong>In this study, we propose a generative multi-object segmentation model for brain PET images with two learning protocols. First, we pretrained a latent mapping model to learn the mapping relationship between PET and MR images so that we could extract anatomical information of the brain. A 3D multi-object segmentation model was subsequently proposed to apply whole-brain segmentation to MR images generated from integrated latent mapping models. Moreover, a custom cross-attention module based on a cross-attention mechanism was constructed to effectively fuse the functional information and structural information. The proposed method was compared with various deep learning-based approaches in terms of the Dice similarity coefficient, Jaccard index, precision, and recall serving as evaluation metrics.</p><p><strong>Results: </strong>Experiments were conducted on real brain PET/MR images from 120 patients. Both visual and quantitative results indicate that our method outperforms the other comparison approaches, achieving 75.53% ± 4.26% Dice, 66.02% ± 4.55% Jaccard, 74.64% ± 4.15% recall and 81.40% ± 2.30% precision. Furthermore, the evaluation of the SUV distribution and correlation assessment in the regions of interest demonstrated consistency with the ground truth. Additionally, clinical tolerance rates, which are determined by the tumor background ratio, have confirmed the ability of the method to distinguish highly metabolic regions accurately from normal regions, reinforcing its clinical applicability.</p><p><strong>Conclusion: </strong>For automatic and accurate whole-brain segmentation, we propose a novel 3D generative multi-object segmentation model for brain PET images, which achieves superior model performance compared with other deep learning methods. In the future, we will apply our whole-brain segmentation method to clinical practice and extend it to other multimodal tasks.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"15"},"PeriodicalIF":3.0,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11805735/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143370526","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":"On the reduction of imaging time-points for dosimetry in radionuclide therapy.","authors":"Johan Gustafsson, Jan Taprogge","doi":"10.1186/s40658-025-00721-y","DOIUrl":"10.1186/s40658-025-00721-y","url":null,"abstract":"<p><strong>Background: </strong>The aim was to develop a theoretical framework for how errors in estimated activities propagate to a dispersion in time-integrated activity in radionuclide-therapy dosimetry and how this affects the comparison of radionuclide-therapy dosimetry schemes.</p><p><strong>Methods: </strong>Formulae for the variance of relative errors of estimated time-integrated activities and relative differences in time-integrated activities between measurement schemes when one or more time-points are removed were derived using the law of propagation of uncertainty for a population of time-activity-curve parameters. The formulae were derived under the assumptions of fixed coefficients of variation for estimated activities, and underlying mono-exponential curves. Analytical predictions were compared with results from numerical simulations and data for kidneys, liver, and spleen from a data-set of 18 patients treated with ¹⁷⁷Lu-DOTA-TATE.</p><p><strong>Results: </strong>The dispersion in time-integrated activity is minimized if the time-points used for curve fitting have a large dispersion and are centered over the mean of <math><mrow><mi>τ</mi> <mo>=</mo> <msubsup><mi>λ</mi> <mrow><mtext>eff</mtext></mrow> <mrow><mo>-</mo> <mn>1</mn></mrow> </msubsup> </mrow> </math> over the population, where <math><msub><mi>λ</mi> <mtext>eff</mtext></msub> </math> is the effective decay constant (i.e., the sum of the biological and physical decay constants). For large dispersions of decay constants in the population, the centering of time-points becomes gradually less important. The analytical expressions replicated the main trends from the numerical simulations. Furthermore, the analytical expressions predicted correctly the optimal reduced imaging schedule in 9 of 12 pairwise comparisons between schedules for patients.</p><p><strong>Conclusions: </strong>The dispersion of errors and deviations in estimated time-activity curves can be predicted using simple formulae. These formulae have the potential to be used for optimization of dosimetry measurement schemes for established and new radiopharmaceuticals as long as the mean and dispersion of biological half-lives are known in the patient population.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"14"},"PeriodicalIF":3.0,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11799503/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143255130","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}