EJNMMI Physics最新文献

{"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":"https://doi.org/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":"","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":"","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":"https://doi.org/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":"","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":"","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":"https://doi.org/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":"","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":"","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}

{"title":"Feasibility of simplified Patlak parametric imaging with scaled population-based input function on pancreatic cancer.","authors":"Zhixin Hao, Haiqiong Zhang, Yonghong Dang, Jiangdong Qiu, Mengshi Yan, Xinchun Yan, Zhenghai Huang, Chao Ren, Taiping Zhang, Wenming Wu, Li Huo","doi":"10.1186/s40658-025-00758-z","DOIUrl":"10.1186/s40658-025-00758-z","url":null,"abstract":"<p><strong>Background: </strong>This study evaluates the feasibility of using a simplified Patlak parametric imaging technique with a scaled population-based input function (sPBIF) in pancreatic cancer.</p><p><strong>Methods: </strong>Twenty-six patients underwent multi-bed, multi-pass [¹⁸F]FDG PET/CT scans, from which both dynamic and static PET images were reconstructed. Patlak parametric images were generated from the dynamic PET series using both the image-derived input function (IDIF) and the sPBIF. The consistency between IDIF and sPBIF was evaluated by comparing the area under the curve (AUC) and Patlak parameters derived from both input functions. The detectability of pancreatic lesions, assessed by tumor-to-background ratio (TBR) and contrast-to-noise ratio (CNR), was compared between SUV and Patlak parametric images. Additionally, the correlation between clinicopathological features and PET parameters, including SUV and Patlak values, was analyzed.</p><p><strong>Results: </strong>We found good agreement between the AUC for IDIF and sPBIF with correlation coefficients of 0.87 and 0.93 for the 0-30 min and 0-50 min intervals, respectively. The Patlak parameters from IDIF and sPBIF presented correlation coefficients higher than 0.94. The SUV and Patlak K_i exhibited correlation coefficients greater than 0.92 and 0.73 in malignant and benign pancreatic lesions, respectively. The SUV and Patlak V₀ correlated with correlation coefficients higher than 0.75 in benign lesions, but exhibited only a weak correlation in malignant lesions. The TBR of Patlak K_i was significantly higher in malignant lesions compared to SUV. However, the CNR of Patlak K_i was lower due to increased noise in the parametric images. Most clinicopathological features showed weak correlation with PET parameters, except for a marginal classification of lesion differentiation by the maximum K_i value.</p><p><strong>Conclusions: </strong>The sPBIF approach enables the acquisition of additional Patlak parametric images alongside static SUV imaging in pancreatic cancer patients. K_i parametric imaging provided higher contrast than static imaging for detecting pancreatic lesions.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"46"},"PeriodicalIF":3.0,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12092890/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144109935","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":"Optimized production of ⁸⁹Zr as a medical radioisotope on a variable energy cyclotron and external beam-line.","authors":"Diana Cocioabă, Simona Baruta, Liviu Crăciun, Radu Leonte, Andrei Necsoiu, Maria-Roxana Tudoroiu-Cornoiu, Alexandru Jipa, Dana Niculae","doi":"10.1186/s40658-025-00755-2","DOIUrl":"10.1186/s40658-025-00755-2","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Background: &lt;/strong&gt;Zirconium-89 (&lt;sup&gt;89&lt;/sup&gt;Zr) is a highly valued diagnostic radionuclide for positron emission tomography (PET) due to its long physical half-life of 78.4 h and decay characteristics, being preferred for the radiolabelling of nanoparticles and slow kinetics macromolecules, such as antibodies. &lt;sup&gt;89&lt;/sup&gt;Zr-based high-resolution PET images can be employed to scan tumours and localize the tracer on a longer timeframe, which allows for real-time therapy monitoring. The goal of this study was to maximize the &lt;sup&gt;89&lt;/sup&gt;Zr production yield by fine-tunning the irradiation parameters of a solid target, in two different experimental set-ups, using a variable energy 14-19 MeV TR-19 cyclotron. Monte Carlo programs simulated the irradiation geometry and estimated the activity and irradiation yields produced by the &lt;sup&gt;89&lt;/sup&gt;Y(p, n)&lt;sup&gt;89&lt;/sup&gt;Zr reaction, at the process optimal parameters. The resulted data were compared with the experimental data collected in our particular irradiation setups.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;&lt;sup&gt;89&lt;/sup&gt;Zr was obtained from &lt;sup&gt;nat&lt;/sup&gt;Y foil target using: (A) the solid target holder placed on the extraction port, and (B) the automated solid target irradiation station, installed on a sloped-down extension of the proton beamline. The two irradiation geometries are differentiated by the distances from the respective extraction ports, beam-geometry and shape, cooling capacity, and degrader's thickness. Based on the specific geometries, A and B, the Monte Carlo simulations output determined the optimal experimental irradiation parameters (extracted energy, degrader thickness, proton current intensity), as well as the target thickness. The 250 μm &lt;sup&gt;nat&lt;/sup&gt;Y foils were irradiated with 14 MeV protons and an integrated current of 32 µA·h, on the solid target configuration A, and with 15.2 MeV protons, 100 µA·h on the solid target configuration B. After the dissolution and purification of the targets, [&lt;sup&gt;89&lt;/sup&gt;Zr]Zr-oxalate solutions of 1.28 ± 0.18 GBq, and 2.95 ± 0.31 GBq respectively, were evaluated, to determine the radionuclidic purity and contaminant levels of &lt;sup&gt;89&lt;/sup&gt;Zr solutions across different incident proton beam energies. The pharmaceutical specifications require the solutions radionuclidic purity to be above 99.9% of the total radioactivity, as criteria of their suitability for use as radiopharmaceutical precursors for antibodies radiolabelling.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions: &lt;/strong&gt;Simulations were providing optimized input parameters to maximize the production yield of &lt;sup&gt;89&lt;/sup&gt;Zr and subsequently, to achieve the highest possible activity with no detriment to radionuclide purity, as per the [&lt;sup&gt;89&lt;/sup&gt;Zr]Zr-oxalate solution pharmaceutical specification. The parameters were then implemented in the experiments, and the production processes were tested on two particular irradiation configurations. The yields and activities produced through &lt;sup&gt;89&lt;/sup&gt;Y(p, ","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"45"},"PeriodicalIF":3.0,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12069782/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144062847","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":"Quantitative capabilities of commercial CZT SPECT-CT cameras with ^99mTc.","authors":"Alain Seret, Claire Bernard","doi":"10.1186/s40658-025-00754-3","DOIUrl":"https://doi.org/10.1186/s40658-025-00754-3","url":null,"abstract":"<p><strong>Background: </strong>This study aimed to analyse the quantitative capabilities of cadmium-zinc-telluride (CZT)-based SPECT-CT cameras using ^99mTc, comparable to the analysis performed a decade ago for the sodium iodide (NaI) SPECT-CT systems available on the market at that time. This survey assessed one dual-head (GE Discovery NM870 CZT) and two ring (GE Starguide, Spectrum Dynamics Veriton 200) CZT cameras, as well as a state-of-the-art NaI dual-head system (Siemens Intevo Bold) that served as reference. Attenuation and scatter correction accuracy was explored, contrast recovery for small cold and hot rods measured, as well as the quantification in a large uniform area using user-determined conversion factors. Tomography reconstruction was performed with the manufacturers' iterative algorithms that allowed for attenuation correction, scatter correction and resolution recovery.</p><p><strong>Results: </strong>Using the NEMA NU-2 1994 dedicated phantom, attenuation and scatter corrections seemed to perform very well. Equally, the contrast recovery of cold rods seemed to be superior for the CZT systems. However, the contrast recovery for the hot rods was inferior to the NaI camera, whereas it was comparable without the scatter correction. Finally, a quantification error of less than 5% was shown to be reachable when using adequate user-determined conversion factors. For the NaI camera, all results were similar to those of the past study.</p><p><strong>Conclusions: </strong>Without scatter correction, the CZT SPECT systems showed contrast performance similar to the NaI camera. With scatter correction, this held true for cold objects but the contrast of hot objects was not significantly improved or was degraded depending on the system considered and the object size. Quantification errors of less than 5% were achievable. It is hoped that on-going developments at both manufacturers will improve the scatter correction accuracy.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"44"},"PeriodicalIF":3.0,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12065687/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143989874","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":"Transfer learning‑based attenuation correction in ^99mTc-TRODAT-1 SPECT for Parkinson's disease using realistic simulation and clinical data.","authors":"Wenbo Huang, Han Jiang, Yu Du, Haiyan Wang, Hao Sun, Guang-Uei Hung, Greta S P Mok","doi":"10.1186/s40658-025-00756-1","DOIUrl":"https://doi.org/10.1186/s40658-025-00756-1","url":null,"abstract":"<p><strong>Purpose: </strong>Dopamine transporter (DAT) SPECT is an effective tool for early Parkinson's disease (PD) detection and heavily hampered by attenuation. Attenuation correction (AC) is the most important correction among other corrections. Transfer learning (TL) with fine-tuning (FT) a pre-trained model has shown potential in enhancing deep learning (DL)-based AC methods. In this study, we investigate leveraging realistic Monte Carlo (MC) simulation data to create a pre-trained model for TL-based AC (TLAC) to improve AC performance for DAT SPECT.</p><p><strong>Methods: </strong>A total number of 200 digital brain phantoms with realistic ^99mTc-TRODAT-1 distribution was used to generate realistic noisy SPECT projections using MC SIMIND program and an analytical projector. One hundred real clinical ^99mTc-TRODAT-1 brain SPECT data were also retrospectively analyzed. All projections were reconstructed with and without CT-based attenuation correction (CTAC/NAC). A 3D conditional generative adversarial network (cGAN) was pre-trained using 200 pairs of simulated NAC and CTAC SPECT data. Subsequently, 8, 24, and 80 pairs of clinical NAC and CTAC DAT SPECT data were employed to fine-tune the pre-trained U-Net generator of cGAN (TLAC-MC). Comparisons were made against without FT (DLAC-MC), training on purely limited clinical data (DLAC-CLI), clinical data with data augmentation (DLAC-AUG), mixed MC and clinical data (DLAC-MIX), TL using analytical simulation data (TLAC-ANA), and Chang's AC (ChangAC). All datasets used for DL-based methods were split to 7/8 for training and 1/8 for validation, and a 1-/2-/5-fold cross-validation were applied to test all 100 clinical datasets, depending on the numbers of clinical data used in the training model.</p><p><strong>Results: </strong>With 8 available clinical datasets, TLAC-MC achieved the best result in Normalized Mean Squared Error (NMSE) and Structural Similarity Index Measure (SSIM) (TLAC-MC; NMSE = 0.0143 ± 0.0082/SSIM = 0.9355 ± 0.0203), followed by DLAC-AUG, DLAC-MIX, TLAC-ANA, DLAC-CLI, DLAC-MC, ChangAC and NAC. Similar trends exist when increasing the number of clinical datasets. For TL-based AC methods, the fewer clinical datasets available for FT, the greater the improvement as compared to DLAC-CLI using the same number of clinical datasets for training. Joint histograms analysis and Bland-Altman plots of SBR results also demonstrate consistent findings.</p><p><strong>Conclusion: </strong>TLAC is feasible for DAT SPECT with a pre-trained model generated purely based on simulation data. TLAC-MC demonstrates superior performance over other DL-based AC methods, particularly when limited clinical datasets are available. The closer the pre-training data is to the target domain, the better the performance of the TLAC model.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"43"},"PeriodicalIF":3.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12055695/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143983981","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":"Auto-segmentation, radiomic reproducibility, and comparison of radiomics between manual and AI-derived segmentations for coronary arteries in cardiac [¹⁸F]NaF PET/CT images.","authors":"Suning Li, Jake Kendrick, Martin A Ebert, Ghulam Mubashar Hassan, Nathaniel Barry, Keaton Wright, Sing Ching Lee, Jamie W Bellinge, Carl Schultz","doi":"10.1186/s40658-025-00751-6","DOIUrl":"https://doi.org/10.1186/s40658-025-00751-6","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Background: &lt;/strong&gt;[&lt;sup&gt;18&lt;/sup&gt;F]NaF is a potential biomarker for assessing cardiac risk. Automated analysis of [&lt;sup&gt;18&lt;/sup&gt;F]NaF positron emission tomography (PET) images, specifically through quantitative image analysis (\"radiomics\"), can potentially enhance diagnostic accuracy and personalised patient management. However, it is essential to evaluate the reproducibility and reliability of radiomic features to ensure their clinical applicability. This study aimed to (i) develop and evaluate an automated model for coronary artery segmentation using [&lt;sup&gt;18&lt;/sup&gt;F]NaF PET and calcium scoring computed tomography (CSCT) images, (ii) assess inter- and intra-observer radiomic reproducibility from manual segmentations, and (iii) evaluate the radiomics reliability from AI-derived segmentations by comparison with manual segmentations.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;141 patients from the \"effects of Vitamin K and Colchicine on vascular calcification activity\" (VikCoVac, ACTRN12616000024448) trial were included. 113 were used to train an auto-segmentation model using nnUNet on [&lt;sup&gt;18&lt;/sup&gt;F]NaF PET and CSCT images. Reproducibility of inter- and intra-observer radiomics and reliability of radiomics from AI-derived segmentations was assessed using lower bound of intraclass correlation coefficient (ICC). The auto-segmentation model achieved an average Dice Similarity Coefficient of 0.61 ± 0.05, having no statistically significant difference compared to the intra-observer variability (p = 0.922). For the unfiltered images, 47(12.6%) CT and 25(7.5%) PET radiomics were inter-observer reproducible, while 133(35.8%) CT and 57(15.3%) PET radiomics were intra-observer reproducible. 7(9.7%) CT and 18(25.0%) PET first-order features, as well as 17(17.7%) CT GLCM features, were reproducible for both inter- and intra-observer analyses. 9.8% and 16.8% of radiomics from AI-derived segmentations showed excellent and good reliability. First-order features were most reliable (ICC &gt; 0.75; 78/144[54.2%]) and shape features least (2/112[1.8%]). CT features demonstrated greater reliability (147/428[34.3%]) than PET (81/428 [18.9%]). Features from the left anterior descending (76/214[35.5%]) and right coronary artery (75/214[35.0%]) were more reliability than the circumflex (49/214[22.9%]) and left main (28/214[13.1%]) arteries.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions: &lt;/strong&gt;An effective segmentation model for coronary arteries was developed and reproducible [&lt;sup&gt;18&lt;/sup&gt;F]NaF PET/CSCT radiomics were identified through inter- and intra-observer assessments, supporting their clinical applicability. The reliability of radiomics from AI-derived segmentations compared to manual segmentations was highlighted. The novelty of [&lt;sup&gt;18&lt;/sup&gt;F]NaF as a biomarker underscores its potential in providing unique insights into vascular calcification activity and cardiac risk assessment.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Clinical trial registration: &lt;/strong&gt;VIKCOVAC trial (\"effects of Vitamin K and Colc","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"42"},"PeriodicalIF":3.0,"publicationDate":"2025-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12034606/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143989871","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":"Do cell culturing influence the radiosensitizing effect of gold nanoparticles: a Monte Carlo study.","authors":"J Antunes, T Pinheiro, I Marques, S Pires, M Filomena Botelho, J M Sampaio, A Belchior","doi":"10.1186/s40658-025-00746-3","DOIUrl":"https://doi.org/10.1186/s40658-025-00746-3","url":null,"abstract":"<p><strong>Background: </strong>Cell culture can be categorized into two major types: adherent and suspension. Both are used in a range of diverse research applications, exhibiting Pros and Cons, depending on what is being studied. In the field of Internal Emitters (IE), different morphological features such as nuclei size, cytoplasm ratio, and shape could influence its non-uniformity deposition and thus impact on the biological outcome. In this work we tested the hypothesis that cellular morphology differences, offered by adherent and suspension cultures, influence the radiosensitizing effect of gold nanoparticles (AuNPs).</p><p><strong>Methods: </strong>Using two PC3 cellular models, taken using confocal microscopy, we conducted Monte Carlo simulations to investigate the effects of different irradiation conditions on cellular Survival Fractions (SF). Our simulations focused on cells exposed to two distinct irradiation sources: ⁶⁰Co and 14 MeV protons, along both the longer and shorter axes of the cells to assess directional influences on cell survival. Additionally, we compared the SF of cells adherent to the culture flask with those in suspension, reflecting different experimental and potentially clinical scenarios.</p><p><strong>Results: </strong>In the absence of AuNPs, neither cell type nor irradiation direction significantly affected SF for the radiation types tested. However, with AuNPs present, SF demonstrated a strong dependence on irradiation direction and cell morphology.</p><p><strong>Conclusions: </strong>Our results indicate that the direction of irradiation plays a crucial role in determining the effectiveness of AuNPs in reducing SF. Furthermore, the results suggest that using cells in suspension will reduce the dependence of cell survival on the beam direction during irradiation, regardless of the radiation quality used.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"41"},"PeriodicalIF":3.0,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12008099/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143958302","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}