EJNMMI Physics最新文献

{"title":"MSA-Net: a multi-scale and adversarial learning network for segmenting bone metastases in low-resolution SPECT imaging.","authors":"Yusheng Wu, Qiang Lin, Yang He, XianWu Zeng, Yongchun Cao, ZhengXing Man, Caihong Liu, Yusheng Hao, Zhengqi Cai, Jinshui Ji, Xiaodi Huang","doi":"10.1186/s40658-025-00785-w","DOIUrl":"10.1186/s40658-025-00785-w","url":null,"abstract":"<p><strong>Background: </strong>Single-photon emission computed tomography (SPECT) plays a crucial role in detecting bone metastases from lung cancer. However, its low spatial resolution and lesion similarity to benign structures present significant challenges for accurate segmentation, especially for lesions of varying sizes.</p><p><strong>Methods: </strong>We propose a deep learning-based segmentation framework that integrates conditional adversarial learning with a multi-scale feature extraction generator. The generator employs cascade dilated convolutions, multi-scale modules, and deep supervision, while the discriminator utilizes multi-scale L1 loss computed on image-mask pairs to guide segmentation learning.</p><p><strong>Results: </strong>The proposed model was evaluated on a dataset of 286 clinically annotated SPECT scintigrams. It achieved a Dice Similarity Coefficient (DSC) of 0.6671, precision of 0.7228, and recall of 0.6196 - outperforming both classical and recent adversarial segmentation models in multi-scale lesion detection, especially for small and clustered lesions.</p><p><strong>Conclusion: </strong>Our results demonstrate that the integration of multi-scale feature learning with adversarial supervision significantly improves the segmentation of bone metastasis in SPECT imaging. This approach shows potential for clinical decision support in the management of lung cancer.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"72"},"PeriodicalIF":3.2,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12290148/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144697909","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 in vivo small animal imaging using a clinical total-body PET/CT system.","authors":"Julia G Mannheim, Wenhong Lan, Maurizio Conti, Franziska Siedler, Marcel A Krueger, Kristina Herfert, Christian la Fougère, Fabian P Schmidt","doi":"10.1186/s40658-025-00782-z","DOIUrl":"10.1186/s40658-025-00782-z","url":null,"abstract":"<p><strong>Background: </strong>Clinical PET scanners have long been explored for preclinical imaging, but limited spatial resolution and sensitivity have restricted their use for preclinical studies. The recent availability of total-body (TB) PET/CT scanners with extended axial fields of view (FOVs) has largely overcome sensitivity limitations, enabling potential new opportunities for small-animal imaging. This study evaluated the feasibility and performance of the Biograph Vision Quadra TB-PET/CT for rodent imaging compared to the dedicated small-animal PET scanner Inveon DPET.</p><p><strong>Material and methods: </strong>Recovery coefficients (RC), image noise, and optimum image reconstruction parameters were assessed using the preclinical NEMA NU 4-2008 image quality phantom and a sub-cohort of three anesthetized mice as a proof-of-concept demonstrating the feasibility of the setup. In vivo quantification accuracy was evaluated by scanning nine frozen mice simultaneously in three different arrangements with the Quadra compared with individual scans at the Inveon. To ensure comparability, all mice were snap-frozen after 1 h uptake of [¹⁸F]FDG, scanned sequentially and individually at the Inveon (90 min p.i.), and subsequently scanned at the Quadra with decay-corrected acquisition times. SUV_mean and SUV_max values were determined for liver, muscle and brain regions on both systems. To evaluate potential position-dependent effects within the extended axial FOV, a single frozen mouse was scanned at multiple positions.</p><p><strong>Results: </strong>Phantom rods ≥ 2 mm could be resolved with the Quadra, showing a comparable RC for larger structures, e.g. for the 5 mm rod of 1.17 compared to 1.09 (Inveon) when using point-spread-function modeling, whilst having lower noise of 5.1%SD vs 9.0%SD. No substantial position-dependent effects were detected in the phantom or single-mouse scan across the axial FOV. SUV_mean values were consistent between both scanner across all investigated organs, with liver and muscle uptake remaining comparable for frame durations down to 5 s. SUV_max values exhibited greater variability, with significant differences observed in muscle and brain regions.</p><p><strong>Conclusion: </strong>Despite the lower spatial resolution of the clinical TB-PET/CT scanner (~ 3-4 mm) compared to the dedicated preclinical scanner (~ 1.5 mm), robust SUV_mean quantification was achievable. Together with successful in vivo imaging of anesthetized mice, these findings support the feasibility of using clinical TB-PET/CT for preclinical research, acknowledging spatial resolution as a limiting factor.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"71"},"PeriodicalIF":3.0,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12286903/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144689586","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":"Modeling of a population-based input function (PBIF) using the Feng model in dynamic ⁶⁸Ga-DOTATOC whole body PET/CT scans: feasibility of shortened imaging protocols on PET/CT Vision 600 system ^®.","authors":"Thomas Godefroy, Mathieu Pavoine, David Bourhis, Romain Le Pennec, Kevin Kerleguer, Romain Floch, Pierre-Yves Salaün, Nicolas Karakatsanis, Philippe Thuillier, Ronan Abgral","doi":"10.1186/s40658-025-00773-0","DOIUrl":"10.1186/s40658-025-00773-0","url":null,"abstract":"<p><strong>Background: </strong>This study focuses on modeling a population-based input function (PBIF) in dynamic ⁶⁸Ga-DOTATOC PET/CT exams, with the aim of developing clinically adoptable protocols. The PBIF is derived from an image-derived input function (IDIF), ensuring a non-invasive and standardized approach to tracer kinetic modeling.</p><p><strong>Methods: </strong>Patients with well-differentiated neuroendocrine tumors were included from the GAPETNET clinical trial (n = 37), divided into a PBIF modeling group (n = 20) and an independent validation group (n = 17). Dynamic whole-body (dWB) PET/CT imaging was performed using a Vision 600 PET/CT system. A population-based input function (PBIF) was modeled using the Feng approach and scaled to individual patient-specific IDIFs over two different time windows (sPBIF_3 - 7: 25-55 min, sPBIF_5 - 7: 40-55 min). The scaled PBIF was normalized to IDIF data from 6 to 55 min post-injection. A full individual patient-specific IDIF using data from 0 to 70 min post-injectionwas used as the reference for AUC and Ki comparisons. IDIFs and scaled PBIFs were compared by assessing the area under the curve (AUC) and radiotracer influx rate (Ki). Linear correlation and Bland-Altman analyses were conducted for AUC and Ki comparisons. Additionally, Mann-Whitney tests were performed to compare Ki values obtained with IDIF and sPBIF in both tumoral lesions and physiological organs.</p><p><strong>Results: </strong>The lowest mean relative AUC bias was observed with sPBIF_3 - 7, calculated to be 2.7 ± 7.9%, and was slightly higher with sPBIF_5 - 7 (7.35 ± 8.58%). The correlation coefficient (R²) with the sPBIFs was high, with a minimum of 0.95 for the sPBIF_5 - 7. When analyzing K_i metrics, biases tended to be lower with the 40-55 min time window (Mean ± SD bias = 1.61 ± 3.33 for K_{i max} and 1.64 ± 2.96 for K_{i mean}). No significant differences in K_i values was observed with the sPBIFs compared to the IDIF (p > 0.05), for either tumoral lesion or physiological organs.</p><p><strong>Conclusion: </strong>Our study has demonstrated the feasibility the PBIF approach to estimate tumor or physiological Ki values from a shortened dWB ⁶⁸Ga-DOTATOC PET acquisition, using the Feng model.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"70"},"PeriodicalIF":3.0,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12271040/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144648851","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":"Assessment and clinical relevance of pulmonary shunt on ¹⁶⁶Ho-Scout Imaging in hepatocellular carcinoma.","authors":"Evelyn Vranken, An De Crop, Victor Nuttens, Ruben Vandenbulcke, Tom Dewaele, Thomas Ryckaert, Jochen Decaestecker, Sofie De Meulder, Pieter De Bondt","doi":"10.1186/s40658-025-00783-y","DOIUrl":"10.1186/s40658-025-00783-y","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Aim: &lt;/strong&gt;Prediction of posttreatment lung mean dose (LMD) during liver radioembolization (RE) work-up is essential for risk evaluation of radiation pneumonitis, especially when treating large hepatocellular carcinoma (HCC) where the chance of arteriovenous shunting is not negligible. In case of holmium-166-([&lt;sup&gt;166&lt;/sup&gt;Ho])-RE, either [&lt;sup&gt;99m&lt;/sup&gt;Tc]TcMAA or &lt;sup&gt;166&lt;/sup&gt;Ho-microspheres can be used as scout tracers. Safety of use of &lt;sup&gt;166&lt;/sup&gt;Ho-scout has been demonstrated previously, but, to our notice, evaluation of lung radiation dose due to &lt;sup&gt;166&lt;/sup&gt;Ho-scout activity in case of significant lung shunting has not been described so far. Therefore, a retrospective study was conducted to evaluate the presence of pulmonary shunting in HCC patients influencing therapeutical approach and to assess lung &lt;sup&gt;166&lt;/sup&gt;Ho-scout dose in these patients.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Materials and methods: &lt;/strong&gt;Twenty-nine HCC patients referred for RE were retrospectively evaluated. All work-ups were performed with &lt;sup&gt;166&lt;/sup&gt;Ho-microspheres. Scout imaging consisted of a hybrid SPECT/CT acquisition covering the thoraco-abdominal region. As mentioned in the manufacturer's instruction for use of &lt;sup&gt;166&lt;/sup&gt;Ho-microspheres, the possibility of &gt; 30 Gy lung radiation exposure in a single treatment is withheld as contra-indication for RE. In patients with lung shunt resulting in predicted posttreatment LMD &gt; 30 Gy, lung &lt;sup&gt;166&lt;/sup&gt;Ho-scout dose due to patient-specific injected activity was calculated, alongside two hypothetical scenarios: lung &lt;sup&gt;166&lt;/sup&gt;Ho-scout dose related to patient's lung shunt fraction (LSF) assuming administration of leaflet prescribed maximum &lt;sup&gt;166&lt;/sup&gt;Ho-scout activity and in case of 100% LSF according to patient-specific injected scout activity. Afterwards, these patients were followed for 3 months or till death.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;In the 29 patients, average predicted posttreatment LMD was 10.0 Gy (range 0.1-138.9 Gy), four of them revealing predicted LMD &gt; 30 Gy. Based on patient-specific injected &lt;sup&gt;166&lt;/sup&gt;Ho-scout activity (range 100-200 MBq), average lung &lt;sup&gt;166&lt;/sup&gt;Ho-scout dose of 0.5 Gy (range 0.1-0.8 Gy) was calculated in these 4 patients. Assuming administration of leaflet prescribed maximum activity of 250 MBq, average lung &lt;sup&gt;166&lt;/sup&gt;Ho-scout dose would be 0.9 Gy (range 0.4-1.7 Gy). In case of a 100% LSF, average lung &lt;sup&gt;166&lt;/sup&gt;Ho-scout dose would be 2.2 Gy (range 1.5-2.7 Gy) due to patient-specific scout activity. In these 4 patients, RE was denied and alternative treatment was started. No pulmonary adverse events related to &lt;sup&gt;166&lt;/sup&gt;Ho-scout were recorded.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;This study supports previous reports that &lt;sup&gt;166&lt;/sup&gt;Ho-scout is a safe alternative to [&lt;sup&gt;99m&lt;/sup&gt;Tc]TcMAA -scout and underlines the importance of predicting posttreatment LMD when treating large HCC since 13.8% of our patient group presented arteriovenous shunt","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"69"},"PeriodicalIF":3.0,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12259507/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144625528","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":"Effect of data-driven motion correction for respiratory movement on lesion detectability in PET-CT: a phantom study.","authors":"Marloes A de Winter, Robin Gevers, Jules Lavalaye, Jan B A Habraken, Matteo Maspero","doi":"10.1186/s40658-025-00784-x","DOIUrl":"10.1186/s40658-025-00784-x","url":null,"abstract":"<p><strong>Purpose: </strong>While data-driven motion correction (DDMC) techniques have proven to enhance the visibility of lesions affected by motion, their impact on overall detectability remains unclear. This study investigates whether DDMC improves lesion detectability in PET-CT using FDG-18F.</p><p><strong>Method: </strong>A moving platform simulated respiratory motion in a NEMA-IEC body phantom with varying amplitudes (0, 7, 10, 20, 30 mm) and target-to-background ratios (2, 5, 10.5). Scans were reconstructed with and without DDMC, and the spherical targets' maximal and mean recovery coefficient (RC) and contrast-to-noise ratio (CNR) were measured.</p><p><strong>Results: </strong>DDMC results in higher RC values in the target spheres. CNR values increase for small, high-motion affected targets but decrease for larger spheres with smaller amplitudes. A sub-analysis shows that DDMC increases the contrast of the sphere along with a 36% increase in background noise.</p><p><strong>Conclusion: </strong>While DDMC significantly enhances contrast (RC), its impact on detectability (CNR) is less profound due to increased background noise. CNR improves for small targets with high motion amplitude, potentially enhancing the detectability of low-uptake lesions. Given that the increased background noise may reduce detectability for targets unaffected by motion, we suggest that DDMC reconstructions are used best in addition to non-DDMC reconstructions.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"68"},"PeriodicalIF":3.0,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12254103/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144607854","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":"S-values for bone marrow dosimetry in preclinical radiopharmaceutical studies with rodents.","authors":"Mohammed Obaid, Arman Rahmim, William P Segars, Julia Brosch-Lenz, Carlos Uribe","doi":"10.1186/s40658-025-00752-5","DOIUrl":"10.1186/s40658-025-00752-5","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Background: &lt;/strong&gt;Development of novel radiopharmaceuticals involves dosimetry calculations to validate safety and aid with selection of those that should be translated into the clinical environment. Dosimetry is critical for limiting radiation damage to organs at risk. The bone marrow is a limiting organ in radiopharmaceutical therapies (RPTs) for metastatic prostate cancer, for example, but there is room for improvement of bone marrow dosimetry in preclinical studies. Bone marrow S-values for Lutetium-177 (&lt;sup&gt;177&lt;/sup&gt;Lu) in rodents have been published but they have not included tumor xenografts inoculated in the shoulder, which is how radiopharmaceuticals are often tested. Here, we aim at performing Monte Carlo simulations on digital mice phantoms including tumor xenografts, and to determine new bone marrow S-values that can potentially improve our understanding of the effect of RPTs in blood cells.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;S-values for &lt;sup&gt;177&lt;/sup&gt;Lu were simulated in the 4D Mouse Whole Body (MOBY) phantom, a hybrid voxel-based mouse model, using GATE v9.3 MC toolkit. Two phantoms of different resolutions and equal mass were created. 3D dose distributions were simulated and the corresponding organ to organ S-values were calculated. The resulting S-values were validated against reference values from OLINDA v2.2.3. Later, tumours of varying sizes were placed in the left shoulder and tumour-to-organ S-values were calculated from MC simulations with a &lt;sup&gt;177&lt;/sup&gt;Lu source placed uniformly in these tumours.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;The phantoms simulated here differed from the OLINDA phantom in both organ mass and geometry for many tissues; S-value deviations from OLINDA were correlated with these differences, as reported in previous studies, and ranged from 2% for the kidney self-dose in the higher resolution (HR) phantom to 477% for S(skeleton←spleen) in the lower resolution (LR) phantom. S-values were simulated for the bone marrow in both phantoms; cross-dose values were greatest from the skeleton, brain, and lungs, while cross-doses from the simulated tumours were approximately constant at 3 × 10&lt;sup&gt;-15&lt;/sup&gt; Gy Bq&lt;sup&gt;-1&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt; across all tumour sizes. The components of the skeleton receiving the greatest tumour cross-doses from the tumours were the spine, skull and marrow. S-values targeting the bone marrow were compared to similar values from a previous study, whose phantom differed in tissue composition-discrepancies ranged from 6% for S(BM←kidneys) at LR to 87% for S(BM←BM) at HR. In general, relative uncertainty in dose and dose factor deposited from one tissue to another was inversely proportional to the corresponding S-value magnitude, and lower uncertainties were yielded from simulations in the LR, large-voxel phantom.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;Using the MOBY digital mouse phantom, we simulated bone marrow S-values for &lt;sup&gt;177&lt;/sup&gt;Lu. We hope these values help researchers pe","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"67"},"PeriodicalIF":3.0,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12238459/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144583385","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":"Evaluation of using small volume of interest regions for clinical kidney dosimetry in ¹⁷⁷Lu-DOTATATE treatments.","authors":"Jehangir Khan, Tobias Rydèn, Martijn Van Essen, Johanna Svensson, Peter Bernhardt","doi":"10.1186/s40658-025-00769-w","DOIUrl":"10.1186/s40658-025-00769-w","url":null,"abstract":"<p><p>Segmentation of the whole-kidney parenchyma (WKP) is considered the reference method for kidney dosimetry of radiopharmaceuticals, as it provides the average absorbed dose to the fully delineated WKP. However manual segmentation of the WKP is time consuming, and automated segmentation requires operator verification and potential manual adjustments to the VOI. The aim is to determine if a small volume of interest (SV) method can generate similar kidney absorbed doses as the WKP method.</p><p><strong>Methods: </strong>We obtained SPECT/CT of 18 patients at 24, 48, and 168 h after injection of [¹⁷⁷Lu]Lu-DOTATATE (7.3-7.8 GBq). The SPECTs were corrected for attenuation, scatter, and collimator detector response with Monte Carlo-based OSEM reconstruction (ASCC-SPECT) and post-filtered with a 0- to 12-mm Gaussian filter or were only attenuation corrected with a Hann post-filter (AC-SPECT). Kidney dosimetry based on the manually segmented WKP was used as reference method. Recovery coefficients (RCs) for each WKP were determined by Monte Carlo simulations, and normalisation factors, NFs, for SVs were determined relative to the WKP method. Kidney absorbed doses were estimated based on measured activity concentrations fitted using the mono-exponential function. The accuracy of the absorbed dose estimates for the SV methods, corrected with the NFs, were assessed using the standard deviation of the percentage difference in agreement with the reference method across all kidneys. Accuracy for kidney dosimetry using the SV method was calculated based on 1-5 VOIs with volumes of 4 mL (SV₄), 2 mL (SV₂), and 0.6 mL (SV_0.6).</p><p><strong>Results: </strong>The mean RCs of the WKP volumes (31-243 mL) in non-filtered ASCC-SPECT and AC-SPECT were 0.85 (0.73-0.90) and 0.62 (0.46-0.51), respectively. In non-filtered images, the absorbed dose was overestimated by a factor of 1.22. However, applying a Gaussian filter with a kernel size of approximately 5 mm yielded absorbed dose estimates comparable to the reference WKP method. The accuracy of kidney dosimetry calculation based on one SV₄ on each SPECT data-point was 12%. The accuracy improved as the number of VOIs increased from 1 to 5. With the SV₂ method, using a mean of 5 VOIs per kidney parenchyma, the accuracy was 8.3%.</p><p><strong>Conclusion: </strong>The small volume of interest (SV) method can provide absorbed dose estimates comparable to the whole-kidney parenchyma (WKP) method when optimized. Non-filtered images overestimated doses by 1.22, but applying a 5 mm Gaussian filter aligned SV results with the WKP method. Using multiple VOIs improved accuracy, with five 2 mL SVs achieving 8.3%. The SV method provides a less time-consuming alternative to WKP; however, its implementation is recommended to be validated and adjusted against a reference method.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"66"},"PeriodicalIF":3.0,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12234931/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144583384","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":"Evaluation of relative biological effectiveness of ²²⁵Ac and its decay daughters with Monte Carlo track structure simulations.","authors":"Ziyi Hu, Shuiyin Qu, Hongming Liu, Yunhao Zhang, Shuchang Yan, Ankang Hu, Rui Qiu, Zhen Wu, Hui Zhang, Junli Li","doi":"10.1186/s40658-025-00765-0","DOIUrl":"10.1186/s40658-025-00765-0","url":null,"abstract":"<p><strong>Background: </strong>²²⁵Ac is a radionuclide that can be utilized in targeted alpha therapy (TAT). To accurately assess the absorbed dose and radiation effects in TAT, it is necessary to calculate the relative biological effectiveness (RBE). This study aims to calculate the RBE of ²²⁵Ac and its decay daughters with a Monte Carlo method.</p><p><strong>Methods: </strong>This study employed the NASIC program to perform microdosimetric simulations of ¹⁷⁷Lu, ²²⁵Ac and its decay daughters in a cell population. Absorbed doses and lineal energy spectra in the cell nucleus were obtained for eight different radionuclides, three different cells, and six radionuclide spatial distribution. The RBE was then calculated using a modified stochastic microdosimetric kinetic model (mSMKM).</p><p><strong>Results: </strong>The results indicated that variations in radionuclide distribution had a greater impact on the absorbed dose in the cell nucleus. Taking ²²⁵Ac in V79 cells as an example, the maximum differences in RBE and absorbed dose due to different distributions were 10% and 80%, respectively. For V79 cells, with a uniform distribution of radionuclides within the cell, the RBE_M, i.e. RBE at zero dose, of ²²⁵Ac was 6.91 ± 0.04. In its decay chain, the RBE_M was 6.81 ± 0.04 for ²²¹Fr, 6.67 ± 0.02 for ²¹⁷At, 6.43 ± 0.05 for ²¹³Po, and 5.91 ± 0.09 for ²¹³Bi. The β-emitting radionuclides ²⁰⁹Tl and ²⁰⁹Pb had RBE close to 1.</p><p><strong>Conclusions: </strong>RBE of each radionuclide in ²²⁵Ac decay chain was evaluated separately with a Monte Carlo track structure code. The RBE of ²²⁵Ac and its decay daughters was found to be influenced by absorbed dose, radionuclide distribution, and cell type. The intracellular distribution of radionuclides had influence on the magnitude of RBE, but was less significant than its impact on the absorbed dose. Additionally, there were differences in the RBE of each radionuclide in the ²²⁵Ac decay chain that could not be neglected. These findings contribute to the calculation of RBE-weighted doses and the assessment of biological effects in ²²⁵Ac-based TAT.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"65"},"PeriodicalIF":3.0,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12234921/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144575076","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":"Dosimetric study on radioembolization with 166Ho poly L-lactic acid microspheres: dead time effects on prediction power.","authors":"Bartolomeo Cassano, Ludovica Miseo, Sara Ungania, Marco D'Andrea, Federica Murtas, Massimiliano Pacilio, Marta Bottero, Daria Maccora, Rosa Sciuto, Giulio Eugenio Vallati, Antonella Soriani, Giuseppe Iaccarino","doi":"10.1186/s40658-025-00779-8","DOIUrl":"10.1186/s40658-025-00779-8","url":null,"abstract":"<p><strong>Background: </strong>¹⁶⁶Ho-poly-L-lactic acid microspheres (¹⁶⁶Ho-PLLA) offer the advantage of using the same microspheres for both Scout and Therapeutic Administrations (SA and TA) in radioembolization compared to ⁹⁰Y. This study aimed to quantify and correct dead time (DT) effects in dose estimation and assess the predictive power of SA on TA.</p><p><strong>Methods: </strong>A 1.9 GBq ¹⁶⁶Ho-PLLA activity source was placed in a CIRS phantom and imaged over a week until activity reached 83 MBq, assessing DT effects. Fifteen patients with a single hepatic lesion underwent SA and TA two weeks apart with following SPECT/CT imaging. The mean absorbed dose (AD) and distribution were calculated using the Local Energy Deposition (LED) method for liver, healthy liver (HL) and tumor contours. Three methods were compared for TA AD estimation: no DT correction (M1), whole-image DT correction (M2), and DT correction only for tumor ROI counts (M3). Linear correlation and percentage differences (ΔD%) between SA and TA AD were analyzed. AD distributions in SA and TA were rigidly registered for gamma index analysis (Dose Difference of 10% and Distance to Agreement of 10 mm).</p><p><strong>Results: </strong>DT effects were significant for activity above 250 MBq (> 11.5%). Strong linear correlations between mean AD values in SA and TA were observed across methods. ΔD% between SA and TA for the liver contour was - 8.6% (M1), 21.5% (M2), and 8.2% (M3). For the HL contour, ΔD% was 8.1% (M1) and 39.0% (M2), while for the tumor contour, it was - 20.1% (M1) and 0.0% (M2). Gamma index pass rates for the liver contour were 76% (M1), 89% (M2), and 92% (M3); for the HL contour, 80% (M1) and 75% (M2); and for the tumor contour, 70% (M1) and 87% (M2).</p><p><strong>Conclusion: </strong>DT significantly affects TA dose estimation, particularly in tumors. Proper DT correction improves the accuracy of dosimetric evaluation of ¹⁶⁶Ho-PLLA for TA in liver and metastases, yielding dose values closer to those obtained in SA, despite the latter not being corrected for DT.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"64"},"PeriodicalIF":3.0,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12229299/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144552615","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 patient size on image quality of OSEM3D and BSREM reconstructions in [⁶⁸Ga]Ga-DOTA-TATE PET/MR.","authors":"Christina P W Cox, Tessa Brabander, Frederik A Verburg, Marcel Segbers","doi":"10.1186/s40658-025-00777-w","DOIUrl":"10.1186/s40658-025-00777-w","url":null,"abstract":"<p><strong>Background: </strong>Previous [⁶⁸Ga]Ga-DOTA-TATE PET/CT studies using ordered subset expectation maximization (OSEM3D) based reconstruction algorithms, demonstrated non-linear relations between body weight and image quality. Block Sequential Regularized Expectation Maximization (BSREM) algorithm reduces noise amplification during reconstruction. The impact of the reconstruction algorithm on the relation between image quality and patient size in [⁶⁸Ga]Ga-DOTA-TATE PET/MR may differ from PET/CT and OSEM3D. Therefore, the aim of this study is to investigate the relation between patient size and image quality in OSEM3D and BSREM [⁶⁸Ga]Ga-DOTA-TATE PET/MR reconstructions.</p><p><strong>Methods: </strong>[⁶⁸Ga]Ga-DOTA-TATE PET/MR images of 55 patients were included. Images were reconstructed using OSEM3D (VUE Point FX SharpIR, 4 iterations, 28 subsets and 7 mm Gaussian filter) and BSREM (Q.Clear, β = 300). Liver signal-to-noise ratio (SNRliver) normalized for injected activity and acquisition time (SNRliver,norm) was measured to perform curve fitting with patient-dependent parameters using fixed, linear and non-linear fit models, followed by Akaike's corrected information criterion (AICc) model selection.</p><p><strong>Results: </strong>BSREM mean SNRliver was significantly (p < 0.001) higher than OSEM3D mean SNRliver. Body mass, the best patient-dependent parameter for both algorithms, clarified 40% (linear model) and 53% (non-linear model) of the variability in SNRliver,norm for OSEM3D and 20% (linear model) and 21% (non-linear model) for BSREM. AICc preferred a non-linear model for OSEM3D and a linear model for BSREM.</p><p><strong>Conclusion: </strong>The image quality predictor body weight is a weaker predictor for BSREM than for OSEM3D image quality in [⁶⁸Ga]Ga-DOTA-TATE PET/MR. Therefore, a linear dosage regimen based on body weight is preferable for BSREM, whereas a quadratic dosage regimen based on body weight is optimal for OSEM3D.</p>","PeriodicalId":11559,"journal":{"name":"EJNMMI Physics","volume":"12 1","pages":"60"},"PeriodicalIF":3.0,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12214164/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144539584","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}