Physics in medicine and biology最新文献

{"title":"Corrigendum: Golden beam data for proton pencil-beam scanning (2012<i>Phys. Med. Biol.</i>57 1147).","authors":"Benjamin Clasie, Nicolas Depauw, Maurice Fransen, Carles Gomà, Hamid Reza Panahandeh, Joao Seco, Jacob B Flanz, Hanne M Kooy","doi":"10.1088/1361-6560/ae0409","DOIUrl":"10.1088/1361-6560/ae0409","url":null,"abstract":"","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145006457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A data-driven approach for spatial alignment of PET add-on detectors with sub-millimeter accuracy.","authors":"Yunlai Chen, Ling Cai, Sergey Komarov, Joseph A O'Sullivan, Yuan-Chuan Tai","doi":"10.1088/1361-6560/adf937","DOIUrl":"10.1088/1361-6560/adf937","url":null,"abstract":"<p><p><i>Objective.</i>The integration of high-resolution add-on detectors with clinical PET scanners has the potential to significantly enhance imaging resolution and sensitivity. Precise geometric alignment of these auxiliary detectors is critical to fully realize their benefits. The objective of this work is to develop a novel data-driven methodology for the precise geometric alignment of high-resolution auxiliary detectors with clinical PET scanners, relying solely on point source measurements.<i>Approach.</i>We modeled the add-on detector as a rigid body with six degrees of freedom (three translations, three rotations). The alignment process involved estimating the unknown pose of the add-on detector by minimizing angular deviations in the lines of response, assuming collinearity among the estimated point source position, the known scanner crystal, and the unknown add-on detector crystal involved in each coincidence event. To improve interaction localization within the crystals, an effective depth-of-interaction model was applied. The method was validated in two stages. First, Monte Carlo simulations enabled direct comparison between the predefined and estimated geometries. Six detector configurations were evaluated-two in their ideal poses and four with realistic positional perturbations-to test the method's robustness. Second, experimental studies on a clinical PET scanner used a point source placed at 54 locations that follow a structured grid alongside multiple line-source setups (both parallel and arbitrary orientations). Images were reconstructed using both the known native scanner geometry, serving as a reference, and the estimated geometry, allowing quantitative evaluation of alignment accuracy by measuring centroid deviations for point sources as well as centroid and angular deviations for line sources.<i>Main Results.</i>In simulation, the alignment error between true and estimated geometries was 0.23 ± 0.10 mm and 0.20 ± 0.07 mm for the two ideal configurations; across the four perturbed setups, mean deviations remained below 0.3 mm. In experimental validation, the centroids of all point sources in PET images reconstructed using coincidence events from the native scanner alone, between the add-on detectors alone, or between the native scanner and add-on detectors, exhibited deviations consistently below 0.5 mm across the field of view with the estimated system geometry. For line source data, the angular deviations were consistently less than 1 degree, and the centroid deviations remained below 1 mm across all slices.<i>Significance.</i>The results demonstrate sub-millimeter accuracy for geometric alignment of high-resolution auxiliary detectors with a clinical PET/CT scanner using our novel data-driven method. The accuracy and simplicity of this approach, combined with not relying on physical phantoms, hold significant promises for improving image quality and diagnostic accuracy of the PET systems with auxiliary devices.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144799933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretical optimal232Th target thicknesses for225Ac production at proton energies of 70-200 MeV.","authors":"Jaewoong Jang, Paul Schaffer, Valery Radchenko, Louis Moskven, Nobuyoshi Akimitsu, Youichiro Wada, Cornelia Hoehr","doi":"10.1088/1361-6560/adfcae","DOIUrl":"10.1088/1361-6560/adfcae","url":null,"abstract":"<p><p><i>Objective</i>. Conventional232Th target thicknesses used for225Ac production are substantially smaller than the proton ranges, underutilizing the225Ac production potential of proton beams. This study explores theoretical optimal thicknesses of232Th targets at widely used proton energies, 70-200 MeV.<i>Approach</i>. Yields of225Ac and impurity levels of227Ac were calculated for proton energies of 70-200 MeV and232Th target thicknesses of 0.05-24 mm using Monte Carlo simulations. Ranges of optimal target thicknesses were defined for each proton energy based on the relative rates of change (RROCs) of225Ac yields per target thickness of 0.25 mm and on energy-adjusted RROC thresholds. Expected225Ac yield gains from using the optimal thicknesses were also estimated.<i>Main results</i>. The ranges of theoretical optimal thicknesses for representative energies, 70, 100, 160, and 200 MeV, were found to be 2-2.25 mm, 4.5-6.25 mm, 7.75-14.5 mm, and 14.25-21.75 mm, respectively. All these thicknesses are markedly larger than those of the conventional thin targets used for medium- to large-scale225Ac production, 0.25 mm and 0.5 mm. By using these optimal target thicknesses,225Ac yields are expected to increase by factors of up to 8.8 at 70 MeV and 63.8 at 200 MeV. Actinium-227 impurity levels were unaffected by target thickness optimization at all proton energies.<i>Significance</i>. Optimizing232Th target thicknesses can provide proton accelerator facilities operating in the 70-200 MeV range with a straightforward means of increasing their225Ac production capacity. Optimal target thicknesses offer greater225Ac yield scalability at higher energies near 200 MeV, while enabling large-scale225Ac production at lower energies close to 70 MeV.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144874688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental assessment of novel PET detector components for online imaging of radioactive ion beams.","authors":"Giulio Lovatti, Munetaka Nitta, Francesco Evangelista, Daria Boscolo, Daria Kostyleva, Mohammad Javad Safari, Georgios Dedes, Chiara Gianoli, Beatrice Foglia, Marco Pinto, Han Gyu Kang, Sivaji Purushotaman, Emma Haettner, Christoph Schuy, Christian Graeff, Uli Weber, Christoph Scheidenberger, Peter G Thirolf, Taiga Yamaya, Marco Durante, Katia Parodi","doi":"10.1088/1361-6560/ae0674","DOIUrl":"https://doi.org/10.1088/1361-6560/ae0674","url":null,"abstract":"<p><strong>Objective: </strong>This work aims to evaluate the ability of novel detector components to measure with submillimeter resolution in beam positron emission tomography (PET) signals produced by¹⁰C and¹¹C radioactive ion beams stopped in PMMA targets and to validate a simulation toolkit for reproducing beam physics and PET detector responses within the framework of the BARB project.&#xD;&#xD;Approach: The PET system response was assessed by visualizing the radioactive distributions of the beams stopped in tissue surrogate phantoms, and the capacity of the simulation toolkit was evaluated by comparing the experimental results with simulations, both for the depth-dose distribution and PET imaging.&#xD;&#xD;Main results: The detector assembly accurately visualized the PET signal with submillimeter resolution, achieving the objective of measuring the difference in the positron range between¹⁰C and¹¹C.&#xD; The simulation toolkit effectively reproduced the beam characteristics and detector responses, showing a high degree of agreement between the simulated and experimental PET profiles under different beam delivery conditions.&#xD;&#xD;Significance: These findings demonstrate the precision and reliability of the novel in-beam PET detector technology and simulation toolkit for small animals, establishing a solid foundation for the second phase of the BARB project, which involves preclinical irradiation of living mice.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145055027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"GAN-based standardization of MR images: a promising approach for the development of multicentre radiomic models.","authors":"Stéphane Niyoteka, Rahimeh Rouhi, Pierre-Antoine Laurent, Samir Achkar, Alexandre Carré, Sébastien Diffetocq, Corinne Balleyguier, Cyrus Chargari, Eric Deutsch, Charlotte Robert","doi":"10.1088/1361-6560/adf2f4","DOIUrl":"10.1088/1361-6560/adf2f4","url":null,"abstract":"<p><p><i>Objective.</i>This study evaluated generative adversarial network (GAN)-based magnetic resonance imaging (MRI) standardization methods by comparing them with conventional preprocessing and<i>a posteriori</i>approaches from the literature in their ability to mitigate the influence of acquisition parameters on radiomic analyses.<i>Approach.</i>MR T2-weighted images (T2w) of 30 patients with locally advanced cervical cancer (LACC) were acquired prospectively (cohort 1). For each patient, three images were taken sequentially on the same scanner with different values of repetition time (TR) and voxel size (VS). A retrospective cohort of 160 LACC patients (cohort 2) was also collected, including 86 and 160 T2w MR images taken before radiation therapy and brachytherapy, respectively. A conditional GAN (cGAN) and a cycleGAN were trained on cohort 1 and cohort 2, respectively, to generate images robust to the impact of acquisition parameters. This generative network-based standardization approach was compared to histogram-matching standardization,<i>z</i>-score standardization, and the ComBat harmonization methods. In this aim, different image quality metrics were extracted from cohort 1 images and the impact of standardization methods was assessed using principal component analysis (PCA). Using intra-class correlation (ICC) and concordance correlation coefficient (CCC), robust features were characterized (CCC&ICC⩾0.75). Different classical ML models were finally trained to investigate the impact of these harmonization methods on stage classification and relapse prediction, respectively.<i>Main results.</i>PCA on quality metrics showed that the changes in TR and VS were mitigated the most with cGAN. Regarding TR/VS modulation, cGAN achieved the best results for the first- and second-order features, with 18/18 and 58/75 robust features, respectively. In both clinical tasks, ROC-AUC improved after standardization. For tumor stage classification, the application of a cycleGAN strategy significantly improved the performance of trained models compared to classification using raw images (ROC-AUC of0.68±0.16before standardization and0.88±0.09after standardization for the best ML model, i.e. logistic regression).<i>Significance.</i>GAN-based standardization in MRI could be an additional building block for robust radiomic signatures on a multicenter scale.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144691232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Iterative reconstruction with a rotating open-ring PET scanner for proton therapy range verification.","authors":"Keegan McNamara, Marina Béguin, Günther Dissertori, Judith Flock, Cristian Fuentes, Jan Hrbacek, Daniel Lempen, Antony J Lomax, Shubhangi Makkar, Christian Ritzer, Benno Rohrer, Carla Winterhalter","doi":"10.1088/1361-6560/adfe51","DOIUrl":"10.1088/1361-6560/adfe51","url":null,"abstract":"<p><p><i>Objective.</i>In-beam positron emission tomography (PET) is a leading contender for non-invasive monitoring of proton therapy. The design constraints for in-beam PET have led to the development of an open-ring scanner as part of the PETITION project, which provides the unique opportunity to image immediately following the delivery of each treatment field. This study introduces computational techniques for the reconstruction of data recorded between delivery of each treatment field by a clinically implementable rotating open-ring design. Our proposed design enables fully-3D imaging of activity induced during proton therapy for verification on a field-by-field basis.<i>Approach.</i>We introduce a modification of the maximum likelihood expectation maximisation (MLEM) algorithm which accounts for imaging a source consisting of multiple isotopes with a rotating open-ring PET system. Pre-calculated system matrices are used to perform timely reconstructions for inter-field and post irradiation imaging for verification. We show the capabilities of our system by simulating a Derenzo-like phantom, as well as the treatment of a superatentorial neoplasm with 3 fields. We also show a proof of principle experimental measurement of a single field delivered to a CIRS 731-HN phantom.<i>Main results.</i>We show an increase in image quality when compared to fixed position imaging with an open-ring scanner, making the rotating open-ring design comparable to a similar full-ring design. The normalised root mean square error (NRMSE) was a factor of 1.6-2.2 better in comparison to imaging in a fixed position with an open-ring scanner. The new MLEM implementation was capable of assigning range to within an average of 0.6 mm along the beam direction for all fields, allowing for range verification of multiple fields.<i>Significance.</i>We have introduced a novel MLEM algorithm for imaging with a rotating open-ring PET device, opening the way for a clinically feasible implementation of fully-3D PET imaging of all treatment fields for verification of proton therapy.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144965107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low frequency magnetic field induction factors for exposure assessment in the human hand.","authors":"Pia Schneeweiss, Rene Hirtl, Gernot Schmid","doi":"10.1088/1361-6560/ae0118","DOIUrl":"10.1088/1361-6560/ae0118","url":null,"abstract":"<p><p>According to European Union (EU) Directive 2013/35/EU, occupational low frequency magnetic field exposure of the hands is assessed by comparing the maximum magnetic induction with the corresponding action level for the limbs (AL_Limb). If AL_Limbis exceeded, it must be demonstrated that the exposure limit values (ELVs) defined by the 2 × 2 × 2 mm³averaged<i>in situ</i>electric field strength (<i>Ê_i,</i>_avg) are not exceeded. However, there is no solid scientific evidence for the currently used AL_Limb. Assuming that AL_Limbensures compliance with the ELV in all limb regions, including areas with larger cross-sections like the lap, questions arise about its conservatism for exposure assessment of localized hand exposure. Therefore, we derived reasonable worst-case induction factors (IFs) for the hand using systematic numerical computations on 16 different MRI-based high-resolution anatomical hand models. Two simplified hand models were also included for comparison. The simulations yielded a robust IF of 0.6 (V m^-1) T^-1Hz^-1for a hand size representing the 95th percentile of adult males. This corresponds to a 33% relaxation of the magnetic induction limit compared to the current AL_Limb, which may reduce unnecessary restrictions in many workplaces with localized hand exposure. However, these relaxed limits must not be applied to other limb regions without proper verification. Furthermore, the study shows that oversimplified hand models, as proposed in the European standard EN 62369-1:2009, tend to significantly underestimate exposure and should therefore no longer be used for dosimetric exposure assessment. Finally, the data obtained confirm that in the case of localized exposure of body parts, comparing the 99th percentile of<i>Ê_i,</i>_avginstead of the (reasonably evaluated) peak spatial<i>Ê_i,</i>_avgwith the ELV leads to a significant underestimation of exposure, because real 'hot spots' of<i>Ê_i,</i>_avgare excluded from the evaluation, although they should be taken into account to avoid localized effects on the nervous system.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144965125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 multiplexing circuit combined with ASIC readout for cost-effective brain PET imaging.","authors":"Fiammetta Pagano, Francis Loignon-Houle, David Sanchez, Julio Barberá, Jorge Alamo, Ezzat Elmoujarkach, Nicolas A Karakatsanis, Sadek A Nehmeh, Antonio J González Martínez","doi":"10.1088/1361-6560/ae05ad","DOIUrl":"https://doi.org/10.1088/1361-6560/ae05ad","url":null,"abstract":"<p><strong>Objective: </strong>A key challenge in PET systems is collecting large amount of data with the most accurate information-time, energy, and position-to produce high-resolution images while limiting the number of channels to reduce costs and improve data collection efficiency. The new Ultra-High-performance Brain (UHB) scanner under development aims to tackle this issue, using a semi-monolithic detector that combines pixelated arrays and monolithic designs, along with signal multiplexing techniques. &#xD;Approach. We assessed the time, energy, and positioning performance of the multiplexing circuit (summing signals along rows and columns) and compared it to the standard readout, both using TOFPET2 ASIC. &#xD;Main Results. While time resolution worsens by about 15%, energy and positioning resolution-more crucial in small diameter scanners-are unaffected by signal summation. Overall, a pair of detector modules (2 × 2 arrays each) features an energy resolution of 16.9 1.3% and 405 29 ps coincidence time resolution. Positioning accuracy-estimated using multilayer perceptron neural network-is 1.9 0.4 mm and 3.0 0.7 mm along the monolithic and depth-of-interaction direction, respectively. &#xD;Significance. This study demonstrates that this channel reduction readout effectively maintains high performance while allowing for reduced costs and enhanced scalability.&#xD.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145034103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dedicated prostate DOI-TOF-PET based on the ProVision detection concept.","authors":"Hong Phuc Vo, Themistoklis Williams, Katayoun Doroud, Crispin Williams, Magdalena Rafecas","doi":"10.1088/1361-6560/adfeb3","DOIUrl":"10.1088/1361-6560/adfeb3","url":null,"abstract":"<p><p><i>Objective.</i>The ProVision scanner is a dedicated prostate positron emission tomography (PET) system with limited angular coverage; it employs a new detector technology that provides high spatial resolution as well as information about depth-of-interaction (DOI) and time-of-flight (TOF). The goal of this work is to develop a flexible image reconstruction framework and study the image performance of the current ProVision scanner.<i>Approach.</i>Experimental datasets, including point-like sources, an image quality phantom, and a pelvic phantom, were acquired using the ProVision scanner to investigate the impact of oblique lines of response introduced via a multi-offset scanning protocol. This approach aims to mitigate data truncation artefacts and further characterise the current imaging performance of the system. For image reconstruction, we applied the list-mode Maximum Likelihood Expectation Maximisation algorithm incorporating TOF information. The system matrix and sensitivity models account for both detector attenuation and position uncertainty.<i>Main results.</i>The scanner provides good spatial resolution on the coronal plane; however, elongations caused by the limited angular coverage distort the reconstructed images. The availability of TOF and DOI information, as well as the addition of a multi-offset scanning protocol, could not fully compensate for these distortions.<i>Significance.</i>The ProVision scanner concept, with innovative detector technology, shows promising outcomes for fast and inexpensive PET without CT. Despite current limitations due to limited angular coverage, which leads to image distortions, ongoing advancements, such as improved timing resolution, regularisation techniques, and artificial intelligence, are expected to significantly reduce these artefacts and enhance image quality.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144965056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linear magnetic nanoparticle structures as key feature in magnetic particle imaging.","authors":"Max Schoenen, Lennart Göpfert, Benedict Bauer, Caroline Emonts, Thomas Gries, Eva M Buhl, Sven Schober, Thomas Schmitz-Rode, Ioana Slabu","doi":"10.1088/1361-6560/ae05e5","DOIUrl":"https://doi.org/10.1088/1361-6560/ae05e5","url":null,"abstract":"<p><strong>Objective: </strong>Magnetic particle imaging (MPI) opens huge possibilities in image-guided therapy. Its effectiveness is strongly influenced by the quality of the magnetic nanoparticles (MNP) used as tracers. Besides MNP optimization following different synthesis routes, MNP assembly into linear structures can significantly enhance their performance in MPI. The present study investigates the influence of linear MNP structures on MPI signal for different MNP types. With regard to theranostic applications the role of linear structures in hybrid stent imaging is explored.</p><p><strong>Approach: </strong>Three MNP types were used to create linear MNP structures. MNP respectively the MNP structures were immobilized in a hydrogel and positioned at various orientations relative to the coordinate system of the MPI. A multi-channel reconstruction approach was applied to assess the orientation-specific signal. The insights gained were used to reconstruct a fibre-based polymer stent with incorporated linear structures.</p><p><strong>Main results: </strong>Different linear structure orientations could be delineated and visualized in multi-colour images. Linear structures orientated parallel to the direction of a magnetic excitation field lead to the highest signal intensities and peak positions of MPI frequency spectra were located near multiples of the frequency of the excitation coil. Image reconstructions of the stent were very sensitive to the orientation of linear structures within the fibres.</p><p><strong>Significance: </strong>This study reveals that the assembly of MNP results in non-linear contributions to the MPI signal. Consequently, the MPI signal intensity is not as usual merely linearly correlated with MNP concentration increasing the complexity in image reconstruction. The findings demonstrate the necessity of accounting for MNP structure orientation in image reconstruction. They also reveal the high potential of MPI to detect different MNP types and structures. Linear structures cause either significant signal reduction or signal increase depending on the angular position of the linear structures relative to the direction of MPI magnetic fields.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145034116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}