1. Magnetic resonance imaging using a straight wire magnetic field for spatial signal encoding : imaging verification with 2D experiments and 3D modelingKaja Tušar, Igor Serša, 2025, izvirni znanstveni članek Povzetek: Spatial encoding in MRI is usually performed using gradient coils that produce a linearly increasing magnetic field Bz in a desired spatial direction such that its gradient is constant. However, it has been shown that spatial encoding in MRI can also be performed with coils that produce nonlinear magnetic fields. In this study, the performance of different types of nonlinear encoding coils, which have a simple design based on the use of a straight wire segment as a building block and a source of a highly nonlinear magnetic field, was experimentally tested in 2D and by simulation in 3D on coils with a nonsymmetric and a symmetric arrangement of these wire segments. All images were reconstructed using our newly presented method, in which the signals are first transformed from the time- to the frequency-domain, yielding a distorted image (spectrum), which is then geometrically and intensity corrected. The quality of the reconstructed images was quantified by comparing them with corresponding reference images obtained with conventional gradient coils. The reconstruction method was accurate for all tested encoding coils and showed that the symmetric coil type produced results that required significantly less corrections compared to the nonsymmetric coil type. Quantitative image quality measurements showed that all encoding coils, despite large differences in the magnetic field of the encoding coils, produce images of similar quality. The results of the study may help advance the design of “gradient” coils towards freer geometries, higher magnetic field gradients or lower inductance and thus faster switching times.
Ključne besede: spatial signal encoding, gradient coils, k-space, nonlinear coils, image reconstruction
Objavljeno v DiRROS: 11.11.2025; Ogledov: 221; Prenosov: 92
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2. Observation of electroplating in a lithium-metal battery model using magnetic resonance microscopyRok Peklar, Urška Mikac, Igor Serša, 2025, izvirni znanstveni članek Povzetek: Accurate imaging methods are important for understanding electrodeposition phenomena in metal batteries. Among the suitable imaging methods for this task is magnetic resonance imaging (MRI), which is a very powerful radiological diagnostic method. In this study, MRmicroscopy was used to image electroplating in a lithium symmetric cell, which was used as a model for a lithium-metal battery. Lithium electrodeposition in this cell was studied by sequential 3D 1H MRI of 1 M LiPF6 in EC/DMC electrolyte under different charging conditions, which resulted in different dynamics of the amount of electroplated lithium and its structure. The acquired images depicted the electrolyte distribution, so that the images of deposited lithium that did not give a detectable signal corresponded to the negatives of these images. With this indirect MRI, phenomena such as the transition from a mossy to a dendritic structure at Sand’s time, the growth of whiskers, the growth of dendrites with arborescent structure, the formation of dead lithium, and the formation of gas due to electrolyte decomposition were observed. In addition, the effect of charge and discharge cycles on electrodeposition was also studied. It was found that it is difficult to correctly predict the occurrence of these phenomena based on charging conditions alone, as seemingly identical conditions resulted in different results.
Objavljeno v DiRROS: 27.06.2025; Ogledov: 420; Prenosov: 140
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3. Assessment of hyperbaric oxygenation treatment response in parotid glands by T2 mapping following radiotherapy for head and neck tumoursJernej Vidmar, Ksenija Cankar, Maja Grošelj, Žarko Finderle, Igor Serša, 2022, izvirni znanstveni članek Povzetek: Background: The study was designed to evaluate the influence of hyperbaric oxygenation therapy (HBOT) on the parotid gland in patients following radiotherapy for head and neck tumours. Patients and methods: HBOT response was monitored by 3T magnetic resonance imaging (MRI) using T 2 mapping and subsequent measurement of mean T 2 and T 2 variability as well as by salivary tests (salivary flow, buffer capacity, and pH). Eighteen patients previously treated with irradiation doses between 50 and 80 Gy as well as 18 healthy gender and age matched controls were enrolled. MRI was performed prior to HBOT (40.2 ± 20 months after radiotherapy) and after 20 daily HBOT at 2.5 ATA (absolute atmosphere). Each HBOT consisted of breathing 100% oxygen for 90 minutes. Results: Significant differences in mean T 2 prior to HBOT were observed between the ipsilateral irradiated (121 ± 20 ms), contralateral parotids (107 ± 21) and control group (96 ± 12 ms). A positive correlation in patients between T 2 variability and irradiation dose was detected in contralateral parotids before HBOT (R = 0.489, p = 0.0287). In addition, negative correlations were observed between mean T 2 in the ipsilateral as well as the contralateral gland and salivary flow before and after HBOT. Negative correlations between mean T 2, T 2 variability and pH of unstimulated saliva were also observed in the sides of parotid before and after HBOT. Conclusions: The study confirmed that T 2 mapping had a potential for monitoring the differences between irradiated and normal parotid glands. It could also be useful in the assessment of the glandular tissue response to HBOT.
Ključne besede: MRI, T2 mapping, hyperbaric oxygenation therapy, head and neck tumours
Objavljeno v DiRROS: 24.07.2024; Ogledov: 899; Prenosov: 503
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7. Human tooth pulp anatomy visualization by 3D magnetic resonance microscopyDušan Šušterčič, Igor Serša, 2012, izvirni znanstveni članek Povzetek: Background. Precise assessment of dental pulp anatomy is of an extreme importance for a successful endodontic treatment. As standard radiographs of teeth provide very limited information on dental pulp anatomy, more capable methods are highly appreciated. One of these is 3D magnetic resonance (MR) microscopy of which diagnostic capabilities in terms of a better dental pulp anatomy assessment were evaluated in the study. Materials and methods. Twenty extracted human teeth were scanned on a 2.35 T MRI system for MR microscopy using the 3D spin-echo method that enabled image acquisition with isotropic resolution of 100 m. The 3D images were then post processed by ImageJ program(NIH) to obtain advanced volume rendered views of dental pulps. Results. MR microscopy at 2.35 T provided accurate data on dental pulp anatomyin vitro. The data were presented as a sequence of thin 2D slices through the pulp in various orientations or as volume rendered 3D images reconstructed form arbitrary view-points. Sequential 2D images enabled only anapproximate assessment of the pulp, while volume rendered 3D images were more precise in visualization of pulp anatomy and clearly showed pulp diverticles, number of pulp canals and root canal anastomosis. Conclusions. This in vitro study demonstrated that MR microscopy could provide very accurate 3D visualization of dental pulp anatomy. A possible future application of the method in vivo may be of a great importance for the endodontic treatment.
Objavljeno v DiRROS: 21.03.2024; Ogledov: 1364; Prenosov: 296
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8. Study of radiation induced changes of phosphorus metabolism in mice by ▫$^{31}P$▫ NMR spectroscopyIgor Serša, Simona Kranjc Brezar, Gregor Serša, Alenka Nemec Svete, Bojan Ložar, Ana Sepe, Jernej Vidmar, Marjeta Šentjurc, 2010, izvirni znanstveni članek Objavljeno v DiRROS: 15.03.2024; Ogledov: 1120; Prenosov: 396
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