National Magnetic Resonance Research Center (UMRAM)

Permanent URI for this collection


Recent Submissions

Now showing 1 - 20 of 301
  • ItemOpen Access
    Haptic discrimination of different types of soft materials
    (Springer Science and Business Media Deutschland GmbH, 2022-05-20) Cavdan, Müge; Doerschner, Katja; Drewing, Knut; Doerschner, Katja
    We interact with different types of soft materials on a daily basis such as salt, hand cream, etc. Recently we have shown that soft materials can be described using four perceptual dimensions which are deformability, granularity, viscosity, and surface softness [1]. Here, we investigated whether humans can actually perceive systematic differences in materials that selectively vary along one of these four dimensions as well as how judgments on the different dimensions are correlated to softness judgments. We selected at least two material classes per dimension (e.g., hair gel and hand cream for viscosity) and varied the corresponding feature (e.g., the viscosity of hair gel). Participants ordered four to ten materials from each material class according to their corresponding main feature, and in addition, according to their softness. Rank orders of materials according to the main feature were consistent across participants and repetitions. Rank orders according to softness were correlated either positively or negatively with the judgments along the associated four perceptual dimensions. These findings support our notion of multiple softness dimensions and demonstrate that people can reliably discriminate materials which are artificially varied along each of these softness dimensions. © 2022, The Author(s).
  • ItemOpen Access
    An Exploratory Analysis of the Neural Correlates of Human-Robot Interactions With Functional Near Infrared Spectroscopy
    (Frontiers Media S.A., 2022-07-18) Yorgancigil, Emre; Yildirim, Funda; Ürgen, Burcu Ayşen; Ürgen, Burcu Ayşen
    Functional near infrared spectroscopy (fNIRS) has been gaining increasing interest as a practical mobile functional brain imaging technology for understanding the neural correlates of social cognition and emotional processing in the human prefrontal cortex (PFC). Considering the cognitive complexity of human-robot interactions, the aim of this study was to explore the neural correlates of emotional processing of congruent and incongruent pairs of human and robot audio-visual stimuli in the human PFC with fNIRS methodology. Hemodynamic responses from the PFC region of 29 subjects were recorded with fNIRS during an experimental paradigm which consisted of auditory and visual presentation of human and robot stimuli. Distinct neural responses to human and robot stimuli were detected at the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) regions. Presentation of robot voice elicited significantly less hemodynamic response than presentation of human voice in a left OFC channel. Meanwhile, processing of human faces elicited significantly higher hemodynamic activity when compared to processing of robot faces in two left DLPFC channels and a left OFC channel. Significant correlation between the hemodynamic and behavioral responses for the face-voice mismatch effect was found in the left OFC. Our results highlight the potential of fNIRS for unraveling the neural processing of human and robot audio-visual stimuli, which might enable optimization of social robot designs and contribute to elucidation of the neural processing of human and robot stimuli in the PFC in naturalistic conditions. Copyright © 2022 Yorgancigil, Yildirim, Urgen and Erdogan.
  • ItemOpen Access
    MNP characterization and signal prediction using a model-based dictionary
    (Infinite Science Publishing, 2022-03-21) Alpman, Asli; Utkur, Mustafa; Saritas, Emine Ulku; Alpman, Asli; Utkur, Mustafa; Saritas, Emine Ulku
    Magnetic Particle Imaging (MPI) utilizes the nonlinear magnetic response of magnetic nanoparticles (MNPs) for signal localization. Accurate modeling of the magnetization behavior of MNPs is crucial for understanding their MPI signal responses. In this work, we propose a model-based dictionary approach using a coupled Brown-Néel rotation model. With experimental results on a Magnetic Particle Spectrometer (MPS), we show that this approach can successfully characterize MNPs and predict their signal responses.
  • ItemOpen Access
    Hand explorations are determined by the characteristics of the perceptual space of real-world materials from silk to sand
    (Nature Research, 2022-08-30) Dövencioǧlu, Dicle N.; Üstün, F. Seyhun; Doerschner, Katja; Drewing, Knut; Doerschner, Katja
    Perceiving mechanical properties of objects, i.e., how they react to physical forces, is a crucial ability in many aspects of life, from choosing an avocado to picking your clothes. There is, a wide variety of materials that differ substantially in their mechanical properties. For example, both, silk and sand deform and change shape in response to exploration forces, but each does so in very different ways. Studies show that the haptic perceptual space has multiple dimensions corresponding to the physical properties of textures, however in these experiments the range of materials or exploratory movements were restricted. Here we investigate the perceptual dimensionality in a large set of real materials in a free haptic exploration task. Thirty-two participants actively explored deformable and non-deformable materials with their hands and rated them on several attributes. Using the semantic differential technique, video analysis and linear classification, we found four haptic dimensions, each associated with a distinct set of hand and finger movements during active exploration. Taken together our findings suggest that the physical, particularly the mechanical, properties of a material systematically affect how it is explored on a much more fine-grained level than originally thought. © 2022, The Author(s).
  • ItemOpen Access
    A z-gradient array coil with a dedicated active-shielded array coil for MRI
    (John Wiley and Sons Inc., 2022-08-02) Takrimi, Manouchehr; Atalar, Ergin; Takrimi, Manouchehr; Atalar, Ergin
    Purpose: An array-based z-gradient coil with a set of programmable power amplifiers can outperform a conventional z-gradient coil and make it highly customizable with a broader range of tunable features. Methods: A dynamically adjustable imaging volume can be achieved using a pair of independent arrays and a modified optimization procedure based on analytic equations. Two modes of operation are provided: (a) standard mode that resembles a conventional coil; (b) advanced mode, where all performance parameters can be adjusted employing a controllable feeding mechanism. Commercial software is used to demonstrate the validity and feasibility of the proposed coil. Results: Primary and shield array diameters are 24 and 30 cm, both of which comprise 12 bundles of 10 turns copper wires. Maximum feeding voltage/current is 250 V/100 A for all array elements. Four distinct magnetic profiles are provided: (a) conventional profile with 140 mm diameter spherical region of interest, 120 mT/m gradient, and up to 4500 T/m/s slew rate; (b) profile of 200 mT/m, 70 mm region of interest, and up to 6900 T/m/s slew rate; (c) 60 mm axially shifted 70 mm region of interest with 120 mT/m strength and 3600 T/m/s slew rate; and (d) profile of 370 mT/m, 120 mm region of interest, and 3700 T/m/s slew rate when the active shield is reverse fed. Conclusion: By using an active-shielded gradient array coil, the magnetic field profile of the imaging volume can be adjusted dynamically, and it can provide new features and a wide range of field profiles for diverse applications in MRI.
  • ItemOpen Access
    Nonlinear droop compensation for current waveforms in MRI gradient systems
    (John Wiley and Sons Inc, 2022-03-28) Babaloo, Reza; Atalar, Ergin; Babaloo, Reza; Atalar, Ergin
    Purpose: Providing accurate gradient currents is challenging due to the gradient chain nonlinearities, arising from gradient power amplifiers and power supply stages. This work introduces a new characterization approach that takes the amplifier and power supply into account, resulting in a nonlinear model that compensates for the current droop. Methods: The gradient power amplifier and power supply stage were characterized by a modified state-space averaging technique. The resulting nonlinear model was inverted and used in feedforward to control the gradient coil current. A custom-built two-channel z-gradient coil was driven by high-switching (1 MHz), low-cost amplifiers (<$200) using linear and nonlinear controllers. High-resolution (<80 ps) pulse-width-modulation signals were used to drive the amplifiers. MRI experiments were performed to validate the nonlinear controller's effectiveness. Results: The simulation results validated the functionality of the state-space averaging method in characterizing the gradient system. The performance of linear and nonlinear controllers in generating a trapezoidal current waveform was compared in simulations and experiments. The integral errors between the desired waveform and waveforms generated by linear and nonlinear controllers were 1.9% and 0.13%, respectively, confirming the capability of the nonlinear controller to compensate for the current droop. Phantom images validated the nonlinear controller's ability to correct droop-induced distortions. Conclusion: Benchtop measurements and MRI experiments demonstrated that the proposed nonlinear characterization and digitally implemented feedforward controller could drive gradient coils with droop-free current waveforms (without a feedback loop). In experiments, the nonlinear controller outperformed the linear controller by a 14-fold reduction in the integral error of a test waveform.
  • ItemOpen Access
    Automated parameter selection for accelerated mri reconstruction via low-rank modeling of local k-space neighborhoods
    (Elsevier GmbH, 2022-02-01) Ilıcak, Efe; Sarıtaş, Emine Ülkü; Çukur, Tolga; Ilıcak, Efe; Sarıtaş, Emine Ülkü; Çukur, Tolga
    Purpose: Image quality in accelerated MRI rests on careful selection of various reconstruction parameters. A common yet tedious and error-prone practice is to hand-tune each parameter to attain visually appealing reconstructions. Here, we propose a parameter tuning strategy to automate hybrid parallel imaging (PI) – compressed sensing (CS) reconstructions via low-rank modeling of local k-space neighborhoods (LORAKS) supplemented with sparsity regularization in wavelet and total variation (TV) domains. Methods: For low-rank regularization, we leverage a soft-thresholding operation based on singular values for matrix rank selection in LORAKS. For sparsity regularization, we employ Stein's unbiased risk estimate criterion to select the wavelet regularization parameter and local standard deviation of reconstructions to select the TV regularization parameter. Comprehensive demonstrations are presented on a numerical brain phantom and in vivo brain and knee acquisitions. Quantitative assessments are performed via PSNR, SSIM and NMSE metrics. Results: The proposed hybrid PI-CS method improves reconstruction quality compared to PI-only techniques, and it achieves on par image quality to reconstructions with brute-force optimization of reconstruction parameters. These results are prominent across several different datasets and the range of examined acceleration rates. Conclusion: A data-driven parameter tuning strategy to automate hybrid PI-CS reconstructions is presented. The proposed method achieves reliable reconstructions of accelerated multi-coil MRI datasets without the need for exhaustive hand-tuning of reconstruction parameters. © 2022
  • ItemOpen Access
    Suppression of aquaporin-4 by antisense oligonucleotides reduces brain edema in experimental traumatic brain injury
    (Turkish Neurosurgical Society, 2022-03-08) Hekimoğlu, Mehdi; Lule, Sevda; Özer, Hıdır; Çakır-Aktas, Canan; Mut, Melike; Karlı Oğuz, Hatice Kader
    AIM: To investigate the suppression of aquaporin-4 (AQP4) synthesis through intracerebroventricular (i.c.v.) injection of antisense oligonucleotide after focal cortical contusion injury in mice. MATERIAL and METHODS: This study used 12-week-old female Swiss albino mice (weight, 20–25 g) to create a focal cortical contusion model by the weight-drop method (35 g blunt weight, 70 cm height) onto the parietal cortex after craniectomy. The sham group underwent craniectomy without trauma. In the control group, weight was dropped onto the parietal cortex immediately after i.c.v. injection of Dulbecco’s Modified Eagle Medium after craniectomy. In addition, 1 nM of aquaporin-4 (AQP4) antisense oligonucleotide (ASO) was injected via the i.c.v. route immediately after trauma (0 hour) and 4 hours after trauma. All animals underwent magnetic resonance (MR) imaging and were sacrificed at 24 hours. The brain–water content was determined using the wet/dry weight method. RESULTS: In the sham group, the average percentage of the brain–water content was 77.75% compared with the control group with 79.87%, and the difference was significant (p=0.017). The average was 78.81% and significantly reduced in the therapy group compared with the control group (p=0.026) at 0 hour. In the 4-hour treatment group, the average of 79.11% was not significant (p=0.39). MR imaging findings also showed a substantial reduction in brain edema in the 0-h treatment group. However, the 4-h treatment results, when compared with the control trauma group, did not show a significant difference. CONCLUSION: This study demonstrated that AQP4-ASO therapy, when administered early after diffuse traumatic brain injury, leads to a significant reduction in brain edema. © 2022, The Korean Society of Clothing and Textiles. All rights reserved.
  • ItemOpen Access
    Attentional modulations of audiovisual interactions in apparent motion: Temporal ventriloquism effects on perceived visual speed
    (Springer New York LLC, 2022-08-22) Duyar, Aysun; Pavan, Andrea; Duyar, Aysun
    The timing of brief stationary sounds has been shown to alter different aspects of visual motion, such as speed estimation. These effects of auditory timing have been explained by temporal ventriloquism and auditory dominance over visual information in the temporal domain. Although previous studies provide unprecedented evidence for the multisensory nature of speed estimation, how attention is involved in these audiovisual interactions remains unclear. Here, we aimed to understand the effects of spatial attention on these audiovisual interactions in time. We utilized a set of audiovisual stimuli that elicit temporal ventriloquism in visual apparent motion and asked participants to perform a speed comparison task. We manipulated attention either in the visual or auditory domain and systematically changed the number of moving objects in the visual field. When attention was diverted to a stationary object in the visual field via a secondary task, the temporal ventriloquism effects on perceived speed decreased. On the other hand, focusing attention on the auditory stimuli facilitated these effects consistently across different difficulty levels of secondary auditory task. Moreover, the effects of auditory timing on perceived speed did not change with the number of moving objects and existed in all the experimental conditions. Taken together, our findings revealed differential effects of allocating attentional resources in the visual and auditory domains. These behavioral results also demonstrate that reliable temporal ventriloquism effects on visual motion can be induced even in the presence of multiple moving objects in the visual field and under different perceptual load conditions.
  • ItemOpen Access
    Design of a web laboratory interface for ECG signal analysis using MATLAB builder NE
    (Walter de Gruyter GmbH, 2022-01-01) Jaber, Hussain A.; Aljobouri, Hadeel K.; Çankaya, Ilyas; Jaber, Hussain A.
    An electrocardiogram (ECG) is a noninvasive test, determining any defect in the heart rate or rhythm or changes in the shape of the QRS complex is very significant to detect cardiac arrhythmia. In this study, novel web-ECG simulation tools were proposed using MATLAB Builder NE with WebFigure and ASP.NET platform. The proposed web-ECG simulation tools consisted of two components. First, involved the analyses of normal real ECG signals by calculating the P, Q, R, S, and T values and detecting heart rate, while the second part related to extracting the futures of several types of abnormality real ECG. For calculating the PQRST values, simple and new mathematical equations are proposed in the current study using MATLAB. The Web ECG is capable to plot normal ECG signals and five arrhythmia cases, so the users are able to calculate PQRST easily using the proposed simple method. ECG simulation tools have been tested for validity and educational contributions with 62 undergraduate and graduate students at the Al-Nahrain University-Biomedical Engineering Department, Iraq. The proposed ECG simulation tools have been designed for academic learning to be run easily by a student using only any web browsers without the need for installing MATLAB or any extra programs. The proposed tools could provide a laboratory course for ECG signal analysis using a few buttons, as well as increase and develop the educational skills of students and researchers. © 2022 Hussain A. Jaber et al., published by De Gruyter.
  • ItemOpen Access
    edaGAN: Encoder-Decoder Attention Generative Adversarial Networks for multi-contrast MR image synthesis
    (Institute of Electrical and Electronics Engineers, 2022-05-16) Dalmaz, Onat; Sağlam, Baturay; Gönç, Kaan; Çukur, Tolga; Dalmaz, Onat; Sağlam, Baturay; Gönç, Kaan; Çukur, Tolga
    Magnetic resonance imaging (MRI) is the preferred modality among radiologists in the clinic due to its superior depiction of tissue contrast. Its ability to capture different contrasts within an exam session allows it to collect additional diagnostic information. However, such multi-contrast MRI exams take a long time to scan, resulting in acquiring just a portion of the required contrasts. Consequently, synthetic multi-contrast MRI can improve subsequent radiological observations and image analysis tasks like segmentation and detection. Because of this significant potential, multi-contrast MRI synthesis approaches are gaining popularity. Recently, generative adversarial networks (GAN) have become the de facto choice for synthesis tasks in medical imaging due to their sensitivity to realism and high-frequency structures. In this study, we present a novel generative adversarial approach for multi-contrast MRI synthesis that combines the learning of deep residual convolutional networks and spatial modulation introduced by an attention gating mechanism to synthesize high-quality MR images. We show the superiority of the proposed approach against various synthesis models on multi-contrast MRI datasets.
  • ItemOpen Access
    Language and communication features of childhood-onset schizophrenia and autism spectrum disorders: a literature review
    (Ankara Universitesi * Egitim Bilimleri Fakultesi,Ankara University * Faculty of Educational Sciences, 2022-09-01) Çabuk, Tuğçe; Özdemir, Şevket; Töret, Gökhan; Çabuk, Tuğçe
    Schizophrenia (SZ) and Autism Spectrum Disorders (ASD) both have life-long and negative impacts on the individuals. In contrast to ASD, SZ occurs “rarely” in childhood (before the age of 13) which is called Childhood-Onset Schizophrenia (COS). Although COS and ASD have distinct pathologies, they exhibit common characteristics since they were described first. One of the most important commonalities is overlapping language and communication features. Till now, it is known that there is no integrative model related to the mutual language characteristics and underlying neurogenetic factors covering both of these disorders. Therefore, this literature review aimed to reveal previous research reporting both diverging and converging language issues with regards to these populations. The information presented in this review also aimed to help special education professionals about noticing the children who might present the features of COS. For this aim, firstly, the historical backgrounds of the disorders were given. Later, the language and communication features of COS and ASD including the overlapping characteristics were presented in light of previous research. Discussion: Studies showed that pragmatic limitations could be observed within both populations. Atypical language characteristics such as echolalia and self-talk could also be mutually observed. A need for future studies exploring the morphological and semantic levels of COS and ASD was emphasized. Furthermore, it was proposed that retrospective and prospective studies could be designed with a large sample. The connection between language and pretend play or executive functions could be examined.
  • ItemOpen Access
    Predicting personality traits with semantic structures and LSTM-based neural networks
    (Elsevier, 2022-10) Kosan, Muhammed Ali; Karacan, Hacer; Ürgen, Burcu Ayşen; Ürgen, Burcu Ayşen
    There is a need to obtain more information about target audiences in many areas such as law enforcement agencies, institutions, human resources, and advertising agencies. In this context, in addition to the information provided by individuals, their personal characteristics are also important. In particular, the predictability of personality traits of individuals is seen as a major parameter in making decisions about individuals. Textual and media data in social media, where people produce the most data, can provide clues about people's personal lives, characteristics, and personalities. Each social media environment may contain different assets and structures. Therefore, it is important to make a structural analysis according to the social media platform. There is also a need for a labelled dataset to develop a model that can predict personality traits from social media data. In this study, first, a personality dataset was created which was retrieved from Twitter and labelled with IBM Personality Insight. Then the unstructured data were transformed into meaningful and processable data, LSTM-based prediction models were created with the structural analysis, and evaluations were made on both our dataset and PAN-2015-EN. © 2022 THE AUTHORS
  • ItemOpen Access
    Effects of psychosis-associated genetic markers on brain volumetry: A systematic review of replicated findings and an independent validation
    (Cambridge University Press, 2022-09-28) Ribeiro, Nuno Vouga; Tavares, Vânia; Bramon, Elvira; Toulopoulou, Timothea; Valli, Isabel; Shergill, Sukhi; Murray, Robin; Prata, Diana; Toulopoulou, Timothea
    Background. Given psychotic illnesses’ high heritability and associations with brain structure, numerous neuroimaging-genetics findings have been reported in the last two decades. However, few findings have been replicated. In the present independent sample we aimed to replicate any psychosis-implicated SNPs (single nucleotide polymorphisms), which had previously shown at least two main effects on brain volume. Methods. A systematic review for SNPs showing a replicated effect on brain volume yielded 25 studies implicating seven SNPs in five genes. Their effect was then tested in 113 subjects with either schizophrenia, bipolar disorder, ‘at risk mental state’ or healthy state, for whole-brain and region-of-interest (ROI) associations with grey and white matter volume changes, using voxel-based morphometry. Results. We found FWER-corrected (Family-wise error rate) (i.e. statistically significant) associations of: (1) CACNA1C-rs769087-A with larger bilateral hippocampus and thalamus white matter, across the whole brain; and (2) CACNA1C-rs769087-A with larger superior frontal gyrus, as ROI. Higher replication concordance with existing literature was found, in decreasing order, for: (1) CACNA1C-rs769087-A, with larger dorsolateral-prefrontal/superior frontal gyrus and hippocampi (both with anatomical and directional concordance); (2) ZNF804Ars11681373-A, with smaller angular gyrus grey matter and rectus gyri white matter (both with anatomical and directional concordance); and (3) BDNF-rs6265-T with superior frontal and middle cingulate gyri volume change (with anatomical and allelic concordance). Conclusions. Most literature findings were not herein replicated. Nevertheless, high degree/ likelihood of replication was found for two genome-wide association studies- and one candidate-implicated SNPs, supporting their involvement in psychosis and brain structure. © The Author(s), 2022. Published by Cambridge University Press.
  • ItemOpen Access
    Connections of the dentate nucleus with the amygdala: Experimental rat and human 3-tesla tractography study
    (Mary Ann Liebert, Inc. Publishers, 2022-12-13) Çavdar, S.; Güneş, Y. C.; Algın, Oktay; Algın, Oktay
    Background: The role of the cerebellum in motor function is well recognized. However, its role in higher nervous system activities such as cognition, emotion, endocrine, and autonomic activities is less known. The present study aims to show direct dento-amygdala projections using a biotinylated dextran amine (BDA) tracer in rats and 3-tesla (T) high-resolution diffusion tensor imaging (DTI)-based tractography in humans. Materials and Methods: The BDA tracer was pressure injected into the dentate nucleus of the cerebellum of Wistar albino rats. Labeled cells and axons were documented. High-resolution 3-T tractography data were obtained from the Human Connectome Project database. Dento-amygdala tracts were analyzed using diffusion spectrum imaging (DSI) Studio software. Results: The experimental study showed bilateral projections between the dentate nucleus and the central and basal nuclei and ipsilateral projections between lateral nuclei of the amygdala. The fibers from the dentate nucleus reached the amygdala through the superior cerebellar peduncle (SCP), and the contralateral fibers crossed in the decussation of SCP at the midbrain. The dento-amygdala results of the experimental study corresponded with the 3-T tractography findings on humans. Additionally, DTI findings showed that most of the dentate fibers passed through the hypothalamus before reaching the amygdala, and the amygdalae of the two sides are connected through the anterior commissure. Discussion: The 3-T DTI data of adult humans showed both direct dento-amygdala and indirect dento-hypothalamo-amygdala projections. Thus, this may indicate cerebellar contribution in modulation of emotional and autonomic functions. Furthermore, this can explain the emotional and cognitive deficits that occur in patients with cerebellar or SCP damage.
  • ItemOpen Access
    Task-dependent warping of semantic representations during search for visual action categories
    (The Journal of Neuroscience, 2022-08-31) Shahdloo, Mo; Çelik, Emin; Urgen, Burcu A.; Gallant, J.L.; Çukur, Tolga; Shahdloo, Mo; Çelik, Emin; Burcu A., Urgen; Çukur, Tolga
    Object and action perception in cluttered dynamic natural scenes relies on efficient allocation of limited brain resources to prioritize the attended targets over distractors. It has been suggested that during visual search for objects, distributed semantic representation of hundreds of object categories is warped to expand the representation of targets. Yet, little is known about whether and where in the brain visual search for action categories modulates semantic representations. To address this fundamental question, we studied brain activity recorded from five subjects (one female) via functional magnetic resonance imaging while they viewed natural movies and searched for either communication or locomotion actions. We find that attention directed to action categories elicits tuning shifts that warp semantic representations broadly across neocortex and that these shifts interact with intrinsic selectivity of cortical voxels for target actions. These results suggest that attention serves to facilitate task performance during social interactions by dynamically shifting semantic selectivity toward target actions and that tuning shifts are a general feature of conceptual representations in the brain.
  • ItemOpen Access
    A comparison of equivalent noise methods in investigating local and global form and motion integration
    (Springer New York LLC, 2022-11-15) Pavan, A.; Contillo, A.; Koç, Şeyma; Kafalıgönül, Hulusi; Donato, R.; O’Hare, L.; Koç, Şeyma; Kafalıgönül, Hulusi
    Static and dynamic cues within certain spatiotemporal proximity are used to evoke respective global percepts of form and motion. The limiting factors in this process are, first, internal noise, which indexes local orientation/direction detection, and, second, sampling efficiency, which relates to the processing and the representation of global orientation/direction. These parameters are quantified using the equivalent noise (EN) paradigm. EN has been implemented with just two levels: high and low noise. However, when using this simplified version, one must assume the shape of the overall noise dependence, as the intermediate points are missing. Here, we investigated whether two distinct EN methods, the 8-point and the simplified 2-point version, reveal comparable parameter estimates. This was performed for three different types of stimuli: random dot kinematograms, and static and dynamic translational Glass patterns, to investigate how constant internal noise estimates are, and how sampling efficiency might vary over tasks. The results indicated substantial compatibility between estimates over a wide range of external noise levels sampled with eight data points, and a simplified version producing two highly informative data points. Our findings support the use of a simplified procedure to estimate essential form-motion integration parameters, paving the way for rapid and critical applications to populations that cannot tolerate protracted measurements.
  • ItemOpen Access
    Cerebrovascular modelling for the management of aneurysm embolization using an intrasaccular flow diverter made by 3D printing
    (Termedia Publishing House Ltd., 2022-10-15) Keles, Ayse; Oto, Cagdas; Algın, Oktay; Algın, Oktay
    Purpose: Using 3-dimensional (3D) printers, the creation of patient-specific models is possible before and after a therapeutic intervention. There are many articles about replicas for training and simulation of aneurysm clipping. However, no paper has focused on 3D replicas obtained from 3-tesla 3D time of flight (3D-TOF) MR angiography for intrasaccular flow diverter (WEB device) embolization of the cerebral aneurysms. In this paper, we aimed to investigate the feasibility of 3D printing models obtained from 3-tesla 3D-TOF data in the management and training of WEB-assisted embolization procedures. Case presentation: We presented a longitudinal case report with several 3D-TOF MRA prints over time. Three-tesla 3D-TOF data were converted into STL and G-code files using an open-source (3D-Slicer) program. We built patient-specific realistic 3D models of a patient with a middle cerebral artery trifurcation aneurysm, which were able to demonstrate the entire WEB device treatment procedure in the pre-intervention and post-intervention periods. The aneurysmatic segment was well displayed on the STL files and the 3D replicas. They allowed visualization of the aneurysmatic segment and changes within a 6-year follow-up period. We successfully showed the possibility of fast, cheap, and easy production of replicas for demonstration of the aneurysm, the parent vessels, and post-intervention changes in a simple way using an affordable 3D printer. Conclusions: 3D printing is useful for training the endovascular team and the patients, understanding the aneurysm/ parent vessels, and choosing the optimal embolization technique/device. 3D printing will potentially lead to greater interventionalist confidence, decreased radiation dose, and improvements in patient safety. © Pol J Radiol 2022.
  • ItemOpen Access
    Exploiting lamina terminalis appearance and motion in prediction of hydrocephalus using convolutional LSTM network
    (Elsevier Masson s.r.l., 2022-08-24) Saygılı, Görkem; Özgöde Yigin, Büşra; Güney, Gökhan; Algın, Oktay; Algın, Oktay
    Background Evaluation of the lamina terminalis (LT) is crucial for non-invasive evaluation of the CSF diversion for the treatment of hydrocephalus. Together with deep learning algorithms, morphological and physiological analyses of the LT may play an important role in the management of hydrocephalus. Aim We aim to show that exploiting the motion of LT can contribute to the evaluation of hydrocephalus using deep learning algorithms. Methods The dataset contains 61 True-fisp data with routine sequences 37 of which are labeled as ‘hydrocephalus’ and the others as ‘normal condition’. A fifteen-year experienced neuroradiologist divided data into two groups. The first group, ‘hydrocephalus’, consists of patients with typical MRI findings (ventriculomegaly, enlargement of the third ventricular recesses and lateral ventricular horns, decreased mamillo-pontine distance, reduced frontal horn angle, thinning/elevation of the corpus callosum, and non-dilated convexity sulci), and the second group contains samples that did not show any symptoms or neurologic abnormality and labeled as ‘normal condition’. The region of interest was determined by the radiologist supervisor to cover the LT. To achieve our purpose, we used both spatial and spatio-temporal analysis with two different deep learning architectures. We utilized Convolutional Neural Networks (CNN) for spatial and Convolutional Long Short-Term Memory (ConvLSTM) models for spatio-temporal analysis using an ROI around LT on sagittal True-fisp images. Results Our results show that 80.7% classification accuracy was achieved with the ConvLSTM model exploiting LT motion, whereas 76.5% and 71.6% accuracies were obtained by the 2D CNN model using all frames, and only the first frame from only spatial information, respectively. Conclusion We suggest that the motion of the LT can be used as an additional attribute to the spatial information to evaluate the hydrocephalus.
  • ItemOpen Access
    An arbitrary waveform MPI scanner
    (Infinite Science Publishing, 2022) Alyuz, Beril; Alyuz, Beril
    In magnetic particle imaging (MPI) systems, impedance matching or tuning circuitry has to be employed at a particular operating frequency to handle the reactive power. In this work, we propose a drive coil design with a Rutherford cable winding comprised of 12 Litz wires twisted together to enable arbitrary waveform (AW) characteristics in an MPI scanner. The AW drive coil achieves a 144-fold reduction in inductance and 12-fold reduction in voltage to generate a given drive field amplitude, compared to a standard drive coil with regular Litz wire windings. With imaging experiments, we show that the proposed design can enable imaging in a wide bandwidth, providing flexibility for different functional imaging applications of MPI.