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- Gomez, Alberto, et al.
(författare)
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Mechanically Powered Motion Imaging Phantoms: Proof of Concept
- 2019
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Ingår i: 2019 41ST ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC). - : IEEE. - 9781538613115 - 9781538613122 ; , s. 2723-2726
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Konferensbidrag (refereegranskat)abstract
- Motion imaging phantoms are expensive, bulky and difficult to transport and set-up. The purpose of this paper is to demonstrate a simple approach to the design of multi-modality motion imaging phantoms that use mechanically stored energy to produce motion. We propose two phantom designs that use mainsprings and elastic bands to store energy. A rectangular piece was attached to an axle at the end of the transmission chain of each phantom, and underwent a rotary motion upon release of the mechanical motor. The phantoms were imaged with MRI and US, and the image sequences were embedded in a 1D non linear manifold (Laplacian Eigenmap) and the spectrogram of the embedding was used to derive the angular velocity over time. The derived velocities were consistent and reproducible within a small error. The proposed motion phantom concept showed great potential for the construction of simple and affordable motion phantoms.
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- Götstedt, Julia, et al.
(författare)
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IMRT patient-specific QA using the Delta4 dosimetry system and evaluation based on ICRU 83 recommendations
- 2013
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Ingår i: Journal of Physics: Conference Series. - 1742-6588 .- 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- Patient-specific IMRT QA is dependent on the dosimetry system and the evaluation procedure. The ICRU report 83 provides recommendations of tolerated deviations between measured and calculated absorbed dose distributions for QA of IMRT treatment plans. The result of doing IMRT patient-specific QA with the Delta4 dosimetry system and using the ICRU recommendations for evaluation is studied. To be able to investigate the QA procedure the original IMRT treatment plans were modified in the treatment planning system to create calculated dose distributions with dosimetric deviations from the original treatment plans. The modified dose distributions were compared to the dose distributions from the Delta4 measurements of the original treatment plans and the differences were evaluated with criteria and tolerance levels according to the recommendations from ICRU. The evaluation for all 28 modified dose distributions have gamma passing rates higher than the tolerance level recommended from ICRU and will therefore pass the patient-specific QA. More than half of the evaluations have a gamma passing rate of 100 %. Evaluation of the differences between the modified and the original calculated dose distributions revealed in several cases large unacceptable dose differences in the PTV volumes and the organs at risk, for example an increase in the near-maximum dose D 2% to the spinal cord of 5.5 Gy. This study indicates that patient-specific QA with the Delta4 dosimetry system and the ICRU recommendations for evaluation can not be used to distinguish differences between planned and measured dose of dosimetrical relevance.
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- Mattsson, Viktor, et al.
(författare)
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Muscle Analyzer System : Exploring Correlation Between Novel Microwave Resonator and Ultrasound-based Tissue Information in the Thigh
- 2022
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Ingår i: 2022 16TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - : Institute of Electrical and Electronics Engineers (IEEE). - 9788831299046
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Konferensbidrag (refereegranskat)abstract
- A microwave sensor to safely measure quality of muscle tissue for diagnosis and screening of diseases and medical conditions characterized by fat infiltration in muscle is presented. Fat infiltration in muscle may be seen by a lower dielectric constant of muscle at microwave frequencies corresponding to the large contrast between fat and muscle tissues. A planar resonator based on a bandstop filter and optimized to noninvasively interrogate muscle in the thigh on tissue quality is proposed. Currently, a study based on clinical trials is carried out, and, here, we present a preliminary correlation between skin and fat thicknesses and rectus femoris cross sectional area (CSA) measured with ultrasound and the proposed sensor's resonance frequency. CST simulations based on the ultrasound information guide the analysis. We see that although there are signs of a potential correlation between CSA and resonance, skin and fat variability is still an issue to overcome.
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| 6. |
- Xie, Long, et al.
(författare)
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Deep Label Fusion : A 3D End-To-End Hybrid Multi-atlas Segmentation and Deep Learning Pipeline
- 2021
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Ingår i: Information Processing in Medical Imaging - 27th International Conference, IPMI 2021, Proceedings. - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. - 9783030781903 ; 12729 LNCS, s. 428-439
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Konferensbidrag (refereegranskat)abstract
- Deep learning (DL) is the state-of-the-art methodology in various medical image segmentation tasks. However, it requires relatively large amounts of manually labeled training data, which may be infeasible to generate in some applications. In addition, DL methods have relatively poor generalizability to out-of-sample data. Multi-atlas segmentation (MAS), on the other hand, has promising performance using limited amounts of training data and good generalizability. A hybrid method that integrates the high accuracy of DL and good generalizability of MAS is highly desired and could play an important role in segmentation problems where manually labeled data is hard to generate. Most of the prior work focuses on improving single components of MAS using DL rather than directly optimizing the final segmentation accuracy via an end-to-end pipeline. Only one study explored this idea in binary segmentation of 2D images, but it remains unknown whether it generalizes well to multi-class 3D segmentation problems. In this study, we propose a 3D end-to-end hybrid pipeline, named deep label fusion (DLF), that takes advantage of the strengths of MAS and DL. Experimental results demonstrate that DLF yields significant improvements over conventional label fusion methods and U-Net, a direct DL approach, in the context of segmenting medial temporal lobe subregions using 3T T1-weighted and T2-weighted MRI. Further, when applied to an unseen similar dataset acquired in 7T, DLF maintains its superior performance, which demonstrates its good generalizability.
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| 8. |
- Buschmann, M. H., et al.
(författare)
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On the proper interpretation of nanofluid convective heat transfer
- 2018
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Ingår i: Proceeding: International Heat Transfer Conference 16. - 2377-424X. ; , s. 2855-2862
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Konferensbidrag (refereegranskat)abstract
- Technological developments of the last decades allow the production and the dispersion of particles of sizes ranging between 10 and 100 nm in liquids. In a large number of recent studies the resulting nanofluids have been reported to display anomalously high increase in convective heat transfer. The present study compiles experiments from five independent research teams investigating convective heat transfer in nanofluid flow in pipes (laminar and turbulent), pipe with inserted twisted tape, annular counter flow heat exchanger, and coil and plate heat exchangers. The results of all these experiments unequivocally confirm that Newtonian nanofluid flow can be consistently characterized by employing Nusselt number correlations obtained for single-phase heat transfer liquids such as water when the correct thermophysical properties of the nanofluid are utilized. It is also shown that the heat transfer enhancement provided by nanofluids equals the increase in the thermal conductivity of the nanofluid as compared to the base fluid independent of the nanoparticle concentration or material. These results demonstrate that no anomalous phenomena are involved in thermal conduction and forced convection based heat transfer of water based nanofluids. The experiments are theoretically supported by a fundamental similarity analysis of nanoparticle motion in nanofluid flow.
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| 9. |
- Bärgman, Jonas, 1972, et al.
(författare)
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Using manual measurements on event recorder video and image processing algorithms to extract optical parameters.
- 2013
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Ingår i: Proceedings of the Seventh International Driving Symposium on Human Factors in Driver Assessment, Training and Vehicle Design. ; , s. 177-183
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Konferensbidrag (refereegranskat)abstract
- Vehicle kinematics and optical parameters such as optical angle, optical expansion rate, and tau are thought to underlie drivers’ ability to avoid and handle critical traffic situations. Analyses of these parameters in naturalistic driving data with video, such as commercial event recordings of near-crashes and crashes, can provide insight into driver behavior in critical traffic situations. This paper describes a pair of methods, one for the range to a lead vehicle and one for its optical angle, that are derived from image processing mathematics and that provide driver behavior researchers with a relatively simple way to extract optical parameters from video-based naturalistic data when automatic image processing is not possible. The methods begin with manual measurements of the size of other road users on a video on a screen. To develop the methods, 20 participants manually measured the width of a lead vehicle on 14 images where the lead vehicle was placed at different distances from the camera. An on-market DriveCam Event Recorder was used to capture these images. A linear model that corrects distortion and modeling optics was developed to transform the on-screen measurements distance (range) to and optical angle of the vehicle. The width of the confidence interval for predicted range is less than 0.1m when the actual distance is less than 10m and the lead-vehicle width estimate is correct. The methods enable driver behavior researchers to easily and accurately estimate useful kinematic and optical parameters from videos (e.g., of crashes and near-crashes) in event-based naturalistic driving data.
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| 10. |
- Engström, Johan A Skifs, 1973, et al.
(författare)
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Analysis of the role of inattention in road crashes based on naturalistic on-board safety monitoring data
- 2013
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Ingår i: PROCEEDINGS of the 3rd International Conference on Driver Distraction and Inattention.
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Konferensbidrag (refereegranskat)abstract
- The general objective of the present analysis was to investigate the role of driver inattention in rear-end crashes and crossing path intersection crashes. To this end, a set of 133 naturalistic crashes (70 rear-end and 63 intersection crashes), obtained by means of the DriveCam on-board safety monitoring (OBSM) system, were analyzed based on a novel methodology for assigning and aggregating crash-contributing factors. The analysis focused on rear-end crashes where the OBSM-instrumented vehicle was striking a lead vehicle and crossing-path intersection crashes where the driver of the instrumented vehicle intended to proceed straight through the intersection. It was found that driver inattention, in particular driver distraction involving a diversion of gaze from the forward roadway, was the dominating factor contributing to the rear-end crashes.Although driver inattention also contributed to the intersection crashes, the patterns of contributing factors for this crash type were quite different compared to the rear-end crashes. In particular, in the intersection crashes, visual occlusion and insufficient selection of safety margins were identified as key contributing factors. Cognitively distracting activities that did not involve a diversion of gaze from the forward roadway, such as cell phone conversation, did not contribute frequently to avoidance failures for any of the crash types. The present results show that the role of driver inattention as acrash-contributing factor depends strongly on the type of crash. They also support previous findings from naturalistic driving studies that visual diversion from theforward roadway is the key mechanism by which inattention leads to rear-end crashes.
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