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Nordebo, S., Dalarsson, M., Khodadad, D., Müller, B., Waldermann, A. D., Becher, T., . . . Bayford, R. (2018). A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing. Journal of Physics D: Applied Physics, 51(20), Article ID 205401.
Open this publication in new window or tab >>A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing
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2018 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 20, article id 205401Article in journal (Refereed) Published
Abstract [en]

Classical homogenization theory based on the Hashin–Shtrikman coated ellipsoids is used to model the changes in the complex valued conductivity (or admittivity) of a lung during tidal breathing. Here, the lung is modeled as a two-phase composite material where the alveolar air-filling corresponds to the inclusion phase. The theory predicts a linear relationship between the real and the imaginary parts of the change in the complex valued conductivity of a lung during tidal breathing, and where the loss cotangent of the change is approximately the same as of the effective background conductivity and hence easy to estimate. The theory is illustrated with numerical examples based on realistic parameter values and frequency ranges used with electrical impedance tomography (EIT). The theory may be potentially useful for imaging and clinical evaluations in connection with lung EIT for respiratory management and control.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
National Category
Medical Image Processing
Research subject
Natural Science, Medicine
Identifiers
urn:nbn:se:lnu:diva-74401 (URN)10.1088/1361-6463/aabc04 (DOI)
Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2019-07-09Bibliographically approved
Khodadad, D., Nordebo, S., Mueller, B., Waldmann, A. D., Yerworth, R., Becher, T., . . . Bayford, R. H. (2018). Optimized breath detection algorithm in electrical impedance tomography. Physiological Measurement, 39(9), Article ID 094001.
Open this publication in new window or tab >>Optimized breath detection algorithm in electrical impedance tomography
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2018 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 39, no 9, article id 094001Article in journal (Refereed) Published
Abstract [en]

Objective: This paper defines a method for optimizing the breath delineation algorithms used in Electrical Impedance Tomography (EIT). In lung EIT the identification of the breath phases is central for generating tidal impedance variation images, subsequent data analysis and clinical evaluation. The optimisation of these algorithms is particularly important in neonatal care since the existing breath detectors developed for adults may give insufficient reliability in neonates due to their very irregular breathing pattern. Approach: Our approach is generic in the sense that it relies on the definition of a gold standard and the associated definition of detector sensitivity and specificity, an optimisation criterion and a set of detector parameters to be investigated. The gold standard has been defined by 11 clinicians with previous experience with EIT and the performance of our approach is described and validated using a neonatal EIT dataset acquired within the EU-funded CRADL project. Main results: Three different algorithms are proposed that are improving the breath detector performance by adding conditions on 1) maximum tidal breath rate obtained from zero-crossings of the EIT breathing signal, 2) minimum tidal impedance amplitude and 3) minimum tidal breath rate obtained from Time-Frequency (TF) analysis. As a baseline the zero crossing algorithm has been used with some default parameters based on the Swisstom EIT device. Significance: Based on the gold standard, the most crucial parameters of the proposed algorithms are optimised by using a simple exhaustive search and a weighted metric defined in connection with the Receiver Operating Characterics (ROC). This provides a practical way to achieve any desirable trade-off between the sensitivity and the specificity of the detectors.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
National Category
Medical Engineering Medical Equipment Engineering
Research subject
Physics, Electrotechnology
Identifiers
urn:nbn:se:lnu:diva-77552 (URN)10.1088/1361-6579/aad7e6 (DOI)000444050400001 ()30074906 (PubMedID)
Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2018-09-20Bibliographically approved
Khodadad, D. & Tayebi, B. (2018). Shape Measurement Based on Combined Reduced Phase Dual-directional Illumination Digital Holography and Speckle Displacements. In: Progress In Electromagnetics Research Symposium 2018: . Paper presented at Progress In Electromagnetics Research Symposium (PIERS), 1-4 August, 2018, Toyama, Japan (pp. 184-189). IEEE
Open this publication in new window or tab >>Shape Measurement Based on Combined Reduced Phase Dual-directional Illumination Digital Holography and Speckle Displacements
2018 (English)In: Progress In Electromagnetics Research Symposium 2018, IEEE, 2018, p. 184-189Conference paper, Published paper (Refereed)
Abstract [en]

We present a dual-directional illumination digital holographic method to increase height range measurement with a reduced phase ambiguity. Small change in the illumination angle of incident introduce phase difference between the recorded complex fields. We decrease relative phase difference between the recorded complex field 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈300μm . Further, numerical re-focusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

Place, publisher, year, edition, pages
IEEE, 2018
Series
Progress in Electromagnetics Research Symposium, ISSN 1559-9450
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Physics, Electrotechnology
Identifiers
urn:nbn:se:lnu:diva-77555 (URN)10.23919/PIERS.2018.8597821 (DOI)000458673700026 ()978-4-8855-2316-8 (ISBN)978-1-5386-5455-2 (ISBN)
Conference
Progress In Electromagnetics Research Symposium (PIERS), 1-4 August, 2018, Toyama, Japan
Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2019-03-15Bibliographically approved
Khodadad, D., Nordebo, S., Seifnaraghi, N., Yerworth, R., Waldmann, A. D., Muller, B., . . . Bayford, R. (2018). The Value of Phase Angle in Electrical Impedance Tomography Breath Detection. In: Progress In Electromagnetics Research Symposium 2018: . Paper presented at Progress In Electromagnetics Research Symposium (PIERS), 1-4 August, 2018, Toyama, Japan (pp. 1040-1043). IEEE
Open this publication in new window or tab >>The Value of Phase Angle in Electrical Impedance Tomography Breath Detection
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2018 (English)In: Progress In Electromagnetics Research Symposium 2018, IEEE, 2018, p. 1040-1043Conference paper, Published paper (Refereed)
Abstract [en]

The objective of this paper is to report our investigation demonstrating that the phase angle information of complex impedance could be a simple indicator of a breath cycle in chest Electrical Impedance Tomography (EIT). The study used clinical neonatal EIT data. The results show that measurement of the phase angle from complex EIT data can be used as a complementary information for improving the conventional breath detection algorithms.

Place, publisher, year, edition, pages
IEEE, 2018
Series
Progress in Electromagnetics Research Symposium, ISSN 1559-9450
National Category
Medical Equipment Engineering
Research subject
Physics, Electrotechnology
Identifiers
urn:nbn:se:lnu:diva-77556 (URN)10.23919/PIERS.2018.8597702 (DOI)000458673700183 ()978-4-8855-2316-8 (ISBN)978-1-5386-5455-2 (ISBN)
Conference
Progress In Electromagnetics Research Symposium (PIERS), 1-4 August, 2018, Toyama, Japan
Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2019-03-15Bibliographically approved
Khodadad, D., Nordebo, S., Seifnaraghi, N., Waldmann, A. D., Müller, B. & Bayford, R. (2017). Breath detection using short-time Fourier transform analysis in electrical impedance tomography. In: 2017 32nd General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2017: . Paper presented at General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), 2017 XXXIInd, Montreal; Canada; 19 - 26 August 2017 (pp. 1-3). IEEE
Open this publication in new window or tab >>Breath detection using short-time Fourier transform analysis in electrical impedance tomography
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2017 (English)In: 2017 32nd General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2017, IEEE, 2017, , p. 3p. 1-3Conference paper, Published paper (Refereed)
Abstract [en]

Spectral analysis based on short-time Fourier transform (STFT) using Kaiser window is proposed to examine the frequency components of neonates EIT data. In this way, a simultaneous spatial-time-frequency analysis is achieved.

Place, publisher, year, edition, pages
IEEE, 2017. p. 3
Keywords
Tomography, Impedance, Lungs, Pediatrics, Monitoring, Ventilation
National Category
Medical Image Processing
Research subject
Computer Science, Information and software visualization
Identifiers
urn:nbn:se:lnu:diva-74403 (URN)10.23919/URSIGASS.2017.8105231 (DOI)000463723600281 ()9789082598704 (ISBN)
Conference
General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), 2017 XXXIInd, Montreal; Canada; 19 - 26 August 2017
Funder
EU, Horizon 2020, 668259
Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2019-05-27Bibliographically approved
Seifnaraghi, N., Tizzard, A., de Gelidi, S., Khodadad, D., Nordebo, S., Van Kaam, A., . . . Bayford, R. (2017). Estimation of thorax shape for forward modelling in lungs EIT. In: Alistair Boyle, Ryan Halter, Ethan Murphy & Andy Adler (Ed.), Proceedings of the 18th International Conference on Biomedical Applications of Electrical Impedance Tomography: . Paper presented at 18th International Conference on Biomedical Applications of Electrical Impedance Tomography (EIT2017), Hanover, New Hampshire, USA, June 21-24, 2017 (pp. 58-58). Hanover, New Hampshire, USA: Thayer School of Engineering at Dartmouth
Open this publication in new window or tab >>Estimation of thorax shape for forward modelling in lungs EIT
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2017 (English)In: Proceedings of the 18th International Conference on Biomedical Applications of Electrical Impedance Tomography / [ed] Alistair Boyle, Ryan Halter, Ethan Murphy & Andy Adler, Hanover, New Hampshire, USA: Thayer School of Engineering at Dartmouth , 2017, p. 58-58Conference paper, Published paper (Refereed)
Abstract [en]

The thorax models for pre-term babies are developed based on the CT scans from new-borns and their effect on image reconstruction is evaluated in comparison with other available models.

Place, publisher, year, edition, pages
Hanover, New Hampshire, USA: Thayer School of Engineering at Dartmouth, 2017
Series
Proceedings of the International Conferences on Biomedical Applications of Electrical Impedance Tomography
National Category
Medical Engineering
Identifiers
urn:nbn:se:lnu:diva-75361 (URN)
Conference
18th International Conference on Biomedical Applications of Electrical Impedance Tomography (EIT2017), Hanover, New Hampshire, USA, June 21-24, 2017
Available from: 2018-06-08 Created: 2018-06-08 Last updated: 2018-09-10Bibliographically approved
Khodadad, D., Singh, A. K., Pedrini, G. & Sjödahl, M. (2016). Full-field 3D deformation measurement: comparison between speckle phase and displacement evaluation. Applied Optics, 55(27), 7735-7743
Open this publication in new window or tab >>Full-field 3D deformation measurement: comparison between speckle phase and displacement evaluation
2016 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 27, p. 7735-7743Article in journal (Refereed) Published
Abstract [en]

The objective of this paper is to describe a full-field deformation measurement method based on 3D speckle displacements. The deformation is evaluated from the slope of the speckle displacement function that connects the different reconstruction planes. For our experiment, a symmetrical arrangement with four illuminations parallel to the planes (x,z)" role="presentation" style="box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(𝑥,𝑧)(x,z) and (y,z)" role="presentation" style="box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(𝑦,𝑧)(y,z) was used. Four sets of speckle patterns were sequentially recorded by illuminating an object from the four directions, respectively. A single camera is used to record the holograms before and after deformations. Digital speckle photography is then used to calculate relative speckle displacements in each direction between two numerically propagated planes. The 3D speckle displacements vector is calculated as a combination of the speckle displacements from the holograms recorded in each illumination direction. Using the speckle displacements, problems associated with rigid body movements and phase wrapping are avoided. In our experiment, the procedure is shown to give the theoretical accuracy of 0.17 pixels yielding the accuracy of 2×10−3" role="presentation" style="box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative 2×10-3in the measurement of deformation gradients.

Place, publisher, year, edition, pages
Optical Society of America, 2016
National Category
Atom and Molecular Physics and Optics
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-56723 (URN)10.1364/AO.55.007735 (DOI)000383996900038 ()27661605 (PubMedID)2-s2.0-84988811675 (Scopus ID)
Available from: 2016-09-26 Created: 2016-09-26 Last updated: 2018-09-10Bibliographically approved
Khodadad, D. (2016). Multiplexed Digital Holography incorporating Speckle Correlation. (Doctoral dissertation). Luleå tekniska universitet
Open this publication in new window or tab >>Multiplexed Digital Holography incorporating Speckle Correlation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In manufacturing industry there is a high demand for on line quality control to minimize therisk of incorrectly produced objects. Conventional contact measurement methods are usuallyslow and invasive, meaning that they cannot be used for soft materials and for complexshapes without influencing the controlled parts. In contrast, interferometry and digitalholography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digitalholography, access to the complex wave field and the possibility to numerically reconstructholograms in different planes introduce a new degree of flexibility to optical metrology. Withdigital holography high resolution and precise three dimensional (3D) images of themanufactured parts can be generated. This technique can also be used to capture data in asingle exposure, which is important when doing measurements in a disturbed environment.

The aim of this thesis is devoted to the theoretical and experimental development of shapeand deformation measurements. To perform online process control of free-formmanufactured objects, the measured shape is compared with the CAD-model to obtaindeviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckledisplacements is demonstrated. Based on an analytical relation between phase gradients andspeckle displacements it is shown that an object is retrieved uniquely to shape, position anddeformation without the unwrapping problems that usually appear in dual-wavelengthholography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual corediode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm isused. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformationmeasurements.

One significant problem when using the dual-wavelength single-shot approach is that phaseambiguities are built in to the system that needs to be corrected. An automatic calibrationscheme is therefore required. The intrinsic flexibility of digital holography gives a possibilityto compensate these aberrations and to remove errors, fully numerically without mechanicalmovements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps andspeckle displacements can be recovered free of chromatic aberrations. This is the first time that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria tomake an automatic procedure.

Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3Ddeformations. In order to do 3D deformation measurement, usually multi-cameras andintricate set-up are required. In this thesis I demonstrate the use of only one single camera torecord four sets of speckle patterns recorded by illuminating the object from four differentdirections. In this manner, meanwhile 3D speckle displacement is calculated and used for themeasurement of the 3D deformations, wrapping problems are also avoided. Further, the samescale of speckle images of the surface for all four images is guaranteed. Furthermore, a needfor calibration of the 3D deformation measurement that occurs in the multi-camera methods,is removed.

By the results of the presented work, it is experimentally verified that the multiplexed singleshotdual wavelength digital holography and numerically generated speckle images can beused together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. Theproposed method is robust to large phase gradients and large movements within the intensitypatterns. The advantage of the approach is that, using speckle displacements, shape anddeformation measurements can be performed even though the synthetic wavelength is out ofthe dynamic range of the object deformation and/or height variation.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016. p. 155
Series
Doctoral thesis / Luleå University of Technology, ISSN 1402-1544
National Category
Signal Processing
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-55810 (URN)978-91-7583-517-4 (ISBN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2018-09-10Bibliographically approved
Tjörnhammar, S., Eklöf, F. K., Yu, Z., Khodadad, D., Hällstig, E., Sjödahl, M. & Laurell, F. (2016). Multiwavelength laser designed for single-frame digital holography. Applied Optics, 55(27), 7517-7521
Open this publication in new window or tab >>Multiwavelength laser designed for single-frame digital holography
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2016 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 27, p. 7517-7521Article in journal (Refereed) Published
Abstract [en]

In this paper, we present a tailored multiwavelength Yb-fiber laser source in the 1.03 μm spectral region for spatially multiplexed digital holographic acquisitions. The wavelengths with bandwidths below 0.1 nm were spectrally separated by approximately 1 nm by employing fiber Bragg gratings for spectral control. As a proof of concept, the shape of a cylindrically shaped object with a diameter of 48 mm was measured. The holographic acquisition was performed in single-shot dual-wavelength mode with a synthetic wavelength of 1.1 mm, and the accuracy was estimated to be 3% of the synthetic wavelength.

Place, publisher, year, edition, pages
Optical Society of America, 2016
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:lnu:diva-56722 (URN)10.1364/AO.55.007517 (DOI)
Available from: 2016-09-26 Created: 2016-09-26 Last updated: 2018-09-10Bibliographically approved
Khodadad, D. (2016). Phase-derivative-based estimation of a digital reference wave from a single off-axis digital hologram. Applied Optics, 55(7), 1663-1669
Open this publication in new window or tab >>Phase-derivative-based estimation of a digital reference wave from a single off-axis digital hologram
2016 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 7, p. 1663-1669Article in journal (Refereed) Published
Abstract [en]

This paper describes a method to obtain an estimated digital reference wave from a single off-axis digital hologram that matches the actual experimental reference wave as closely as possible. The proposed method is independent of a reference flat plate and speckles. The digital reference wave parameters are estimated directly from the recorded phase information. The parameters include both the off-axis tilt angle and the curvature of the reference wave. Phase derivatives are used to extract the digital reference wave parameters without the need for a phase unwrapping process. Thus, problems associated with phase wrapping are avoided. Experimental results for the proposed method are provided. The simulated effect of the digital reference wave parameters on the reconstructed image phase distribution is shown. The pseudo phase gradient originating from incorrect estimation of the digital reference wave parameters and its effect on object reconstruction are discussed.

National Category
Signal Processing
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-55811 (URN)10.1364/AO.55.001663 (DOI)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2018-09-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2960-3094

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