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Khodadad, D. (2019). Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement. International Journal of Optics, 2019, Article ID 4906109.
Open this publication in new window or tab >>Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement
2019 (English)In: International Journal of Optics, ISSN 1687-9384, E-ISSN 1687-9392, Vol. 2019, article id 4906109Article in journal (Refereed) Published
Abstract [en]

We present a digital holographic method to increase height range measurement with a reduced phase ambiguity using a dual-directional illumination. Small changes in the angle of incident illumination introduce phase differences between the recorded complex fields. We decrease relative phase difference between the recorded complex fields 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 ≈300  . Further, numerical refocusing 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
Hindawi Limited, 2019
National Category
Engineering and Technology Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:oru:diva-72613 (URN)10.1155/2019/4906109 (DOI)000459030200001 ()
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-06-18Bibliographically approved
Shiraz, A., Khodadad, D., Nordebo, S., Yerworth, R., Frerichs, I., van Kaam, A., . . . Demosthenous, A. (2019). Compressive sensing in electrical impedance tomography for breathing monitoring. Physiological Measurement, 40(3), Article ID 034010.
Open this publication in new window or tab >>Compressive sensing in electrical impedance tomography for breathing monitoring
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2019 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 40, no 3, article id 034010Article in journal (Refereed) Published
Abstract [en]

Objective: Electrical impedance tomography (EIT) is a functional imaging technique in which cross-sectional images of structures are reconstructed based on boundary trans-impedance measurements. Continuous functional thorax monitoring using EIT has been extensively researched. Increasing the number of electrodes, number of planes and frame rate may improve clinical decision making. Thus, a limiting factor in high temporal resolution, 3D and fast EIT is the handling of the volume of raw impedance data produced for transmission and its subsequent storage. Owing to the periodicity (i.e. sparsity in frequency domain) of breathing and other physiological variations that may be reflected in EIT boundary measurements, data dimensionality may be reduced efficiently at the time of sampling using compressed sensing techniques. This way, a fewer number of samples may be taken.

Approach: Measurements using a 32-electrode, 48-frames-per-second EIT system from 30 neonates were post-processed to simulate random demodulation acquisition method on 2000 frames (each consisting of 544 measurements) for compression ratios (CRs) ranging from 2 to 100. Sparse reconstruction was performed by solving the basis pursuit problem using SPGL1 package. The global impedance data (i.e. sum of all 544 measurements in each frame) was used in the subsequent studies. The signal to noise ratio (SNR) for the entire frequency band (0 Hz–24 Hz) and three local frequency bands were analysed. A breath detection algorithm was applied to traces and the subsequent error-rates were calculated while considering the outcome of the algorithm applied to a down-sampled and linearly interpolated version of the traces as the baseline.

Main results: SNR degradation was generally proportional with CR. The mean degradation for 0 Hz–8 Hz (of interest for the target physiological variations) was below ~15 dB for all CRs. The error-rates in the outcome of the breath detection algorithm in the case of decompressed traces were lower than those associated with the corresponding down-sampled traces for CR  ⩾  25, corresponding to sub-Nyquist rate for breathing frequency. For instance, the mean error-rate associated with CR  =  50 was ~60% lower than that of the corresponding down-sampled traces.

Significance: To the best of our knowledge, no other study has evaluated the applicability of compressive sensing techniques on raw boundary impedance data in EIT. While further research should be directed at optimising the acquisition and decompression techniques for this application, this contribution serves as the baseline for future efforts.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
Breath detection, compressive sensing, electrical impedance tomography
National Category
Engineering and Technology Signal Processing
Identifiers
urn:nbn:se:oru:diva-73510 (URN)10.1088/1361-6579/ab0daa (DOI)000463392300006 ()30844770 (PubMedID)
Funder
EU, Horizon 2020, 668259
Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-06-19Bibliographically approved
Nordebo, S., Dalarsson, M., Khodadad, D., Müller, B., Waldman, A. D., Becher, T., . . . Seifnaraghi, N. (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
IOP Publishing, 2018
Keywords
homogenization theory, dielectric properties of biological tissue, dielectric properties of lung tissue, electrical impedance tomography
National Category
Physical Sciences
Identifiers
urn:nbn:se:oru:diva-72593 (URN)10.1088/1361-6463/aabc04 (DOI)000430961300001 ()2-s2.0-85047182230 (Scopus ID)
Note

Funding Agencies:

European Union's Horizon research and innovation programme  668259 

Swedish Foundation for Strategic Research (SSF) under the programme Applied Mathematics  

project Complex Analysis and Convex Optimization for EM Design 

Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-27Bibliographically approved
Khodadad, D., Nordebo, S., Müller, B., Waldmann, A., Yerworth, R., Becher, T., . . . Bayford, R. (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 improve 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 analysis. As a baseline a 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. 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
IOP Publishing, 2018
Keywords
electrical impedance tomography, breath detection, respiratory system, global optimisation, lung imaging, receiver operating characteristics, inspiration
National Category
Medical Engineering
Identifiers
urn:nbn:se:oru:diva-72592 (URN)10.1088/1361-6579/aad7e6 (DOI)000444050400001 ()30074906 (PubMedID)2-s2.0-85054669051 (Scopus ID)
Note

Funding Agency:

European Union's Framework Program for Research and Innovation Horizon 2020 (CRADL)  668259

Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-27Bibliographically approved
Khodadad, D. & Tayebi, B. (2018). Shape Measurement Based on Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements. In: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama): . Paper presented at 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Toyama, Japan, August 1-4, 2018 (pp. 184-189). Electromagnetics Academy
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: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Electromagnetics Academy , 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
Electromagnetics Academy, 2018
Series
Progress in Electromagnetics Research Symposium, ISSN 1559-9450
Keywords
height measurement, holographic interferometry, shape measurement, speckle, shape measurement, height range measurement, reduced phase ambiguity, illumination angle, relative phase difference, cent Euro coin edge groove, speckle displacements, complex field, reduced phase dual-directional illumination digital holography, groove depth, numerical refocusing, Speckle, Lighting, Phase measurement, Shape measurement, Shape, Holography
National Category
Atom and Molecular Physics and Optics Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:oru:diva-72606 (URN)10.23919/PIERS.2018.8597821 (DOI)000458673700026 ()2-s2.0-85060910902 (Scopus ID)
Conference
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Toyama, Japan, August 1-4, 2018
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-03-07Bibliographically approved
Khodadad, D., Nordebo, S., Seifnaraghi, N., Yerworth, R., Waldmann, A. D., Müller, B., . . . Bayford, R. (2018). The Value of Phase Angle in Electrical Impedance Tomography Breath Detection. In: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama): . Paper presented at 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Toyama, Japan, August 1-4, 2018 (pp. 1040-1043). Electromagnetics Academy
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: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Electromagnetics Academy , 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
Electromagnetics Academy, 2018
Series
Progress in Electromagnetics Research Symposium, ISSN 1559-9450
Keywords
electric impedance imaging, electric impedance measurement, medical image processing, paediatrics, pneumodynamics, electrical impedance tomography breath detection, phase angle information, complex impedance, breath cycle, chest Electrical Impedance Tomography, clinical neonatal EIT data, complex EIT data, conventional breath detection algorithms, Tomography, Impedance, Pediatrics, Lung, Phase measurement, Electromagnetics, Physics
National Category
Medical Laboratory and Measurements Technologies Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:oru:diva-72605 (URN)10.23919/PIERS.2018.8597702 (DOI)000458673700183 ()2-s2.0-85060960836 (Scopus ID)
Conference
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Toyama, Japan, August 1-4, 2018
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-03-07Bibliographically 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 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS): . Paper presented at 2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), Montreal, QC, Canada, August 19-26, 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 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), IEEE, 2017, p. 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
Keywords
electric impedance imaging, Fourier transforms, medical image processing, medical signal detection, pneumodynamics, spectral analysis, time-frequency analysis, Kaiser window, simultaneous spatial-time-frequency analysis, breath detection, electrical impedance tomography, spectral analysis, short-time Fourier transform analysis, neonates EIT data, Tomography, Impedance, Lungs, Pediatrics, Monitoring, Ventilation
National Category
Medical Image Processing Signal Processing
Identifiers
urn:nbn:se:oru:diva-72589 (URN)10.23919/URSIGASS.2017.8105231 (DOI)2-s2.0-85046145323 (Scopus ID)
Conference
2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), Montreal, QC, Canada, August 19-26, 2017
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-03-08Bibliographically 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
National Category
Medical Engineering
Identifiers
urn:nbn:se:oru:diva-72607 (URN)
Conference
18th International Conference on Biomedical Applications of Electrical Impedance Tomography (EIT2017), Hanover, New Hampshire, USA, June 21-24, 2017
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-27Bibliographically 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) and (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 x 10(-3) in the measurement of deformation gradients.

Place, publisher, year, edition, pages
Optical Society of America, 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:oru:diva-72588 (URN)10.1364/AO.55.007735 (DOI)000383996900038 ()27661605 (PubMedID)2-s2.0-84988811675 (Scopus ID)
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-03-01Bibliographically approved
Khodadad, D. (2016). Multiplexed Digital Holography incorporating Speckle Correlation. (Doctoral dissertation). Paper presented at . 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 the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing the controlled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digital holography, access to the complex wave field and the possibility to numerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured 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 shape and deformation measurements. To perform online process control of free-form manufactured objects, the measured shape is compared with the CAD-model to obtain deviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape, position and deformation without the unwrapping problems that usually appear in dual-wavelength holography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformation measurements. One significant problem when using the dual-wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps and speckle 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 3D deformations. In order to do 3D deformation measurement, usually multi-cameras and intricate 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 different directions. In this manner, meanwhile 3D speckle displacement is calculated and used for the measurement of the 3D deformations, wrapping problems are also avoided. Further, the same scale of speckle images of the surface for all four images is guaranteed. Furthermore, a need for 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 singleshot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. The proposed method is robust to large phase gradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, shape and deformation measurements can be performed even though the synthetic wavelength is out of the dynamic range of the object deformation and/or height variation.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016
National Category
Applied Mechanics
Identifiers
urn:nbn:se:oru:diva-73181 (URN)978-91-7583-517-4 (ISBN)978-91-7583-518-1 (ISBN)
Available from: 2019-03-18 Created: 2019-03-18 Last updated: 2019-03-18Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2960-3094

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