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Johansson, Anders
Publications (10 of 43) Show all publications
Johansson, A., Kuiper, J.-H., Sundqvist, T., Persson, F., Speier, C., DAlfonso, D., . . . Öberg, Å. (2012). Spectroscopic Measurement of Cartilage Thickness in Arthroscopy: Ex Vivo Validation in Human Knee Condyles. Arthroscopy: The Journal of Arthroscopy And Related, 28(10), 1513-1523
Open this publication in new window or tab >>Spectroscopic Measurement of Cartilage Thickness in Arthroscopy: Ex Vivo Validation in Human Knee Condyles
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2012 (English)In: Arthroscopy: The Journal of Arthroscopy And Related, ISSN 0749-8063, E-ISSN 1526-3231, Vol. 28, no 10, p. 1513-1523Article in journal (Refereed) Published
Abstract [en]

Purpose: To evaluate the accuracy of articular cartilage thickness measurement when implementing a new technology based on spectroscopic measurement into an arthroscopic camera. Methods: Cartilage thickness was studied by ex vivo arthroscopy at a number of sites (N = 113) in human knee joint osteoarthritic femoral condyles and tibial plateaus, removed from 7 patients undergoing total knee replacement. The arthroscopic image spectral data at each site were used to estimate cartilage thickness. Arthroscopically derived thickness values were compared with reference cartilage thickness as measured by 3 different methods: needle penetration, spiral computed tomography scanning, and geometric measurement after sample slicing. Results: The lowest mean error (0.28 to 0.30 mm) in the regression between arthroscopic and reference cartilage thickness was seen for reference cartilage thickness less than 1.5 mm. Corresponding values for cartilage thickness less than 2.0 and 2.5 mm were 0.32 to 0.40 mm and 0.37 to 0.47 mm, respectively. Cartilage thickness images-created by pixel-by-pixel regression model calculations applied to the arthroscopic images-were derived to demonstrate the clinical use of a camera implementation. Conclusions: On the basis of this investigation on osteoarthritic material, when one is implementing the spectroscopic method for estimating cartilage thickness into an arthroscopic camera, errors in the range of 0.28 to 0.30 mm are expected. This implementation does not, however, influence the fact that the spectral method performs less well in the cartilage thickness region from 1.5 to 2.5 mm and cannot assess cartilage thicker than 2.5 mm. Clinical Relevance: Imaging cartilage thickness directly in the arthroscopic camera video stream could serve as an interesting image tool for in vivo cartilage quality assessment, in connection with cartilage diagnosis, repair, and follow-up.

Place, publisher, year, edition, pages
WB Saunders, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-85201 (URN)10.1016/j.arthro.2012.03.009 (DOI)000309602500026 ()
Note

Funding Agencies|BioOptico AB||ConMed||

Available from: 2012-11-09 Created: 2012-11-09 Last updated: 2017-12-07
Johansson, A., Sundqvist, T., Kuiper, J.-H. & Öberg, Å. (2011). A spectroscopic approach to imaging and quantification of cartilage lesions in human knee joints. Physics in Medicine and Biology, 56(6), 1865-1878
Open this publication in new window or tab >>A spectroscopic approach to imaging and quantification of cartilage lesions in human knee joints
2011 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 56, no 6, p. 1865-1878Article in journal (Refereed) Published
Abstract [en]

We have previously described a technology based on diffuse reflectance of broadband light for measuring joint articular cartilage thickness, utilizing that optical absorption is different in cartilage and subchondral bone. This study is the first evaluation of the technology in human material. We also investigated the prospects of cartilage lesion imaging, with the specific aim of arthroscopic integration. Cartilage thickness was studied ex vivo in a number of sites (n = 87) on human knee joint condyles, removed from nine patients during total knee replacement surgery. A reflectance spectrum was taken at each site and the cartilage thickness was estimated using the blue, green, red and near-infrared regions of the spectrum, respectively. Estimated values were compared with reference cartilage thickness values (taken after sample slicing) using an exponential model. Two-dimensional Monte Carlo simulations were performed in a theoretical analysis of the experimental results. The reference cartilage thickness of the investigated sites was 1.60 ± 1.30 mm (mean ± SD) in the range 0–4.2 mm. Highest correlation coefficients were seen for the calculations based on the near-infrared region after normalization to the red region (r = 0.86) and for the green region (r = 0.80).

Place, publisher, year, edition, pages
IOP, 2011
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-66090 (URN)10.1088/0031-9155/56/6/021 (DOI)000287848600021 ()
Available from: 2011-03-07 Created: 2011-03-03 Last updated: 2017-12-11Bibliographically approved
Nilsson, L., Goscinski, T., Lindenberger, M., Länne, T. & Johansson, A. (2010). Respiratory variations in the photoplethysmographic waveform: acute hypovolaemia during spontaneous breathing is not detected. Physiological Measurement, 31(7), 953-962
Open this publication in new window or tab >>Respiratory variations in the photoplethysmographic waveform: acute hypovolaemia during spontaneous breathing is not detected
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2010 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 31, no 7, p. 953-962Article in journal (Refereed) Published
Abstract [en]

Recent studies using photoplethysmographic (PPG) signals from pulse oximeters have shown potential to assess hypovolaemia during spontaneous breathing. This signal is heavily filtered and reports are based on respiratory variations in the small pulse synchronous variation of PPG. There are stronger respiratory variations such as respiratory synchronous variation (PPGr) in the baseline of the unfiltered PPG signal. We hypothesized that PPGr would increase during hypovolaemia during spontaneous breathing. Hemodynamic and respiratory data were recorded together with PPG infrared signals from the finger, ear and forearm from 12 healthy male volunteers, at rest and during hypovolaemia created by the application of a lower body negative pressure (LBNP) of 15, 30 and 60 cmH(2)O. Hemodynamic and respiratory values changed significantly. From rest to the LBNP of 60 cmH(2)O systolic blood pressure fell from median (IQR) 116 (16) to 101 (23) mmHg, the heart rate increased from 58 (16) to 73 (16) beats min(-1), and the respiratory rate increased from 9.5 (2.0) to 11.5 (4.0) breaths min(-1). The amplitude of PPGr did not change significantly at any measurement site. The strongest effect was seen at the ear, where the LBNP of 60 cmH(2)O gave an amplitude increase from 1.0 (0.0) to 1.31 (2.24) AU. PPG baseline respiratory variations cannot be used for detecting hypovolaemia in spontaneously breathing subjects.

Place, publisher, year, edition, pages
Iop Publishing, 2010
Keywords
photoplethysmography; monitoring; cardiopulmonary; monitoring; non-invasive; blood volume; hypovolaemia
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-58255 (URN)10.1088/0967-3334/31/7/006 (DOI)000279269900006 ()
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12
Ahlström, C., Länne, T., Ask, P. & Johansson, A. (2008). A method for accurate localization of the first heart sound and possible applications. Physiological Measurement, 29(3), 417-428
Open this publication in new window or tab >>A method for accurate localization of the first heart sound and possible applications
2008 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 29, no 3, p. 417-428Article in journal (Refereed) Published
Abstract [en]

We have previously developed a method for localization of the first heart sound (S1) using wavelet denoising and ECG-gated peak-picking. In this study, an additional enhancement step based on cross-correlation and ECG-gated ensemble averaging (EA) is presented. The main objective of the improved method was to localize S1 with very high temporal accuracy in (pseudo-) real time. The performance of S1 detection and localization, with and without EA enhancement, was evaluated on simulated as well as experimental data. The simulation study showed that EA enhancement reduced the localization error considerably and that S1 could be accurately localized at much lower signal-to-noise ratios. The experimental data were taken from ten healthy subjects at rest and during invoked hyper- and hypotension. For this material, the number of correct S1 detections increased from 91% to 98% when using EA enhancement. Improved performance was also demonstrated when EA enhancement was used for continuous tracking of blood pressure changes and for respiration monitoring via the electromechanical activation time. These are two typical applications where accurate localization of S1 is essential for the results.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik, 2008
Keywords
ensemble averaging, detection, localization, heart sound, bioacoustics
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-11856 (URN)10.1088/0967-3334/29/3/011 (DOI)
Note
Original publication: C Ahlstrom, T Länne, P Ask and A Johansson, A method for accurate localization of the first heart sound and possible applications, 2008, Physiological Measurement, (29), 3, 417-428. http://dx.doi.org/10.1088/0967-3334/29/3/011. Copyright: Institute of Physics and IOP Publishing Limited, http://www.iop.org/EJ/journal/PMAvailable from: 2008-05-20 Created: 2008-05-20 Last updated: 2017-12-13
Nilsson, L., Goscinski, T., Kalman, S., Lindberg, L.-G. & Johansson, A. (2007). Combined photoplethysmographic monitoring of respiration rate and pulse: A comparison between different measurement sites in spontaneously breathing subjects. Acta Anaesthesiologica Scandinavica, 51(9), 1250-1257
Open this publication in new window or tab >>Combined photoplethysmographic monitoring of respiration rate and pulse: A comparison between different measurement sites in spontaneously breathing subjects
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2007 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 51, no 9, p. 1250-1257Article in journal (Refereed) Published
Abstract [en]

Background: The non-invasive photoplethysmographic (PPG) signal reflects blood flow and volume in a tissue. The PPG signal shows variation synchronous with heartbeat (PPGc), as used in pulse oximetry, and variations synchronous with breathing (PPGr). PPGr has been used for non-invasive monitoring of respiration with promising results. Our aim was to investigate PPG signals recorded from different skin sites in order to find suitable locations for parallel monitoring of variations synchronous with heartbeat and breathing. Methods: PPG sensors were applied to the forearm, finger, forehead, wrist and shoulder on 48 awake healthy volunteers. From these sites, seven PPG signals were simultaneously recorded during normal spontaneous breathing over 10 min. Capnometry served as respiration and electrocardiogram (ECG) as pulse reference signals. PPG signals were compared with respect to power spectral content and squared coherence. Results: Forearm PPG measurement showed significantly higher power within the respiratory region of the power spectrum [median (quartile range) 42 (26)%], but significantly lower power within the cardiac region [9 (10)%] compared with the other skin sites. PPG finger measurement showed the opposite, in transmission mode, the power within the respiratory region was significantly lower [4 (10)%] and within the cardiac region significantly higher [45 (25)%] than the other sites. PPGc coherence values were generally high [>0.96 (0.08)], and PPGr coherence values lower [0.83 (0.35)-0.94 (0.17)]. Conclusion: Combined PPG respiration and pulse monitoring is possible, but there are significant differences between the respiratory and cardiac components of the PPG signal at different sites. © 2007 Acta Anaesthesiol Scand.

Keywords
Monitoring, Photoplethysmography, Pulse, Pulse oximetry, Respiration
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-48544 (URN)10.1111/j.1399-6576.2007.01375.x (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Ahlström, C., Johansson, A., Länne, T. & Ask, P. (2007). Monitorering av andning and blodtrycksförändringar baserat på EKG och hjärtljud. In: Medicinteknik dagarna,2007.
Open this publication in new window or tab >>Monitorering av andning and blodtrycksförändringar baserat på EKG och hjärtljud
2007 (Swedish)In: Medicinteknik dagarna,2007, 2007Conference paper, Published paper (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-40377 (URN)53178 (Local ID)53178 (Archive number)53178 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-03-27
Nilsson, L., Goscinski, T., Johansson, A., Lindberg, L.-G. & Kalman, S. (2006). Age and gender do not influence the ability to detect respiration by photoplethysmography. Journal of clinical monitoring and computing, 20(6), 431-436
Open this publication in new window or tab >>Age and gender do not influence the ability to detect respiration by photoplethysmography
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2006 (English)In: Journal of clinical monitoring and computing, ISSN 1387-1307, E-ISSN 1573-2614, Vol. 20, no 6, p. 431-436Article in journal (Refereed) Published
Abstract [en]

Objective  The non-invasive technique photopl- ethysmography (PPG) can detect changes in blood volume and perfusion in a tissue. Respiration causes variations in the peripheral circulation, making it possible to monitor breaths using an optical sensor attached to the skin. The respiratory-synchronous part of the PPG signal (PPGr) has been used to monitor respiration during anaesthesia, and in postoperative and neonatal care. Studies addressing possible differences in PPGr signal characteristics depending on gender or age are lacking.

Methods  We studied three groups of 16 healthy subjects each during normal breathing; young males, old males and young females, and calculated the concordance between PPGr, derived from a reflection mode PPG sensor on the forearm, and a reference CO2 signal. The concordance was quantified by using a squared coherence analysis. Time delay between the two signals was calculated. In this process, we compared three different methods for calculating time delay.

Results  Coherence values ≥0.92 were seen for all three groups without any significant differences depending on age or gender (p = 0.67). Comparison between the three different methods for calculating time delay showed a correlation r = 0.93.

Conclusions  These results demonstrate clinically important information implying the possibility to register qualitative PPGr signals for respiration monitoring, regardless of age and gender.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-37154 (URN)10.1007/s10877-006-9050-z (DOI)33808 (Local ID)33808 (Archive number)33808 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-03-23Bibliographically approved
Ahlström, C., Johansson, A., Hult, P. & Ask, P. (2006). Chaotic dynamics of respiratory sounds. Chaos, Solitons & Fractals, 29(5), 1054-1062
Open this publication in new window or tab >>Chaotic dynamics of respiratory sounds
2006 (English)In: Chaos, Solitons & Fractals, ISSN 0960-0779, E-ISSN 1873-2887, Vol. 29, no 5, p. 1054-1062Article in journal (Refereed) Published
Abstract [en]

There is a growing interest in nonlinear analysis of respiratory sounds (RS), but little has been done to justify the use of nonlinear tools on such data. The aim of this paper is to investigate the stationarity, linearity and chaotic dynamics of recorded RS. Two independent data sets from 8 + 8 healthy subjects were recorded and investigated. The first set consisted of lung sounds (LS) recorded with an electronic stethoscope and the other of tracheal sounds (TS) recorded with a contact accelerometer. Recurrence plot analysis revealed that both LS and TS are quasistationary, with the parts corresponding to inspiratory and expiratory flow plateaus being stationary. Surrogate data tests could not provide statistically sufficient evidence regarding the nonlinearity of the data. The null hypothesis could not be rejected in 4 out of 32 LS cases and in 15 out of 32 TS cases. However, the Lyapunov spectra, the correlation dimension (D2) and the Kaplan-Yorke dimension (DKY) all indicate chaotic behavior. The Lyapunov analysis showed that the sum of the exponents was negative in all cases and that the largest exponent was found to be positive. The results are partly ambiguous, but provide some evidence of chaotic dynamics of RS, both concerning LS and TS. The results motivate continuous use of nonlinear tools for analysing RS data. © 2005 Elsevier Ltd. All rights reserved.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-50139 (URN)10.1016/j.chaos.2005.08.197 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Johansson, A., Ahlström, C., Länne, T. & Ask, P. (2006). Pulse wave transit time for monitoring respiration rate. Medical and Biological Engineering and Computing, 44(6), 471-478
Open this publication in new window or tab >>Pulse wave transit time for monitoring respiration rate
2006 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 6, p. 471-478Article in journal (Refereed) Published
Abstract [en]

In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring. © International Federation for Medical and Biological Engineering 2006.

Keywords
Pulse wave transit time, Respiration rate, Respiration monitoring, Blood pressure, Photoplethysmography
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-34605 (URN)10.1007/s11517-006-0064-y (DOI)22250 (Local ID)22250 (Archive number)22250 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Eneling, M., Wickström, M., Johansson, A. & Hult, P. (2006). Vätternrundan.  Fjärr-registrering av fysiologiska parametrar under idrottsutövning.. In: : . Paper presented at Medicinteknikdagarna 2006, 3-4 oktober Uppsala.
Open this publication in new window or tab >>Vätternrundan.  Fjärr-registrering av fysiologiska parametrar under idrottsutövning.
2006 (Swedish)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-122289 (URN)
Conference
Medicinteknikdagarna 2006, 3-4 oktober Uppsala
Available from: 2015-10-28 Created: 2015-10-28 Last updated: 2015-11-06
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