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Movement artifact reduction in laser Doppler blood flowmetry: myocardial perfusion applications
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laser Doppler perfusion monitoring (LDPM) and imaging (LDPI) enable assessment of tissue microvascular perfusion. The techniques are based on the Doppler broadening of the optical spectrum occurring when coherent laser light is scattered by moving red blood cells (RBC). However, if tissue motion not related to moving RBCs is present, artifacts arise in the derived perfusion estimate. The aim of this thesis was to develop and evaluate methods to reduce tissue motion influence on the perfusion estimate in general and for the specific purpose of enabling myocardial perfusion monitoring in the beating heart.

An LDPM system, based on digital signal processing, was developed for myocardial perfusion assessment. To achieve an accurate estimate of the local microvascular perfusion, the varying myocardial tissue motion during the cardiac cycle is taken into account. By means of ECG-triggering, periods of minimum myocardial tissue motion can be pinpointed. The system and proposed methods were successfully evaluated both in an animal model (3 calves) and during coronary artery bypass grafting (CABG) on 13 humans. Animal studies showed the importance of processing during minimum tissue motion, at late diastole and/or late systole, to reduce movement artifacts. The human evaluation confirmed earlier animal findings and revealed low flow situations in the intraoperative phase. Influence of mechanical ventilation on the myocardial blood flow was found. The results justify investigation postoperative of CABG, where myocardial perfusion monitoring may give a rapid response to potential ischemia.

The influence of tissue motion on LDPI was studied in model measurements and on the skin. A relatively large tissue velocity, compared to microvascular flow velocities, was needed to significantly influence the perfusion signal. Movement artifact magnitude depended on the movement direction and the surface structure. An LDPI system utilizing a polarization technique that blocks specularly reflected light is proposed. The method was evaluated in a flow model and on the skin of 12 subjects and was found to significantly reduce influence from tissue motion. Finally, a theoretical explanation of the origin of LDPI movement artifacts is proposed. Reduction of movement artifacts makes measurements more reliable and increases the potential of LDPI as a clinical tool.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2005. , 84 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 935
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-28804Local ID: 13992ISBN: 91-85297-73-9 (print)OAI: oai:DiVA.org:liu-28804DiVA: diva2:249616
Public defence
2005-04-29, Linden, ingång 65, Campus US, Linköpings universitet, Linköping, 09:15 (English)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-11-30Bibliographically approved
List of papers
1. Analysis and processing of laser Doppler perfusion monitoring signals recorded from the beating heart
Open this publication in new window or tab >>Analysis and processing of laser Doppler perfusion monitoring signals recorded from the beating heart
2003 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 41, no 3, 255-262 p.Article in journal (Refereed) Published
Abstract [en]

Laser Doppler perfusion monitoring (LDPM) can be used for monitoring myocardial perfusion in the non-beating heart. However, the movement of the beating heart generates large artifacts. Therefore the aim of the study was to develop an LDPM system capable of correlating the laser Doppler signals to the cardiac cycle and to process the signals to reduce the movement artifacts. Measurements were performed on three calves, both on the normal beating heart and during occlusion of the left anterior descending coronary artery (LAD). The recorded LDPM signals were digitally processed and correlated to the sampled ECG. Large variations in the output (perfusion) and DC signals during the cardiac cycle were found, with average coefficients of variation of 0.36 and 0.14 (n-14), respectively. However, sections with a relatively low, stable output signal were found in late diastole, where the movement of the heart is at a minimum. Occlusion of the LAD showed the importance of recording the laser Doppler signals at an appropriate point in the cardiac cycle, in this case late systole, to minimise movement artifacts. It is possible to further reduce movement artifacts by increasing the lower cutoff frequency when calculating the output signal.

Place, publisher, year, edition, pages
Springer, 2003
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-24478 (URN)10.1007/BF02348429 (DOI)000183399600004 ()2-s2.0-0037842891 (Scopus ID)6594 (Local ID)6594 (Archive number)6594 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-02-22Bibliographically approved
2. Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging
Open this publication in new window or tab >>Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging
Show others...
2004 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, no 6, 770-776 p.Article in journal (Refereed) Published
Abstract [en]

Tissue motion of the beating heart generates large movement artifacts in the laser Doppler perfusion monitoring (LDPM) signal. The aim of the study was to use tissue Doppler imaging (TDI) to localise intervals during the cardiac cycle where the influence of movement artifacts on the LDPM signal is minimum. TDI velocities and LDPM signals were investigated on three calves, for normal heartbeat and during occlusion of the left anterior descending coronary artery. Intervals of low tissue velocity (TDIint<1 cm s−1) during the cardiac cycle were identified. During occlusion, these intervals were compared with low LDPM signal intervals (LDPMint<50% compared with baseline). Low-velocity intervals were found in late systole (normal and occlusion) and late diastole (normal). Systolic intervals were longer and less sensitive to heart rate variation compared with diastolic ones. The overlap between LDPMint and TDIint in relation to TDIint length was 84±27% (n=14). The LDPM signal was significantly (p<0.001, n=14) lower during occlusion if calculated during minimum tissue motion inside TDIint), compared with averaging over the entire cardiac cycle without taking tissue motion into consideration. In conclusion, movement artifacts are reduced if the LDPM signal is correlated to the ECG and investigated during minimum wall motion. The optimum interval depends on the application; late systole and late diastole can be used.

Place, publisher, year, edition, pages
Springer, 2004
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-22150 (URN)10.1007/BF02345210 (DOI)000225543500006 ()2-s2.0-10244245509 (Scopus ID)1260 (Local ID)1260 (Archive number)1260 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-02-22Bibliographically approved
3. Myocardial perfusion monitoring during coronary artery bypass using an electrocardiogram-triggered laser Doppler technique
Open this publication in new window or tab >>Myocardial perfusion monitoring during coronary artery bypass using an electrocardiogram-triggered laser Doppler technique
2005 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 5, 582-588 p.Article in journal (Refereed) Published
Abstract [en]

Electrocardiogram (ECG)—triggered laser Doppler perfusion monitoring (LDPM) was used to assess myocardial perfusion, with minimum myocardial tissue motion influence, during coronary artery bypass grafting (CABG). Thirteen subjects were investigated at six phases: pre- and post-CABG; post aorta cross-clamping; pre and post left internal mammary artery (LIMA) graft declamping; and post aorta declamping. The perfusion signal was calculated in late systole and late diastole, with expected minimum tissue motion, and compared with arrested heart measurements. Patient conditions or artifacts caused by surgical activity made it impossible to perform and analyse data in all six phases for some patients. No significant (n=5) difference between perfusion signals pre- and post-CABG was found. Diastolic perfusion signal levels were significantly (p<0.02) lower compared with systolic levels. After aorta cross-clamping, the signal level was almost zero. A distinct perfusion signal increase after LIMA and aorta declamping, compared with pre-LIMA declamping, was found in ten cases out of 13. A significantly (p<0.04) lower perfusion signal in the arrested heart compared with in the beating heart was registered. Influence from mechanical ventilation was observed in 14 measurements out of 17. In conclusion, ECG-triggered LDPM can be used to assess myocardial perfusion during CABG. Perfusion signals were lower in the arrested heart compared with in the beating heart and in late diastole compared with late systole. No significant difference between pre- and post-CABG was found.

Place, publisher, year, edition, pages
Springer, 2005
Keyword
Laser Doppler perfusion monitoring, Coronary artery bypass grafting, Beating heart, Myocardial microcirculation, Movement artifacts, Electrocardiography
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-14612 (URN)10.1007/BF02351031 (DOI)000234262300007 ()2-s2.0-29244438810 (Scopus ID)
Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2017-02-21Bibliographically approved
4. Influence of tissue movement on laser Doppler perfusion imaging
Open this publication in new window or tab >>Influence of tissue movement on laser Doppler perfusion imaging
2002 (English)In: Proc. SPIE 4624, Optical Diagnostics and Sensing of Biological Fluids and Glucose and Cholesterol Monitoring II, 106 (May 24, 2002), Vol. 4624 / [ed] Alexander V. Priezzhev and Gerard L. Cote, SPIE , 2002, 106-114 p.Conference paper, Published paper (Refereed)
Abstract [en]

The microvascular perfusion can be measured using laser Doppler blood flowmetry (LDF), a technique sensitive to the concentration of moving blood cells and their velocity. However, movements of the tissue itself can cause artifacts in the perfusion readings. In a clinical situation, these movement induced artifacts may arise from patient movements or from movements of internal organs e.g. the intestines or the beating heart. Therefore, we have studied how a well-controlled tissue movement affects the LDF signals during different flow conditions and for different surface structures. Tissue perfusion was recorded non-touch in one point using a laser Doppler perfusion imager. During the measurements the object was placed on a shaker that generated the movement (both horizontal and vertical). Measurements were carried out both on DELRIN® (polyacetal plastic) and the fingertip, for a wide range of velocities (0-3 cm/s). The influence of the microvascular perfusion was evaluated by occluding the brachial artery as well as blood emptying the finger and by using a flow model. The LDF signals were correlated to the movement. In vivo measurements showed that velocities above 0.8 cm/s gave a significant contribution to the perfusion signal. Corresponding velocities for the DELRIN® piece were higher (1.4 – 2.6 cm/s), and dependent on the surface structures and reflecting properties. By reducing the amount of specular reflection the movement influence was substantially lowered.

Place, publisher, year, edition, pages
SPIE, 2002
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-31098 (URN)10.1117/12.468313 (DOI)16829 (Local ID)16829 (Archive number)16829 (OAI)
Conference
Optical Diagnostics and Sensing of Biological Fluids and Glucose and Cholesterol Monitoring II, San Jose, CA, USA, January 19, 2002
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2016-08-31Bibliographically approved
5. Polarized laser Doppler perfusion imaging—reduction of movement-induced artifacts
Open this publication in new window or tab >>Polarized laser Doppler perfusion imaging—reduction of movement-induced artifacts
2005 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 10, no 6Article in journal (Refereed) Published
Abstract [en]

Laser Doppler perfusion imaging (LDPI) enables superficial tissue perfusion assessment, but is sensitive to tissue motion not related to blood cells. The aim was to investigate if a polarization technique could reduce movement-induced artifacts. A linearly polarized laser and a cross-polarized filter, placed in front of the detectors, were used to block specular reflection. Measurements were performed with, and without, the polarization filter, at a single site during horizontal and vertical movement of skin tissue (index finger, twelve subjects, n=112) and of a flow model (n=432), with varying surface structures. Measurements were repeated during different flow conditions and at increased skin specular reflection. Statistical analysis was performed using ANOVA models. The perfusion signal was lower (p<0.001, skin and p<0.05, flow model) using the polarization filter, due to movement artifact reduction. No significant influence from surface structure was found when using the polarization filter. Movement artifacts were lower (p<0.05) in the vertical movement direction, however, depending on flow conditions for skin measurements. Increased skin specular reflection gave rise to large movement artifacts without the polarization filter. In conclusion, the polarized LDPI technique reduces movement artifacts and is particularly appropriate when assessing, e.g., ulcers and burns, where specular reflection is high.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2005
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-30112 (URN)10.1117/1.2120467 (DOI)000234859400005 ()16409068 (PubMedID)2-s2.0-33645238951 (Scopus ID)15582 (Local ID)15582 (Archive number)15582 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-02-22Bibliographically approved

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Karlsson, MG Daniel

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