1. |
- Strömberg, N O, et al.
(author)
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Improved accuracy and extended flow range for a Fleisch pneumotachograph
- 1999
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 37:4, s. 456-460
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Journal article (peer-reviewed)abstract
- A large linear flow range and a small instrumental dead space volume are incompatible properties for a pneumotachometer (PTM). The linearity of a Fleisch number 2 PTM is studied for flows up to 6 litre s-1 (nominal range 0-2 litre s-1) with various up- and downstream geometries. It is hypothesised that using an array of calibration factors (conductance; flow/pressure), instead of a single calibration factor over the entire flow range, could improve accuracy and also extend the applicable flow range. The conductance against pressure characteristics are calculated with a previously described weighted averaging technique based on multiple strokes from a precision syringe. A single conductance value gives stroke volume errors in the range of -5 to 3% (0-2 litre s-1) and -6 to 11% (0-6 litre s-1) for validation using the same geometry as for calibration. The pressure dependent conductance improves accuracy to within -3% and 1% independent of flow range. However, for validation using a different geometry than for calibration, errors range from -5% to +8%. The degree of non-linearity varies between the geometries (range 3-15%) and is highest when using a one-directional valve upstream of the PTM and a Y-shaped connector. In conclusion, a pressure-dependent conductance improves accuracy and can also be used to extend the applicable flow range up to at least three times the nominal flow range.
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3. |
- Albin, Maria, et al.
(author)
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Cytogenetic and morphologic subgroups of myelodysplastic syndromes in relation to occupational and hobby exposures.
- 2003
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In: Scandinavian Journal of Work, Environment and Health. - 0355-3140. ; 29:5, s. 378-387
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Journal article (peer-reviewed)abstract
- OBJECTIVES: This study investigated the association between occupational and hobby exposure and the risk of myelodysplastic syndromes (MDS) while focusing on differential patterns of clonal chromosome aberrations and morphologic subgroups. METHODS: A case-referent study was conducted with 330 MDS patients investigated cytogenetically in 1976-1993 (cases) and matched referents. Telephone interviews with either the person or a next-of-kin were used. The participation rate of the cases and referents was 85% and 60%, respectively. Information was obtained from the next-of-kin more often for the cases (88%) than for the referents (26%). Occupational hygienists assessed the exposure using interview data on worktasks and hobbies. Associations with disease risk were evaluated for 10 exposures with a logistic regression analysis. RESULTS: The investigated exposures were generally not associated with cytogenetically abnormal MDS. Effect estimates for specific cytogenetic or morphologic subgroups were generally imprecise. Occupational exposure to extremely low-frequency magnetic fields (EMF) was associated with MDS with a normal karyotype [odds ratio (OR) 2.0, 95% confidence interval (95% CI) 1.0-4.0]. The exposure-response association was consistent for intensity but inconclusive for duration. A decreased risk was observed for MDS, irrespective of karyotypic pattern, among farmers and farmhands (OR 0.53, 95% CI 0.35-0.81). CONCLUSIONS: Cytogenetically abnormal MDS was generally not associated with occupational or hobby exposure to known or suspected genotoxic agents. However, exposure prevalences and intensities were low for several agents. An association was suggested between occupational exposure to EMF and MDS with a normal karyotype. Biases due to differential information quality and selective participation cannot be ruled out.
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4. |
- Andreu-Cabedo, Yasmina, et al.
(author)
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MIRROR MIRROR ON THE WALL... AN INTELLIGENT MULTISENSORY MIRROR FOR WELL-BEING SELF-ASSESSMENT
- 2015
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In: 2015 IEEE INTERNATIONAL CONFERENCE ON MULTIMEDIA and EXPO (ICME). - : IEEE. - 9781479970827
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Conference paper (peer-reviewed)abstract
- The face reveals the healthy status of an individual, through a combination of physical signs and facial expressions. The project SEMEOTICONS is translating the semeiotic code of the human face into computational descriptors and measures, automatically extracted from videos, images, and 3D scans of the face. SEMEOTICONS is developing a multisensory platform, in the form of a smart mirror, looking for signs related to cardio-metabolic risk. The goal is to enable users to self-monitor their well-being status over time and improve their life-style via tailored user guidance. Building the multisensory mirror requires addressing significant scientific and technological challenges, from touch-less data acquisition, to real-time processing and integration of multimodal data.
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5. |
- Arildsson, Mikael, 1967-, et al.
(author)
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Effects on skin blood flow by provocation during local analgesia
- 2000
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In: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 59:1, s. 122-130
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Journal article (peer-reviewed)abstract
- Although topical analgesia cream has been used for several years, little is known about its effects on the microcirculation. Previous studies have shown a vasoconstrictive effect after short application times and a vasodilatation after longer application. It has also been shown that vasomotion does not occur in the analgesized skin. The present study was undertaken to investigate the alterations in skin blood perfusion following local cooling, local heating and pin-pricking after the establishment of analgesia. In 11 healthy volunteers, skin analgesia was attained by use of a eutectic mixture of lidocaine and prilocaine (EMLA, Astra Pain Control AB, Sweden) applied to the skin three hours prior to provocation. The changes in skin blood perfusion, after applying three different provocation methods, were studied using the laser Doppler technique. Local cooling and heating to temperatures of +10 and +45°C, respectively, were applied for 9 s by use of a copper probe (Ø12 mm). In the pin-prick provocation method, a combined effect of deflection and penetration of the skin to in total 3 mm was attained. Identical provocation methods were applied to placebo treated and untreated skin areas. After heat provocation, significant differences in the perfusion response between the treatments were seen (P < 0.0001). Skin areas treated with analgesia cream responded with a slow increase in perfusion that persisted beyond the four minute measurement period. Placebo and untreated areas decreased their perfusion over time. After cooling a significant reduction in skin perfusion was seen, irrespective of the treatment. Similarly, after pin-pricking a perfusion increase was seen for all treatments. The findings indicate that topical analgesia influences the myogenic control of the blood flow in those vascular plexa measured by laser Doppler following heat provocation. No differences could be seen in the response to pin-pricking and cooling for the different treatments.
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6. |
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7. |
- Arildsson, Mikael, 1967-, et al.
(author)
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Skin capillary appearance and skin microvascular perfusion due to topical application of analgesia cream
- 2000
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In: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 59:1, s. 14-23
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Journal article (peer-reviewed)abstract
- Local topical analgesia changes basal skin perfusion and its regulation. In particular, the response induced by local heating, which in nontreated skin comprises a rapidly increased perfusion followed by a normalization within 30 s, is altered to a delayed and persistent perfusion increase. The response dependency to the analgesia cream application time, that is, the intradermal penetration of the analgesics and in which vascular plexa the response occurs, is not known. The aim of this study was to assess changes in the appearance of superficial skin capillaries and skin microvascular perfusion changes due to different application periods of topical analgesia cream (EMLA). Twelve subjects were treated with EMLA and placebo applied to the volar side of each forearm, respectively. The treatment areas were assigned different application times (20 min, 40 min, 1 h, 2 h, and 3 h). The areas were cleared from the creams and shortly thereafter provoked during 9 s with a probe heated to 45°C. To assess capillary number density and skin perfusion, capillary microscopy, and Laser Doppler perfusion imaging (LDPI), respectively, were used. The number density of physiologically active capillary was significantly decreased with longer application times of EMLA (P < 0.005). The LDPI-signal showed a persistent perfusion increase after provocation associated with increasing application time of the cream. This perfusion pattern was not seen after 20 min of treatment, but was present in 9 of 12 subjects after 3 h of treatment. No significant relationship between changes in the capillary number density and the LDF measurement was found. In conclusion, a longer application time and therefore a higher intradermal concentration and a deeper penetration of the analgesics was associated with a delayed and persistent perfusion increase after local heating. There was a discrepancy between changes in capillary number density and skin perfusion, indicating that the perfusion increase does not occur in the capillaries but in the deeper lying vessels. Hence, the contribution of the capillary perfusion to the LDF-signal is smaller than previously anticipated. Capillary number density and presumably their perfusion were decreased with longer application times.
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8. |
- Arildsson, Mikael, et al.
(author)
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Spectral signature and heterodyne efficiency for different wavelengths in laser Doppler flowmetry
- 2002
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 40:1, s. 85-89
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Journal article (peer-reviewed)abstract
- Laser Doppler perfusion monitoring and imaging technologies generate time traces and two-dimensional flow maps of the microcirculation. With the goal of reaching different tissue depths, these technologies are equipped with lassers operating at different wavelengths λ. The fact that the average scattering angle, at a single scattering event, between a photon and a red blood cell increases with λ is compensated for by a 1/λ effect in the scattering vector, rendering the average frequency shift virtually independent of the choice of wavelength. Monte Carlo simulations showed that the corresponding spectral signature of the Doppler signals for λ=632.8nm and 780nm were close to identical. The theoretical predictions were verified by calculating the centre-of-gravity (COG) frequency of the laser Doppler power spectral density for the two wavelengths from forearm and finger skin, representing a low and high perfusion area, respectively (forearm COG=123 against 121Hz, finger COG=220 against 212 Hz). When the wavelength changes from 632.8nm to 780nm, the heterodyne efficiency of the detector and, thereby, the inherent system amplifcation increase. For tissues with identical microvascular flow conditions, the output signal therfore tends to increase in magnitude when shifting to longer wavelengths.
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10. |
- Backström, Tomas, et al.
(author)
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Shared vision as an order parameter
- 2010
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In: Society for chaos in psychology and life sciences international conference. - Palermo.
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Conference paper (peer-reviewed)abstract
- This paper is dealing with a way to temporarily change the patterns of thinking and acting of a team. Or more specific; to move a team through a phase transition from an ordered phase to a complex phase. The aim is to make it possible for production personnel to contribute and be integrated in idea development processes. Innovation and improvement are important to ensure long term competitiveness for most companies. Since patterns of thinking and acting in idea development is different from the ones needed in production it is often recommended to perform this work in a department not connected to production. The division between production and idea development may lead to several problems; e.g. impoverishment of the work of production personnel, no input from common days experience in idea development, and harder for production personnel to understand and take responsibility for the production of new products resulting from the idea development, and thus e.g. hamper future work with improvements of it. The ideal for team creativity is to be able to make use of all members' different ideas, experiences and different ways to understand things, in a common creative process. This is possible if each team member at the same time is both autonomous, independently using its competence in action, and integrated, relating each action to an emerging idea shared by all team members. When independent agents interact, and an organization which controls the actions of the agents emerges in this interaction, then we have a complex system, by definition. The agents are at the same time autonomous, following their individual organization, and integrated to the system, following the organization of the system. Most of the work tasks for normal teams in work life demands predictability, not creativity. Such teams develop patterns of thinking and acting that is good for repeatedly producing with high efficiency and quality. This is possible for an ordered system with low autonomy, not a complex system. The question of this paper is: Is it possible to find a strategy that may be used to support a team to reach a complex phase, were it is creative sooner than predictable? An important inspiration writing this paper has been an article Movie making as a mediator in dialogue (Palus & Drath). The thoughts presented in the article were similar to our understanding of how to support creativity of teams and we have decided to use this technique in our creativity lab. In our paper we describe how to understand this technique from a complexity perspective, and start a discussion about how to measure the complexity of a team's social interaction.
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11. |
- Belcastro, Luigi, et al.
(author)
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Beneath the skin: multi-frequency SFDI to detect thin layers of skin using light scattering
- 2023
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In: PHOTONICS IN DERMATOLOGY AND PLASTIC SURGERY 2023. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510658097 - 9781510658103
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Conference paper (peer-reviewed)abstract
- Wound healing assessment is usually performed visually by a trained physician. This type of evaluation is very subjective and returns limited information about the wound progression. In contrast, optical imaging techniques are non-invasive ways to quantitatively measure biological parameters. Spatial frequency domain imaging (SFDI) is an optical technique that exploits sinusoidal patterns of light with multiple spatial frequencies to measure the tissue frequency-specific response, from which the absorption and scattering coefficient of the material can be derived. While SFDI is based on models of light transport that assume the tissue is homogeneous, skin is composed by several layer with very different optical properties. An underutilized property of SFDI, however, is that the spatial frequency of the patterns determines the penetration depth of photons in the tissue. By using multiple ranges of spatial frequencies, we are developing a means to obtain morphological data from different volumes of tissue. This data is used to reconstruct the optical properties in depth, allowing us to differentiate between different thin layers of tissue. In this study we have developed a 2-layer optical phantom model with realistic optical properties and dimensions, that mimics the physiology of wound healing. We have used this physical model to validate the accuracy of this approach in obtaining layer specific optical properties.
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12. |
- Belcastro, Luigi, et al.
(author)
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Handheld multispectral imager for quantitative skin assessment in low resource settings
- 2020
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In: Journal of Biomedical Optics. - : SPIE - The International Society for Optics and Photonics. - 1083-3668 .- 1560-2281. ; 25:8
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Journal article (peer-reviewed)abstract
- Significance: Spatial frequency domain imaging (SFDI) is a quantitative imaging method to measure absorption and scattering of tissue, from which several chromophore concentrations (e.g., oxy-/deoxy-/meth-hemoglobin, melanin, and carotenoids) can be calculated. Employing a method to extract additional spectral bands from RGB components (that we named cross-channels), we designed a handheld SFDI device to account for these pigments, using low-cost, consumer-grade components for its implementation and characterization.Aim: With only three broad spectral bands (red, green, blue, or RGB), consumer-grade devices are often too limited. We present a methodology to increase the number of spectral bands in SFDI devices that use RGB components without hardware modification.Approach: We developed a compact low-cost RGB spectral imager using a color CMOS camera and LED-based mini projector. The components’ spectral properties were characterized and additional cross-channel bands were calculated. An alternative characterization procedure was also developed that makes use of low-cost equipment, and its results were compared. The device performance was evaluated by measurements on tissue-simulating optical phantoms and in-vivo tissue. The measurements were compared with another quantitative spectroscopy method: spatial frequency domain spectroscopy (SFDS).Results: Out of six possible cross-channel bands, two were evaluated to be suitable for our application and were fully characterized (520 ± 20 nm; 556 ± 18 nm). The other four cross-channels presented a too low signal-to-noise ratio for this implementation. In estimating the optical properties of optical phantoms, the SFDI data have a strong linear correlation with the SFDS data (R2 = 0.987, RMSE = 0.006 for μa, R2 = 0.994, RMSE = 0.078 for μs′).Conclusions: We extracted two additional spectral bands from a commercial RGB system at no cost. There was good agreement between our device and the research-grade SFDS system. The alternative characterization procedure we have presented allowed us to measure the spectral features of the system with an accuracy comparable to standard laboratory equipment.
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13. |
- Bergkvist, Max, et al.
(author)
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Assessment of oxygenation with polarized light spectroscopy enables new means for detecting vascular events in the skin
- 2020
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In: Microvascular Research. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0026-2862 .- 1095-9319. ; 130
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Journal article (peer-reviewed)abstract
- Introduction: Impaired oxygenation in the skin may occur in disease states and after reconstructive surgery. We used tissue viability imaging (TiVi) to measure changes in oxygenation and deoxygenation of haemoglobin in an in vitro model and in the dermal microcirculation of healthy individuals. Materials and methods: Oxygenation was measured in human whole blood with different levels of oxygenation. In healthy subjects, changes in red blood cell concentration (C-RBC,(TiVi)), oxygenation (Delta C-OH,(TiVi)) and deoxygenation (Delta C-DOH,(TiVi)) of haemoglobin were measured during and after arterial and venous occlusion using TiVi and were compared with measurements from the enhanced perfusion and oxygen saturation system (EPOS). Results: During arterial occlusion, C-RBC,(TiVi) remained unchanged while Delta C-OH,(TiVi) decreased to -44.2 (10.4) AU (p = 0.04), as compared to baseline. After release, C-RBC,C-TiVi increased to 39.2 (18.8) AU (p < 0.001), Delta C-OH,C-TiVi increased to 38.5. During venous occlusion, C-RBC,C-TiVi increased to 28.9 (11.2) AU (p < 0.001), Delta C-OH,C-TiVi decreased to -52.2 (46.1) AU (p < 0.001) compared to baseline after 5 min of venous occlusion. There was a significant correlation between the TiVi Oxygen Mapper and EPOS, for arterial (r = 0.92, p < 0.001) and venous occlusion (r = 0.87, p < 0.001), respectively. Conclusion: This study shows that TiVi can measure trends in oxygenation and deoxygenation of haemoglobin during arterial and venous stasis in healthy individuals.
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14. |
- Berglund, Tomas, et al.
(author)
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Epi-convergence of minimum curvature variation B-splines
- 2003
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Reports (other academic/artistic)abstract
- We study the curvature variation functional, i.e., the integral over the square of arc-length derivative of curvature, along a planar curve. With no other constraints than prescribed position, slope angle, and curvature at the endpoints of the curve, the minimizer of this functional is known as a cubic spiral. It remains a challenge to effectively compute minimizers or approximations to minimizers of this functional subject to additional constraints such as, for example, for the curve to avoid obstacles such as other curves. In this paper, we consider the set of smooth curves that can be written as graphs of three times continuously differentiable functions on an interval, and, in particular, we consider approximations using quartic uniform B- spline functions. We show that if quartic uniform B-spline minimizers of the curvature variation functional converge to a curve, as the number of B-spline basis functions tends to infinity, then this curve is in fact a minimizer of the curvature variation functional. In order to illustrate this result, we present an example of sequences of B-spline minimizers that converge to a cubic spiral.
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15. |
- Bergstrand, Sara, et al.
(author)
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Association between cardiovascular risk profile and impaired microvascular function in a Swedish middle-aged cohort (the SCAPIS study)
- 2024
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In: European Journal of Preventive Cardiology. - : OXFORD UNIV PRESS. - 2047-4873 .- 2047-4881.
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Journal article (peer-reviewed)abstract
- Aims The aim was to investigate the relationship between microvascular function, cardiovascular risk profile, and subclinical atherosclerotic burden. Methods and results The study enrolled 3809 individuals, 50-65 years old, participating in the population-based observational cross-sectional Swedish CArdioPulmonary bioImage Study. Microvascular function was assessed in forearm skin using an arterial occlusion and release protocol determining peak blood oxygen saturation (OxyP). Cardiovascular risk was calculated using the updated Systematic Coronary Risk Evaluation [SCORE2; 10-year risk of fatal and non-fatal cardiovascular disease (CVD) events]. The OxyP was compared with coronary artery calcification score (CACS) and to plaques in the carotid arteries. Individuals with OxyP values in the lowest quartile (Q1; impaired microvascular function) had a mean SCORE2 of 5.8% compared with 3.8% in those with the highest values of OxyP (Q4), a relative risk increase of 53%. The risk of having a SCORE2 > 10% was five times higher for those in Q1 (odds ratio: 4.96, 95% confidence interval: 2.76-8.93) vs. Q4 when adjusting for body mass index and high-sensitivity C-reactive protein. The OxyP was lower in individuals with CACS > 0 and in those with both carotid plaques and CACS > 0, compared with individuals without subclinical atherosclerotic burdens (87.5 +/- 5.6% and 86.9 +/- 6.0%, vs. 88.6 +/- 5.8%, P < 0.01). Conclusion In a population without CVD or diabetes mellitus, impaired microvascular function is associated with cardiovascular risk profiles such as higher SCORE2 risk and CACS. We suggest that OxyP may serve as a microcirculatory functional marker of subclinical atherosclerosis and CVD risk that is not detected by structural assessments.
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16. |
- Bergstrand, Sara, et al.
(author)
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The relationship between forearm skin speed-resolved perfusion and oxygen saturation, and finger arterial pulsation amplitudes, as indirect measures of endothelial function
- 2018
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In: Microcirculation. - : WILEY. - 1073-9688 .- 1549-8719. ; 25:2
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Journal article (peer-reviewed)abstract
- Objective: Endothelial function is important for regulating peripheral blood flow to meet varying metabolic demands and can be measured indirectly during vascular provocations. In this study, we compared the PAT finger response (EndoPAT) after a 5-minutes arterial occlusion to that from forearm skin comprehensive microcirculation analysis (EPOS). Methods: Measurements in 16 subjects with varying cardiovascular risk factors were carried out concurrently with both methods during arterial occlusion, while forearm skin was also evaluated during local heating. Results: Peak values for EPOS skin Perf(conv) and speed-resolved total perfusion after the release of the occlusion were significantly correlated to the EndoPAT RHI (rho =.68, P = .007 and rho =.60, P = .025, respectively), mainly due to high-speed blood flow. During local heating, EPOS skin oxygen saturation, SO2, was significantly correlated to RHI (rho = .62, P =.043). This indicates that SO2 may have diagnostic value regarding endothelial function. Conclusions: We have demonstrated for the first time a significant relationship between forearm skin microcirculatory perfusion and oxygen saturation and finger PAT. Both local heating and reactive hyperemia are useful skin provocations. Further studies are needed to understand the precise regulation mechanisms of blood flow and oxygenation during these tests.
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17. |
- Bergström, Göran, et al.
(author)
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Self-report tool for identification of individuals with coronary atherosclerosis : the Swedish cardiopulmonary bioimage study
- 2024
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In: Journal of the American Heart Association. - : John Wiley & Sons. - 2047-9980. ; 13:14
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Journal article (peer-reviewed)abstract
- BACKGROUND: Coronary atherosclerosis detected by imaging is a marker of elevated cardiovascular risk. However, imaging involves large resources and exposure to radiation. The aim was, therefore, to test whether nonimaging data, specifically data that can be self-reported, could be used to identify individuals with moderate to severe coronary atherosclerosis.METHODS AND RESULTS: We used data from the population-based SCAPIS (Swedish CardioPulmonary BioImage Study) in individuals with coronary computed tomography angiography (n=25 182) and coronary artery calcification score (n=28 701), aged 50 to 64 years without previous ischemic heart disease. We developed a risk prediction tool using variables that could be assessed from home (self-report tool). For comparison, we also developed a tool using variables from laboratory tests, physical examinations, and self-report (clinical tool) and evaluated both models using receiver operating characteristic curve analysis, external validation, and benchmarked against factors in the pooled cohort equation. The self-report tool (n=14 variables) and the clinical tool (n=23 variables) showed high-to-excellent discriminative ability to identify a segment involvement score ≥4 (area under the curve 0.79 and 0.80, respectively) and significantly better than the pooled cohort equation (area under the curve 0.76, P<0.001). The tools showed a larger net benefit in clinical decision-making at relevant threshold probabilities. The self-report tool identified 65% of all individuals with a segment involvement score ≥4 in the top 30% of the highest-risk individuals. Tools developed for coronary artery calcification score ≥100 performed similarly.CONCLUSIONS: We have developed a self-report tool that effectively identifies individuals with moderate to severe coronary atherosclerosis. The self-report tool may serve as prescreening tool toward a cost-effective computed tomography-based screening program for high-risk individuals.
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18. |
- Bergström, Göran, et al.
(author)
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Self-Report Tool for Identification of Individuals With Coronary Atherosclerosis : The Swedish CardioPulmonary BioImage Study
- 2024
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In: Journal of the American Heart Association. - : American Heart Association. - 2047-9980. ; 13:14
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Coronary atherosclerosis detected by imaging is a marker of elevated cardiovascular risk. However, imaging involves large resources and exposure to radiation. The aim was, therefore, to test whether nonimaging data, specifically data that can be self-reported, could be used to identify individuals with moderate to severe coronary atherosclerosis. METHODS AND RESULTS: We used data from the population-based SCAPIS (Swedish CardioPulmonary BioImage Study) in individuals with coronary computed tomography angiography (n=25 182) and coronary artery calcification score (n=28 701), aged 50 to 64 years without previous ischemic heart disease. We developed a risk prediction tool using variables that could be assessed from home (self-report tool). For comparison, we also developed a tool using variables from laboratory tests, physical examinations, and self-report (clinical tool) and evaluated both models using receiver operating characteristic curve analysis, external validation, and benchmarked against factors in the pooled cohort equation. The self-report tool (n=14 variables) and the clinical tool (n=23 variables) showed high-to-excellent discriminative ability to identify a segment involvement score ≥4 (area under the curve 0.79 and 0.80, respectively) and significantly better than the pooled cohort equation (area under the curve 0.76, P<0.001). The tools showed a larger net benefit in clinical decision-making at relevant threshold probabilities. The self-report tool identified 65% of all individuals with a segment involvement score ≥4 in the top 30% of the highest-risk individuals. Tools developed for coronary artery calcification score ≥100 performed similarly. CONCLUSIONS: We have developed a self-report tool that effectively identifies individuals with moderate to severe coronary atherosclerosis. The self-report tool may serve as prescreening tool toward a cost-effective computed tomography-based screening program for high-risk individuals.
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19. |
- Björkman, Stina, et al.
(author)
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Microvascular dysfunction in women with a history of hypertensive disorders of pregnancy: A population-based retrospective cohort study
- 2024
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In: British Journal of Obstetrics and Gynecology. - : WILEY. - 1470-0328 .- 1471-0528. ; 131:4, s. 433-443
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Journal article (peer-reviewed)abstract
- ObjectiveTo evaluate microvascular function in women with previous hypertensive disorders of pregnancy (HDP).DesignRetrospective population-based cohort study.SettingLinkoping, Sweden.PopulationWomen aged 50-65 years, participating in the Swedish CArdioPulmonary bioImage Study (SCAPIS) at one site (Linkoping) 2016-18, who underwent microcirculatory assessment (N = 1222).MethodsForearm skin comprehensive microcirculatory assessment was performed with a PeriFlux PF6000 EPOS (Enhanced Perfusion and Oxygen Saturation) system measuring oxygen saturation and total speed resolved perfusion. Obstetric records were reviewed to identify women with previous HDP. Data on cardiovascular risk factors, comorbidities, medication, lifestyle, anthropometric data, and biochemical analyses were obtained from SCAPIS. The microcirculatory data were compared between women with and without previous HDP.Main outcome measuresSkin microcirculatory oxygen saturation and total speed resolved perfusion at baseline and post-ischaemic peak.ResultsWomen with previous pre-eclampsia displayed impaired post-ischaemic peak oxygen saturation compared with women with normotensive pregnancies (88%, interquartile range [IQR] 84-89% vs 91%, IQR 87-94%, p = 0.001) 6-30 years after pregnancy. The difference remained after multivariable adjustment (& beta; -2.69, 95% CI -4.93 to -0.45).ConclusionsThe findings reveal microvascular dysfunction at long-term follow up in women with previous pre-eclampsia and strengthen the possible role of endothelial dysfunction as a link to the increased risk of cardiovascular disease in women with HDP.
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20. |
- Bonander, Carl, et al.
(author)
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The value of combining individual and small area sociodemographic data for assessing and handling selective participation in cohort studies: Evidence from the Swedish CardioPulmonary bioImage Study
- 2022
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 17:3
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Journal article (peer-reviewed)abstract
- Objectives To study the value of combining individual- and neighborhood-level sociodemographic data to predict study participation and assess the effects of baseline selection on the distribution of metabolic risk factors and lifestyle factors in the Swedish CardioPulmonary bioImage Study (SCAPIS). Methods We linked sociodemographic register data to SCAPIS participants (n = 30,154, ages: 50-64 years) and a random sample of the study's target population (n = 59,909). We assessed the classification ability of participation models based on individual-level data, neighborhood-level data, and combinations of both. Standardized mean differences (SMD) were used to examine how reweighting the sample to match the population affected the averages of 32 cardiopulmonary risk factors at baseline. Absolute SMDs >0.10 were considered meaningful. Results Combining both individual-level and neighborhood-level data gave rise to a model with better classification ability (AUC: 71.3%) than models with only individual-level (AUC: 66.9%) or neighborhood-level data (AUC: 65.5%). We observed a greater change in the distribution of risk factors when we reweighted the participants using both individual and area data. The only meaningful change was related to the (self-reported) frequency of alcohol consumption, which appears to be higher in the SCAPIS sample than in the population. The remaining risk factors did not change meaningfully. Conclusions Both individual- and neighborhood-level characteristics are informative in assessing study selection effects. Future analyses of cardiopulmonary outcomes in the SCAPIS cohort can benefit from our study, though the average impact of selection on risk factor distributions at baseline appears small.
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21. |
- Briers, David, et al.
(author)
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Laser speckle contrast imaging: theoretical and practical limitations
- 2013
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In: Journal of Biomedical Optics. - : Society of Photo-optical Instrumentation Engineers (SPIE). - 1083-3668 .- 1560-2281. ; 18:6
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Journal article (peer-reviewed)abstract
- When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide information about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale-the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle contrast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimensional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its limitations and problems are investigated. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
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22. |
- Brännström, Sara, et al.
(author)
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Bioråvara till plast : nuläge och trender
- 2022
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Reports (other academic/artistic)abstract
- I denna rapport presenteras möjliga bioråvaror som kan användas för att producera biobaserad plast och potentiella plastalternativ som är under utveckling eller redan finns tillgängliga på marknaden. Kartläggningen har utgjorts av litteraturgranskning samt intervjuer med olika aktörer inom området.Kartläggningen av bioråvarupotentialen hade fokus på råvara från skog, jordbruk, hav samt från biologiskt avfall. Generellt framgår att potentialen är störst för skogsbaserad råvara, följt av jordbruksbaserad råvara och biologiskt avfall, medan potentialen för havsbaserad råvara är minst. Projektet har kartlagt vilken produktionskapacitet som finns tillgänglig för biobaserad plast, främst avseende drop-in-plaster, som är direkt utbytbara med etablerade plaster, men även ersättningsplaster. Globalt är idag endast cirka en procent av plastproduktionen biobaserad. En övervägande del av dagens petrokemibaserade plaster produceras helt eller delvis via krackning av nafta och av det följer att om man kan konvertera biomassa in i det flödet får man in biobaserad råvara i alla dessa plaster, således för polyeten (PE), liksom för polypropen (PP) och polyetentereftalat (PET), som är de tre mängdmässigt största plastsorterna. Biobaserade plaster med annan molekylstruktur än dagens högvolymplaster, här kallat ersättningsplaster, är ännu ganska sparsamt förekommande på marknaden. Det är främst polymjölksyra (PLA) som används, och produktionskapaciteten ökar globalt. En slutsats som dras i studien är att det pågår lovande utveckling och en långsam men stadig ökning av biobaserad plast, men att det är först runt 2030, och därefter, som bioråvara till plast, och plast från bioråvara, kommer att vara tillgänglig i större mängder.
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23. |
- Colantonio, Sara, et al.
(author)
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SEMEOTICONS - READING THE FACE CODE OF CARDIO-METABOLIC RISK
- 2015
-
In: 2015 INTERNATIONAL WORKSHOP ON COMPUTATIONAL INTELLIGENCE FOR MULTIMEDIA UNDERSTANDING (IWCIM). - : IEEE. - 9781467384575
-
Conference paper (peer-reviewed)abstract
- What if you could discover your health status by looking at yourself in the mirror? Since November 2013, the EU FP7 Project SEMEOTICONS is working to make this possible. The Project is building a multi-sensory device, having the form of a conventional mirror, able to read the semeiotic code of the face and detect possible evidence of the onset of cardio-metabolic diseases. The device, called Wize Mirror, integrates unobtrusive imaging sensors used to capture videos, images and 3D scans of the face. These are processed to assess the risk of a cardio-metabolic disease and thereby suggest possible strategies to prevent its onset.
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24. |
- Danielis, Alessandro, et al.
(author)
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Lip segmentation based on Lambertian shadings and morphological operators for hyper-spectral images
- 2017
-
In: Pattern Recognition. - : ELSEVIER SCI LTD. - 0031-3203 .- 1873-5142. ; 63, s. 355-370
-
Journal article (peer-reviewed)abstract
- Lip segmentation is a non-trivial task because the colour difference between the lip and the skin regions maybe not so noticeable sometimes. We propose an automatic lip segmentation technique for hyper-spectral images from an imaging prototype with medical applications. Contrarily to many other existing lip segmentation methods, we do not use colour space transformations to localise the lip area. As input image, we use for the first time a parametric blood concentration map computed by using narrow spectral bands. Our method mainly consists of three phases: (i) for each subject generate a subset of face images enhanced by different simulated Lambertian illuminations, then (ii) perform lip segmentation on each enhanced image by using constrained morphological operations, and finally (iii) extract features from Fourier-based modeled lip boundaries for selecting the lip candidate. Experiments for testing our approach are performed under controlled conditions on volunteers and on a public hyper-spectral dataset. Results show the effectiveness of the algorithm against low spectral range, moustache, and noise.
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25. |
- Drobni, Mirva, et al.
(author)
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A host-derived pentapeptide enhancing host-bacteria commensalisms and communication
- 2006
-
In: Infection and Immunity. - Washington : American society for microbiology. - 0019-9567 .- 1098-5522. ; 74:11, s. 6293-6299
-
Journal article (peer-reviewed)abstract
- Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordond. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif and selectively stimulated oral colonization of this organism in a rat model in vivo. In contrast, the growth of Streptococcus mutans, implicated in caries, was not affected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated the pH increase (i.e., ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PR-P degradation and Arg catabolism, whereas cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition, and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 of 10 strains) but not of S. gordonii (n = 5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordond to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacterium interaction in which a host peptide released by bacterial proteolysis affects key properties in biofilm formation.
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26. |
- Drobni, Mirva, et al.
(author)
-
Host-derived pentapeptide affecting adhesion, proliferation, and local pH in biofilm communities composed of Streptococcus and Actinomyces species.
- 2006
-
In: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 74:11, s. 6293-6299
-
Journal article (peer-reviewed)abstract
- Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordonii. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif and selectively stimulated oral colonization of this organism in a rat model in vivo. In contrast, the growth of Streptococcus mutans, implicated in caries, was not affected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated the pH increase (i.e., ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PRP degradation and Arg catabolism, whereas cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition, and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 of 10 strains) but not of S. gordonii (n=5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordonii to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacterium interaction in which a host peptide released by bacterial proteolysis affects key properties in biofilm formation.
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27. |
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28. |
- Eriksson, Christer, et al.
(author)
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Variant size- and glycoforms of the scavenger receptor cysteine-rich protein gp-340 with differential bacterial aggregation
- 2007
-
In: Glycoconjugate Journal. - : Springer Science and Business Media LLC. - 1573-4986 .- 0282-0080. ; 24:2-3, s. 131-142
-
Journal article (peer-reviewed)abstract
- Glycoprotein gp-340 aggregates bacteria in saliva as part of innate defence at mucosal surfaces. We have detected size- and glycoforms of gp-340 between human saliva samples (n=7) and lung gp-340 from a proteinosis patient using antibodies and lectins in Western blots and ELISA measurements. Western blots of saliva samples, and of gp-340 purified, from the seven donors using a gp-340 specific antibody distinguished four gp-340 size variants, designated I to IV (n=2,2,2 and 1). While saliva gp-340 variants I to III had single bands of increasing sizes, variant IV and lung gp-340 had double bands. Purified I to IV proteins all revealed a N-terminal sequence TGGWIP upon Edman degradation. Moreover, purified gp-340 from the seven donors and lung gp-340 shared N-glycans, sialylated Gal beta 1-3GalNAc and (poly)lactosamine structures. However, the larger size gp-340 grouping II/III (n=4) and smaller size grouping I/IV correlated with a secretor, Se(+), and a non secretor, Se(-), dependent glycoform of gp-340, respectively (p=0.03). The Se(+) glycoforms contained ABH, Le(b), Le(y) and polylactosamine structures, while the Se(-) glycoforms lacked ABH antigens but expressed Lea, Lex and lactosamine structures. By contrast, lung gp- 340 completely lacked ABH, Le(a/b), Le(x/y) or sLe(x) structures. Gp-340 and secretor typing of saliva from additional donors (n=29) showed gp-340 glycoforms I to IV for 6, 16, 4 and 0 donors, respectively, and 3 non-typeable donors, and verified that gp-340 glycoforms I and II/III correlate with Se(-) and Se(+) phenotypes, respectively (p < 0.0001). The glycoforms of saliva and lung gp-340 mediated differential aggregation of Le(b)-(Helicobacter pylori), sialylpolylactosamine(Streptococcus suis) or sialic acid- (Streptococcus mutans) binding bacteria. In conclusion, variant size- and glycoforms of gp-340 are expressed by different individuals and may modulate the biological properties of gp-340 pertinent to health and disease.
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29. |
- Ewerlöf, Maria, et al.
(author)
-
Estimating skin blood saturation by selecting a subset of hyperspectral imaging data
- 2015
-
In: Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XIII. - SPIE : SPIE. - 9781628414189
-
Conference paper (peer-reviewed)abstract
- Skin blood haemoglobin saturation (?b) can be estimated with hyperspectral imaging using the wavelength (λ) range of 450-700 nm where haemoglobin absorption displays distinct spectral characteristics. Depending on the image size and photon transport algorithm, computations may be demanding. Therefore, this work aims to evaluate subsets with a reduced number of wavelengths for ?b estimation. White Monte Carlo simulations are performed using a two-layered tissue model with discrete values for epidermal thickness (?epi) and the reduced scattering coefficient (μ's ), mimicking an imaging setup. A detected intensity look-up table is calculated for a range of model parameter values relevant to human skin, adding absorption effects in the post-processing. Skin model parameters, including absorbers, are; μ's (λ), ?epi, haemoglobin saturation (?b), tissue fraction blood (?b) and tissue fraction melanin (?mel). The skin model paired with the look-up table allow spectra to be calculated swiftly. Three inverse models with varying number of free parameters are evaluated: A(?b, ?b), B(?b, ?b, ?mel) and C(all parameters free). Fourteen wavelength candidates are selected by analysing the maximal spectral sensitivity to ?b and minimizing the sensitivity to ?b. All possible combinations of these candidates with three, four and 14 wavelengths, as well as the full spectral range, are evaluated for estimating ?b for 1000 randomly generated evaluation spectra. The results show that the simplified models A and B estimated ?b accurately using four wavelengths (mean error 2.2% for model B). If the number of wavelengths increased, the model complexity needed to be increased to avoid poor estimations.
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30. |
- Ewerlöf, Maria, 1987-, et al.
(author)
-
Estimation of skin microcirculatory hemoglobinoxygen saturation and red blood cell tissue fractionusing a multispectral snapshot imaging system : a validation study
- 2021
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In: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 26:2
-
Journal article (peer-reviewed)abstract
- Significance: Hemoglobin oxygen saturation and red blood cell (RBC) tissue fraction are important parameters when assessing microvascular status. Functional information can be attained using temporally resolved measurements performed during stimulus–response protocols. Pointwise assessments can currently be conducted with probe-based systems. However, snapshot multispectral imaging (MSI) can be used for spatial–temporal measurements.Aim: To validate if hemoglobin oxygen saturation and RBC tissue fraction can be quantified using a snapshot MSI system and an inverse Monte Carlo algorithm.Approach: Skin tissue measurements from the MSI system were compared to those from a validated probe-based system during arterial and venous occlusion provocation on 24 subjects in the wavelength interval 450 to 650 nm, to evaluate a wide range of hemoglobin oxygen saturation and RBC tissue fraction levels.Results: Arterial occlusion results show a mean linear regression R2 = 0.958 for hemoglobin oxygen saturation. Comparing relative RBC tissue fraction during venous occlusion results in R2 = 0.925. The MSI system shows larger dynamic changes than the reference system, which might be explained by a deeper sampling including more capacitance vessels.Conclusions: The snapshot MSI system estimates hemoglobin oxygen saturation and RBC tissue fraction in skin microcirculation showing a high correlation (R2 > 0.9 in most subjects) with those measured by the reference method.
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31. |
- Ewerlöf, Maria, 1987-
(author)
-
Multispectral imaging of hemoglobin oxygen saturation in skin microcirculation
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The ability to measure microcirculatory parameters such as hemoglobin oxygen saturation is important since it mirrors the microcirculatory state of the body. The microcirculation delivers oxygen and nutrients to the cells of the body and, if impaired, may be a sign of circulatory failure. Human skin microcirculation can be accessed non-invasively with bio-optical technologies, where skin acts as a diagnostic window. Diffuse reflectance spectroscopy (DRS) is a technique that access skin microcirculatory parameters, especially hemoglobin oxygen saturation. Basic systems are fiber optic probebased and measure in one point, often in firm contact with the skin. Multispectral diffuse reflectance imaging (MSI) enables spatially resolved DRS, imaging skin optical parameters from spectrally resolved backscattered intensities. Spectral information detected by MSI systems contain information on, e.g., hemoglobin oxygen saturation and optical properties of the tissue. Both spatial and temporal resolved information of hemoglobin oxygen saturation is beneficial for better diagnostics in most clinical applications, e.g., to monitor progression of wound healing processes, or other microcirculatory diseases reflected in hemoglobin spectral changes. Analysis of acquired MSI multispectral data cubes to access information on tissue parameters with high contrast to these variations can be performed in several ways using models and simulations. Time resolved continuous measurements that are spectrally and spatially resolved generate large amounts of data, requiring both storage space and fast analysis. Reducing the number of wavelengths is one way to limit the amount of data, if it does not reduce the quality of interpreted results. Therefore, in my work, I investigated theoretically how to reduce the number of wavelengths, and later implemented my findings using a snapshot MSI camera. Monte Carlo (MC) simulations were used to estimate hemoglobin oxygen saturation from captured MSI data. I also performed temporally resolved in vivo measurements on healthy test subjects during vascular occlusion provocations with a 16-channel snapshot MSI system. The acquired data were analyzed using two different methods: inverse MC and trained artificial neural networks (ANNs). For inverse MC, the acquired spectrum was iteratively compared to simulated spectra, where different optical properties were used for the simulation, trying to find the best fit. ANNs were trained to intensity data measured with the MSI system, using concurrently measured hemoglobin oxygen saturation values from a validated probe-based system as target data. The results and outcome of this thesis indicate good possibility to accurately estimate hemoglobin oxygen saturation with as few as four wavelengths. Estimated hemoglobin oxygen saturation values from analysis of in vivo measurements from the 16-channel snapshot MSI camera show high conformance to values measured by the validated probe-based system. Using the ANN-approach reduces time for analysis of a 512 × 270-pixel image to 0.056 s, compared to 1 h 58 min required by the inverse MC algorithm to analyze the same data. The method enables real-time analysis, and is, consequently, preferable in many clinical situations.
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32. |
- Ewerlöf, Maria, 1987-, et al.
(author)
-
Multispectral snapshot imaging of skin microcirculatory hemoglobin oxygen saturation using artificial neural networks trained on in vivo data
- 2022
-
In: Journal of Biomedical Optics. - Bellingham, WA, United States : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 27:3
-
Journal article (peer-reviewed)abstract
- Significance: Developing algorithms for estimating blood oxygenation from snapshot multispectral imaging (MSI) data is challenging due to the complexity of sensor characteristics and photon transport modeling in tissue. We circumvent this using a method where artificial neural networks (ANNs) are trained on in vivo MSI data with target values from a point-measuring reference method.Aim: To develop and evaluate a methodology where a snapshot filter mosaic camera is utilized for imaging skin hemoglobin oxygen saturation (SO2), using ANNs.Approach: MSI data were acquired during occlusion provocations. ANNs were trained to estimate SO2 with MSI data as input, targeting data from a validated probe-based reference system. Performance of ANNs with different properties and training data sets was compared.Results: The method enables spatially resolved estimation of skin tissue SO2. Results are comparable to those acquired using a Monte-Carlo-based approach when relevant training data are used.Conclusions: Training an ANN on in vivo MSI data covering a wide range of target values acquired during an occlusion protocol enable real-time estimation of SO2 maps. Data from the probe-based reference system can be used as target despite differences in sampling depth and measurement position.
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33. |
- Faresjö, Tomas, et al.
(author)
-
Elevated levels of cortisol in hair precede acute myocardial infarction
- 2020
-
In: Scientific Reports. - : NATURE RESEARCH. - 2045-2322. ; 10:1
-
Journal article (peer-reviewed)abstract
- Long term stress exposure is typical for modern societies and might trigger different diseases. This case-control study reveals that persons who had suffered an acute myocardial infarction (AMI) had elevated cortisol concentrations in the month before the acute event. Middle-aged patients admitted to cardiology clinics with acute myocardial infarction (AMI) (n=174) were compared to 3156 controls from a population-based cohort in southeast Sweden. The median Hair Cortisol Concentrations (HCC) for those who had suffered an AMI was 53.2 pg/mg compared to 22.2 pg/mg for the control group (p<0.001). In bivariate analysis, higher levels of HCC were strongly (OR=5.69) and statistically significantly associated with current AMI status. The discrimination of cases with AMI from controls remained statistically significant (OR=5.04) even after controlling for established cardiovascular risk factors in a multivariate analysis. Middle-aged persons with acute myocardial infarction had significantly elevated cortisol levels during the month before the cardiac event. This was evident for both men and women. The biomarker cortisol concentration was independently and statistically significantly related to AMI. Chronic stress seems to be a new promising risk factor for AMI.
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34. |
- Fellman, Vineta, et al.
(author)
-
One-year survival of extremely preterm infants after active perinatal care in Sweden.
- 2009
-
In: JAMA : the journal of the American Medical Association. - : American Medical Association (AMA). - 1538-3598 .- 0098-7484. ; 301:21, s. 2225-33
-
Journal article (peer-reviewed)abstract
- Up-to-date information on infant survival after extremely preterm birth is needed for assessing perinatal care services, clinical guidelines, and parental counseling.
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35. |
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36. |
- Fredriksson, Ingemar, et al.
(author)
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Absolute flow velocity components in laser Doppler flowmetry
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : IEEE. - 0277-786X .- 1996-756X. ; 6094, s. 60940A-
-
Journal article (peer-reviewed)abstract
- A method to separate a Doppler power spectrum into a number of flow velocity components, measured in absolute units (mm/s), is presented. A Monte Carlo software was developed to track each individual Doppler shift, to determine the probability, p(n), for a photon to undergo n Doppler shifts. Given this shift distribution, a mathematical relationship was developed and used to calculate a Doppler power spectrum originating from a certain combination of velocity components. The non linear Levenberg-Marquardt optimization method could thus be used to fit the calculated and measured Doppler power spectra, giving the true set of velocity components in the measured sample. The method was evaluated using a multi tube flow phantom perfused with either polystyrene microspheres or undiluted/diluted human blood (hct = 0.45). It estimated the velocity components in the flow phantom well, during both low and high concentrations of moving scatterers (microspheres or blood). Thus, further development of the method could prove to be a valuable clinical tool to differentiate capillary blood flow.
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37. |
- Fredriksson, Ingemar, et al.
(author)
-
Accuracy of vessel diameter estimated from a vessel packaging compensation in diffuse reflectance spectroscopy
- 2011
-
In: Clinical and Biomedical Spectroscopy and Imaging II. - : SPIE - International Society for Optical Engineering. - 9780819486837 ; , s. 8087 1M-1-8087 1M-8
-
Conference paper (other academic/artistic)abstract
- Light absorption in tissue is generally decreased when chromophores are spatially concentrated rather than being homogeneously distributed. In tissue, this applies to hemoglobin located in blood vessels (vessel packaging). In this paper, the diffusely reflected light from 41 tissue models with discrete blood vessels with diameters ranging from 6.25 to 100 μm were simulated using the Monte Carlo technique. A reverse engineering approach was then utilized to find the model that had an optimal spectral fit to each of the simulated models. The average vessel diameter was one fitting parameter in the adaptive model. The estimated vessel diameter from the optimal fit model was compared to the known diameter from the simulated models. Two different methods to calculate the vessel packaging effect were used, one existing based on a simple analytic expression and a new method based on path length distributions. Both methods had similar performance. For the new method, the absolute RMS deviation of the estimated vessel diameter was 5.5 μm for vessel diameters ≤ 25 μm, and the relative RMS deviation was 21 % for vessel diameters > 25 μm.
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38. |
- Fredriksson, Ingemar, et al.
(author)
-
Evaluation of a multi-layer diffuse reflectance spectroscopy system using optical phantoms
- 2017
-
In: DESIGN AND QUALITY FOR BIOMEDICAL TECHNOLOGIES X. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510605534 - 9781510605541
-
Conference paper (peer-reviewed)abstract
- A fiber probe-based device for assessing microcirculatory parameters, especially red blood cell (RBC) tissue fraction, their oxygen saturation and speed resolved perfusion, has been evaluated using state-of-the-art multi-layer tissue simulating phantoms. The device comprises both diffuse reflectance spectroscopy (DRS) at two source-detector separations (0.4 and 1.2 mm) and laser Doppler flowmetry (LDF) and use an inverse Monte Carlo method for identifying the parameters of a multi-layered tissue model. First, model parameters affecting scattering, absorption and geometrical parameters are fitted to measured DRS spectra, then speed parameters are fitted to LDF spectra. In this paper, the accuracy of the spectral parameters is evaluated. The measured spectral shapes at the two source-detector separations were in good agreement with forward calculated spectral shapes. In conclusion, the multi-layer skin model based on spectral features of the included chromophores, can reliably estimate the tissue fraction of RBC, its oxygen saturation and the reduced scattering coefficient spectrum of the tissue. Furthermore, it was concluded that some freedom in the relative intensity difference between the two DRS channels is necessary in order to compensate for non-modeled surface structure effects.
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39. |
- Fredriksson, Ingemar, et al.
(author)
-
Evaluation of a pointwise microcirculation assessment method using liquid and multilayered tissue simulating phantoms
- 2017
-
In: Journal of Biomedical Optics. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1083-3668 .- 1560-2281. ; 22:11
-
Journal article (peer-reviewed)abstract
- A fiber-optic probe-based instrument, designed for assessment of parameters related to microcirculation, red blood cell tissue fraction (f(RBC)), oxygen saturation (S-O2), and speed resolved perfusion, has been evaluated using state-of-the-art tissue phantoms. The probe integrates diffuse reflectance spectroscopy (DRS) at two source-detector separations and laser Doppler flowmetry, using an inverse Monte Carlo method for identifying the parameters of a multilayered tissue model. Here, we characterize the accuracy of the DRS aspect of the instrument using (1) liquid blood phantoms containing yeast and (2) epidermis-dermis mimicking solid-layered phantoms fabricated from polydimethylsiloxane, titanium oxide, hemoglobin, and coffee. The rootmean-square (RMS) deviations for f(RBC) for the two liquid phantoms were 11% and 5.3%, respectively, and 11% for the solid phantoms with highest hemoglobin signatures. The RMS deviation for SO2 was 5.2% and 2.9%, respectively, for the liquid phantoms, and 2.9% for the solid phantoms. RMS deviation for the reduced scattering coefficient (mus), for the solid phantoms was 15% (475 to 850 nm). For the liquid phantoms, the RMS deviation in average vessel diameter (D) was 1 mu m. In conclusion, the skin microcirculation parameters fRBC and SO2, as well as, mu(s) and D are estimated with reasonable accuracy. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
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40. |
- Fredriksson, Ingemar, et al.
(author)
-
Forced detection Monte Carlo algorithms for accelerated blood vessel image simulations
- 2009
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In: JOURNAL OF BIOPHOTONICS. - : Wiley. - 1864-063X .- 1864-0648. ; 2:3, s. 178-184
-
Journal article (peer-reviewed)abstract
- Two forced detection (FD) variance reduction Monte Carlo algorithms for image simulations of tissue-embedded objects with matched refractive index are presented. The principle of the algorithms is to force a fraction of the photon weight to the detector at each and every scattering event. The fractional weight is given by the probability for the photon to reach the detector without further interactions. Two imaging setups are applied to a tissue model including blood vessels, where the ID algorithms produce identical results as traditional brute force simulations, while being accelerated with two orders of magnitude. Extending the methods to include refraction mismatches is discussed. The principle of forced detection; a part of the photon weight. based on the probability of reaching the detector without further interactions, is forced to the detector at each and every scattering event.
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41. |
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42. |
- Fredriksson, Ingemar, et al.
(author)
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Improved calibration procedure for laser Doppler perfusion monitors
- 2011
-
In: Optical Diagnostics and SensingXI: Toward Point-of-CareDiagnostics; and Design andPerformance Validation ofPhantoms Used in Conjunctionwith Optical Measurement ofTissue III. - : SPIE - International Society for Optical Engineering. - 9780819484437 ; , s. 790602-1-790602-7
-
Conference paper (other academic/artistic)abstract
- Commercial laser Doppler perfusion monitors are calibrated using the perfusion value, i.e. the first order moment of the Doppler power spectrum, from a measurement in a standardized microsphere colloidal suspension under Brownian motion. The calibration perfusion value depends on several parameters of the suspension that are difficult to keep constant with adequate accuracy, such as the concentration, temperature and the microsphere size distribution. The calibration procedure itself may therefore introduce significant errors in the measured values.An altered calibration procedure, where the zero order moment is used is described and demonstrated in this paper. Since the above mentioned parameters only affect the frequency content of the Doppler power spectrum and not the total power, the zero order moment will be independent of those parameters. It is shown that the variation in the calibration value, as given by measurements on different scattering liquids with a wide range of scattering properties and temperatures, is only a few percent using the proposed method. For the conventional calibration procedure, this variation corresponds to an error introduced by merely a 1°C variation in the reference liquid temperature. The proposed calibration method also enables absolute level comparisons between measured and simulated Doppler power spectra.
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43. |
- Fredriksson, Ingemar, 1980-, et al.
(author)
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Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry
- 2013
-
In: Journal of Biomedical Optics. - Bellingham, WA, United States : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 18:12, s. 127004-1-127004-14
-
Journal article (peer-reviewed)abstract
- The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion areestimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry(LDF). The DRS spectra (450 to 850 nm) are assessed at two source–detector separations (0.4 and 1.2 mm), allowingfor a relative calibration routine, whereas LDF spectra are assessed at 1.2mmin the same fiber-optic probe. Data areanalyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayeredtissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information.Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluatethe method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations arepresented. The method offers several advantages such as simultaneous quantification of RBC tissue fractionand oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speedresolved, absolute (% RBC × mm∕s), and more accurate due to the combination with DRS.
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44. |
- Fredriksson, Ingemar, et al.
(author)
-
Inverse Monte Carlo method in a multilayered tissue model for diffuse reflectance spectroscopy
- 2012
-
In: Journal of Biomedical Optics. - 1083-3668 .- 1560-2281. ; 17:4, s. 047004-
-
Journal article (peer-reviewed)abstract
- Model based data analysis of diffuse reflectance spectroscopy data enables the estimation of optical and structural tissue parameters. The aim of this study was to present an inverse Monte Carlo method based on spectra from two source-detector distances (0.4 and 1.2 mm), using a multilayered tissue model. The tissue model variables include geometrical properties, light scattering properties, tissue chromophores such as melanin and hemoglobin, oxygen saturation and average vessel diameter. The method utilizes a small set of presimulated Monte Carlo data for combinations of different levels of epidermal thickness and tissue scattering. The path length distributions in the different layers are stored and the effect of the other parameters is added in the post-processing. The accuracy of the method was evaluated using Monte Carlo simulations of tissue-like models containing discrete blood vessels, evaluating blood tissue fraction and oxygenation. It was also compared to a homogeneous model. The multilayer model performed better than the homogeneous model and all tissue parameters significantly improved spectral fitting. Recorded in vivo spectra were fitted well at both distances, which we previously found was not possible with a homogeneous model. No absolute intensity calibration is needed and the algorithm is fast enough for real-time processing.
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45. |
- Fredriksson, Ingemar, 1980-, et al.
(author)
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Laser doppler flowmetry
- 2012
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In: Microcirculation imaging. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 3527328947 - 9783527328949 - 9783527651238 ; , s. 67-86
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Book chapter (other academic/artistic)abstract
- Adopting a multidisciplinary approach with input from physicists, researchers and medical professionals, this is the first book to introduce many different technical approaches for the visualization of microcirculation, including laser Doppler and laser speckle, optical coherence tomography and photo-acoustic tomography. It covers everything from basic research to medical applications, providing the technical details while also outlining the respective strengths and weaknesses of each imaging technique. Edited by an international team of top experts, this is the ultimate handbook for every clinician and researcher relying on microcirculation imaging.
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46. |
- Fredriksson, Ingemar, et al.
(author)
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Machine learning for direct oxygen saturation and hemoglobin concentration assessment using diffuse reflectance spectroscopy
- 2020
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In: Journal of Biomedical Optics. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1083-3668 .- 1560-2281. ; 25:11
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Journal article (peer-reviewed)abstract
- Significance: Diffuse reflectance spectroscopy (DRS) is frequently used to assess oxygen saturation and hemoglobin concentration in living tissue. Methods solving the inverse problem may include time-consuming nonlinear optimization or artificial neural networks (ANN) determining the absorption coefficient one wavelength at a time. Aim: To present an ANN-based method that directly outputs the oxygen saturation and the hemoglobin concentration using the shape of the measured spectra as input. Approach: A probe-based DRS setup with dual source-detector separations in the visible wavelength range was used. ANNs were trained on spectra generated from a three-layer tissue model with oxygen saturation and hemoglobin concentration as target. Results: Modeled evaluation data with realistic measurement noise showed an absolute root-mean-square (RMS) deviation of 5.1% units for oxygen saturation estimation. The relative RMS deviation for hemoglobin concentration was 13%. This accuracy is at least twice as good as our previous nonlinear optimization method. On blood-intralipid phantoms, the RMS deviation from the oxygen saturation derived from partial oxygen pressure measurements was 5.3% and 1.6% in two separate measurement series. Results during brachial occlusion showed expected patterns. Conclusions: The presented method, directly assessing oxygen saturation and hemoglobin concentration, is fast, accurate, and robust to noise. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.
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47. |
- Fredriksson, Ingemar, et al.
(author)
-
Machine learning in multiexposure laser speckle contrast imaging can replace conventional laser Doppler flowmetry
- 2019
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In: Journal of Biomedical Optics. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1083-3668 .- 1560-2281. ; 24:1
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Journal article (peer-reviewed)abstract
- Laser speckle contrast imaging (LSCI) enables video rate imaging of blood flow. However, its relation to tissue blood perfusion is nonlinear and depends strongly on exposure time. By contrast, the perfusion estimate from the slower laser Doppler flowmetry (LDF) technique has a relationship to blood perfusion that is better understood. Multiexposure LSCI (MELSCI) enables a perfusion estimate closer to the actual perfusion than that using a single exposure time. We present and evaluate a method that utilizes contrasts from seven exposure times between 1 and 64 ms to calculate a perfusion estimate that resembles the perfusion estimate from LDF. The method is based on artificial neural networks (ANN) for fast and accurate processing of MELSCI contrasts to perfusion. The networks are trained using modeling of Doppler histograms and speckle contrasts from tissue models. The importance of accounting for noise is demonstrated. Results show that by using ANN, MELSCI data can be processed to LDF perfusion with high accuracy, with a correlation coefficient R = 1.000 for noise-free data, R = 0.993 when a moderate degree of noise is present, and R = 0.995 for in vivo data from an occlusion-release experiment. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.
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48. |
- Fredriksson, Ingemar, et al.
(author)
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Measurement depth and volume in laser Doppler flowmetry
- 2009
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In: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 78:1, s. 4-13
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Journal article (peer-reviewed)abstract
- A new method for estimating the measurement depth and volume in laser Doppler flowmetry (LDF) is presented. The method is based on Monte Carlo simulations of light propagation in tissue. The contribution from each individual Doppler shift is calculated and thereby multiple Doppler shifts are handled correctly. Different LDF setups for both probe based (0.0, 0.25, 0.5, and 1.2 mm source-detector separation) and imaging systems (0.5 and 2.0 mm beam diameter) are considered, at the wavelengths 543 nm, 633 nm, and 780 nm. Non-linear speckle pattern effects are accounted for in the imaging system setups. The effects of tissue optical properties, blood concentration, and blood oxygen saturation are evaluated using both homogeneous tissue models and a layered skin model. The results show that the effect on the measurement depth of changing tissue properties is comparable to the effect of changing the system setup, e.g. source-detector separation and wavelength. Skin pigmentation was found to have a negligible effect on the measurement depth. Examples of measurement depths are (values are given for a probe based system with 0.25 mm source-detector separation and an imaging system with a 0.5 mm beam diameter, respectively, both operating at 780 nm): muscle - 0.55/0.79 mm; liver - 0.40/0.53 mm; gray matter - 0.48/0.68 mm; white matter - 0.20/0.20 mm; index finger pulp - 0.41/0.53 mm; forearm skin - 0.53/0.56 mm; heat provoked forearm skin - 0.66/0.67 mm.
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49. |
- Fredriksson, Ingemar, 1980-, et al.
(author)
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Microcirculatory changes in type 2 diabetes assessed with velocity resolved quantitative laser Doppler flowmetry
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Other publication (other academic/artistic)abstract
- The response to local heating (44oC for 20 min) was evaluated in 28 type 2 diabetes patients (DM) and 29 non-diabetes controls (ND). Microcirculatory perfusion was assessed using conventional and quantitative Laser Doppler flowmetry (cLDF and qLDF), respectively. The qLDF estimates perfusion in a physiological relevant unit (g RBC / 100 g tissue × mm/s) in a fixed output volume, separated into three velocity regions, v < 1 mm/s, 1 - 10 mm/s, and v > 10 mm/s. Perfusion in cLDF is given in arbitrary units with unknown velocity distribution and measurement volume. A significantly lower response in DM than in ND was found after heat provocation both for the initial peak and the plateau response, while no significant differences were found at baseline. The qLDF showed increased perfusion for the velocity regions 1-10 mm/s and above 10 mm/s, while no significant increase was found for v < 1 mm/s. In conclusion, we found a lowered LDF response to local heating in DM. The new qLDF method showed that the increased blood flow occurs in vessels with a velocity above 1 mm/s. Baseline qLDF-data indicated that a redistribution of flow to higher velocity regions was associated with longer DM duration and for DM a negative correlation between perfusion and BMI.
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50. |
- Fredriksson, Ingemar, 1980-, et al.
(author)
-
Model-based quantification of skin microcirculatory perfusion
- 2015. - 1
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In: Computational biophysics of the skin. - Boca Raton : CRC Press. - 9789814463843 - 9789814463850 ; , s. 395-418
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Book chapter (other academic/artistic)abstract
- During the last decades new tools, such as magnetic resonance imaging and Doppler ultra sound imaging, have rapidly been taken into clinical practice for studying the flow dynamics of the macrocirculation. M eanw hile, techniques for quantifying the microcirculation have struggled to become clinically accepted. This includes the use of laser Doppler flow metry (LDF), an optical technique that is capable of monitoring either spatial or temporal changes in the microcirculation by analyzing the backscattered Doppler shifted light from a laser illuminated tissue. Until now , LDF has only been capable of producing non-absolute relative measures, w hich has limited its cl inical acceptance. With a model based analysis approach, as presented here, this can be overcome, and objective diagnosis of the microcirculation may finally be a part of everyday clinical praxis. The most important advantages w ith the proposed method are that a quantitative perfusion estimate (% RBC × mm/ s) can be extracted, and that this measure can be resolved into different speed regions.
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