| 1. |
- Bergkvist, Max, 1976-, et al.
(författare)
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Vascular Occlusion in a Porcine Flap Model : Effects on Blood Cell Concentration and Oxygenation.
- 2017
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Ingår i: Plastic and Reconstructive Surgery - Global Open. - : Wolters Kluwer. - 2169-7574. ; 5:11
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Tidskriftsartikel (refereegranskat)abstract
- Background: Venous congestion in skin flaps is difficult to detect. This study evaluated the ability of tissue viability imaging (TiVi) to measure changes in the concentration of red blood cells (CRBC), oxygenation, and heterogeneity during vascular provocations in a porcine fasciocutaneous flap model.Methods: In 5 pigs, cranial gluteal artery perforator flaps were raised (8 flaps in 5 pigs). The arterial and venous blood flow was monitored with ultrasonic flow probes. CRBC, tissue oxygenation, and heterogeneity in the skin were monitored with TiVi during baseline, 50% and 100% venous occlusion, recovery, 100% arterial occlusion and final recovery, thereby simulating venous and arterial occlusion of a free fasciocutaneous flap. A laser Doppler probe was used as a reference for microvascular perfusion in the flap.Results: During partial and complete venous occlusion, increases in CRBC were seen in different regions of the flap. They were more pronounced in the distal part. During complete arterial occlusion, CRBC decreased in all but the most distal parts of the flap. There were also increases in tissue oxygenation and heterogeneity during venous occlusion.Conclusions: TiVi measures regional changes in CRBC in the skin of the flap during arterial and venous occlusion, as well as an increase in oxygenated hemoglobin during venous occlusion that may be the result of reduced metabolism and impaired delivery of oxygen to the tissue. TiVi may provide a promising method for measuring flap viability because it is hand-held, easy to-use, and provides spatial information on venous congestion.
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| 2. |
- Bergkvist, Max, et al.
(författare)
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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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Ingår i: Microvascular Research. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0026-2862 .- 1095-9319. ; 130
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Bergkvist, Max, 1976-
(författare)
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Studies on Polarised Light Spectroscopy
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis project focuses on measurements of dermal microcirculation during vascular provocations with polarised light spectroscopy. This is done with a non-invasive method commercially available as Tissue viability imaging (TiVi) which measures concentration and oxygenation of red blood cells in the papillary dermis. Three studies were done with human subjects and one with an animal model, to validate and compare the TiVi technique with laser Doppler flowmetry, which is an established method of measuring dermal microcirculation.The TiVi consists of a digital camera with polarisation filters in front of the flash and lens, with software for analysis of the picture. When taking a picture with the TiVi, the polarised light that is reflected on the skin surface is absorbed by the second filter over the lens (which is perpendicular to the first filter) but a portion of light penetrates the surface of the skin and is scattered when it is reflected on tissue components. This makes the light depolarised, passes the second filter, and produces a picture for analysis. The red blood cell (RBC) has a distinct absorption pattern that differs between red and green colour compared to melanin and other components of tissue. This difference is used by the software that calculates differences in each picture element and produces a measure of output which is proportional to the concentration of red blood cells. The oxygenation of RBC can also be calculated, as there is a difference in absorption depending on oxygen state.The first paper takes up possible sources of error such as ambient light, and the angle and distance of the camera. The main experiment was to investigate how the local heating reaction is detected with TiVi compared to LDF.In the second paper arterial and venous stasis are examined in healthy subjects with TiVi.The Third paper is an animal study where skin flaps were raised on pigs, and the vascular pedicle is isolated to enable control of inflow and outflow of blood.The measurements were made during partial venous, total venous, and total arterial occlusion. The TiVi recorded changes in the concentration of RBC, oxygenation and heterogeneity and the results were compared with those of laser Doppler flowmetry.In the fourth paper oxygenation and deoxygenation of RBC: s was studied. Studies were made on the forearms of healthy subjects who were exposed to arterial and venous occlusion. Simultaneous measurements were made with TiVi and Enhanced perfusion and oxygen saturation or EPOS, which is a new device that combines laser Doppler flowmetry and diffuse reflectance spectroscopy in one probe.With TiVi, one can measure RBC concentration and oxygenation in the area of an entire picture or in one or multiple user defined regions of interest (ROI). Methods such as laser Doppler flowmetry makes single point measurements, which is a potential source of error both because of the heterogeneity of the microcirculation, and that the circulation be insufficient in the margins of the investigated area. TiVi has been able to measure venous stasis more accurately than laser Doppler flowmetry, and venous stasis is the more common reason for flaps to fail.The TiVi is an accurate way to measure the concentration of RBC and trends in oxygenation of the dermal microcirculation. It has interesting possible applications for microvascular and dermatological research, monitoring of flaps, and diagnosis of peripheral vascular disease. Future clinical studies are needed as well as development of the user interface.
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| 4. |
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| 5. |
- Droog Tesselaar, Erik, 1977-
(författare)
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Assessment of microvascular function by use of transdermal iontophoresis : methodological aspects
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Assessment of the microcirculation is of major importance in understanding the physiology of the vasculature and in assessing te vascular effects of pathological conditions such as diabetes, hypertension and sepsis. Transdermal iontophoresis can be used to non‐invasively introduce vasoactive drugs into the skin. The response to these drugs of the local cutaneous microvasculature can be measured by laser Doppler flowmetry methods. Although these techniques have been used together for over two decades, there are still important methodological issues to be resolved. This work is aimed at optimizing transdermal iontophoresis as a tool for microvascular assessment by focusing on the main methdological issues: non‐specific vasodilatation, drug delivery protocols and analysis of blood flow data.Non‐specific vasodilatation, an increase blood flow during iontophoresis of non‐vasoactive compounds, is an important problem as it interferes with the response to the administered drug. By investigating this effect in healthy volunteers, we found that the extent of the non‐specific response differs between the positive and negative electrode and that it is dependent on the voltage over the skin andon the ionic strength of the vehicle in which the drug is dissolved. We also found that the extent of the non‐specific response could be reduced by applying local anesthetics and by pre‐treatment with antihistamine drugs. These results suggest that non‐specific effects could be mediated by depolarization or hyperpolarisation of cells, triggering neural and histamine related mechanisms that finally lead to vasodilatation of the local microvasculature.To prevent non‐specific effects from occurring during the experiments, our results show that the current strength and the total electric charge during iontophoresis should be limited to 0.02 mA and12 mC, respectively. Furthermore, drug solutions at physiological ionic strengths should be used. Under these conditions, adequate responses to the most commonly used drugs, acetylcholine (ACh) and sodium nitroprusside (SNP), are obtained while no significant non‐specific vasodilatation occurs.The results of our investigations show that blood responses to ACh and SNP applied by a single iontophoretic pulse can well be escribed by conventional dose‐response models, which enables a more powerful analysis and comparison between drugs or possibly patient groups as compared with conventional aalysis methods. Finally, we have incorporated drug transport and physiological response to the local drug concentration during iontophoresis of vasoactve drugs into a single model. Validation of this model using measured responses to ACh and SNP shows that the commonly used assumption that the local drug concentration during iontophoresis is linearly proportional to the electric charge may not be valid.
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| 6. |
- Droog Tesselaar, Erik, 1977-, et al.
(författare)
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Changes in skin microcirculation during radiation therapy for breast cancer
- 2017
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Ingår i: Acta Oncologica. - Oxfordshire : Taylor & Francis. - 0284-186X .- 1651-226X. ; 56:8, s. 1072-1080
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The majority of breast cancer patients who receive radiation treatment are affected by acute radiation-induced skin changes. The assessment of these changes is usually done by subjective methods, which complicates the comparison between different treatments or patient groups. This study investigates the feasibility of new robust methods for monitoring skin microcirculation to objectively assess and quantify acute skin reactions during radiation treatment.MATERIAL AND METHODS: Laser Doppler flowmetry, laser speckle contrast imaging, and polarized light spectroscopy imaging were used to measure radiation-induced changes in microvascular perfusion and red blood cell concentration (RBC) in the skin of 15 patients undergoing adjuvant radiation therapy for breast cancer. Measurements were made before treatment, once a week during treatment, and directly after the last fraction.RESULTS: In the treated breast, perfusion and RBC concentration were increased after 1-5 fractions (2.66-13.3 Gy) compared to baseline. The largest effects were seen in the areola and the medial area. No changes in perfusion and RBC concentration were seen in the untreated breast. In contrast, Radiation Therapy Oncology Group (RTOG) scores were increased only after 2 weeks of treatment, which demonstrates the potential of the proposed methods for early assessment of skin changes. Also, there was a moderate to good correlation between the perfusion (r = 0.52) and RBC concentration (r = 0.59) and the RTOG score given a week later.CONCLUSION: We conclude that radiation-induced microvascular changes in the skin can be objectively measured using novel camera-based techniques before visual changes in the skin are apparent. Objective measurement of microvascular changes in the skin may be valuable in the comparison of skin reactions between different radiation treatments and possibly in predicting acute skin effects at an earlier stage.
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| 7. |
- Elawa, Sherif, et al.
(författare)
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Microcirculatory changes in the skin after postmastectomy radiotherapy in women with breast cancer
- 2024
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Postmastectomy radiotherapy (PMRT) increases the risk for complications after breast reconstruction. The pathophysiological mechanism underlying this increased risk is not completely understood. The aim of this study was to examine if there is a relationship between PMRT and microvascular perfusion in the skin directly after, and at 2 and 6 months after PMRT and to assess if there is impaired responsiveness to a topically applied vasodilator (Methyl nicotinate-MN) after PMRT. Skin microvascular responses after PMRT were measured on two sites in the irradiated chest wall of 22 women before, immediately after, and at 2 and 6 months after unilateral PMRT with the contralateral breast as a control. A significant increase in basal skin perfusion was observed in the irradiated chest wall immediately after RT (p < 0.0001). At 2 and 6 months after RT, there was no longer a difference in basal skin perfusion compared to the contralateral breast and compared to baseline. Similarly, the blood flow response in the skin after application of MN was stronger immediately after RT compared to before RT (p < 0.0001), but there was no difference at later time points. These results indicate that the increased risk for complications after surgical procedures are not directly related to changes in skin perfusion and microvascular responsiveness observed after postmastectomy RT.
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| 8. |
- Elawa, Sherif, 1988-
(författare)
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Microvascular Function Assessment after Mastectomy and Radiation Therapy in Breast Cancer Patients : From Methodology to Clinical Application
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Post-mastectomy radiotherapy (PMRT) is an important part of the treatment of breast cancer. It reduces the risk of recurrence and improves overall survival. Scaring and fibrotization of the skin and subcutaneous tissue of the chest wall or remaining breast are among its side-effects. These late side-effects of PMRT may in turn affect skin microcirculation and oxygenation, although this connection is not completely established. In patients that later require breast reconstruction, it is difficult as a plastic surgeon to evaluate if the microcirculatory changes have been affected by PMRT, and how such effects should have an impact on the choice of reconstructive method. In the work presented in this thesis, laser speckle contrast imaging (LSCI), laser-doppler flowmetry (LDF) and diffuse reflectance spectroscopy (DRS) have been used with a strong vasodilator, methyl nicotinate (MN) to study the microcirculatory changes after PMRT.In studies I and II, we aimed to find the optimal concentration of MN and its main mechanisms of action. In healthy volunteers, the microvascular response to different concentrations of MN was evaluated on the forearm using LSCI. It was found that a concentration of 20 mmol/l resulted in a quick vasodilatory response with a long plateau phase, minimal tissue edema and no non-responders. In study II, we utilized locally administered drugs to block the three main pathways responsible for skin vasodilation. Subsequently, we provoked the skin with MN and assessed its effect with LSCI. From this study we could conclude that MN’s mechanism of action is largely mediated by prostaglandins and partly by local sensory nerves.In study III, we examined the skin microcirculatory response in breast cancer patients before, immediately after, and at two and six months following unilateral PMRT, using the contralateral breast as a control. A significant increase in basal skin perfusion and perfusion after application of MN was observed on the irradiated chest wall immediately after RT compared to the contralateral breast and compared to before RT. At six months after RT, there was no longer a difference in basal skin perfusion or after application of MN in the irradiated chest wall compared to the contralateral breast and compared to before RT was given. The results from this study concluded that skin perfusion in the irradiated chest wall had returned to normal when measured six months after RT.In study IV, the late effects on skin microvascular function were studied in women who had undergone mastectomy and PMRT several years prior to the study. Skin perfusion and oxygen saturation was measured with white light diffuse reflectance spectroscopy (DRS) combined with Laser Doppler Flowmetry (LDF) before and after application of MN on the irradiated chest wall with the contralateral non-irradiated breast as control. In this study we found that skin perfusion and oxygenation in the breast are affected several years after radiotherapy and that our method could be a valuable clinical tool prior to deciding surgical procedures after PMRT.To conclude, MN can be topically applied to the skin to reliably assess microvascular function and the microvascular capacity. LSCI and LDF have different strengths and drawbacks, with LSCI having the advantage of having a large spatial resolution that allows for measurements of control areas in the same field of view as the provoked areas. LDF in combination with DRS enabled us to further assess perfusion and oxygenation simultaneously which could be an advantage in fibrotic skin where skin perfusion and oxygen saturation may not correlate with each other. Although the study groups differed between the study examining the early effects of PMRT with the late effects of PMRT, we have been able to non-invasively visualize changes in microcirculation in relation to the acute and chronic phase after PMRT. Future studies are needed to investigate the value of pre-operative measurements with MN provocation for predicting surgical outcome.
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| 9. |
- Elawa, Sherif, et al.
(författare)
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Skin perfusion and oxygen saturation after mastectomy and radiation therapy in breast cancer patients
- 2024
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Ingår i: Breast. - : Elsevier. - 0960-9776 .- 1532-3080. ; 75
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Tidskriftsartikel (refereegranskat)abstract
- The pathophysiological mechanism behind complications associated with postmastectomy radiotherapy (PMRT) and subsequent implant-based breast reconstruction are not completely understood. The aim of this study was to examine if there is a relationship between PMRT and microvascular perfusion and saturation in the skin after mastectomy and assess if there is impaired responsiveness to a topically applied vasodilator (Methyl nicotinate - MN). Skin microvascular perfusion and oxygenation >2 years after PMRT were measured using white light diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) in the irradiated chest wall of 31 women with the contralateral breast as a control. In the non-irradiated breast, the perfusion after application of MN (median 0.84, 25th-75th centile 0.59-1.02 % RBC × mm/s) was higher compared to the irradiated chest wall (median 0.51, 25th-75th centile 0.21-0.68 % RBC × mm/s, p < 0.001). The same phenomenon was noted for saturation (median 91 %, 25th-75th centile 89-94 % compared to 89 % 25th-75th centile 77-93 %, p = 0.001). Eight of the women (26%) had a ≥10 % difference in skin oxygenation between the non-irradiated breast and the irradiated chest wall. These results indicate that late microvascular changes caused by radiotherapy of the chest wall significantly affect skin perfusion and oxygenation.
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| 10. |
- Elgström, Henrik, et al.
(författare)
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Signal-To-Noise Ratio Rate Measurement in Fluoroscopy For Quality Control and Teaching Good Radiological Imaging Technique
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 407-415
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Tidskriftsartikel (refereegranskat)abstract
- Visibility of low-contrast details in fluoroscopy and interventional radiology is important. Assessing detail visibility with human observers typically suffers from large observer variances. Objective, quantitative measurement of low-contrast detail visibility using a model observer, such as the square of the signal-to-noise ratio rate (SNR2rate), was implemented in MATLAB™ and evaluated. The expected linear response of SNR2rate based on predictions by the so-called Rose model and frame statistics was verified. The uncertainty in the measurement of SNR2rate for a fixed imaging geometry was 6% based on 16 repeated measurements. The results show that, as expected, reduced object thickness and x-ray field size substantially improved SNR2rate/PKA,rate with PKA,rate being the air kerma area product rate. The measurement precision in SNR2rate/PKA,rate (8–9%) is sufficient to detect small but important improvements, may guide the selection of better imaging settings and provides a tool for teaching good radiological imaging techniques to clinical staff.
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