| 1. |
- 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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| 2. |
- Booij, Ronald, et al.
(författare)
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Assessment of visibility of bone structures in the wrist using normal and half of the radiation dose with photon-counting detector CT
- 2023
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Ingår i: European Journal of Radiology. - : ELSEVIER IRELAND LTD. - 0720-048X .- 1872-7727. ; 159
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To quantitatively and qualitatively assess the visibility of bone structures in the wrist on photon-counting detector computed tomography (PCD-CT) images compared to state-of-the-art energy-integrating de-tector CT (EID-CT).Method: Four human cadaveric wrist specimens were scanned with EID-CT and PCD-CT at identical CTDIvolof 12.2 mGy and with 6.1 mGy (half dose PCD-CT). Axial images were reconstructed using the thinnest possible slice thickness, i.e. 0.4 mm on EID-CT and 0.2 mm on PCD-CT, with the largest image matrix size possible using reconstruction kernels optimized for bone (EID-CT: Ur68, PCD-CT: Br92). Quantitative evaluation was performed to determine contrast-noise ratio (CNR) of bone/ fat, cortical and trabecular sharpness. An observer study using visual grading characteristics (VGC) analysis was performed by six observers to assess the visibility of nutrient canals, trabecular architecture, cortical bone and the general image quality.Results: At equal dose, images obtained with PCD-CT had 39 +/- 6 % lower CNR (p = 0.001), 71 +/- 57 % higher trabecular sharpness in the radius (p = 0.02) and 42 +/- 8 % (p < 0.05) sharper cortical edges than those obtained with EID-CT. This was confirmed by VGC analysis showing a superior visibility of nutrient canals, trabeculae and cortical bone area under the curve (AUC) > 0.89) for PCD-CT, even at half dose.Conclusions: Despite a lower CNR and increased noise, the trabecular and cortical sharpness were twofold higher with PCD-CT. Visual grading analysis demonstrated superior visibility of cortical bone, trabeculae, nutrient canals and an overall improved image quality with PCD-CT over EID-CT. At half dose, PCD-CT also yielded superior image quality, both in quantitative measures and as evaluated by radiologists.
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| 3. |
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| 4. |
- Detert, Hedvig, et al.
(författare)
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Microcirculatory response to cold stress test in the healthy hand
- 2023
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Ingår i: Microvascular Research. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0026-2862 .- 1095-9319. ; 148
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Cold sensitivity of the fingers is common in several conditions. It has been linked to digital vasospasm, microvascular dysfunction, and neural mechanisms. This study aimed to investigate the normal digital micro-vascular response to a cold stress test in healthy individuals using Laser Speckle Contrast Imaging (LSCI).Methods: Twenty-six healthy individuals, mean age 31 (SD 9) years were included. Skin perfusion of digits II-V was measured using Laser Speckle Contrast Imaging before and after a standardized cold stress test. Changes in skin perfusion from baseline were analyzed between hands, digits, and sexes.Results: Skin perfusion was significantly (p < 0.0001) affected by cold provocation in both the cold exposed and the contralateral hands in all participants of the study. This effect was significantly different between the radial (digit II and III) and the ulnar (digit V) side of the hands (p < 0.001). There was a trend towards a larger decrease in perfusion in men (ns), and a faster recovery to baseline values in women (ns). A larger inter subject variability was seen in perfusion values in women.Conclusions: The normal microvascular response to cold provocation may involve both centrally and regionally mediated processes. When exposing one hand to a cold stress test, the contralateral hand responds with simul-taneous but smaller decreases in perfusion.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Elawa, Sherif, et al.
(författare)
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Skin blood flow response to topically applied methyl nicotinate: Possible mechanisms
- 2020
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Ingår i: Skin research and technology. - : WILEY. - 0909-752X .- 1600-0846. ; 26:3, s. 343-348
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Tidskriftsartikel (refereegranskat)abstract
- Background Methyl nicotinate (MN) induces a local cutaneous erythema in the skin and may be valuable as a local provocation in the assessment of microcirculation and skin viability. The mechanisms through which MN mediates its vascular effect are not fully known. The aim of this study was to characterize the vasodilatory effects of topically applied MN and to study the involvement of nitric oxide (NO), local sensory nerves, and prostaglandin-mediated pathways. Methods MN was applied on the skin of healthy subjects in which NO-mediated (L-NMMA), nerve-mediated (lidocaine/prilocaine), and cyclooxygenase-mediated (NSAID) pathways were selectively inhibited. Microvascular responses in the skin were measured using laser speckle contrast imaging (LSCI). Results NSAID reduced the MN-induced perfusion increase with 82% (P < .01), whereas lidocaine/prilocaine reduced it with 32% (P < .01). L-NMMA did not affect the microvascular response to MN. Conclusion The prostaglandin pathway and local sensory nerves are involved in the vasodilatory actions of MN in the skin.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Engstrand, Fredrik, et al.
(författare)
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Validation of a smartphone application and wearable sensor for measurements of wrist motions
- 2021
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Ingår i: Journal of Hand Surgery, European Volume. - : Sage Publications. - 1753-1934 .- 2043-6289. ; 46:10, s. 1057-1063
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Tidskriftsartikel (refereegranskat)abstract
- We developed a smartphone application to measure wrist motion using the mobile devices built-in motion sensors or connecting it via Bluetooth to a wearable sensor. Measurement of wrist motion with this method was assessed in 33 participants on two occasions and compared with those obtained with a standard goniometer. The test-retest reproducibility in healthy individuals ranged from good to excellent (intraclass correlation (ICC) 0.76-0.95) for all motions, both with and without the wearable sensor. These results improved to excellent (ICC 0.90-0.96) on the second test day, suggesting a learning effect. The day-to-day reproducibility was overall better with the wearable sensor (mean ICC 0.87) compared with the application without using sensor or goniometer (mean ICC 0.82 and 0.60, respectively). This study suggests that smartphone-based measurements of wrist range of motion are feasible and highly accurate, making it a powerful tool for outcome studies after wrist surgery.
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| 11. |
- Fredäng Kämmerling, Nina, et al.
(författare)
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A comparative study of image quality and diagnostic confidence in diagnosis and follow-up of scaphoid fractures using photon-counting detector CT and energy-integrating detector CT
- 2024
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Ingår i: European Journal of Radiology. - : ELSEVIER IRELAND LTD. - 0720-048X .- 1872-7727. ; 173
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Scaphoid fractures in patients and assessment of healing using PCD-CT have, as far as we know, not yet been studied. Therefore, the aim was to compare photon counting detector CT (PCD-CT) with energy integrating detector CT (EID-CT) in terms of fracture visibility and evaluation of fracture healing. Method: Eight patients with scaphoid fracture were examined with EID-CT and PCD-CT within the first week posttrauma, and with additional scans at 4, 6 and 8 weeks. Our clinical protocol for wrist examination with EID-CT was used (CTDIvol 3.1 +/- 0.1 mGy, UHR kernel Ur77). For PCD-CT matched radiation dose, reconstruction kernel Br89. Quantitative analyses of noise, CNR, trabecular and cortical sharpness, and bone volume fraction were conducted. Five radiologists evaluated the images for fracture visibility, fracture gap consolidation and image quality, and rated their confidence in the diagnosis. Results: The trabecular and cortical sharpness were superior in images obtained with PCD-CT compared with EIDCT. A successive reduction in trabecular bone volume fraction during the immobilized periods was found with both systems. Despite higher noise and lower CNR with PCD-CT, radiologists rated the image quality of PCD-CT as superior. The visibility of the fracture line within 1 -week post -trauma was rated higher with PCD-CT as was diagnostic confidence, but the subsequent assessments of fracture gap consolidation during healing process and the confidence in diagnosis were found equivalent between both systems. Conclusion: PCD-CT offers superior visibility of bone microstructure compared with EID-CT. The evaluation of fracture healing and confidence in diagnosis were rated equally with both systems, but the radiologists found primary fracture visibility and overall image quality superior with PCD-CT.
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| 12. |
- Hackethal, Johannes, et al.
(författare)
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Microvascular effects of microneedle application
- 2021
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Ingår i: Skin research and technology. - : WILEY. - 0909-752X .- 1600-0846. ; 27, s. 121-125
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Tidskriftsartikel (refereegranskat)abstract
- Background The efficiency of transdermal drug delivery may be increased by pretreating the skin with microneedles, but distinct effects of microneedles and the microneedle-enhanced delivery of vasoactive drugs on the skin microvasculature are still not well investigated. Materials and Methods In eight healthy human subjects, we measured the microvascular response to microneedle-induced microtraumas in the skin microvasculature using polarized light spectroscopy imaging (Tissue Viability imaging, TiVi). The microvascular response was assessed for up to 48 hours for three microneedle sizes (300 mu m, 500 mu m, and 750 mu m) and for different pressures and application times. Results In our results, microneedle application increased the local red blood cell (RBC) concentration for up to 24 hours dependent on the needle lengths, applied time, and force. Conclusion Optimization of microneedles size, pressure, and application time should be taken into account for future protocols for drug delivery and experimental provocations.
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| 13. |
- Högstedt, Alexandra, et al.
(författare)
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Effect of N-G-monomethyl l-arginine on microvascular blood flow and glucose metabolism after an oral glucose load
- 2020
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Ingår i: Microcirculation. - : WILEY. - 1073-9688 .- 1549-8719. ; 27:3
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Tidskriftsartikel (refereegranskat)abstract
- Objective The aim of this study was to investigate whether the effects on local blood flow and metabolic changes observed in the skin after an endogenous systemic increase in insulin are mediated by the endothelial nitric oxide pathway, by administering the nitric oxide synthase inhibitor N-G-monomethyl l-arginine using microdialysis. Methods Microdialysis catheters, perfused with N-G-monomethyl l-arginine and with a control solution, were inserted intracutaneously in 12 human subjects, who received an oral glucose load to induce a systemic hyperinsulinemia. During microdialysis, the local blood flow was measured by urea clearance and by laser speckle contrast imaging, and glucose metabolites were measured. Results After oral glucose intake, microvascular blood flow and glucose metabolism were both significantly suppressed in the N-G-monomethyl l-arginine catheter compared to the control catheter (urea clearance: P amp;lt; .006, glucose dialysate concentration: P amp;lt; .035). No significant effect of N-G-monomethyl l-arginine on microvascular blood flow was observed with laser speckle contrast imaging (P = .81). Conclusion Local delivery of N-G-monomethyl l-arginine to the skin by microdialysis reduces microvascular blood flow and glucose delivery in the skin after oral glucose intake, presumably by decreasing local insulin-mediated vasodilation.
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| 14. |
- Högstedt, Alexandra, et al.
(författare)
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Investigation of proteins important for microcirculation using in vivo microdialysis after glucose provocation : a proteomic study
- 2021
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Ingår i: Scientific Reports. - : NATURE PORTFOLIO. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Insulin has metabolic and vascular effects in the human body. What mechanisms that orchestrate the effects in the microcirculation, and how the responds differ in different tissues, is however not fully understood. It is therefore of interest to search for markers in microdialysate that may be related to the microcirculation. This study aims to identify proteins related to microvascular changes in different tissue compartments after glucose provocation using in vivo microdialysis. Microdialysis was conducted in three different tissue compartments (intracutaneous, subcutaneous and intravenous) from healthy subjects. Microdialysate was collected during three time periods; recovery after catheter insertion, baseline and glucose provocation, and analyzed using proteomics. Altogether, 126 proteins were detected. Multivariate data analysis showed that the differences in protein expression levels during the three time periods, including comparison before and after glucose provocation, were most pronounced in the intracutaneous and subcutaneous compartments. Four proteins with vascular effects were identified (angiotensinogen, kininogen-1, alpha-2-HS-glycoprotein and hemoglobin subunit beta), all upregulated after glucose provocation compared to baseline in all three compartments. Glucose provocation is known to cause insulin-induced vasodilation through the nitric oxide pathway, and this study indicates that this is facilitated through the interactions of the RAS (angiotensinogen) and kallikrein-kinin (kininogen-1) systems.
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| 15. |
- Högstedt, Alexandra, 1993-
(författare)
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Microvascular effects of insulin in the skin
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The microcirculation in the skin is essential for skin homeostasis. In instances of altered microvascular function, that may be the result of insulin resistance, tissue morbidity may ensue. The underlying mechanisms are however complex and not fully understood. By studying the physiological effects of insulin in the skin, the understanding of the complex interplay between glucose metabolism and skin microcirculation can be improved. The general aim of this thesis was to develop an experimental in vivo model to study metabolic and microvascular responses to insulin in the skin in healthy subjects. Microdialysis is a suiting technique as it allows for both local delivery of drugs and simultaneous monitoring of the local metabolic and vascular effects in the very same tissue compartment. The effects of local and systemic insulin provocation on skin blood flow and metabolism were investigated using microdialysis urea clearance and laser speckle contrast imaging (paper I). An insulin dependent increase in skin blood flow was observed, presumably induced through the nitric oxide pathway (paper II). Investigating the protein expression during an oral glucose provocation using proteomic approaches however indicates interactions with other pathways, such as the renin-angiotensin system and the kallikrein-kinin system (paper IV). Paper III also investigated methodological concerns regarding the sampling of insulin using microdialysis. This in vivo model can, in the future, be applied to assess the microvascular effects of insulin in the skin in different patient groups, including those with micro-vascular dysfunction due to, for instance, insulin resistance.
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| 16. |
- Högstedt, Alexandra, et al.
(författare)
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Sampling insulin in different tissue compartments using microdialysis: methodological aspects
- 2020
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Ingår i: Scientific Reports. - : NATURE RESEARCH. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Sampling the concentration of insulin in human skin using microdialysis is challenging because of low intracutaneous concentrations and low recovery, presumably due to adsorption of insulin to the microdialysis system. In this study, we aimed to (1) measure how the concentration of insulin varies in three different tissue compartments (intracutaneous, subcutaneous and intravenous) and (2) to study how much insulin is adsorbed to the microdialysis catheter membranes and tubing during a typical microdialysis experiment, both in vivo and in vitro. We hypothesized that (1) the concentration of insulin decreases from the intravenous compartment to the intracutaneous and subcutaneous tissue, and that (2) adsorption of insulin to the microdialysis membrane and tubing impairs the recovery of insulin from the tissue. In this experimental study, microdialysis catheters were inserted intracutaneously, subcutaneously and intravenously in 11 healthy subjects. Systemic endogenous hyperinsulinemia was induced by intake of an oral glucose load. Insulin concentration was measured in the dialysate and in the extracted samples from the catheter membrane and tubings. In vitro microdialysis was performed to investigate the temporal resolution of the adsorption. After an oral glucose load insulin concentration increased intravenously, but not in the intracutaneous or subcutaneous compartments, while glucose, lactate and pyruvate concentrations increased in all compartments. The adsorption of insulin to the microdialysis membrane in vivo was highest in the intravenous compartment (p=0.01), compared to the intracutaneous and subcutaneous compartments. In vitro, the adsorption to the microdialysis membrane was highest one hour after sampling, then the concentration gradually decreased after three and five hours of sampling. The concentration of insulin in peripheral tissues is low, probably due to decreasing tissue vascularity. Adsorption of insulin to the microdialysis membrane is modest but time-dependent. This finding highlights the importance of a stabilization time for the microdialysis system before sampling tissue analytes.
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| 17. |
- Kämmerling, Nina, et al.
(författare)
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Assessment of image quality in photon-counting detector computed tomography of the wrist - An ex vivo study
- 2022
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Ingår i: European Journal of Radiology. - : Elsevier Ireland Ltd. - 0720-048X .- 1872-7727. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to evaluate the effect of reconstruction parameters on image quality in wrist imaging using photon-counting detector CT (PCD-CT) and to compare the results with images from an energyintegrating detector CT (EID-CT). Methods: Twelve cadaveric wrist specimens were examined using a prototype PCD-CT and a clinical EID-CT using similar radiation dose. Reconstruction parameters were matched between scanners. Also, sharper reconstruction kernels, a larger matrix size, and smaller slice thicknesses were evaluated for PCD-CT. Image noise, contrast-tonoise ratio (CNR) and image sharpness in trabecular structures were quantitatively measured. Image quality with respect to the visibility of cortical and trabecular bone structures was assessed by six radiologists using visual grading methods.Results: Images obtained with PCD-CT had lower noise (42.6 +/- 3.9 HU vs 75.1 +/- 6.3 HU), higher CNR (38.9 +/- 4.5 vs 19.0 +/- 2.4) and higher trabecular sharpness (63.5 +/- 6.0 vs 53.7 +/- 8.5) than those obtained with EID-CT using similar scan and reconstruction parameters (p < 0.001). The image sharpness in trabecular structures was further improved by using sharper kernels, despite higher noise levels. Radiologists had a strong preference for PCD-CT images both in terms of spatial resolution and suitability for bone imaging. Visual grading analysis showed an improved visibility of cortical bone, trabeculae and nutritive canals (p < 0.005).Conclusion: PCD-CT offers improved image quality regarding bone structures in the wrist relative to EID-CT systems, particularly when sharper reconstruction kernels, smaller slice thickness and a larger image matrix size are used.
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| 18. |
- Mirdell, Robin, et al.
(författare)
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Using blood flow pulsatility to improve the accuracy of laser speckle contrast imaging in the assessment of burns
- 2020
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Ingår i: Burns. - : ELSEVIER SCI LTD. - 0305-4179 .- 1879-1409. ; 46:6, s. 1398-1406
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Measurement of perfusion is an establishedmethod to evaluate the depth of burns. However, high accuracy is only achievable >48 h after injury. The aim of the study was to investigate if measurement of blood flow pulsatility, combined with perfusion measurement, can improve early assessment of burn depth using laser speckle contrast imaging (LSCI). Methods: Perfusion and pulsatility were measured with LSCI in 187 regions of interest in 32 patients, between 0 and 5 days after injury. The reproducibility of pulsatility was tested for recording durations between 1 and 12 s. The most reproducible duration was chosen, and receiver operator characteristics were created to find suitable pulsatility cut-offs to predict surgical need. Results: A measurement duration of 8 s resulted in a good reproducibility of the pulsatility (% CV: 15.9%). Longer measurement durations resulted in a small improvement of the accuracy of the assessment. A pulsatility of <1.45 (Perfusion Units)(2) on day 0-2 after injury predicted surgical need with a sensitivity of 100% (95% CI: 83.2-100%), specificity of 100% (95% CI: 95.2-100%), a positive predictive value of 100%, and a negative predictive value of 100%. Pulsatility was not significantly different when comparing measurements done day 0-2 today 3-5. Perfusion was however significantly higher day 3-5 compared today 0-2 for wound shealing with in 3 weeks. Conclusion: Measurement of pulsatility improves the accuracy of the assessment of burns with LSCI and makes it possible to predict the need for surgery during day 0-2 after injury with a high accuracy. (C) 2020 Elsevier Ltd and ISBI. All rights reserved.
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| 19. |
- Tesselaar, Erik, 1977-, et al.
(författare)
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MEASUREMENT OF SKIN DOSE AND RADIATION-INDUCED CHANGES IN SKIN MICROCIRCULATION IN CHRONIC TOTAL OCCLUSION PERCUTANEOUS CARDIAC INTERVENTIONS (CTO-PCI)
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 257-263
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Tidskriftsartikel (refereegranskat)abstract
- Skin injuries may occur when radiation doses to the skin exceed 2 Gy. This study aimed to measure changes in skin microcirculation in patients undergoing chronic total occlusion percutaneous coronary interventions (CTO-PCI). In 14 patients, peak skin dose (PSD) was estimated with radiographic films and skin microcirculation was assessed with laser speckle contrast imaging (LSCI), before, 1 day after the intervention, and 4–6 weeks later. The mean PSD was 1.8 ± 0.9 Gy. Peak skin microcirculation increased by 12% from 45 ± 6 PU before to 50 ± 9 PU 1 day after the intervention (p = 0.01), and returned to 46 ± 8 PU after 4–6 weeks (p = 0.15). There was no significant correlation between PSD and the change in perfusion, neither 1 day (r = −0.13, p = 0.69) nor 4–6 weeks after the intervention (r = 0.33, p = 0.35). These results suggest that there are no radiation-induced microvascular changes in the skin after CTO-PCI at skin doses below 2 Gy.
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| 20. |
- Tesselaar, Erik, et al.
(författare)
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Objective assessment of skin microcirculation using a smartphone camera
- 2021
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Ingår i: Skin research and technology. - : WILEY. - 0909-752X .- 1600-0846. ; 27:2, s. 138-144
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Tidskriftsartikel (refereegranskat)abstract
- Background Existing techniques for assessment of microcirculation are limited by their large size and high costs and are often not so easy to use. Advances in mobile technology have enabled great improvements in smartphone sensor technology. In this study, we used SkinSight, an app for iPhone and iPad, to measure changes in skin microcirculation during physiological provocations. The system estimates changes in the concentration of hemoglobin in the skin by analyzing the reflected light emitted from the built-in light-emitting diode and detected by the camera of the smartphone. Methods A relative hemoglobin (Hb) index was measured during a 5-min arterial occlusion, post-occlusive reactive hyperemia, and a 5-min venous occlusion in 10 healthy subjects, on two separate days. The index was calculated in an area of the skin from the color information in the images acquired by the phone camera. Polarized light spectroscopy imaging was used to measure changes in red blood cell concentration for comparison. Results During arterial occlusion, relative Hb index was unchanged compared to baseline (P= .40). After release of the cuff, a sudden 60%-75% increase in Hb index was observed (P< .001) followed by a gradual return to baseline. During venous occlusion, Hb index increased by 80% (P< .001) followed by a gradual decrease to baseline after reperfusion. Day-to-day reproducibility of the relative Hb index was excellent (ICC: 0.92, r = 0.94), although relative Hb index was consistently higher during the second day, possibly as a result of changed lighting conditions or calibration issues. Conclusion Microvascular responses to physiological provocations in the skin can be accurately and reproducibly measured using a smartphone application. Although the system offers a handheld, easy to use and flexible technique for skin microvascular assessment, the effects of lighting on the measured values and need for calibration need to be further investigated.
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| 21. |
- Verstraeten, Sabine, et al.
(författare)
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Comparison of true non-contrast and virtual noncontrast images in the characterization of renal lesions using detector-based spectral CT
- 2023
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 96:1149
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Renal lesions are sometimes incidentally detected during computed tomography (CT) examinations in which an unenhanced series is not included, preventing the lesions from being fully characterized. The aim of this study was to investigate the feasibility to use virtual non-contrast (VNC) images, acquired using a detector-based dual-energy CT, for the characterization of renal lesions. Methods: Twenty-seven patients (12 women) underwent a renal CT scan, including a non-contrast, an arterial, and a venous phase contrast-enhanced series, using a detector-based dual-energy CT scanner. VNC images were reconstructed from the venous contrast-enhanced series. The mean attenuation values of 65 renal lesions in both the VNC and true non-contrast (TNC) images were measured and compared quantitatively. Three radiologists blindly assessed all lesions using either VNC or TNC images in combination with contrast-enhanced images. Results: Sixteen patients had cystic lesions, five had angiomyolipoma (AML), and six had suspected renal cell carcinomas (RCC). Attenuation values in VNC and TNC images were strongly correlated (ρ = 0.7, mean difference −6.0 ± 13 HU). The largest differences were found for unenhanced high-attenuation lesions. Radiologists classified 86% of the lesions correctly using VNC images. Conclusions: In 70% of the patients, incidentally detected renal lesions could be accurately characterized using VNC images, resulting in less patient burden and a reduction in radiation exposure. Advances in knowledge: This study shows that renal lesions can be accurately characterized using VNC images acquired by detector-based dual-energy CT, which is in agreement with previous studies using dual-source and rapid X-ray tube potential switching technique. © 2023 The Authors.
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| 22. |
- Vroman, Heleen, et al.
(författare)
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Continuous vital sign monitoring in patients after elective abdominal surgery: a retrospective study on clinical outcomes and costs
- 2023
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Ingår i: Journal of Comparative Effectiveness Research. - : Becaris Publishing. - 2042-6305 .- 2042-6313. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Plain language summary What is this article about?Continuous vital sign monitoring assists in identifying deteriorating patients outside intensive care. This study analyses changes in clinical outcomes and costs before and after implementation of a clinical vital sign monitoring device in postsurgical patients on a general ward in a Dutch hospital. What were the results?Results show that after implementation, patients were less likely to be admitted to the intensive care unit, had shorter length of stay and had lower hospital stay costs. Aim: To assess changes in outcomes and costs upon implementation of continuous vital sign monitoring in postsurgical patients. Materials & methods: Retrospective analysis of clinical outcomes and in-hospital costs compared with a control period. Results: During the intervention period patients were less frequently admitted to the intensive care unit (ICU) (p = 0.004), had shorter length of stay (p < 0.001) and lower costs (p < 0.001). The intervention was associated with a lower odds of ICU admission (odds ratio: 0.422; p = 0.007) and ICU related costs (odds ratio: -662.4; p = 0.083). Conclusion: Continuous vital sign monitoring may have contributed to fewer ICU admissions and lower ICU costs in postsurgical patients. Tweetable abstractA retrospective study of clinical outcomes and costs compared with a control period indicated that implementation of continuous vital sign monitoring in postsurgical patients in a general hospital in The Netherlands may have contributed to fewer intensive care unit admissions and lower intensive care unit costs.
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| 23. |
- Woisetschläger, Mischa, et al.
(författare)
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Improved visualization of the bone-implant interface and osseointegration in ex vivo acetabular cup implants using photon-counting detector CT
- 2023
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Ingår i: EUROPEAN RADIOLOGY EXPERIMENTAL. - : SPRINGERNATURE. - 2509-9280. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundSuccessful osseointegration of joint replacement implants is required for long-term implant survival. Accurate assessment of osseointegration could enable clinical discrimination of failed implants from other sources of pain avoiding unnecessary surgeries. Photon-counting detector computed tomography (PCD-CT) provides improvements in image resolution compared to conventional energy-integrating detector CT (EID-CT), possibly allowing better visualization of bone-implant-interfaces and osseointegration. The aim of this study was to assess the quality of visualization of bone-implant-interfaces and osseointegration in acetabular cup implants, using PCD-CT compared with EID-CT.MethodsTwo acetabular implants (one cemented, one uncemented) retrieved during revision surgery were scanned using PCD-CT and EID-CT at equal radiation dose. Images were reconstructed using different reconstruction kernels and iterative strengths. Delineation of the bone-implant and bone-cement-interface as an indicator of osseointegration was scored subjectively for image quality by four radiologists on a Likert scale and assessed quantitatively.ResultsDelineation of bone-implant and bone-cement-interfaces was better with PCD-CT compared with EID-CT (p <= 0.030). The highest ratings were given for PCD-CT at sharper kernels for the cemented cup (PCD-CT, median 5, interquartile range 4.25-5.00 versus EID-CT, 3, 2.00-3.75, p < 0.001) and the uncemented cup (5, 4.00-5.00 versus 2, 2-2, respectively, p < 0.001). The bone-implant-interface was 35-42% sharper and the bone-cement-interface was 28-43% sharper with PCD-CT compared with EID-CT, depending on the reconstruction kernel.ConclusionsPCD-CT might enable a more accurate assessment of osseointegration of orthopedic joint replacement implants.
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| 24. |
- Zötterman, Johan, et al.
(författare)
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Correlation between Indocyanine Green Fluorescence Angiography and Laser Speckle Contrast Imaging in a Flap Model
- 2023
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Ingår i: Plastic and Reconstructive Surgery - Global Open. - : LIPPINCOTT WILLIAMS & WILKINS. - 2169-7574. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- Background:Indocyanine green fluorescence angiography (ICG-FA) is used to assess tissue intraoperatively in reconstructive surgery. This requires an intra-venous dye injection for each assessment. This is not necessary in laser speckle contrast imaging (LSCI); therefore, this method may be better suited for tissue evaluation. To determine this, we compared the two methods in a porcine flap model.Methods:One random and one pedicled flap were raised on each buttock of six animals. They were assessed with LSCI at baseline, when raised (T0), at 30 minutes (T30) and with ICG-FA at T0 and T30. Regions of interest (ROI) were chosen along the flap axis. Perfusion, measured as perfusion units (PU) in the LSCI assessment and pixel-intensity for the ICG-FA video uptake, was calculated in the ROI. Correlation was calculated between PU and pixel-intensity measured as time to peak (TTP) and area under curve for 60 seconds (AUC60).Results:Correlation between LSCI and AUC60 for the ICG-FA in corresponding ROI could be seen in all flaps at all time points. The correlation was higher for T0 (r=0.7 for random flap and r=0.6 for pedicled flap) than for T30 (r=0.57 for random flap and r=0.59 for pedicled flap). Even higher correlation could be seen PU and TTP (T0: random flap r=-0.8 and pedicled flap r=0.76. T30: random flap r=-0.8 and pedicled flap r=0.71)Conclusion:There is a correlation between PU from LSCI and TTP and AUC60 for ICG-FA, indicating that LSCI could be considered for intraoperative tissue assessment.
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| 25. |
- Zötterman, Johan, 1975-, et al.
(författare)
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Intraoperative Laser Speckle Contrast Imaging in DIEP Breast Reconstruction : A Prospective Case Series Study
- 2020
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Ingår i: Plastic and Reconstructive Surgery - Global Open. - : Wolters Kluwer. - 2169-7574. ; 8:1, s. e2529-e2529
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Tidskriftsartikel (refereegranskat)abstract
- Laser speckle contrast imaging (LSCI) is a laser-based perfusion imaging technique that recently has been shown to predict ischemic necrosis in an experimental flap model and predicting healing time of scald burns. The aims were to investigate perfusion in relation to the selected perforator during deep inferior epigastric artery perforator (DIEP) flap surgery, and to evaluate LSCI in assisting of prediction of postoperative complications. METHODS: Twenty-three patients who underwent DIEP-procedures for breast reconstruction at 2 centers were included. Perfusion was measured in 4 zones at baseline, after raising, after anastomosis, and after shaping the flap. The perfusion in relation to the selected perforator and the accuracy of LSCI in predicting complications were analyzed. RESULTS: After raising the flap, zone I showed the highest perfusion (65 ± 10 perfusion units, PU), followed by zone II (58 ± 12 PU), zone III (53 ± 10 PU), and zone IV (45 ± 10 PU). The perfusion in zone I was higher than zone III (P = 0.002) and zone IV (P < 0.001). After anastomosis, zone IV had lower perfusion than zone I (P < 0.001), zone II (P = 0.01), and zone III (P = 0.02). Flaps with areas <30 PU after surgery had partial necrosis postoperatively (n = 4). CONCLUSIONS: Perfusion is highest in zone I. No perfusion difference was found between zones II and III. Perfusion <30 PU after surgery was correlated with partial necrosis. LSCI is a promising tool for measurement of flap perfusion and assessment of risk of postoperative ischemic complications.
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| 26. |
- Zötterman, Johan, 1975-
(författare)
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Laser Speckle Contrast Imaging in Reconstructive Surgery
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- ObjectivesReconstructive surgery aims to restore function or normal appearance by reconstructing defective organs after trauma or disease. In patients undergoing reconstructive surgery, previous trauma, surgery or radiotherapy can result in compromised blood supply. This will affect the viability of the tissue and increases the risk for postoperative complications, such as ischemia and infection. It is therefore important to assess the tissue viability, both before, during and after the surgery. This can be done using different techniques that monitor the perfusion of the skin covering the affected area. In this thesis, LSCI have been evaluated for tissue monitoring in reconstructive surgery. The technique allows for a fast and noninvasive assessment of superficial tissue perfusion over a wide field. Based on previous work on the technology, we have seen clear advantages with LSCI compared to other methods, for example laser Doppler flowmetry (LDF). We have evaluated laser speckle contrast imaging (LSCI) as a tool for tissue monitoring in reconstructive surgery in four studies.MethodsIn study I we used a bench top model and healthy subjects to address methodological concerns subjected to the LSCI technology. We investigated the effect of motion distance and angle on the assessed perfusion value In study II we used a porcine model to compare LSCI and LDF as tools to detect partial and full venous outflow obstruction. We used both methods to assess a flap based on the cranial gluteal artery perforator with partial and complete occlusion of the vein and artery. In study III we used the same porcine model as in study II to investigate the possibility to use LSCI intraoperatively to identify flap areas with compromised circulation and thereby predict areas with a high risk of postoperative necrosis. In study IV we used LSCI for intraoperative evaluation of tissue viability during deep inferior epigastric perforator (DIEP) free flap surgery and to investigate the perfusion distribution according to the Hartrampf zones, as measured with LSCI, in relation to the selected perforator in the deep inferior epigastric perforator free flap.ResultsIn study I we saw that tissue perfusion as measured with LSCI increases with increasing tissue motion, independent of frame rate, number of images, and tissue perfusion. Measured perfusion will decrease when images are acquired at an angle larger than 45° but distances between 15 and 40 cm do not affect the measured perfusion. In study II we observed significant decreases in perfusion during both partial and complete venous occlusion with both LSCI and LDF. However, higher variability seen with LDF, measured as % coefficient of variation. In study III a decrease in perfusion during the first 30 min after raising the flap and a perfusion value below 25 PU after 30 min was a predictor for tissue morbidity 72h after surgery. In study IV the highest perfusion values were found in zone I and higher perfusion in zone II compared to zone III, directly after the flap was raised. No remaining significant difference between zone I, II and III could be seen after anastomosis of the vessels. All flaps with a minimum perfusion <30 PU, measured after the flap was shaped and inserted, later suffered from partial flap necrosis.ConclusionLSCI is a technology that has the potential to contribute to tissue monitoring in reconstructive surgery. It has many advantages over other techniques, such as the fast acquisition time, the spatial resolution and the fact that it is completely non-invasive. However, the current system is still too bulky to be easily introduced into a clinical setting and the technology is also subject to certain drawbacks which limit its usability. It is sensitive to motion artefacts; only superficial tissue is assessed and cannot offer absolute perfusion data. If these disadvantages could be addressed, LSCI could contribute to a more accurate survey of tissue perfusion and thus better outcome in reconstructive surgery.
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