Introduction: Hypertension is linked to endothelial dysfunction, but causality and direction is not entirely known. The aim was to study the cross-sectional associations between home, office, and central BP and microcirculatory peak oxygen saturation (OxyP). Methods: In the observational Swedish CArdioPulmonary bioImage Study (SCAPIS) Linköping subsample, office and home BP were measured using an oscillometric device and OxyP was measured in forearm skin after a 5-min occlusion of the brachial artery. A linear regression was fitted to evaluate the mean change in OxyP per SD increase in BP. A logistic regression was fitted to evaluate the associations between BP above the median and OxyP below the median. Results: Of participants, 3,291 were included in the analyses. Per SD increase in systolic home BP, the adjusted mean (95% CI) difference in OxyP was −0.4 (−0.6 to −0.1%). In subgroup analyses, the association remained for women but not men, although the interaction by sex was not statistically significant. Also, in women but not in men, OxyP was lower in those with white coat hypertension vs. sustained normotension, i.e., mean (95% CI) 88.8 (88.2–89.4%) vs. 89.6 (89.3–90.0%), and in those with masked hypertension vs. sustained normotension, i.e., 87.5 (85.9–89.1%) vs. 89.6 (89.3–90.0%). Conclusion: Home BP, which better predicts cardiovascular disease than office BP, was inversely associated with OxyP. This correlation remained in subgroup analyses of women but not men, suggesting possible sex-dependent microcirculatory dysfunction or that masked hypertension could be a more important cardiovascular risk marker in women, despite its higher prevalence in men.

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.

To enable interactive remote education on electrical safety in biomedical engineering, a real-life problem-based laboratory module is proposed, implemented and evaluated. The laboratory module was implemented in a freestanding distance course in hospital safety for three consecutive years and was based on electrical safety for medical devices, where standard equipment existing in most hospitals could be used. The course participants were from a total of 42 geographical locations in or near Sweden. To allow a high level of interaction, especially among peer students, a graphical digital platform (Gather Town) was used. The digital platform was additionally used in two group work sessions. The experience of the participants in terms of usefulness and satisfaction was rated on a range of [-2, 2] using a van der Laan 5-point Likert-based acceptance scale questionnaire. The laboratory module overall was scored 4.1/5 by the participants (n= 29) in the final course assessments. The evaluation of the digital platform alone showed that in the first usage instance, the participants (n=21) found the platform to be useful (0.54±0.67) and satisfactory (0.37±0.60). The participants’ experience of the digital platform improved when comparing two identical group work assignments so that ratings of usefulness and satisfaction were 1.11±0.59 and 1±0.71, respectively, after they had used it in the second group work session (n=38). This study provides an instance of an interactive remote electrical safety laboratory module that is envisioned to contribute to further implementations of sustainable education in biomedical engineering.

Significance: Tissue simulating phantoms are an important part of validating biomedical optical techniques. Tissue pathology in inflammation and oedema involves changes in both water and hemoglobin fractions.

Aim: We present a method to create solid gelatin-based phantoms mimicking inflammation and oedema with adjustable water and hemoglobin fractions.

Approach: One store-bought gelatin and one research grade gelatin were evaluated. Different water fractions were obtained by varying the water-to-gelatin ratio. Ferrous stabilized human hemoglobin or whole human blood was added as absorbers, and the stability and characteristics of each were compared. Intralipid® was used as the scatterer. All phantoms were characterized using spatial frequency domain spectroscopy.

Results: The estimated water fraction varied linearly with expected values (R2  =  0.96 for the store-bought gelatin and R2  =  0.99 for the research grade gelatin). Phantoms including ferrous stabilized hemoglobin stayed stable up to one day but had methemoglobin present at day 0. The phantoms with whole blood remained stable up to 3 days using the store-bought gelatin.

Conclusions: A range of physiological relevant water fractions was obtained for both gelatin types, with the stability of the phantoms including hemoglobin differing between the gelatin type and hemoglobin preparation. These low-cost phantoms can incorporate other water-based chromophores and be fabricated as thin sheets to form multilayered structures.

Autologous keratinocytes or stem cell based therapies are modern approaches for the treatment of skin loss in burn victims and chronic wound patients. The aim of this study is to identify depth-resolved structural changes in treated burn wounds using Spatial Frequency Domain Imaging (SFDI). When altering the investigated depth into tissue via the spatial frequency used in our calculations, we found changes in the scattering parameters for the treated samples. These scattering changes are correlated with histology, indicating a potential means to monitor re-epithelization and collagen formation during the treatment process across the entire wound area.

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.

Spatial Frequency Domain Imaging (SFDI) is a quantitative imaging method that measures optical properties of tissue. We present the design of a compact spectral imager to perform SFDI in low resource settings, which exploits a low-cost color CMOS camera and mini-projector. These devices are usually limited to three broad spectral bands (RGB). We have developed a novel method to extrapolate two additional wavelengths without hardware modifications, improving the spectral resolution of the device, allowing to account for additional sources of skin pigmentation. Our device performance was evaluated on tissue-simulating phantoms. In-vivo measurements were compared to a commercial probe-based system (EPOS).