Quality smartphone cameras and affordable dermatoscopes have enabled teledermoscopy to become a popular medical and veterinary tool for analyzing skin lesions such as melanoma and erythema. However, smartphones acquire images in an unknown RGB color space, which prevents a standardized colorimetric skin analysis. In this work, we supplemented a typical veterinary teledermoscopy system with a conventional color calibration procedure, and we studied two mid-priced smartphones in evaluating native and erythematous canine skin color. In a laboratory setting with the ColorChecker, the teledermoscopy system reached CIELAB-based color differences ΔE of 1.8–6.6 (CIE76) and 1.1–4.5 (CIE94). Intra- and inter-smartphone variability resulted in the color differences (CIE76) of 0.1, and 2.0–3.9, depending on the selected color range. Preliminary clinical measurements showed that canine skin is less red and yellow (lower a* and b* for ΔE of 10.7) than standard Caucasian human skin. Estimating the severity of skin erythema with an erythema index led to errors between 0.5–3%. After constructing a color calibration model for each smartphone, we expedited clinical measurements without losing colorimetric accuracy by introducing a simple image normalization on a white standard. To conclude, the calibrated teledermoscopy system is fast and accurate enough for various colorimetric applications in veterinary dermatology.

Measuring pulse rate (PR) and blood oxygenation (also peripheral oxygen saturation, SpO2) is a common monitoring procedure in veterinary medicine which gives important information about the patient's cardiovascular and respiratory systems. It can be performed as a part of physical examination (ASAVA 2013), surgical procedure (Bednarski et al 2011) or intensive care treatment (Humm and Kellett-Gregory 2016). In addition to veterinary professionals, pet owners are also becoming interested in painless and stress-free monitoring of their animals. This trend is reflected in the pet market, where gadget devices for monitoring the canine or feline location and activity are on the rise (Weiss et al 2013).Measuring PR and SpO2 can be done by the same optical probe, which is based on a pulse oximetry sensor comprising continuously emitting light sources. The probe first emits and then, by the form of design, receives either the transmitted (e.g. on finger, tongue) or the reflected (e.g. on tail) red and infrared (IR) light (Allen 2007). If the acquired data is evaluated in time from a single spectral band, the technique is generally called photoplethysmography (PPG). In this way, pulse oximetry is based on comparing red and IR PPG signal baselines. The acquired PPG signal consists of non-pulsatile (DC) and pulsatile (AC) components. A baseline of PPG signal (i.e. non-pulsatile DC) reflects the collective light absorption due to blood and other tissues while the pulsatile PPG component (AC) is a consequence of local blood volume changes in accordance with the cardiac cycle.In humans, PPG is one of the most popular monitoring tools (Orphanidou 2018) since the device is small, reliable and low cost. In addition to PR and SpO2, PPG is also used to monitor blood pressure, cardiac output, and respiration rate, to detect various vascular diseases (Erts et al 2005, Karlen et al 2012, Bartels and Thiele 2015 and to assess regional anesthesia efficiency (Nijboer and Dorlas 1985, Rubins et al 2010). PPG probes are normally placed on the fingertip for direct bedside monitoring. Recently, imaging PPG (iPPG) has become increasingly valuable since the PPG signals can be obtained from a camera or a mobile phone video (Huelsbusch and Blazek 2002, Jonathan and Leahy 2010, Remer and Bilenca 2015. It was shown that the PPG pulse varies significantly among measurement sites such as fingertips, toes, and ears (Spigulis 2005, Allen 2007). This phenomenon probably occurs due to differences in the cutaneous blood supply of the different anatomic regions (Maeda et al

In this study, we applied photoplethysmography (PPG) as an alternative, convenient, and affordable method for bovine heat detection. Heat detection is an essential part of effective herd reproduction management. Currently, there are many different heat detection techniques, but they can be ineffective or impractical to use. Since heat affects local vulvar blood circulation (resulting in swelling and erythema), photoplethysmography could represent an affordable alternative to detect this bovine phenomenon. In this study, we enrolled 20 animals in heat and other stages of the bovine reproduction cycle. We analyzed the PPG signal in terms of baseline (DC component), power, kurtosis, and erythema index. One vaginal measurement site, approximately 8 cm from the vulva, exhibited significant differences in mucous color (PPG green and red baseline, both erythema indices). What is more, cows in heat displayed higher PPG signal power and kurtosis, but differences were not significant. Photoplethysmography exhibited the potential to detect bovine heat.

The regular monitoring of erythema, one of the most important skin lesions in atopic (allergic) dogs, is essential for successful anti-allergic therapy. The smartphone-based dermatoscopy enables a convenient way to acquire quality images of erythematous skin. However, the image sampling to evaluate erythema severity is still done manually, introducing result variability. In this study, we investigated the correlation between the most popular erythema indices (EIs) and dermatologists’ erythema perception, and we measured intra- and inter-rater variability of the currently-used manual image-sampling methods (ISMs). We showed that the EIBRG, based on all three RGB (red, green, and blue) channels, performed the best with an average Spearman coefficient of 0.75 and a typical absolute disagreement of less than 14% with the erythema assessed by clinicians. On the other hand, two image-sampling methods, based on either selecting specific pixels or small skin areas, performed similarly well. They achieved high intra- and inter-rater reliability with the intraclass correlation coefficient (ICC) and Krippendorff’s alpha well above 0.90. These results indicated that smartphone-based dermatoscopy could be a convenient and precise way to evaluate skin erythema severity. However, better outlined, or even automated ISMs, are likely to improve the intra- and inter-rater reliability in severe erythematous cases.

In this study, we clinically evaluated a pulse oximeter-based device for automated capillary refill time (CRT) estimation in dogs and cats. CRT can reveal conditions like shock or anemia in dogs and cats. However, visual CRT estimation has low repeatability, and the available optical systems for automated estimation are not suitable for pets. We evaluated a custom-made portable CRT measuring device on various measurement sites of 12 dogs and 11 cats with parallel visual CRT estimation on the gum by treating veterinarian. The capillary refill was also recorded by a video camera for reference. The visual and video procedures were moderately correlated with the coefficient of 0.61; visual CRT values were on average for 0.18 s longer than the reference. On average, ~32% of measurements with the proposed device were successful. The rest failed due to excessive pigmentation, motion artifacts, and other pressure-induced effects. The measurement sites of the metacarpal pad, digit, and tail were moderately correlated with the reference values with coefficients of 0.53, 0.58, and 0.42, respectively.