Evaluation of Thermographic Imaging in Canine Hindlimb Muscles After 6 Min of Walking—A Pilot Study

Abstract

Objective: To evaluate changes in superficial temperature of hindlimb muscles before and after a 6-min walk in healthy dogs. Methods: Two infrared thermographic images were captured of the proximal and distal hindlimbs of 11 healthy dogs before and after a 6-min walk. Orthopedic exam and objective gait analysis confirmed the healthy status of study subjects. Superficial temperatures of the gastrocnemius, biceps femoris, and gracilis were assessed. Analysis of images was performed using 2 different methods of region of interest (ROI) selection. ROI were selected first using one point (single pixel) in the muscle and then separately by selecting a line (LN) corresponding to many points of each muscle belly from which an average was taken. P < 0.05 was considered significant. Results: There was no significant change in temperature using point ROI before and after 6 min of walking of the gastrocnemius, gracilis, and biceps femoris muscles (p = 0.273, p = 0.349, p = 0.351, respectively). Using linear ROI, both biceps femoris and gracilis muscles exhibited significant increases in temperature (p < 0.0001, p = 0.032, respectively). There was no significant increase in temperature of gastrocnemius muscle for both point and linear ROI selection (p = 0.273, p = 0.448, respectively). The right biceps femoris temperatures were higher compared to left biceps femoris using the linear ROI before and after walks (p < 0.0001). The overall (left and right limbs pooled) standard deviation of point selected values were greater than LN selected values of the biceps femoris (1.35 and 1.11) and gastrocnemius (1.51 and 1.23). In contrast, standard deviation for the gracilis measurements were decreased using point selection vs. LN selection (1.09 and 1.3). Conclusions: The biceps femoris and gracilis muscles demonstrated significant increases in surface temperature after 6 min of walking using the linear method of ROI. Measurement of numerous points along the entire length of the biceps femoris and gastrocnemius muscles may provide a more accurate assessment of the increased vascularity within the tissues resulting from work compared to single point selection. Clinical Significance: Prior activity and ROI selection method should be considered when interpreting thermography results.

Thermal imaging evaluation of the felines paw pad temperature before and after walking: A pilot study

“…Furthermore, we also compared the difference in the SI between the point and line ROI both before and after the 6MWT, but no significant results were found. Interestingly, previous research investigating the muscle temperature change of healthy dogs after a walking test using a similar ROI selection as the current study also found some different results (Repac et al 2020). Authors of this study demonstrated that the line ROI would be greater for early pathology detection as there were significant temperature increases in the muscles (e.g., biceps femoris) after walking when using the line ROI, rather than the point ROI.…”

“…Authors of this study demonstrated that the line ROI would be greater for early pathology detection as there were significant temperature increases in the muscles (e.g., biceps femoris) after walking when using the line ROI, rather than the point ROI. One explanation may contribute to the difference between the above-mentioned study and the current one -since we only investigated the temperature change of a cat's paw pad, the length of the line used in this study would be much shorter than the length Repac et al (2020). Consequently, the average temperature of the line ROI measured in this study may be more localised.…”

“…There are two different methods that have previously been used to select the region of interest (ROI) in thermal imaging, the point ROI and line ROI. Repac et al (2020) conducted a study on healthy dogs which evaluated the temperature changes of the hindlimb muscles after walking using both ROI methods. They found that the line ROI is more accurate in detecting temperature changes than the point ROI.…”

“…Thus, measuring the temperature differences between the paw pads could help to detect the initial lameness or muscle injuries in cats, especially after a certain amount of exercise. The 6-min walking test (6MWT), which was originally used to assess the cardiopulmonary function in humans, has been widely applied to veterinary medicine to differentiate healthy animals from ones with cardiopulmonary or neuromuscular diseases (Boddy et al 2004;Swimmer and Rozanski 2011;Acosta et al 2016;Repac et al 2020). Due to its simplicity, the effectiveness of recognising a gait disability in animals when combining with thermal imaging is worth investigating more.…”

Thermal Imaging Following Exercise in Working Dogs

“…Infrared thermal imaging technology offers a method to indirectly investigate differential dog muscle activity after exercise on a simulated disaster rubble pile compared to treadmill exercise (10)(11)(12). It is hypothesized that the circulation, visualized by infrared thermal imagery, of dog muscles following treadmill exercise would be different than that following rubble search, due to the different movement patterns required for the two activities.…”