# Infrared Thermal Imaging Analysis in Screening for Toddler's Fracture: A Proof-of-Concept Study
## 2 Materials and Methods
### Data Acquisition  
Prior to infrared thermal imaging, the participant's relevant details were recorded. These included:  
* Age;
* Sex;
* Time and date of the injury;
* Time and date of arrival at the hospital;
* Details of any medication taken;
* Cause of the injury;
* Diagnosis type (fracture or not fracture) using an X-ray radiograph on an initial admission and, if required, the follow-on visit to the hospital;
* Fracture details in cases where fracture is confirmed.  
A dedicated room close to the X-ray imaging department was used for infrared thermal imaging. The room did not have heat sources that could have interfered with the recording. The single window in the room was kept closed and the recording was kept furthest from the window. Any possible sources of draught were minimized. Temperature variations in the recording room conformed to be within the acceptable range of 18-25 \({}^{\circ}\)C [24].  
To the best of our knowledge, there has not been a study determining the minimum requirements (e.g., temperature sensitivity, image resolution, etc.) for the infrared thermal camera to screen bone fractures; however, the camera needs to be able to differentiate between temperature changes caused by the injury, resulting in a fracture, and those without a fracture. Cameras with higher specifications tend to be significantly more expensive; therefore, there is a balance between cost vs. a camera's ability to carry out the expected task. The infrared thermal camera used in this study was a FLIRT T630 sc (Teledyne FLIR, Wilsonville, OR, USA) [25]. The camera's noise-equivalent temperature difference (NETD: a measure indicating how well the camera can differentiate between very small differences in infrared thermal radiation) is less than 40 mK; its image resolution is 640 \(\times\) 480 pixels; its spectral range is 7.5 \(\upmu\)m-13 \(\upmu\)m; its dynamic range is 14 bits; its operating temperature is \(-\)14 \({}^{\circ}\)C-50 \({}^{\circ}\)C; and the camera's integrated lens is 18 mm (25\({}^{\circ}\)). A computer, connected to the camera, facilitated data storage. Emissivity was set to 0.95, which is suitable for human body infrared thermal recordings. The participants acclimatized to the recording room temperature for 10 min prior to the recordings. The 10-min acclimatization period struck a balance between ensuring the participants (very young children) were accustomed to the room temperature and ensuring their cooperation with the recording. The aim was to minimize their hospital stay at a time when they might be stressed due to their injury while obtaining suitable recordings. This period was in line with our study's ethical approval. The infrared thermal camera was kept in the recording room, thus it did not need acclimatization. The distance between the camera and the participant was 1 m.  
For the recording, the participant sat on the side of hospital bed with their legs uncovered and clearly visible in the thermal camera's field of view. In some cases, parents held their child by sitting next to them for safety and reassurance. The data analysis was carried out using Matlab(r) (version R2023b, Mathworks Inc., Cambridge, UK [26]).  
A 10-s video (frame rate 30 frames per second) was recorded. This allowed for the averaging of the recorded frames (across the 300 frames) to reduce thermal noise.