# Infrared Thermal Imaging Analysis in Screening for Toddler's Fracture: A Proof-of-Concept Study
## 1 Introduction
### Infrared Imaging and Its Application in Bone Fracture Detection  
Objects with a temperature above absolute zero (\(-273.15\)\({}^{\circ}\)C) radiate infrared (IR). IR radiation (wavelength 700 nm-1 mm) is part of the electromagnetic spectrum that can be detected using either photon detectors or thermal detectors [7]. In photon detectors, the IR radiation is absorbed by interaction with the object's electrons. An electrical signal results from a change in electronic energy distribution. These detectors exhibit excellent signal-to-noise performance and a very fast response, but they require cryogenic cooling [7]. In thermal detectors, the absorbed incident radiation increases the object's temperature, and the changes in its physical properties are used to generate an electrical output.  
IR thermal imaging has received growing attention in the medical field [8; 9]. A review of infrared thermal imaging for diagnosing bone fractures [10] summarized the findings of studies utilizing infrared thermal imaging for detecting fractures in the radius, ulna, carpus, metacarpal and phalanges, tibia, fibula, tarsus, metatarsal and phalanges, clavicle, scapula, and facial and spinal bones where thermal changes appear at the skin level, due to vascular physiological changes.  
Infrared thermal imaging has been effective in detecting and monitoring musculoskeletal injuries [11]. Statistical analysis of infrared thermal images has demonstrated that the temperature of a fractured wrist is significantly higher than an uninjured wrist [12]. The study was based on 40 children admitted to a hospital's emergency department for an injury to one of their wrists. The participants' mean age was 10.5 years (standard deviation 2.63 years). Nineteen participants were diagnosed with a wrist fracture using X-ray radiography; the remaining 21 patients were diagnosed with a sprain. Overall, the temperature of the fractured wrists was 1.52% higher than the uninjured wrists. The temperature of sprained wrists was 0.97% higher than the uninjured contralateral wrist but, unlike the fractured wrist, the increase in temperature was not statistically significant. In a continuation of this study with the same participants, a multilayer perceptron artificial neural network was trained to differentiate between fractured and sprained wrists [13]. The method provided a sensitivity and specificity of 84.2% and 71.4%, respectively, in differentiating between wrist fractures and wrist sprains. Infrared thermal imaging has shown potential in identifying fractured thoracic vertebrae in children (number: 11; age: 5-18 years) with osteogenesis imperfecta [14]. Osteogenesis imperfecta is a genetic disorder in which bones become more fragile, thus increasing the risk of fracture. The authors concluded that infrared thermal imaging could provide a cost-effective and quick (as compared with magnetic resonance imaging or computerized tomography) modality for detecting fractures. The mean temperature of fractured distal forearms in 25 patients (mean age 65.9 \(\pm\) 10.4 years) were compared with the uninjured contralateral. The temperature difference initially increased up to 3 weeks and then subsided in the following weeks [6]. A related study compared the temperature difference between forearm fractures and the contralateral uninjured side in 19 children aged 4-14 years and found an increase in the temperature of the injured area followed by a reduction in the following weeks [15]. Infrared thermal imaging has been applied to detect fractures associated with leg, hand, forearm, clavicle, foot, and ankle in a study involving 45 patients [16]. The study concluded that infrared thermal imaging could be a valuable complementary diagnostic modality to the X-ray radiograph.