Thermal Imaging (TI)
TI and dynamic infrared thermography (DIRT), have now shown promise as an innovative tool in several medical specialties. [42] Thermal imaging technology utilizes electromagnetic radiation in the near-infrared (NIR) range, specifically wavelengths ranging from 780 to 1400 nm. Unlike visible light, which is perceived by the human eye, NIR radiation is invisible and requires technology-based recording, analysis, and interpretation. By employing specialized cameras sensitive to NIR wavelengths, such as infrared cameras, it becomes possible to capture and visualize NIR radiation. [43]
Using the detection of infrared radiation emitted by the body, thermography produces accurate visual representations of surface temperatures, allowing areas of increased or decreased blood flow to be highlighted. [44] (see Figure 4.)
As an advanced, non-invasive and low-cost, mostly smartphone-based [45-49] imaging technique, TI offers valuable insights into graduation of burn depths [45, 46], as well as thermal physiology[42].
TI can provide postoperative monitoring in pedicled flaps that supports clinical assessment with high sensitivity and specificity. A study by Rabbani et al on 84 pedicled and distant flaps showed a 96 per cent accuracy of TI with a sensitivity of 98.7 per cent and specificity of 75 per cent in detecting vascular insults of the flap. [49] DIRT was further described in intraoperative Monitoring in which the skin surface is exposed to a cold challenge and then the pattern of skin rewarming is analyzed. [27]
Since 1968, TI has been known for the first time as an accurate way to assess perforating vessels, so this technique has assisted in finding so-called perforasomes in flap planning. [50-54] In a meta-analysis by Hudson et al, smartphone-based TI was able to detect 378/405 (93.3%) perforating vessels here, while the state-of-the-art method of CT angiography (CTA) detected 402/405 (99.2%). The authors concluded that they had found a cost-effective, safe non-invasive and radiation-free way of assessing free flaps that is independent of all levels of training. [55] TI technology is also already represented in some experiences for monitoring microvascular free flaps [47, 56, 57] For example, Meyer et al were able to confirm a high accuracy of TI in flap assessment in 21 free head and neck reconstructions. [47]
Thus, thrombosis and secondary vessel occlusion can be detected significantly earlier using TI, thus shortening the response time for revision and significantly increasing the probability of survival of the free flap. [57]