Detection of Perforators Using Smartphone Thermal Imaging

1 Songsak Suphachokauychai, MD Faculty of Medicine Department of Orthopaedics Bhumibol Adulyadej Hospital Bangkok, Thailand Kidakorn Kiranantawat, MD, FRCST Division of Plastic and Maxillofacial Surgery Department of Surgery Ramathibodi Hospital Mahidol University Bangkok, Thailand Kanit Sananpanich, MD Faculty of Medicine Department of Orthopaedics Chiang Mai University Chiang Mai, Thailand Sir: W read with interest the article by Hardwicke et al1 on the concept of using low-cost thermal imaging for perforator identification. We agree with the authors that low-cost thermal imaging (thermoscan) provides an adjunct investigation because handheld Doppler has a 45% chance of producing a false positive overall2; with an inexperienced surgeon, the number is even higher. In addition, high-quality 3-dimensional computed tomography angiogram is not available in every hospital. We would like to share our experiences using 2 low-cost thermoscan (second-generation FLIR One and FLIR C2). The second-generation FLIR One has a better thermal resolution, but sometimes the application is not stable and locks for a short period of time (important images can be missed). The FLIR C2 does not have this problem, but its price is also higher ($700 vs $200). The second-generation FLIR One is able to lock the thermal range but it does not show the data on the screen; this could be a big problem that we will discuss later. We would like to share some tips from our experiences to minimize imaging errors while using lowcost thermoscan. First, always operate on dry skin. Thermoscan detects temperature from the surface, and it is critical to scan a dry surface. Even small amounts of moisture on the skin surface will produce an emission error that could block the perforator. Second, when an attempt was made to move the unit closer to the skin, the image was not in focus; to produce a clear image with the first-generation FLIR One, you need to be at least 100 cm from the skin. The second generation of the FLIR One and FLIR C2 allow a much shorter distance from the skin, about 15 cm. Third, you must focus in the cen-