A study conducted by a team of UK researchers suggests that smartphone-compatible thermal-imaging technology can be used in certain medical contexts, such as detecting cutaneous perforators and assessing burn depth.
“Although not designed for use in the medical sector,” says study co-author Joseph T. Hardwicke, Ph.D., of the School of Clinical and Experimental Medicine at the University of Birmingham Medical School, “this emerging technology has opened up the application of this technology to plastic surgeons worldwide, as the smartphone is now a ubiquitous item and with the thermal-imaging camera attached it can fit easily in the pocket and is ideal for use in the clinic, on the ward or in the operating theatre.”
In their proof-of-concept study, the researchers used the FLIR ONE (from FLIR Systems Inc., Wilsonville, Ore.), a miniature, smartphone-compatible thermal-imaging camera that costs less than $200. The camera uses a long-wave infrared sensor that has a working temperature range of 0° C to 100°C, though due to its compactness it offers a lower resolution image and narrower temperature-detection range, than more sophisticated — and expensive — thermal-imaging cameras. The simple “point-and-shoot” technology requires minimal training.
To enhance image display and interpretation, the researchers used a visible-light camera to take photos that are digitally merged with the thermal images. The authors note that the images — especially close-ups — do not superimpose perfectly on each other, something to be taken into account when using this technology. Still images and video recordings can be created from real-time images via a free app.
Researchers assessed patients and healthy volunteers using this thermal imaging procedure in three areas: detecting and mapping perforators, defining perforasomes and monitoring free flaps. All images were recorded at 22°C and 50% relative humidity.
To assess the sensitivity for perforator mapping, 10 healthy volunteers were imaged at a distance of 70 cm, after exposure of the abdominal wall or thigh. Multiple abdominal cutaneous perforators, as signified by hotspots on the thermal images, were identified for hand-held ultrasound localization.
The researchers also performed intraoperative perforasome imaging on a 55-year-old woman undergoing a right mastectomy with an immediate deep inferior epigastric artery perforator flap. Preoperative computed tomographic angiography confirmed a right medial row perforator. A thermal image was recorded and the perforasome delineated, allowing excision of affected tissues. Thermal imaging was also used post-op as an adjunct to clinical free-flap monitoring. A thermal image showed both hotspots at the site of the skin paddle and cutaneous perforators to the mastectomy skin flaps.
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“The most important finding of this study was that a commercial thermal imaging camera, designed for the home-user and hobbyist, can be used to assess the cutaneous blood flow in patients,” study co-author Joseph T. Hardwicke, Ph.D., of the School of Clinical and Experimental Medicine at the University of Birmingham Medical School, tells Cosmetic Surgery Times. “This is vital for the successful planning of reconstructive surgery, which we as plastic surgeons know relies on the identification and preservation of blood supply to the tissues we are using. Although other technologies have been established for this process — MRI/CT/Doppler — this is cheap, non-invasive and requires minimal training. Previous experimental studies using thermal imaging have used equipment that costs tens of thousands of dollars.”
Dr. Hardwicke says that although image resolution is less in the FLIR ONE device, it is satisfactory for the identification of perforator blood vessels that supply the skin.
According to the study abstract, none of the authors has a financial interest in the products or devices mentioned.
The study appears in the January issue of Plastic and Reconstructive Surgery.
