Reply: Detection of Perforators Using Smartphone Thermal Imaging

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Sir: We would like to thank Drs. Ko and Chiu for their informed commentary on our recently published Ideas and Innovations article.1 Thermal imaging is still in its infancy and as such should be considered more of an art than a science in the acquisition of thermograms that can be used in conjunction with established imaging modalities. The effect of background infrared radiation was highlighted in the article, and in our department, we too have tried dynamic image acquisition to optimize the capture of clinically relevant thermograms. In other pilot studies that we have performed, a “cold challenge” by way of conductive surface cooling using a topical cold compress, evaporative surface cooling using ethyl chloride spray, or convective surface cooling with an electric fan was evaluated. We have found that dynamic images collected in this way take longer and do not add significantly to the overall result—adding a layer of complexity to the image capture, we feel, may put people off from attempting to use thermography. The largest “hotspots” from the exposure method correlate well with the most rapid rewarming hotspots after a cold challenge. We have also found that patients may not be happy to undergo a cold challenge during their clinical consultation or preoperative assessment. High-resolution thermal imaging may be cost-prohibitive, and although the images can be of both high image and high thermal resolution, unless the technology is inexpensive and simple to use with minimal training, it will not catch on. Doppler ultrasound is relatively cheap and, with training and practice, can provide information about perforators in the clinic, on the ward, and in the operating room—as such, this is probably the “mainstay” technology used around the world. In our article, we attempted to provide the simplest protocol for the greatest improvement in data capture. The exposure method, in our experience, provided adequate information with the caveat that it is only an adjunct, and must be used in conjunction with other modalities. We disagree that the delineation of the perforasome with thermal imaging is too inconsistent or inaccurate—it is purely an indicator of possible tissue perfusion. A simple “back-of-the-hand” test during the raising of the deep inferior epigastric perforator flap indicates cool zones that may lack vascular supply. Confirmation of these cool zones by thermography must also be confirmed clinically with evidence of bleeding at the cut edge. We do not advocate the reliance on thermography to indicate the size of the perforasome, and the use of allied technologies such as indocyanine green angiography will play an important role here. We hope that this simple and inexpensive technology will be tried and tested by more surgeons to truly establish its role in all areas of plastic and reconstructive surgery. At present, we have only presented it as an idea and innovation, rather than a fully appraised technology. It is a safe, noncontact, noncontrast imaging modality that definitely does need further evaluation, and possibly it will now be brought to the awareness of more surgeons worldwide. All new techniques and technologies must be challenged to determine their true efficacy. DISCLOSURE The authors have no financial interest in any of the products or devices mentioned in this communication. Joseph T. Hardwicke, Ph.D., F.R.C.S.(Plast.)Department of Plastic SurgeryUniversity Hospitals of Coventry and WarwickshireCoventry, andSchool of Clinical and Experimental MedicineUniversity of BirminghamBirmingham Joanna M. Skillman, M.A.(Cantab.), F.R.C.S.(Plast.)Department of Plastic SurgeryUniversity Hospitals of Coventry and WarwickshireCoventry, United Kingdom

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