Plastic and Reconstructive Surgery • November 2014 at this wavelength, but any adverse reaction would be photothermal in nature and require much higher irradiances than used in our study, where temperature elevation is not sufficient for a thermal coagulation effect. Although we did not have a laser-only control (no rose bengal) and did not perform histologic examination of the surrounding tissue immediately after treatment, we do not expect photothermal damage under the conditions applied in our study. Because we saw no evidence of reduced blood supply to the tissue following treatment, we do not think that immune changes generated as described by Drs. Tambasco and Salgarello are occurring in this manner. Although we demonstrated that cross-linking did occur, as stated in our article, the exact mechanism behind our work requires further study. We continue to evaluate the passivation technique and anticipate future dialogue. DOI: 10.1097/PRS.0000000000000628
Justin Fernandes, M.D. William G. Austen, Jr., M.D. Division of Plastic and Reconstructive Surgery Massachusetts General Hospital Boston, Mass. Correspondence to Dr. Austen Division of Plastic and Reconstructive Surgery Massachusetts General Hospital 15 Parkman Street, WAC 435 Boston, Mass. 02114 [email protected]
DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication. REFERENCES 1. He L, Vicente CP, Westrick RJ, Eitzman DT, Tollefsen DM. Heparin cofactor II inhibits arterial thrombosis after endothelial injury. J Clin Invest. 2002;109:213–219. 2. Apfelberg DB, Maser MR, Lash H. Argon laser treatment of cutaneous vascular abnormalities: Progress report. Ann Plast Surg. 1978;1:14–18.
Detection of Perforators Using Thermal Imaging Sir:
W
e read with interest the article by Sheena et al.,1 an interesting experimental study on the use of infrared thermography for perforator mapping. Handheld Doppler imaging was used to verify the accuracy of thermal imaging in identifying perforators. They located more perforators with thermal imaging than could be confirmed by hand-held Doppler imaging. Given the high concordance, they are confident that this was a reflection of the higher accuracy of thermal imaging over hand-held Doppler imaging.
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Giunta et al. evaluated the use of hand-held Doppler imaging in the planning of perforator flaps.2 The technique created many false-positive results, attributed to the high sensitivity of the method. Very small perforators unsuitable for surgery were also detected. It is therefore important to differentiate between detection of perforators as a part of the thermal pattern in the area of interest and detection of perforators suitable for surgery. Sheena et al. could be right that thermal imaging is more accurate than hand-held Doppler imaging for perforator mapping. However, the purpose of perforator mapping is to find suitable perforators with respect to their hemodynamic properties and locations. With a method similar to that of Sheena et al., Tenorio et al. used thermal imaging without a cold challenge in perforator mapping.3 In our experience, the use of dynamic infrared thermography increases the usefulness of thermal imaging in preoperative mapping.4 In dynamic infrared thermography, the area of interest is exposed to a mild cold challenge that is well tolerated by patients. The rate and pattern of rewarming at the first appearing hotspots are analyzed. We use a desktop fan blowing air at room temperature over the skin surface. Intraoperatively, a sterile metal plate at room temperature is applied to the skin for 10 seconds. Rapid hotspot rewarming indicates that the perforator transports more blood to the skin surface than perforators that produce slower rewarming. A progressive rewarming around the hotspot indicates a well-vascularized network around the hotspot. We use dynamic infrared thermography in the preoperative planning and intraoperative evaluation of perforators in both free flaps and free-style flaps. Sheena et al. were unable to detect arterial Doppler sounds that were not associated with hotspots. This is in contrast to the results from our studies where not all locations of arterial Doppler sounds were associated with hotspots. In addition, the hand-held Doppler device creates false-positive results when axial vessels run superficially.2 On computed tomographic angiography, we also detected large medial perforators with a lateral course in the subcutaneous tissue that produced arterial Doppler sounds but no hotspots. The selected perforators based on dynamic infrared thermography correlated well with clearly visible perforators on computed tomographic angiography. We reported earlier that a high number of the selected hotspots were related to perforators at the tendinous intersection on computed tomographic angiography and intraoperatively.4 Blondeel et al. found that perforators at the tendinous intersection are often larger than average.5 In the planning of deep inferior epigastric perforator flaps, it is also important to realize that not all hotspots are related to perforators from the deep inferior epigastric artery but may also be associated with the superficial inferior epigastric system.4 DOI: 10.1097/PRS.0000000000000595
Volume 134, Number 5 • Letters Louis de Weerd, M.D., Ph.D. Department of Plastic Surgery and Hand Surgery
Sven Weum, M.D., Ph.D. Department of Radiology
James B. Mercer, Ph.D. University Hospital North Norway Medical Imaging Research Group Institute of Clinical Medicine Faculty of Health Sciences UIT The Artic University of Norway Tromsø, Norway Correspondence to Dr. de Weerd Department of Plastic Surgery and Hand Surgery University Hospital North Norway Sykehusveien 38 9038 Tromsø, Norway [email protected]
disclosure The authors have no financial interest in any of the products or devices mentioned in this communication. references 1. Sheena Y, Jennison T, Hardwicke JT, Titley OG. Detection of perforators using thermal imaging. Plast Reconstr Surg. 2013;132:1603–1610. 2. Giunta RE, Geisweid A, Feller AM. The value of preoperative Doppler sonography for planning free perforator flaps. Plast Reconstr Surg. 2000;105:2381–2386. 3. Tenorio X, Mahajan AL, Elias B, et al. Locating perforator vessels by dynamic infrared imaging and flow Doppler with no thermal cold challenge. Ann Plast Surg. 2011;67: 143–146. 4. de Weerd L, Weum S, Mercer JB. The value of dynamic infrared thermography (DIRT) in perforator selection and planning of free DIEP flaps. Ann Plast Surg. 2009;63:274–279. 5. Blondeel PN, Beyens G, Verhaeghe R, Van Landuyt K, Monstrey SJ, Matton G. Doppler flowmetry in planning of perforators. Br J Plast Surg. 1998;51:202–209.
Reply: Detection of Perforators Using Thermal Imaging Sir:
We thank Drs. de Weerd et al. for their letter regarding our article1 and their pioneering work on surgical thermal imaging. We hope to address their considered observations here. Our confidence that thermal imaging was more sensitive than hand-held Doppler imaging was because nearly all thermal imaging hotspots were eventually confirmed by hand-held Doppler imaging, with only 3 percent of all thermal imaging hotspots not confirmed by hand-held Doppler imaging. The initial discrepancy was greater, but diminished with careful and prolonged hand-held Doppler imaging attempts, as some smaller
thermal imaging hotspots generated faint hand-held Doppler signals that took longer to define. We agree that some hotspots may represent false-positives in the reconstructive context; furthermore, there may be false-negatives also, but correlation with actual perforators can only be confirmed intraoperatively. Our study therefore did not aim to test the true sensitivity or specificity of thermal imaging regarding suitable perforators as a primary endpoint, but simply to compare thermal imaging to the currently widely used hand-held Doppler imaging assessment of potential perforators. Our findings clearly confirm that thermal imaging is as effective and, perhaps more importantly, faster and more complete at mapping all perforators identified using hand-held Doppler imaging, thus affording the surgeon an instant image for locating all potential skin perforators in an anatomical region of interest. Hand-held Doppler imaging cannot match this level of data acquisition on a whole region, which might explain why we could not find any hand-held Doppler signals away from the thermal imaging hotspots. The blind process is just that—too inefficient at screening a whole body region completely, and with known accuracy limitations.2 Although the easy, cheap, and portable hand-held Doppler device still has an important role, we should also acknowledge that its predictive accuracy might be improved by the perforator compression test.3 That said, we feel that we demonstrated the superiority of adjunctive thermal imaging. Our article discussed the dynamic infrared thermography method,4 and we are aware of the purported advantages of determining perforator physiology. However, in testing, we found the artifacts of cooling harder to control, and hypothesize that the size (skin surface area) of each thermal imaging hotspot would correlate with perforator perfusion potential or surgical “dominance,” making dynamic infrared thermography cooling unnecessary. Further studies are required to investigate this as a research priority; correlating thermal imaging with computed tomographic angiography and operative findings is the best way to do this, as mentioned in our article. Incidentally, we have noted that if patients are cooled (by exposure as part of the perioperative preparations), confirmation of previously identified (by whatever method) perforators with hand-held Doppler imaging can prove difficult and sometimes impossible. We agree that differentiating (1) perforators from deep and superficial inferior epigastric origin and (2) hand-held Doppler imaging false-positives from deeper irrelevant vessels is an issue. Ultimately, each imaging modality has pros and cons and thus a multiple-imaging modality approach may have the best accuracy. DOI: 10.1097/PRS.0000000000000631
Yezen Sheena, B.Sc., M.R.C.S. Joseph Hardwicke, Ph.D., F.R.C.S.(Plast.) Toby Jennison, M.Sc., M.R.C.S.(Eng.) O. Garth Titley, M.Sc., F.R.C.S.(Plast.) University Hospitals of Birmingham NHS Foundation Trust Birmingham, United Kingdom
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Justin Fernandes, M.D. William G. Austen, Jr., M.D. Division of Plastic and Reconstructive Surgery Massachusetts General Hospital Boston, Mass. Correspondence to Dr. Austen Division of Plastic and Reconstructive Surgery Massachusetts General Hospital 15 Parkman Street, WAC 435 Boston, Mass. 02114 [email protected]
DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication. REFERENCES 1. He L, Vicente CP, Westrick RJ, Eitzman DT, Tollefsen DM. Heparin cofactor II inhibits arterial thrombosis after endothelial injury. J Clin Invest. 2002;109:213–219. 2. Apfelberg DB, Maser MR, Lash H. Argon laser treatment of cutaneous vascular abnormalities: Progress report. Ann Plast Surg. 1978;1:14–18.
Detection of Perforators Using Thermal Imaging Sir:
W
e read with interest the article by Sheena et al.,1 an interesting experimental study on the use of infrared thermography for perforator mapping. Handheld Doppler imaging was used to verify the accuracy of thermal imaging in identifying perforators. They located more perforators with thermal imaging than could be confirmed by hand-held Doppler imaging. Given the high concordance, they are confident that this was a reflection of the higher accuracy of thermal imaging over hand-held Doppler imaging.
850e
Giunta et al. evaluated the use of hand-held Doppler imaging in the planning of perforator flaps.2 The technique created many false-positive results, attributed to the high sensitivity of the method. Very small perforators unsuitable for surgery were also detected. It is therefore important to differentiate between detection of perforators as a part of the thermal pattern in the area of interest and detection of perforators suitable for surgery. Sheena et al. could be right that thermal imaging is more accurate than hand-held Doppler imaging for perforator mapping. However, the purpose of perforator mapping is to find suitable perforators with respect to their hemodynamic properties and locations. With a method similar to that of Sheena et al., Tenorio et al. used thermal imaging without a cold challenge in perforator mapping.3 In our experience, the use of dynamic infrared thermography increases the usefulness of thermal imaging in preoperative mapping.4 In dynamic infrared thermography, the area of interest is exposed to a mild cold challenge that is well tolerated by patients. The rate and pattern of rewarming at the first appearing hotspots are analyzed. We use a desktop fan blowing air at room temperature over the skin surface. Intraoperatively, a sterile metal plate at room temperature is applied to the skin for 10 seconds. Rapid hotspot rewarming indicates that the perforator transports more blood to the skin surface than perforators that produce slower rewarming. A progressive rewarming around the hotspot indicates a well-vascularized network around the hotspot. We use dynamic infrared thermography in the preoperative planning and intraoperative evaluation of perforators in both free flaps and free-style flaps. Sheena et al. were unable to detect arterial Doppler sounds that were not associated with hotspots. This is in contrast to the results from our studies where not all locations of arterial Doppler sounds were associated with hotspots. In addition, the hand-held Doppler device creates false-positive results when axial vessels run superficially.2 On computed tomographic angiography, we also detected large medial perforators with a lateral course in the subcutaneous tissue that produced arterial Doppler sounds but no hotspots. The selected perforators based on dynamic infrared thermography correlated well with clearly visible perforators on computed tomographic angiography. We reported earlier that a high number of the selected hotspots were related to perforators at the tendinous intersection on computed tomographic angiography and intraoperatively.4 Blondeel et al. found that perforators at the tendinous intersection are often larger than average.5 In the planning of deep inferior epigastric perforator flaps, it is also important to realize that not all hotspots are related to perforators from the deep inferior epigastric artery but may also be associated with the superficial inferior epigastric system.4 DOI: 10.1097/PRS.0000000000000595
Volume 134, Number 5 • Letters Louis de Weerd, M.D., Ph.D. Department of Plastic Surgery and Hand Surgery
Sven Weum, M.D., Ph.D. Department of Radiology
James B. Mercer, Ph.D. University Hospital North Norway Medical Imaging Research Group Institute of Clinical Medicine Faculty of Health Sciences UIT The Artic University of Norway Tromsø, Norway Correspondence to Dr. de Weerd Department of Plastic Surgery and Hand Surgery University Hospital North Norway Sykehusveien 38 9038 Tromsø, Norway [email protected]
disclosure The authors have no financial interest in any of the products or devices mentioned in this communication. references 1. Sheena Y, Jennison T, Hardwicke JT, Titley OG. Detection of perforators using thermal imaging. Plast Reconstr Surg. 2013;132:1603–1610. 2. Giunta RE, Geisweid A, Feller AM. The value of preoperative Doppler sonography for planning free perforator flaps. Plast Reconstr Surg. 2000;105:2381–2386. 3. Tenorio X, Mahajan AL, Elias B, et al. Locating perforator vessels by dynamic infrared imaging and flow Doppler with no thermal cold challenge. Ann Plast Surg. 2011;67: 143–146. 4. de Weerd L, Weum S, Mercer JB. The value of dynamic infrared thermography (DIRT) in perforator selection and planning of free DIEP flaps. Ann Plast Surg. 2009;63:274–279. 5. Blondeel PN, Beyens G, Verhaeghe R, Van Landuyt K, Monstrey SJ, Matton G. Doppler flowmetry in planning of perforators. Br J Plast Surg. 1998;51:202–209.
Reply: Detection of Perforators Using Thermal Imaging Sir:
We thank Drs. de Weerd et al. for their letter regarding our article1 and their pioneering work on surgical thermal imaging. We hope to address their considered observations here. Our confidence that thermal imaging was more sensitive than hand-held Doppler imaging was because nearly all thermal imaging hotspots were eventually confirmed by hand-held Doppler imaging, with only 3 percent of all thermal imaging hotspots not confirmed by hand-held Doppler imaging. The initial discrepancy was greater, but diminished with careful and prolonged hand-held Doppler imaging attempts, as some smaller
thermal imaging hotspots generated faint hand-held Doppler signals that took longer to define. We agree that some hotspots may represent false-positives in the reconstructive context; furthermore, there may be false-negatives also, but correlation with actual perforators can only be confirmed intraoperatively. Our study therefore did not aim to test the true sensitivity or specificity of thermal imaging regarding suitable perforators as a primary endpoint, but simply to compare thermal imaging to the currently widely used hand-held Doppler imaging assessment of potential perforators. Our findings clearly confirm that thermal imaging is as effective and, perhaps more importantly, faster and more complete at mapping all perforators identified using hand-held Doppler imaging, thus affording the surgeon an instant image for locating all potential skin perforators in an anatomical region of interest. Hand-held Doppler imaging cannot match this level of data acquisition on a whole region, which might explain why we could not find any hand-held Doppler signals away from the thermal imaging hotspots. The blind process is just that—too inefficient at screening a whole body region completely, and with known accuracy limitations.2 Although the easy, cheap, and portable hand-held Doppler device still has an important role, we should also acknowledge that its predictive accuracy might be improved by the perforator compression test.3 That said, we feel that we demonstrated the superiority of adjunctive thermal imaging. Our article discussed the dynamic infrared thermography method,4 and we are aware of the purported advantages of determining perforator physiology. However, in testing, we found the artifacts of cooling harder to control, and hypothesize that the size (skin surface area) of each thermal imaging hotspot would correlate with perforator perfusion potential or surgical “dominance,” making dynamic infrared thermography cooling unnecessary. Further studies are required to investigate this as a research priority; correlating thermal imaging with computed tomographic angiography and operative findings is the best way to do this, as mentioned in our article. Incidentally, we have noted that if patients are cooled (by exposure as part of the perioperative preparations), confirmation of previously identified (by whatever method) perforators with hand-held Doppler imaging can prove difficult and sometimes impossible. We agree that differentiating (1) perforators from deep and superficial inferior epigastric origin and (2) hand-held Doppler imaging false-positives from deeper irrelevant vessels is an issue. Ultimately, each imaging modality has pros and cons and thus a multiple-imaging modality approach may have the best accuracy. DOI: 10.1097/PRS.0000000000000631
Yezen Sheena, B.Sc., M.R.C.S. Joseph Hardwicke, Ph.D., F.R.C.S.(Plast.) Toby Jennison, M.Sc., M.R.C.S.(Eng.) O. Garth Titley, M.Sc., F.R.C.S.(Plast.) University Hospitals of Birmingham NHS Foundation Trust Birmingham, United Kingdom
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