Dynamic Infrared Thermography

Smartphone Thermal Imaging as an Adjunct to Identify Free Flap Perforators and Assisting Flap Design: A Pilot Study

Background

The main technique for identification of free flap perforator vessels is Doppler sonography, which is not always accurate, user dependent and affected by the patient's body habitus.

Methods

Adult patients undergoing head and neck resection and free flap reconstruction at two academic institutions were enrolled. Doppler sonography was used to identify perforators, and were marked using a skin marker. The donor site was cooled down for 3 min using a sterile iced saline bag. FLIR-ONE (FLIR Systems Inc., Wilsonville, OR) camera was used to assess for "hot spots" during a 3-5 min period of re-warming as a surrogate for cutaneous blood flow. The distance between the Doppler signal location, and the "hot spot" was recorded. The position of the perforator was then identified intraoperatively and the distances between the surgical position, the Doppler and "hot spot" were recorded.

Results

A total of 28 patients were included. For all flap types, FLIR thermal imaging measurements consistently tended to be closer to the surgical site compared to Doppler ultrasound. In anterolateral thigh flaps (n = 20), thoracodorsal artery perforator flaps (n = 5), and fibula osteocutaneous flaps (n = 3), absolute mean differences ranged from 0.62 to 1.33 cm, with trends favoring FLIR. While paired t-tests did not reach statistical significance, both methods correlated with intraoperatively identified skin perforators, and distances generally ranged between 0 and 2 cm.

Conclusion

We demonstrate that a smartphone-based thermal imaging system has the potential to serve as an adjunct for identifying flap perforators, with the possibility of reducing operative times and minimizing patient morbidity.

Level of Evidence

Level 3.

[Using a smartphone-compatible thermal camera (FLIR One) for preoperative mapping of DIEP perforators]

INTRODUCTION

The success of surgeries involving free flaps largely depends on accurate preoperative mapping of perforator arteries. Various imaging techniques, such as Doppler ultrasound and CT angiography, are typically used, each having its advantages and disadvantages in terms of cost, accuracy, and patient risk. The main objective of our study is to compare the effectiveness of the FLIR One device for detecting these arteries compared with traditional methods. Thermal imaging appears to be a simpler, less expensive, and less invasive alternative for surgical planning.

MATERIAL AND METHOD

The study, conducted at the Regional Hospital Center of Nancy, included 25 free flaps (DIEP) on an exclusively female cohort of 22 patients, with follow-up from 2022 to 2023. Before the procedure, an abdominal-pelvic CT angiography was performed, followed by additional evaluation with thermal imaging using FLIR One and acoustic Doppler examination on the eve of the operation. This approach aimed to provide precise mapping of vascular perforators for each patient. Three different operators performed these markings, and the results were then compared with intraoperative observations. The imaging protocol also included a Doppler examination to validate the results of the thermal imaging. Statistical analyses with intraclass correlation coefficients (ICC) were performed to evaluate the correlation between different preoperative localization methods of perforating vessels.

RESULTS

In 22 patients undergoing 25 DIEP flaps for breast reconstructions, three imaging techniques were used to identify vascular perforators: thermal imaging with FLIR, acoustic Doppler, and CT angiography. FLIR identified the most perforators (n=137), followed by acoustic Doppler (n=128) and CT angiography (n=126). Comparing these with intraoperative results, 66% of perforators identified by FLIR were confirmed, 70% for acoustic Doppler, and 95% for CT angiography. The ICCs shows a significant correlation between these imaging techniques and intraoperative results. FLIR demonstrated a strong correlation with intraoperative observations (ICC of 0.74, P<0.001), followed by a moderate correlation with acoustic Doppler (ICC of 0.56, P<0.03) and CT angiography (ICC of 0.52, P<0.006).

CONCLUSION

The study concludes that thermal imaging with FLIR is a reliable and effective tool for locating vascular perforators. Although the study and FLIR have their own limitations, the tool presents several advantages such as ease of use, speed, and affordability. These characteristics make FLIR particularly attractive as a complement to traditional detection methods, such as acoustic Doppler and CT angiography.

Preoperative perforator mapping of anterolateral thigh perforators via Projected Augmented Reality and Dynamic Infrared Thermography

BACKGROUND

The anterolateral thigh (ALT) flap is a reliable and versatile flap with the ideal characteristics for soft-tissue reconstruction. However, as it is known for its highly variable anatomy, it requires preoperative perforator localization to optimize flap design and dissection of the flap. Dynamic Infrared Thermography (DIRT) is a non-invasive and quick imaging method that provides real-time information. This study aimed to provide a proof-of-principle for the feasibility of projecting DIRT hotspots directly onto patient's skin before ALT flap harvest.

METHODS

The portable and self-aligning projection device prototype (Anatomy Projector) with an embedded thermal sensor was used to obtain and automatically project thermal images of DIRT on the patient's thigh before ALT flap dissection. Preoperatively projected DIRT hotspots were validated using a hand-held Doppler (HHD) and compared with the locations of intraoperative perforators.

RESULTS

A total of 133 DIRT hotspots were projected in 20 patients, of which 97.3% could be verified with HHD within a 1 cm radius. Intraoperative measurements identified 26 perforators, of which 53.8% could be matched to a DIRT hotspot within a 1 cm radius, 76.9% within a 2 cm radius, and 92.3% within a 3 cm radius.

CONCLUSION

This study highlights the clinical applicability of projecting thermal images directly onto a patient's thigh before ALT flap reconstruction. Visualization of DIRT hotspots simplifies perforator localization and provides high consistency with Doppler and intraoperative findings. Future research should explore its applicability for the intraoperative- and postoperative settings as well as other fields of plastic surgery.

Supercooling preservation of vascularized composite allografts through CPA optimization, thermal tracking, and stepwise loading techniques

Vascularized composite allografts (VCAs) present unique challenges in transplant medicine, owing to their complex structure and vulnerability to ischemic injury. Innovative preservation techniques are crucial for extending the viability of these grafts, from procurement to transplantation. This study addresses these challenges by integrating cryoprotectant agent (CPA) optimization, advanced thermal tracking, and stepwise CPA loading strategies within an ex vivo rodent model. CPA optimization focused on various combinations, identifying those that effectively suppress ice nucleation while mitigating cytotoxicity. Thermal dynamics were monitored using invasive thermocouples and non-invasive FLIR imaging, yielding detailed temperature profiles crucial for managing warm ischemia time and optimizing cooling rates. The efficacy of stepwise CPA loading versus conventional flush protocols demonstrated that stepwise (un)loading significantly improved arterial resistance and weight change outcomes. In summary, this study presents comprehensive advancements in VCA preservation strategies, combining CPA optimization, precise thermal monitoring, and stepwise loading techniques. These findings hold potential implications for refining transplantation protocols and improving graft viability in VCA transplantation.

Advancing DIEP Flap Monitoring with Optical Imaging Techniques: A Narrative Review

OBJECTIVES

This review aims to explore recent advancements in optical imaging techniques for monitoring the viability of Deep Inferior Epigastric Perforator (DIEP) flap reconstruction. The objectives include highlighting the principles, applications, and clinical utility of optical imaging modalities such as near-infrared spectroscopy (NIRS), indocyanine green (ICG) fluorescence angiography, laser speckle contrast imaging (LSCI), hyperspectral imaging (HSI), dynamic infrared thermography (DIRT), and short-wave infrared thermography (SWIR) in assessing tissue perfusion and oxygenation. Additionally, this review aims to discuss the potential of these techniques in enhancing surgical outcomes by enabling timely intervention in cases of compromised flap perfusion.

MATERIALS AND METHODS

A comprehensive literature review was conducted to identify studies focusing on optical imaging techniques for monitoring DIEP flap viability. We searched PubMed, MEDLINE, and relevant databases, including Google Scholar, Web of Science, Scopus, PsycINFO, IEEE Xplore, and ProQuest Dissertations & Theses, among others, using specific keywords related to optical imaging, DIEP flap reconstruction, tissue perfusion, and surgical outcomes. This extensive search ensured we gathered comprehensive data for our analysis. Articles discussing the principles, applications, and clinical use of NIRS, ICG fluorescence angiography, LSCI, HSI, DIRT, and SWIR in DIEP flap monitoring were selected for inclusion. Data regarding the techniques' effectiveness, advantages, limitations, and potential impact on surgical decision-making were extracted and synthesized.

RESULTS

Optical imaging modalities, including NIRS, ICG fluorescence angiography, LSCI, HSI, DIRT, and SWIR offer a non- or minimal-invasive, real-time assessment of tissue perfusion and oxygenation in DIEP flap reconstruction. These techniques provide objective and quantitative data, enabling surgeons to monitor flap viability accurately. Studies have demonstrated the effectiveness of optical imaging in detecting compromised perfusion and facilitating timely intervention, thereby reducing the risk of flap complications such as partial or total loss. Furthermore, optical imaging modalities have shown promise in improving surgical outcomes by guiding intraoperative decision-making and optimizing patient care.

CONCLUSIONS

Recent advancements in optical imaging techniques present valuable tools for monitoring the viability of DIEP flap reconstruction. NIRS, ICG fluorescence angiography, LSCI, HSI, DIRT, and SWIR offer a non- or minimal-invasive, real-time assessment of tissue perfusion and oxygenation, enabling accurate evaluation of flap viability. These modalities have the potential to enhance surgical outcomes by facilitating timely intervention in cases of compromised perfusion, thereby reducing the risk of flap complications. Incorporating optical imaging into clinical practice can provide surgeons with objective and quantitative data, assisting in informed decision-making for optimal patient care in DIEP flap reconstruction surgeries.

Projected augmented reality in DIEP flap breast reconstruction: Projecting perforators on the skin using dynamic infrared thermography

BACKGROUND

Dynamic infrared thermography (DIRT) is a quick and non-invasive technique for perforator mapping in free flaps that provides real-time information. After a cold challenge, areas best supplied with blood become visible hotspots on color-coded maps, indicating perforators. This study presents a proof of principle for a new and innovative feature of DIRT, where projected augmented reality is used to directly display thermal images on the patient's abdomen prior to the deep inferior epigastric artery perforator (DIEP) flap breast reconstruction.

METHODS

A self-aligning projection device prototype (Anatomy Projector) equipped with an integrated thermal camera was used to obtain thermal information and project the color-coded map directly on the patient's abdomen before DIEP flap breast reconstruction. Projected DIRT hotspots were verified using a hand-held Doppler, and compared to the vascularity on computed tomography angiography (CTA), and intraoperative perforator measurements following a Cartesian grid.

RESULTS

A total of 514 DIRT hotspots were projected in 50 patients, among them 97.3% could be verified using Doppler. The positive predictive value for CTA was 74.5%. Intraoperative measurements yielded 132 perforators in 71 flaps, among them 75 perforators (56.8%) correlated with projected DIRT hotspots, and half of them (54.7%) appeared within the first 5 emerging hotspots.

CONCLUSION

This study showed that real-time display of thermal data in DIEP flap breast reconstruction is feasible via projected augmented reality. Projection facilitates convenient marking of hotspots, and a high resemblance to Doppler and CTA data was observed. Further research should assess the added value of projecting thermal images intraoperatively and in other fields of plastic surgery.

Is thermography an effective screening tool for differentiating benign and malignant skin lesions in the head and neck? A systematic review

The aim of this study was to assess, through a systematic review, the status of infrared thermography (IRT) as a diagnostic tool for skin neoplasms of the head and neck region and in order to validate its effectiveness in differentiating benign and malignant lesions. A search was carried out in the LILACS, PubMed/MEDLINE, SCOPUS, Web of Science and EMBASE databases including studies published between 2004 and 2024, written in the Latin-Roman alphabet. Accuracy studies with patients aged 18 years or over presenting benign and malignant lesions in the head and neck region that evaluated the performance of IRT in differentiating these lesions were included. Lesions of mesenchymal origin and studies that did not mention histopathological diagnosis were excluded. The systematic review protocol was registered in the PROSPERO database (CRD42023416079). Reviewers independently analyzed titles, abstracts, and full-texts. After extracting data, the risk of bias of the selected studies was assessed using the QUADAS - 2 tool. Results were narratively synthesized and the certainty of evidence was measured using the GRADE approach. The search resulted in 1,587 records and three studies were included. Only one of the assessed studies used static IRT, while the other two studies used cold thermal stress. All studies had an uncertain risk of bias. In general, studies have shown wide variation in the accuracy of IRT for differentiating between malignant and benign lesions, with a low level of certainty in the evidence for both specificity and sensitivity.

Enhancing Vascularized Composite Allograft Supercooling Preservation: A Multifaceted Approach with CPA Optimization, Thermal Tracking, and Stepwise Loading Techniques

Vascularized composite allografts (VCAs) present unique challenges in transplant medicine, owing to their complex structure and vulnerability to ischemic injury. Innovative preservation techniques are crucial for extending the viability of these grafts, from procurement to transplantation. This study addresses these challenges by integrating cryoprotectant agent (CPA) optimization, advanced thermal tracking, and stepwise CPA loading strategies within an ex vivo rodent model. CPA optimization focused on various combinations, identifying those that effectively suppress ice nucleation while mitigating cytotoxicity. Thermal dynamics were monitored using invasive thermocouples and non-invasive FLIR imaging, yielding detailed temperature profiles crucial for managing warm ischemia time and optimizing cooling rates. The efficacy of stepwise CPA loading versus conventional flush protocols demonstrated that stepwise (un)loading significantly improved arterial resistance and weight change outcomes. In summary, this study presents comprehensive advancements in VCA preservation strategies, combining CPA optimization, precise thermal monitoring, and stepwise loading techniques. These findings hold potential implications for refining transplantation protocols and improving graft viability in VCA transplantation.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 2: physiological measurements

In this, the second of four historical reviews on human thermoregulation during exercise, we examine the research techniques developed by our forebears. We emphasise calorimetry and thermometry, and measurements of vasomotor and sudomotor function. Since its first human use (1899), direct calorimetry has provided the foundation for modern respirometric methods for quantifying metabolic rate, and remains the most precise index of whole-body heat exchange and storage. Its alternative, biophysical modelling, relies upon many, often dubious assumptions. Thermometry, used for >300 y to assess deep-body temperatures, provides only an instantaneous snapshot of the thermal status of tissues in contact with any thermometer. Seemingly unbeknownst to some, thermal time delays at some surrogate sites preclude valid measurements during non-steady state conditions. To assess cutaneous blood flow, immersion plethysmography was introduced (1875), followed by strain-gauge plethysmography (1949) and then laser-Doppler velocimetry (1964). Those techniques allow only local flow measurements, which may not reflect whole-body blood flows. Sudomotor function has been estimated from body-mass losses since the 1600s, but using mass losses to assess evaporation rates requires precise measures of non-evaporated sweat, which are rarely obtained. Hygrometric methods provide data for local sweat rates, but not local evaporation rates, and most local sweat rates cannot be extrapolated to reflect whole-body sweating. The objective of these methodological overviews and critiques is to provide a deeper understanding of how modern measurement techniques were developed, their underlying assumptions, and the strengths and weaknesses of the measurements used for humans exercising and working in thermally challenging conditions.

The application of infrared thermography technology in flap: A perspective from bibliometric and visual analysis

The application of infrared thermography technology (IRT) in flap has become a major focus of research, as it provides a non-invasive, real-time, and quantitative approach for monitoring flap perfusion. In this regard, we conducted a comprehensive visualization and scientometric analysis to systematically summarize and discuss the current state of research in this field. We systematically reviewed publications on the application of IRT in flap procedures from 1999 to 2022, using the Web of Science Core Collection (WoSCC). Through scientometric analysis, we examined annual trends, affiliations, countries, journals, authors, and their relationships, providing insights into current hotspots and future developments in this area. We analysed 522 English studies and found a steady increase in annual publications. The United States and Germany had the highest publication rates, with Beth Israel Deaconess Medical Center and Shanghai Jiaotong University being leading institutions. Notably, Lee BT and Alex Keller emerged as influential authors in this field. Compared to existing techniques, infrared-based technology offers significant advantages for non-invasive monitoring of flap perfusion, including simplicity of operation and objective results. Future trends should focus on interdisciplinary collaborations to develop new infrared devices and achieve intelligent image processing, enabling broader application in various clinical scenarios. This bibliometric study summarizes the progress and landscape of research on 'the Application of infrared thermography technology in flap' over the past two decades, providing valuable insights and serving as a reliable reference to drive further advancements and spark researchers' interest in this field.

Uses of Smartphone Thermal Imaging in Perforator Flaps as a Versatile Intraoperative Tool: The Microsurgeon's Third Eye

Introduction

In this study, we evaluate the versatility of smartphone thermal imaging technology as a valuable intraoperative modality in different stages of perforator flap surgery aiming to minimize the complications and achieve the best postoperative outcome.

Patients and methods

Thermography was performed in 20 perforator flaps in 20 patients at different surgical stages in three different ways to identify the most dominant perforator: first, by measuring the surface temperature of the skin; second, by using the dynamic infrared thermography technique; and third, by assessing the perfusion pattern when the flap was supplied by each perforator separately. Thermography was used to help in discarding the least perfused area of the flap. After microvascular anastomosis, the flap reheating pattern was evaluated.

Results

Seventeen free and three pedicled perforator flaps were included. Intraoperatively, each of the selected perforators had a corresponding hotspot. The perforator with the hottest hotpot, best rewarming, and provision of best flap perfusion on thermography was found clinically dominant. After microvascular anastomosis in free flaps, rapid rewarming was recorded in 15 cases. In two deep inferior epigastric perforator flaps, no rapid rewarming was observed. The pedicle was kinked in one case and there was a venous insufficiency in another case that required a cephalic turndown. All flaps showed good perfusion on thermography after inset.

Conclusion

Smartphone thermography has proven to be a valuable, cheap, rapidly employed, and objective tool not only for the design of perforator flaps, but also for the decision making intraoperatively to achieve the best surgical outcome.

Utility of Thermographic Imaging for Callus Identification in Wound and Foot Care

Calluses are thickened skin areas that develop due to repeated friction, pressure, or other types of irritation. While calluses are usually harmless and formed as a protective surface, they can lead to skin ulceration or infection if left untreated. As calluses are often not clearly visible to the patients, and some areas of dead skin can be missed during debridement, accessory tools can be useful in assessment and follow-up. The practical question addressed in this article is whether or not thermal imaging adds value to callus assessment. We have performed a theoretical analysis of the feasibility of thermographic imaging for callus identification. Our analytical calculations show that the temperature drop in the epidermis should be on the order of 0.1 °C for the normal epidermis in hairy skin, 0.9 °C for glabrous skin, and 1.5-2 °C or higher in calluses. We have validated our predictions on gelatin phantoms and demonstrated the feasibility of thermographic imaging for callus identification in two clinical case series. Our experimental results are in agreement with theoretical predictions and support the notion that local skin temperature variations can indicate epidermis thickness variations, which can be used for callus identification. In particular, a surface temperature drop on the order of 0.5 °C or more can be indicative of callus presence, particularly in callus-prone areas. In addition, our analytical calculations and phantom experiments show the importance of ambient temperature measurements during thermographic assessments.

Value of the combination of a smartphone-compatible infrared camera and a hand-held doppler ultrasound in preoperative localization of perforators in flaps

This study was conducted to evaluate the effectiveness of the FLIR ONE PRO, a thermal imaging camera for smartphones, combined with handheld Doppler (HHD) in the localization of perforator arteries and to assess the efficacy of the FLIR ONE PRO in distinguishing perforators of the descending branch of the lateral circumflex femoral artery (LCFA) from other perforators of the anterolateral thigh perforator (ALTP) flap. We enrolled 29 free perforator flaps from 22 patients in our study. Before surgery, dynamic infrared thermography was performed using a FLIR ONE PRO to visualize hotspots on the flaps. Subsequently, HHD was used to further determine the perforators under the hotspots, which were ultimately identified and confirmed through intraoperative findings. Additionally, infrared images of the ALTP flap were analyzed using FLIR Tools. The performances of the FLIR ONE PRO and FLIR ONE PRO + HHD groups were evaluated by comparing the intraoperative findings. Using FLIR ONE PRO + HHD, 119 hotspots and 106 perforators were identified during surgery. Using FLIR ONE PRO + HHD, sensitivity and positive predictive value were 97.87% and 88.46%, respectively, in the young (age≤45 years). In the elderly group (age>45 years), these percentages were 93.22% and 82.09%, respectively. In addition, we found that the FLIR ONE PRO could be useful for differentiating perforators in the descending branch of the LCFA from other perforators within 5 min. The results showed a sensitivity of 96.15%, a specificity of 98.9%, a positive predictive value of 96.15%, and a negative predictive value of 98.9%. Compared to using FLIR ONE PRO alone, the combined application of HHD and FLIR ONE PRO had a higher value in perforator localization by increasing the positive predictive value. The FLIR ONE PRO may have significance in the rapid prediction of perforators deriving from the descending branch of the LCFA.

Cutaneous Perfusion Dynamics of the Lower Abdomen in Healthy Normal Weight, Overweight and Obese Women: Methods Development Using Infrared Thermography with Applications for Future Wound Management after Caesarean Section

BACKGROUND

Evidence has shown an association between obesity and an increased risk of wound infection after caesarean section. This study was designed to examine if abdominal subcutaneous adiposity impacts upon cutaneous perfusion dynamics.

METHODS

Mild cool challenge, followed by real-time video thermography, was developed to map the appearance of abdominal 'hot spots'. Correspondence of marked 'spots' with audible Doppler and colour and power Doppler ultrasound was performed.

RESULTS

60 healthy, afebrile, women (20-68 years; BMI 18.5-44 kg/m2) were recruited. Hot spot appearance consistently corresponded with audible Doppler sounds. Colour and power Doppler ultrasound revealed vessels at depths of 3-22 mm. No statistically significant interactions for BMI, abdominal circumference or environmental parameters were observed for hot spot count. The temperature of cold stimulus was significant for effects on spot count, but only for the first minute (p = 0.001). Thereafter, effects on spot numbers were not significant.

CONCLUSIONS

Cutaneous 'perforator' mapping of the abdomen (via hot spot appearance) in healthy women, as a potential and future method for risk of perfusion-dependent wound healing complications, reveals that bedside mapping of skin perfusion is feasible over a short interval. Hot spot number was not influenced by BMI or indicators of central fat distribution (abdominal circumference) indicating variability in an individual's vascular anatomy. This study provides the underpinning methodology for personalised perfusion assessment after incisional surgery which may be a more reliable indicator of potential healing complications than body habitus as is currently the norm.

Chronic and Acute Effects on Skin Temperature from a Sport Consisting of Repetitive Impacts from Hitting a Ball with the Hands

Valencian handball consists in hitting the ball with the hands and it may contribute to injury development on the hands. This study aimed to analyze skin temperature asymmetries and recovery after a cold stress test (CST) in professional players of Valencian handball before and after a competition. Thirteen professional athletes and a control group of ten physically active participants were measured. For both groups, infrared images were taken at the baseline condition; later they underwent a thermal stress test (pressing for 2 min with the palm of the hand on a metal plate) and then recovery images were taken. In athletes, the images were also taken after their competition. Athletes at baseline condition presented lower temperatures (p < 0.05) in the dominant hand compared with the non-dominant hand. There were asymmetries in all regions after their match (p < 0.05). After CST, a higher recovery rate was found after the game. The regions with the most significant differences in variation, asymmetries and recovery patterns were the index, middle and ring fingers, and the palm of the dominant hand. Taking into account that lower temperatures and the absence of temperature variation may be the consequence of a vascular adaptation, thermography could be used as a method to prevent injuries in athletes from Valencian handball.

Thermography Supported Color Duplex Ultrasound Accelerates ALT Perforator Imaging

BACKGROUND

 The anterolateral thigh flap is a versatile and dependable perforator flap and is a popular choice in the reconstruction of various body sites. The variable perforator anatomy suggests preoperative perforator imaging to improve safety and speed of dissection. An innovative perforator imaging technique is thermography, which lately gained attention in plastic surgery.

METHODS

 Thirty-two healthy participants were included in this randomized study. One thigh was examined with dynamic infrared thermography and consecutively with ultrasound, while the contralateral thigh was examined with ultrasound as standalone technology.

RESULTS

 The application of dynamic infrared thermography prior to ultrasound perforator identification significantly accelerated the ultrasound examination duration by 90 to 130 seconds. The mean duplex ultrasound examination duration correlated positively with the hotspot and perforator quantity per thigh.

CONCLUSION

 The addition of thermographic perforator mapping can accelerate color duplex ultrasound anterolateral thigh perforator imaging. Furthermore, thermography supplements color duplex ultrasound with crucial information on angiosome location.

Infrared Thermography in Wound Care, Surgery, and Sports Medicine: A Review

For many years, the role of thermometry was limited to systemic (core body temperature) measurements (e.g., pulmonary catheter) or its approximation using skin/mucosa (e.g., axillary, oral, or rectal) temperature measurements. With recent advances in material science and technology, thermal measurements went beyond core body temperature measurements and found their way in many medical specialties. The article consists of two primary parts. In the first part we overviewed current clinical thermal measurement technologies across two dimensions: (a) direct vs. indirect and (b) single-point vs. multiple-point temperature measurements. In the second part, we focus primarily on clinical applications in wound care, surgery, and sports medicine. The primary focus here is the thermographic imaging modality. However, other thermal modalities are included where relevant for these clinical applications. The literature review identified two primary use scenarios for thermographic imaging: inflammation-based and perfusion-based. These scenarios rely on local (topical) temperature measurements, which are different from systemic (core body temperature) measurements. Quantifying these types of diseases benefits from thermographic imaging of an area in contrast to single-point measurements. The wide adoption of the technology would be accelerated by larger studies supporting the clinical utility of thermography.

The Kempe incision for decompressive craniectomy, craniotomy, and cranioplasty in traumatic brain injury and stroke

OBJECTIVE

Decompressive craniectomy (DC) is an effective, lifesaving option for reducing intracranial pressure (ICP) in traumatic brain injury (TBI), stroke, and other pathologies with elevated ICP. Most DCs are performed via a standard trauma flap shaped like a reverse question mark (RQM), which requires sacrificing the occipital and posterior auricular arteries and can be complicated by wound dehiscence and infections. The Ludwig Kempe hemispherectomy incision (Kempe) entails a T-shaped incision, one limb from the midline behind the hairline to the inion and the other limb from the root of the zygoma to the coronal suture. The authors' objective in this study was to define their implementation of the Kempe incision for DC and craniotomy, report clinical outcomes, and quantify the volume of bone removed compared with the RQM incision.

METHODS

A retrospective review of a single-surgeon experience with DC in TBI and stroke was performed. Patient demographics, imaging, and outcomes were collected for all DCs from 2015 to 2020, and the incisions were categorized as either Kempe or RQM. Preoperative and postoperative CT scans were obtained and processed using a combination of automatic segmentation (in Python and SimpleITK) with manual cleanup and further subselection in ITK-SNAP. The volume of bone removed was quantified, and the primary outcome was percentage of hemicranium removed. Postoperative surgical wound infections, estimated blood loss (EBL), and length of surgery were compared between the two groups as secondary outcomes. Cranioplasty data were collected.

RESULTS

One hundred thirty-six patients were included in the analysis; there were 57 patients in the craniotomy group (44 patients with RQM incisions and 13 with Kempe incisions) and 79 in the craniectomy group (41 patients with RQM incisions and 38 Kempe incisions). The mean follow-up for the entire cohort was 251 ± 368 days. There was a difference in the amount of decompression between approaches in multivariate modeling (39% ± 11% of the hemicranium was removed via the Kempe incision vs 34% ± 10% via the RQM incision, p = 0.047), although this did not achieve significance in multivariate modeling. Wound infection rates, EBL, and length of surgery were comparable between the two incision types. No wound infections in either cohort were due to wound dehiscence. Cranioplasty outcomes were comparable between the two incision types.

CONCLUSIONS

The Kempe incision for craniectomy or craniotomy is a safe, feasible, and effective alternative to the RQM. The authors advocate the Kempe incision in cases in which contralateral operative pathology or subsequent craniofacial/skull base repair is anticipated.

Comparison of Various Modalities Utilized for Preoperative Planning in Microsurgical Reconstructive Surgery

BACKGROUND

 The benefits of preoperative perforator imaging for microsurgical reconstruction have been well established in the literature.

METHODS

 An extensive literature review was performed to determine the most commonly used modalities, and their applicability, advantages and disadvantages.

RESULTS

 The review demonstrated varioius findings including decreases in operative time and cost with the use of CT angiography to identification of perforators for inclusion in flap design with hand-held Doppler ultrasound. Modalities like MR angiography offer alternatives for patients with contrast allergies or renal dysfunction while maintaining a high level of clarity and fidelity. Although the use of conventional angiography has decreased due to the availability of less invasive alternatives, it continues to serve a role in the preoperative evaluation of patients for lower extremity reconstruction. Duplex ultrasonography has been of great interest recently as an inexpensive, risk free, and extraordinarily accurate diagnostic tool. Emerging technologies such as indocyanine green fluorescence angiography and dynamic infrared thermography provide real-time information about tissue vascularity and perfusion without requiring radiation exposure.

CONCLUSION

 This article presents an in-depth review of the various imaging modalities available to reconstructive surgeons and includes hand held Doppler ultrasound, CT angiography, MR angiography, conventional angiography, duplex ultrasonography, Indocyanine Green Fluorescence Angiography and Dynamic Infrared Thermography.

Perforator Detection by Thermographic Imaging Augmented With Tourniquet-Reperfusion: A Modified Approach and Preliminary Report in Distal Lower Leg Reconstruction

BACKGROUND

Dynamic infrared thermography provides a new imaging method of perforator detection. This study introduces an augmented technique to improve its accuracy by tourniquet-reperfusion and reports its preliminary use in the distal lower leg reconstruction.

METHODS

A tourniquet (450 mm Hg) was applied for 3 minutes on proximal thighs. After the tourniquet release, the rewarming rate and pattern of hotspots were observed by thermography to delineate the location and quality of perforators. The results were compared with those detected by computed tomographic angiography. Clinically, the local transferred posterior tibial artery or peroneal artery propeller perforator flap was performed in 9 patients for the distal lower leg reconstruction.

RESULTS

There was a 20- to 140-second "perforator observing window" after the tourniquet release. Tourniquet-reperfusion augmented thermal imaging method (TRATIM) had a sensitivity of 90.3% and a positive predictive value of 93.3%. The TRATIM and computed tomographic angiography had an excellent concordance with a kappa index value of 0.839 (P < 0.001). Based on the TRATIM, 9 propeller perforator flaps were successfully designed and raised for the distal lower leg resurfacing. All flaps survived entirely, except one with size of 1.0 cm × 2.0 cm that had terminal necrosis.

CONCLUSIONS

The TRATIM is a quick, easy, cheap, and reliable approach for perforator detection in the lower leg. With the aid of TRATIM, a customized propeller perforator flap could be raised efficiently for the distal lower leg reconstruction.

Diagnostic Value and Application of Infrared Thermography in the Analysis of Circumanal Gland Tumors

In dogs, circumanal tumors are the third most common skin neoplasm. Circumanal gland adenomas (CAGAs) have a good prognosis. Contrastingly, circumanal gland adenocarcinomas (CAGAC) have high relapse rates and may be metastatic. This study aimed to investigate the utility of thermal imaging as an ancillary modality for the diagnosis of canine CAGA and CAGAC. We analyzed the following parameters: SpT, temperature measured at the tumor center; SpNT, temperature measured at a healthy sphincter skin spot distant from the tumor; TA, temperature measured at a tumor-encompassing ellipse-shaped area; and NTA, temperature measured at an ellipse-shaped area of the healthy sphincter skin distant from the tumor. In CAGAs, the mean SpT and SpNT temperature values differed by −1.45°C (p < 0.01) while the mean TA and NTA temperature values differed by −0.96°C (p < 0.05). In CAGACs, mean SpT and SpNT temperatures differed by −1.71°C (p < 0.01) while the mean TA and NTA temperatures differed by −1.69°C (p < 0.01). The mean SpT and TA temperature values measured in CAGAs and CAGACs differed by −0.10°C (p = 0.87) and 0.52°C (p = 0.38), respectively. Both tumors were colder than healthy sphincter skin. However, a substantial number of CAGACs were colder than CAGAs. Temperature differences ≥ 1°C between tumors and healthy sphincter skin increased the probability of CAGAC diagnosis by 17.45%. Thermal imaging allowed discrimination between healthy and tumoral tissues; therefore, it could be a good ancillary diagnostic modality.

In Vivo Perforasome Perfusion in Hemi-DIEP Flaps Evaluated with Indocyanine-green Fluorescence Angiography and Infrared Thermography

There are no in vivo studies that evaluate the effect of perforator dissection on the perfusion territory of a perforator (perforasome). In this study, indocyanine green fluorescence angiography (ICG-FA) and infrared thermography (IRT) were used intraoperatively to evaluate perforasome perfusion in hemi-DIEP flaps.

Performance of infrared thermography and thermal stress test in perforator mapping and flap monitoring: A meta-analysis of diagnostic accuracy

BACKGROUND

Accurate mapping of perforators prior to flap reconstruction and early detection of poor flap perfusion reduces the risk of flap failure. Infrared thermography (IRT) has recently regained popularity within reconstructive surgery to aid flap design, reduce operative time and assess flap viability based on surface temperature changes. The aim of this review is to quantify the diagnostic ability of IRT in perforator mapping preoperatively and monitor flap perfusion perioperatively.

METHODS

We conducted a systematic review of literature and included all studies that evaluated the use of IRT for perforator mapping and flap perfusion monitoring. We used a mixed-effects logistic regression bivariate model to estimate the summary sensitivity and specificity and constructed hierarchical summary receiver operative characteristic (HSROC) curves.

OUTCOME

We identified 18 studies and observed IRT to have sensitivities of 99.6% and 89.6% with specificities of 99.9% and 96.0% for perforator mapping and flap monitoring, respectively. Moreover, IRT recognises patterns of perfusion within interperforator zones through visualisation of angiosomal rewarming and may improve flap outcomes.

Impact on Abdominal Skin Perfusion following Abdominoplasty

Wound healing problems following abdominoplasty may be a result of impaired tissue perfusion. This study evaluated the impact a standard abdominoplasty may have on abdominal skin perfusion.

Accuracy of infrared thermography for perforator mapping: A systematic review and meta-analysis of diagnostic studies

INTRODUCTION

Infrared thermography allows the detection of infrared radiation which can be reliably associated with skin temperature. Modern portable thermography devices have been used to identify the location of skin perforators by detecting subtle differences in skin temperature. The aim of this study is to conduct a diagnostic accuracy systematic review to determine the specificity and sensitivity of infrared thermography.

MATERIALS AND METHODS

A PRISMA-compliant systematic review and meta-analysis was conducted, scrutinising PUBMED and EMBASE databases for diagnostic studies measuring the accuracy of infrared thermography for perforator identification. Article screening, review and data gathering was conducted in parallel by two independent authors. Eligible studies were subject to a formal risk of bias was assessment using the QUADAS2 instrument.

RESULTS

A total of 254 entries were obtained, of which 7 satisfied our pre-established inclusion criteria. These studies reported a total of 435 perforators in 133 individuals. The most commonly investigated locations were the antero-lateral thigh and abdominal wall. Reported sensitivity values ranged from 73.7% to 100%. A meta-analysis demonstrated a cumulative sensitivity of 95%. Specificity was not routinely reported. All studies presented a moderate to high risk of bias according to QUADAS2.

DISCUSSION

Affordable infrared thermography devices are an interesting alternative to traditional preoperative investigations for perforator mapping. They are sensitive enough to reliably identify a large proportion of perforators as "hot-spots". However, there is limited evidence to estimate the specificity of this technology, as studies have failed to report true negative values associated with "cold-spots".

The accuracy of different modalities of perforator mapping for unilateral DIEP flap breast reconstruction: A systematic review and meta-analysis

BACKGROUND

Perforator mapping may be performed prior to deep inferior epigastric perforator (DIEP) flap breast reconstruction to guide perforator selection. However, the accuracy of different imaging modalities remains unknown. This review aimed to evaluate the accuracy of different modalities for locating perforators for unipedicled DIEP flap breast reconstruction.

METHODS

MEDLINE and EMBASE were searched from inception to 24th September 2019 for studies concerning adult women undergoing DIEP flap breast reconstruction with preoperative perforator mapping. The index test was pre-operative imaging and the reference standard was intraoperative identification.

RESULTS

21 articles with 1146 women were included. Six methods were described; handheld doppler, colour doppler (duplex) ultrasonography, computed tomography angiography, magnetic resonance angiography (MRA), direct infrared thermography with and without doppler. Meta-analysis revealed 94% (95% CI 88-99%) of DIEPs identified as the 'dominant perforator' on imaging were chosen as dominant perforators intraoperatively. Colour doppler (Duplex) ultrasonography had the lowest agreement (mean 74% [95% CI 67-81%]) whilst MRA had the highest agreement (mean 97% [95% CI 86-100%]). There was no statistically significant difference in the performance of different tests. All studies were subject to bias as the operators had knowledge of the index test prior to conducting the reference standard.

CONCLUSIONS

Based upon limited evidence, cross sectional (CT/MR) imaging modalities for preoperative DIEP mapping appear to have similar accuracy and perform better than ultrasound.

The use of smartphone thermography to more safely unmask and preserve circulation to keystone advancement flaps in the lower extremity

BACKGROUND

The keystone perforator flap is a simple, popular form of advancement flap that can solve many defects of the lower extremity that can avoid consideration of a microsurgical tissue transfer. The actual circulation to this local flap subtype has not yet been delineated. The recent introduction of inexpensive thermal imaging cameras that can be coupled with a SmartPhone allows thermagrams of these flaps where "hot spots" are known to correspond to the location of pertinent perforators that will provide the requisite flap vascularization.

METHODS

Over the past year, 10 patients were considered for a keystone flap of the lower extremity in lieu of a skin graft or free flap. All patients had a "cold challenge" or thermal stress followed by a thermal recovery recorded by serial thermography to determine perforator "hot spot" location as well as their absence or "cold spots." Flaps were designed and harvested according to these findings.

RESULTS

In one patient, inadequate "hot spots" were found in all adjacent donor regions that could have allowed a keystone flap alternative. Instead, more safely a skin graft was done. The other 9 patients had 10 flaps. Intra-operative thermagrams predicted 100% flap survival for 9 flaps and marginal ischemia for 1 flap, and was a correct assessment in all cases. Dehiscence occurred in the latter flap that healed by secondary intention, while the rest healed uneventfully.

CONCLUSION

The use of the SmartPhone for thermography is a simple, rapid, cheaper means for the evaluation of viability of keystone flaps in all surgical phases. This provides a safe method for checking not only flap circulation, but also identification of "cold spots" or flap regions where means to augment advancement by deep fascia interruption or undermining will not interfere with flap perfusion. There is virtually no learning curve in acquiring the skills to use this device, which should now allow anyone to raise actually any kind of local perforator flap as they find suitable.

Abdominal Cutaneous Thermography and Perfusion Mapping after Caesarean Section: A Scoping Review

Introduction: Caesarean section (CS) is the most prevalent surgical procedure in women. The incidence of surgical site infection (SSI) after CS remains high but recent observations of CS wounds using infrared thermography has shown promise for the technique in SSI prognosis. Although thermography is recognised as a 'surrogate' of skin perfusion, little is known of the relationship between skin temperature and skin perfusion in the context of wound healing. Aim: To assess the extent of literature regarding the application of infrared thermography and mapping of abdominal cutaneous perfusion after CS. Methods: Wide eligibility criteria were used to capture all relevant studies of any design, published in English, and addressing thermal imaging or skin perfusion mapping of the abdominal wall. The CINAHL and MEDLINE databases were searched, with two independent reviewers screening the title and abstracts of all identified citations, followed by full-text screening of relevant studies. Data extraction from included studies was undertaken using a pre-specified data extraction chart. Data were tabulated and synthesised in narrative format. Results: From 83 citations identified, 18 studies were considered relevant. With three additional studies identified from the reference lists, 21 studies were screened via full text. None of the studies reported thermal imaging and cutaneous perfusion patterns of the anterior abdominal wall. However, two observational studies partially met the inclusion criteria. The first explored analysis methodologies to 'interrogate' the abdominal thermal map. A specific thermal signature ('cold spots') was identified as an early 'flag' for SSI risk. A second study, by the same authors, focusing on obesity (a known risk factor for SSI after CS) showed that a 1 °C lower abdominal skin temperature led to a 3-fold odds of SSI. Conclusion: There is a significant gap in knowledge on how to forewarn of wound complications after CS. By utilising the known association between skin temperature and blood flow, thermographic assessment of the wound and adjacent thermal territories has potential as a non-invasive, independent, imaging option with which to identify tissue 'at risk'. By identifying skin 'hot' or 'cold' spots, commensurate with high or low blood flow regions, there is potential to shed light on the underlying mechanisms leading to infective and non-infective wound complications.

Smartphone Thermal Imaging Can Enable the Safer Use of Propeller Flaps

The use of thermography for the identification of cutaneous "hot spots" that coincide with perforators is not a new concept, but the required professional cameras may be prohibitively expensive. Only relatively recently, incredibly cheap but adequate thermal imaging cameras have become available that work in concert with the ubiquitous cell phone. This can now serve as a rapid, accurate, and complementary method for finding a perforator sufficient to serve as the hub for a perforator pedicled propeller flap. In addition, the preferred direction of rotation about that hub, effect of flap insetting on perfusion, and then postoperative monitoring are possible by proper interpretation of corresponding thermograms. Every reconstructive surgeon should be able to obtain this device, and then easily learn what potential attributes for them are available when planning a propeller flap.

Advances in infrared thermography: Surgical aspects, vascular changes, and pain monitoring in veterinary medicine

One of the main functions of infrared thermography (IRT) consists in detecting temperature changes in organisms caused by variations in surface blood circulation. IRT is a useful tool that has been used mainly as a diagnostic method for various stress-causing pathologies, though recent suggestions indicate that it can be used to assess the block quality of certain body regions. In the field of anaesthesiology, IRT has been applied to brachial and epidural blocks, while in algology, changes in surface blood circulation associated with sympathetic activity have been investigated. Thermography has also been employed to complement pain level scales based on the facial expressions of patients in critical condition, or after surgery. In addition, it has been used as a tool in research designed to evaluate different surgical procedures in human medicine, as in the case of surgical burrs for placing dental implants, where IRT helps assess the degree of heating associated with bone devascularisation, reduction in vascular perfusion as a consequence of stroke, and changes in the autonomous nervous system, or the degree of vascular changes in flaps applied to burn patients. In veterinary medicine, thermography has brought several benefits for animals in terms of evaluating lesions, diseases, and surgical procedures. The aim of this review is to evaluate how IRT can be used as a tool in surgical procedures, cases of vascular change, and pain monitoring in veterinary medicine with an emphasis on small animals.

DIEP flap breast reconstructions: thermographic assistance as a possibility for perforator mapping and improvement of DIEP flap quality

In the modern world, one-third or more of breast cancer patients still undergo uni- or bilateral mastectomy. Breast cancer patients, in general, have a good prognosis and long-term survival. Therefore, the treatment must not only focus on survival but also on the quality of life. Breast reconstruction with an autologous free deep inferior epigastric artery perforator (DIEP) flap is one of the preferred options after mastectomy. A challenging step in this procedure is the selection of a suitable perforator that provides sufficient blood supply for the flap to prevent necrosis after anastomosis. In this pilot study, the possibilities for dynamic infrared thermography (DIRT) are investigated to select the best suitable perforator. The measurements are done with external cooling in the preoperative stage to accurately predict the location of the dominant perforators. During the surgery, in the peroperative stage, measurements are done for mapping the influence of a specific perforator on the perfused areas of the abdominal flap. Perforators are sequentially closed and opened again to map the influence of that perforator on the vascularization of the flap, visualized with the help of the thermographic camera. The acquired steady-state thermal images could help decide which parts of the abdominal flap to use for the reconstruction so that the chance of (partial) necrosis is reduced. In the postoperative stage, DIRT could visualize the arterial and or venous thrombosis before they become clinically obvious as (partial) necrosis. At present DIRT seems to be a valuable investigation for the pre-, per-, and postoperative phases of DIEP-flap reconstructions. Large, high-quality clinical studies are needed to determine its definitive role.

The Impact of Indocyanine-Green Fluorescence Angiography on Intraoperative Decision-Making and Postoperative Outcome in Free Flap Surgery

Background Reliable perfusion of the distal portions of free flaps is decisive for the reconstructive success. Indocyanine green near-infrared video angiography (ICG-NIR-VA) has been adopted for objective assessment of free flap tissue perfusion but is thus far not used on a routine basis. Therefore, we investigated its intraoperative impact on decision-making and postoperative outcome.

Methods From January 2017 to June 2019, 88 consecutive adipo- or fasciocutaneus free flaps were performed in conjunction with intraoperative ICG-NIR-VA. Free flap tissue perfusion was first assessed clinically and then compared with ICG-NIR-VA findings. Based on the results, the decision for intraoperative trimming of critically perfused flap zones was made. The way of decision-making, flap success, and failure rates as well as intra- and postoperative complication rates were analyzed.

Results The overall free flap success rate was 92.0%. Partial flap necrosis occurred in five cases (5.7%) and total flap necrosis in two cases (2.3%). ICG-NIR-VA aided decision-making and flap design in 34 cases (38.6%) and led to complication-free postoperative courses. When ICG-NIR-VA was relied on (82 out of 88 flaps; 93.2%), there was no unpredicted postoperative tissue necrosis (overestimation). When ICG-NIR-VA was not relied on (6 out of 88 flaps; 6.8%), there were five cases of postoperative partial flap necrosis and one case of uneventful healing (underestimation). The sensitivity of ICG-NIR-VA was 100% (95% confidence interval [CI]: 64.6–100) and the specificity was 98.8% (95% CI: 93.3–100) with a positive predictive value of 87.5% (95% CI: 52.9–99.4) and a negative predictive value of 100% (95% CI: 95.4–100).

Conclusion Intraoperative ICG-NIR-VA objectified free flap perfusion and thus refined surgical decision-making on flap design in all cases. It could always predict tissue necrosis and subjectively improved outcomes in free flap surgery at our institution. Furthermore, it could be easily implemented in intraoperative routine, only adding minimal additional operative time.

High-end versus Low-end Thermal Imaging for Detection of Arterial Perforators

Supplemental Digital Content is available in the text.

Thermal imaging was first reported as a method for detection of arterial perforators in 1968 and has since been shown to be an extremely accurate way to assess perforators with an audible Doppler signal, using high-end professional thermal cameras. This technology has recently become easily accessible with the advent of smartphone-compatible, low-end thermal cameras. Several groups have reported on the use of these devices in the pre-, intra-, and postoperative phase, yet there have been few attempts to validate them against existing methods or compare them with high-end thermal cameras.

Smartphone Thermography for Lower Extremity Local Flap Perforator Mapping

BACKGROUND

 The versatile application of local perforator flaps for coverage throughout the lower extremity has already been well proven. Often a "free-style" approach has been used to design these flaps, as conventional imaging devices for perforator identification may be too expensive or unavailable. The recent adaptation of Smartphone thermal digital imaging may now prove to be a cheaper and more readily available means for identifying the requisite perforators that will sustain these local flaps.

METHODS

 Over the past year, a prospective study was undertaken of all patients having a local perforator flap for coverage of a lower extremity defect. Twenty-eight local perforator flaps involving all subtypes were utilized in 25 patients. Smartphone thermography was used in all patients preoperatively to identify preferable perforator or vascular network "hot spots" that allowed appropriate flap design. Intraoperative and postoperative monitoring was similarly done for all flaps to determine outcomes.

RESULTS

 All local perforator flaps were based on perforators identified using smartphone thermography. All flaps (23 or 82.1%) that the thermal digital image predicted 100% viability totally survived. Five flaps were predicted to have marginal viability, but two nevertheless survived completely while the others required only minor readjustments. Peninsular and keystone variety perforator flaps were those most commonly used.Thermography always facilitated making the correct decision as to whether a proximal- or distal-based peninsular flap would be superior. Subfascial elevation of cool spots in keystone flaps were found to be least likely to interfere with flap perfusion.

CONCLUSION

 Smartphone thermography is an inexpensive and expeditious means for identification of "hot spots" that is always used by us to ensure perfusion to lower extremity perforator local flaps. This is a complementary technique for their safer design, harvest, and subsequent monitoring in conjunction with more complex screening tools as indicated.

Use of infrared thermography for the assessment of free flap perforators in autologous breast reconstruction: A systematic review

Perforator-based flaps have in recent years become the mainstay of autologous breast reconstruction practice. Imaging modalities ranging from Doppler ultrasound to CT angiography demonstrate varying utility in the preoperative identification and localisation of perforators. Despite these available radiological investigations, finding and quantitatively assessing perforators remain a time-consuming and tedious process that is often complicated by a number of factors including variable anatomy prior surgery and body habitus. Thermographic imaging shows promise as a novel modality for preoperative localisation of perforator vessels. This review summarises the currently available evidence for its application in perforator mapping for abdominal-based autologous breast reconstruction. We discuss the development of the technology over the years, its current use, its advantages and how it may impact on reconstructive breast surgery.

Dynamic infrared thermography (DIRT) in Deep Inferior Epigastric Perforator (DIEP) flap breast reconstruction: standardization of the measurement set-up

Breast reconstruction with an autologous free Deep Inferior Epigastric Perforator (DIEP) flap is one of the preferred options following mastectomy. A challenging step in this procedure is the selection of a suitable perforator that provides sufficient blood supply for the flap. The current golden standard for perforator mapping is computed tomography angiography (CTA). However, this is a relatively expensive imaging modality that requires intravenous contrast injection and exposes patients to ionizing radiation. More recently, dynamic infrared thermography (DIRT) has been proposed as an alternative imaging modality for perforator identification. DIRT appears to be an ideal alternative technique not only for the identification of the dominant perforators, but also for the mapping of the individual influence of each perforator on the flap perfusion. Multiple studies have been performed with the use of DIRT, unfortunately without standardisation of the measurement set-up. In this technical note we propose a standardised and reproducible measurement set-up for the use of DIRT during breast reconstructions with a free DIEP flap. This set-up can be used pre-, intra- and postoperatively. A standardised measurement set-up will improve the quality of measured data and ensure reproducibility.

Dynamic InfraRed Thermography (DIRT) in DIEP-flap breast reconstruction: A review of the literature

In the industrialised world still 34% of the breast cancer patients are surgically treated by a mastectomy. Breast cancer patients in general have a good prognosis and a long-term survival. Therefore, it is important that the treatment doesn't focus only on survival but also on the quality of life. Breast reconstruction improves the quality of life. A breast reconstruction with an autologous free DIEP (Deep Inferior Epigastric artery Perforator) flap is one of the preferred options after mastectomy. A challenging step in this procedure is the selection of a suitable perforator that provides sufficient blood supply for the flap. Current techniques to locate the perforator vessels include handheld Doppler, colour Doppler ultrasound (CDU), Magnetic resonance angiography (MRA), computer tomographic angiography (CTA) and dynamic infrared thermography (DIRT). At present CTA is the golden standard and DIRT a new option. The objective of this article is to document whether DIRT can accurately map the position of the perforators and measure their influence on the perfusion of the flap in order to select the best perforators to improve the outcome of breast reconstructions with free DIEP flaps. A systematic review of the literature published between January 1998 and November 23th 2018 was conducted regarding the possible benefit of dynamic infrared thermography (DIRT) in DIEP-flap breast reconstructions. The databases PubMed and Web of Science were used to search for qualified articles. Inclusion criteria were women who underwent a breast reconstruction by means of a DIEP flap where DIRT was used to analyse the blood supply of the flap. The search yielded a total of fourteen suitable articles: six articles being descriptive clinical studies, three case reports, three expert opinions/Overview articles and two systematic reviews. There are only a limited number of studies looking at the use of DIRT in breast reconstruction with DIEP-flaps. Adequate identification of the dominate vessel(s) in DIEP reconstruction is essential for a successful outcome. DIRT appears to be an ideal alternative technique for the identification of the dominant perforators of the flap. With the use of DIRT it is possible to identify the dominant vessel(s) preoperatively. The use of DIRT during the operation allows the tailoring of the surgery and postoperative use may identify vascularisation problems in an early stage. Additional high-quality studies are needed, but DIRT seems to be a valuable investigation for the pre-, per- and postoperative phase of DIEP-flap reconstructions.

Multimodal Device for Real-Time Monitoring of Skin Oxygen Saturation and Microcirculation Function

The present study introduces a recently developed compact hybrid device for real-time monitoring of skin oxygen saturation and temperature distribution. The prototype involves a snapshot hyperspectral camera, multi-wavelength illuminator, thermal camera, and built-in computer with custom-developed software. To validate this device in-vivo we performed upper arm vascular occlusion on eight healthy volunteers. Palm skin oxygen saturation maps were analyzed in real-time using k-means segmentation algorithm and two-layer optical diffuse model. The prototype system demonstrated a satisfying performance of skin hyperspectral measurements in the spectral range of 507–625 nm. The results confirmed the reliability of the proposed system for in-vivo assessment of skin hemoglobin saturation with oxygen and microcirculation.

Thermal Imaging Facilitates Design of a Keystone Perforator Island Flap for a Myxofibrosarcoma Resection Reconstruction: Case Report

Lower extremity defects are challenging to reconstruct. The keystone perforator island flap proves useful in difficult cases. Traditionally, a handheld Doppler is used to confirm perforator vessel(s) within the flap but has disadvantages including low sensitivity/specificity. Surgeons can use thermal imaging to localize "hot spots" on the skin, corresponding to perforators. FLIR ONE (FLIR Systems Inc., Wilsonville, OR) is a portable thermal camera with high concordance with computed tomographic angiography. In this case, when faced with handheld Doppler failure, we used intraoperative thermal imaging to continue planning and raising of a complex lower extremity keystone perforator island flap.

Variability in peripheral rewarming after cold stress among 255 healthy Norwegian army conscripts assessed by dynamic infrared thermography

Exposure to cold climate is an inevitable consequence of military training in Norway. Adequate peripheral microcirculation in the extremities is important to maintain temperature, and to protect against freezing cold injuries. The aim of this study was to investigate the variability in skin rewarming ability. The study subjects consisted of 260 healthy Norwegian army conscripts, following a mild cold provocation test (hands immersed in 20°C water for 1 min) using dynamic infrared thermography (DIRT). Thermal images were obtained to investigate any differences in skin rewarming ability of the hand (fingers). DIRT took place under standardised and stable study conditions. Conscripts were characterised as either slow, intermediate or rapid rewarmers. While 90% could recover, partially or completely, within 4 min to the skin temperature values before the provocation test, 10% showed a slow rewarming pattern. In the slow rewarmers, the rewarming ability was correlated with a low average temperature of the hands prior to the cooling test. The healthy young army conscripts in this study showed a large variability in their rewarming ability following a standardised mild cold provocation test.