Infrared Thermal Imaging Camera Research Articles

75 Intraoperative Use of Infrared Thermal Imaging Camera – a Clinical Aid for Pedicled Flaps in Hand Reconstruction

Abstract Introduction Venous insufficiency remains one of the commonest causes for flap failure. Forward-looking infrared (FLIR) thermography measures infrared emissions from dissipated heat and converts temperature values into an image. This has various advantages to the current use of indocyanine green (ICG) angiography to assess flap perfusion. Case A man in his mid-30s was involved in a road traffic accident and sustained extensive injuries to his right hand. These included multiple metacarpal fractures, degloving of the proximal aspect of the entire thumb and significant skin loss on the volar distal forearm. After several washouts and tissue debridement, a pedicled chest wall flap was performed. Five weeks later the chest wall flap was divided using an infrared thermal imaging camera (FLIR E5) intraoperatively as a clinical aid to assess perfusion. This detected a small area of venous congestion which was not detectable by clinical assessment. Discussion There are drawbacks to the current intraoperative use of ICG angiography to assess flap perfusion. These include hot flushes and skin rashes, and the technique requires an intraoperative injection, extensive equipment involving a screen and a specialised camera. In comparison FLIR cameras are handheld, easy to use and involves a one-off cost of purchasing the camera that is relatively inexpensive compared to ICG angiography. Conclusions Thermal imaging techniques such as FLIR provides an alternative intraoperative option for patients who are unable to have ICG, for centres that do not have access to ICG and for surgeons looking for more convenient alternatives.

Assessment of Rectal Temperature using Infrared Thermal Camera in Pigs

Objective: To develop substitute measures for assessing accurate Rectal Temperature with an Infrared Thermal Imaging Camera in pigs. Methods: In the experiment, three different genetic groups were used: Hampshire, crossbred (Hampshire X Niang-Megha) and Niang-Megha. Apparently healthy 90 adult pigs (1-3 years) consisting 30 numbers from different group were used for each season; namely, summer (July) and winter (December). Thermal images were taken at different anatomical body sites. Appropriate anatomical sites were selected based on close association with rectal temperature (Trectal ). Developed a constant correction factors (CF) as a substitute measures using selected sites and validated for assessing accurate Trectal . Findings: Base of the Ear Temperature (Tear) and Eye Temperature (Teye) were highly correlated with Trectal . The correction factor was developed as substitute measures for assessing rectal temperature using base of the ear and eye temperature. Accordingly, the rectal temperature was recorded ranging from 36.45 to 38.25◦C with Tear and 35 to 38.2◦C with Teye based on the developed correction factor. Novelty: Developed correction factors as a substitute measures for accurate assessment of rectal temperature by non-invasive techniques by measuring base of the ear and eye temperature with an infrared thermal imaging camera. Keywords: Rectal temperature; Correction factor; Infrared thermography; Swine; Disease

Temperature Accuracy Analysis by Land Cover According to the Angle of the Thermal Infrared Imaging Camera for Unmanned Aerial Vehicles

Land surface temperature (LST) is one of the crucial factors that is important in various fields, including the study of climate change and the urban heat island (UHI) phenomenon. The existing LST was acquired using satellite imagery, but with the development of unmanned aerial vehicles (UAV) and thermal infrared (TIR) cameras, it has become possible to acquire LST with a spatial resolution of cm. The accuracy evaluation of the existing TIR camera for UAV was conducted by shooting vertically. However, in the case of a TIR camera, the temperature value may change because the emissivity varies depending on the viewing angle. Therefore, it is necessary to evaluate the accuracy of the TIR camera according to each angle. In this study, images were simultaneously acquired at 2–min intervals for each of the three research sites by TIR camera angles (70°, 80°, 90°). Then, the temperature difference by land cover was evaluated with respect to the LST obtained by laser thermometer and the LST obtained using UAV and TIR. As a result, the image taken at 80° showed the smallest difference compared with the value obtained with a laser thermometer, and the 70° image showed a large difference of 1–6 °C. In addition, in the case of the impervious surface, there was a large temperature difference by angle, and in the case of the water-permeable surface, there was no temperature difference by angle. Through this, 80° is best when acquiring TIR data, and if it is impossible to take images at 80°, it is considered good to acquire TIR images between 80° and 90°. To obtain more accurate LST, correction studies considering the external environment, camera attitude, and shooting height are needed in future studies.

Investigation of in-plane heat distribution, thermal stability and mechanical properties of SS-(Fe3O4)/Ti/AlN/Ti/SiO2 as absorber coatings for efficient high temperature concentrated solar power systems

Despite numerous achievements recorded so far in developing solar absorber coatings for photothermal applications, the study of the thermal stability in humid and cold environment remains very scarce and the underlaying physics behind the transfer of the absorbed energy to the working fluid has never been investigated. In this perspective, we developed Ti/AlN/Ti/SiO2 film as multilayer selective solar absorber coating (MSSAC) on Fe3O4 modified stainless steel substrate using Direct Current (DC)/Radio Frequency (RF) magnetron sputtering at room temperature. The coating exhibited solar absorptance of 0.969 and thermal emittance of 0.220 in the solar and infrared spectrum regions respectively. The MSSAC was found to be thermally stable up to 500 °C in air. Further increase in annealing temperature to 600 °C resulted to a slight decrease in solar absorptance from 0.969 to 0.953 and a small rise in the emittance value from 0.220 to 0.258. A high humidity test and rapid heating-cooling cycling (RHCC) test revealed the stability of this coating and its potential application in humid (90 mmHg) and cold (− 50 °C) environments. Additionally, the coating shows good adhesion strength even after humidity and RHCC tests. The in-plane heat distribution analysis using thermal infrared imaging camera illustrated that there is a good possible transfer of the absorbed heat to the working fluid due to high surface temperature exhibited by Ti/AlN/Ti/SiO2 coated modified stainless steel (SS) substrate than the other boundary conditions. Overall, these results indicate that the present coating has the potential application in both high temperature, humid and cold environments.

Roof Color-Based Warm Roof Evaluation in Cold Regions Using a UAV Mounted Thermal Infrared Imaging Camera

Existing studies on reducing urban heat island phenomenon and building temperature have been actively conducted; however, studies on investigating the warm roof phenomenon to in-crease the temperature of buildings are insufficient. A cool roof is required in a high-temperature region, while a warm roof is needed in a low-temperature or cold region. Therefore, a warm roof evaluation was conducted in this study using the roof color (black, blue, green, gray, and white), which is relatively easier to install and maintain compared to conventional insulation materials and double walls. A remote sensing method via an unmanned aerial vehicle (UAV)-mounted thermal infrared (TIR) camera was employed. For warm roof evaluation, the accuracy of the TIR camera was verified by comparing it with a laser thermometer, and the correlation between the surface temperature and the room temperature was also confirmed using Pearson correlation. The results showed significant surface temperature differences ranging from 8 °C to 28 °C between the black-colored roof and the other colored roofs and indoor temperature differences from 1 °C to 7 °C. Through this study, it was possible to know the most effective color for a warm roof according to the color differences. This study gave us an idea of which color would work best for a warm roof, as well as the temperature differences from other colors. We believe that the results of this study will be helpful in heating load research, providing an objective basis for determining whether a warm roof is applied.

Could infrared thermal imaging be a new diagnostic tool for acute appendicitis?

Appendicitis is the most frequent acute abdominal disease and there are actual effective diagnostic tools for its detection. The objective of this study was to determine whether a thermal imaging camera is a useful tool for diagnosing acute appendicitis on the basis of abdominal skin surface temperature changes which reflect intra-abdominal inflammation. The prospective data consisting of surgical and pathological findings of 51 patients who had undergone appendectomy between January 2013 and December 2014 with the diagnosis of acute appendicitis was collected, as well as thermal imaging camera recordings. A handheld infrared (IR) thermal imaging camera (ITIC) was used to take measurements. Of the 51 patients studied, 30 were male and 21 were female. Of these, 12 had their highest temperature measurement in the epigastric and 17 in the umbilical areas. These 2 groups constituted 56.9% of the patients. Regarding the lowest temperature measurement, 10 patients had the lowest temperature in the right inguinal and 15 in the hypogastric area. These 2 numbers constituted 49% of the patients. This is the first report concerning the use of a thermal camera as a diagnostic tool for the evaluation of acute abdominal illness. Considering the results of our study, ITIC is not feasible as a new diagnostic tool for acute appendicitis. It may be suitable for determining superficial inflammation; however, it is not suitable for determining deep inflammation.

Effect of Pre-strain on Tensile Properties of Al5052-H32 under an Electropulsing Condition

Abstract This paper is concerned with the effect of pre-strain on tensile properties of Al5052-H32 under an electropulsing condition. The electroplasticity of Al5052-H32 considering the pre-strain effect is investigated to confirm the formability focused on the level of flow stress and the elongation at fracture. Tensile tests for the pre-strain effect are carried out under two different conditions: pre-straining without the electropulsing and tensile testing continuously with the electropulsing; pre-straining with the electropulsing and tensile testing continuously without the electropulsing. Under the test conditions, electropulsing tensile tests were conducted at the quasi-static of 0.001 s −1 to investigate the effect of the starting point for applying electric current and that of the accumulated electrical energy on the material behavior in terms of the formability. In order to identify the pre-strain effect, the levels of the pre-strain were determined based on the uniform elongation of Al5052-H32 obtained from tensile tests without the electric current. The Digital Image Correlation (DIC) method was used to measure the strain of a specimen. The temperature history of a specimen during the test was measured by using the infra-red thermal imaging camera of FLIR-T621. Experimental results show that the elongation is enhanced as the starting point of applying electric current is delayed for uniform deformation and the elongation increases as the amount of elevated temperature increases with increasing the accumulated electrical energy.

전자레인지의 가열조리 시 포장재의 열변형 원인 규명을 위한 온도 측정 방법 비교

To investigate the causes of the thermal deformations of packaging materials when microwave-heating ready-to-eat sauce products packaged in stand-up pouches, patterns of temperature changes were determined using an infra-red thermal imaging camera, a thermo-sensitive tape, and a fiver-optic thermometer. The temperature distributions of spicy chicken sauce and Indian curry samples in a stand-up pouch were found to be uneven during micrewave heating. A sharp increase in the temperature was detected, especially above the filling layers and in the corners of sealing layers of the package. The temperature measurements using an infra-red thermal imaging camera are restricted to the surface, and therefore might underestimate the actual temperature. Using a thermo-sensitive tape, temperature up to 200℃ were measured in the spicy chicken sauce sample showing package deformation. When the temperature is measured using a fiber-optic thermometer, it is crucial to have precise sensor performance to accurately measure the temperature in a narrow hot-spot area of the package. In this experiment, the fiber-optic thermometer was attached to a GaAs crystal sensor, which obtained more sensitive and accurate temperature measurements than those by a convectional sensor.

Influence of boiling initiation surface superheat on subcooled water flow boiling critical heat flux in a SUS304 circular tube at high liquid Reynolds number

The subcooled boiling heat transfer and the steady-state critical heat flux (CHF) in a vertical circular tube for the liquid Reynolds numbers (Red=3.65×104–3.08×105) and the flow velocities (u=3.95–30.80m/s) were systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter (d=6mm) and heated length (L=59.5mm) was used in this work. The boiling initiation noise of outer surface of the test tube in the open air was simultaneously measured up to CHF point by the sound level meter (SLM) and the microphone of a video camera (MP). The outer surface temperatures of the SUS304 test tube with heating were also observed by an infrared thermal imaging camera (ITIC) and the color temperatures of outer surface of the test tube in the open air were observed by a video camera (VC). The subcooled boiling heat transfer and CHF for SUS304 circular tube were compared with the values calculated by authors’ and other researchers’ correlations for the subcooled flow boiling heat transfer. The influences of flow velocity on the boiling initiation surface heat flux, the boiling initiation surface superheat, the subcooled boiling heat transfer and the CHF were investigated into details based on the experimental data. At the flow velocities higher than 13.3m/s, boiling initiation surface heat fluxes were close to the CHFs and surface superheats at the CHF were over to the homogeneous spontaneous nucleation temperature as well as the lower limit of the heterogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled water flow boiling CHF on the SUS304 circular tube was discussed at high liquid Reynolds number.

Modeling of cutting temperature in the biomedical stainless steel turning process

Stainless steel is widely used as material in many industries and medicine. As biomedical material, it has been used for making devices, implants as well as tools and equipment in surgery and dentistry. The most of them is processed by turning. Modeling of temperature in the metal cutting process is very important step in understanding and analysis of the metal cutting process. The objective of this study is to develop an artificial neural network model which can be used successfully for accurate prediction of cutting temperature while performing turning of the biomedical stainless steel. Before the modeling, cutting temperature was measured, as one of the significant parameters in turning process, by using the infrared thermal imaging camera. Finally, based on the mathematical model, the effects of the turning parameters on the cutting temperature were examined.

The effects of a spray slurry nozzle on copper CMP for reduction in slurry consumption

The environmental impact of semiconductor manufacturing has been a big social problem, like greenhouse gas emission. Chemical mechanical planarization (CMP), a wet process which consumes chemical slurries, seriously impacts environmental sustainability and cost-effectiveness. This paper demonstrates the superiority of a full-cone spray slurry nozzle to the conventional tube-type slurry nozzle in Cu CMP. It was observed that the spray nozzle made a weak slurry wave at the retaining ring unlike a conventional nozzle, because the slurry was supplied uniformly in broader areas. Experiments were implemented with different slurry flow rates and spray nozzle heights. Spray nozzle performance is controlled by the spray angle and spray height. The process temperature was obtained with an infrared (IR) sensor and an IR thermal imaging camera to investigate the cooling effect of the spray. The results show that the spray nozzle provides a higher Material removal rate (MRR), lower non-uniformity (NU), and lower temperature than the conventional nozzle. Computational fluid dynamics techniques show that the turbulence kinetic energy and slurry velocity of the spray nozzle are much higher than those of the conventional nozzle. Finally, it can be summarized that the spray nozzle plays a significant role in slurry efficiency by theory of Minimum quantity lubrication (MQL).

Retrieval of sulfur dioxide from a ground-based thermal infrared imaging camera

Abstract. Recent advances in uncooled detector technology now offer the possibility of using relatively inexpensive thermal (7 to 14 μm) imaging devices as tools for studying and quantifying the behaviour of hazardous gases and particulates in atmospheric plumes. An experimental fast-sampling (60 Hz) ground-based uncooled thermal imager (Cyclops), operating with four spectral channels at central wavelengths of 8.6, 10, 11 and 12 μm and one broadband channel (7–14 μm) has been tested at several volcanoes and at an industrial site, where SO2 was a major constituent of the plumes. This paper presents new algorithms, which include atmospheric corrections to the data and better calibrations to show that SO2 slant column density can be reliably detected and quantified. Our results indicate that it is relatively easy to identify and discriminate SO2 in plumes, but more challenging to quantify the column densities. A full description of the retrieval algorithms, illustrative results and a detailed error analysis are provided. The noise-equivalent temperature difference (NEΔT) of the spectral channels, a fundamental measure of the quality of the measurements, lies between 0.4 and 0.8 K, resulting in slant column density errors of 20%. Frame averaging and improved NEΔT's can reduce this error to less than 10%, making a stand-off, day or night operation of an instrument of this type very practical for both monitoring industrial SO2 emissions and for SO2 column densities and emission measurements at active volcanoes. The imaging camera system may also be used to study thermal radiation from meteorological clouds and the atmosphere.

Plasma Uniformity Analysis of Inductively Coupled Plasma Assisted Magnetron Sputtering by a 2D Voltage Probe Array

A real-time monitoring of immersed antenna type inductively coupled plasma (ICP) was done with a homemade 2 dimensional voltage probe array to check the uniformity of the plasma. Measured voltage values with a high impedance voltmeter are close to the floating potential of the plasma. As the substrate carrier was moving into a magnetron sputtering plasma diffusive from a <TEX>$125mm{\times}625mm$</TEX> size cathode, measured results showed reliably separation of plasma into the upper and lower empty space over the carrier. Infra red thermal imaging camera was used to observe the cross corner effect in situ without eroding a target to the end of the usage. 3 dimensional particle trace model was used to analyze the magnetron discharge's behavior.

Particle Filter Tracking of Camouflaged Targets by Adaptive Fusion of Thermal and Visible Spectra Camera Data

This paper presents a method for tracking a moving target by fusing bi-modal visual information from a deep infra-red thermal imaging camera and a conventional visible spectrum color camera. The tracking method builds on well-known methods for color-based tracking using particle filtering, but it extends these to handle fusion of color and thermal information when evaluating each particle. The key innovation is a method for continuously relearning local background models for each particle in each imaging modality, comparing these against a model of the foreground object being tracked, and thereby adaptively weighting the data fusion process in favor of whichever imaging modality is currently the most discriminating at each successive frame. The method is evaluated by testing on a variety of extremely challenging video sequences, in which people and other targets are tracked past occlusion, clutter, and distracters causing severe and sustained camouflage conditions in one or both imaging modalities.

Temporal variability of thermal refuges and water temperature patterns in an Atlantic salmon river

In response to high summer river temperatures, salmonids avoid heat stress by making use of discrete units of cold water termed thermal refuges. Although recent research has documented how their spatial arrangement within a river affects salmonid distribution and behaviour, no information is currently available concerning temporal variation in the abundance and types of thermal refuges. In this study, a FLIR SC660 thermal infrared imaging camera (640×480 pixels, NETD <30mK, 7.5–13μm) mounted on a helicopter platform was used to acquire thermal imagery of an Atlantic salmon river in Québec, Canada on six occasions between 2009 and 2011, with a view to characterising temporal variability in thermal refuges and broader scale water temperature complexity. Thermal refuges detected from TIR imagery were classified into a series of process-based categories, revealing notable inter-survey variability in the absolute counts of each refuge type. Downstream temperature complexity, quantified as the standard deviation of derivatives taken of temperature long profiles of each survey, was highly temporally variable, exposing the presence of several warm and cool reaches which varied in magnitude between surveys. Data from local meteorological and discharge logging stations was used to examine whether hydrometeorological conditions could account for observed temporal variability trends. Temporal variability in the absolute counts of lateral groundwater seeps, the most frequently observed thermal refuge class, was shown to correlate strongly with long duration hydrometeorological metrics such as seasonal mean discharge (R2=0.94, p<0.01). Conversely, thermal refuges resulting from cold water tributaries were more temporally stable and exhibited a weaker correlation with hydrometeorological metrics. Downstream temperature complexity was shown to correlate best with short duration metrics such as cumulative precipitation depth within a 5-day period prior to each survey (R2=0.90, p<0.01). This study is the first of its kind to link thermal refuge dynamics to hydrometeorological conditions and may offer valuable insights into how changing climatic regimes could influence these important cold water units in the future.

Usefulness of Infrared Thermal Imaging Camera for Screening of Postoperative Surgical Site Infection after the Nuss Procedure

Introduction and Objective. The Nuss procedure is widely used in the treatment of pectus excavatum worldwide. Postoperative pectus bar infection is one of the most serious complications associated with this procedure. Therefore, early detection of signs of implant infection is very important. However, this is difficult, and effective methods have yet to be established. Methods. We use a handheld infrared thermal imaging camera to screen patients for postoperative infection following the Nuss procedure. Here, we report a 28-year-old man with recurrent postoperative (Ravitch procedure) pectus excavatum. Results. Infrared thermography camera clearly indicated slight cellulitis in the right chest. Conclusion. Our technique may assist in preventing postoperative bar infection and removal caused by severe bar infection. Furthermore, this camera is potentially suitable for many situations in infection monitoring following subcutaneous implant surgery.

EFFECT OF AIRFLOW PROFILE ON REDUCING HEAT STRESS, ENHANCING AIR DISTRIBUTION AND DILUTING GASEOUS CONCENTRATIONS IN DAIRY BARNS

Heat stress in dairy cows is one of the leading causes of decreased production and fertility. Increasing air velocity, using ceiling fans, to enhance convective heat transfer and accordingly body heat dissipation is highly required. However, this might have negative effects such as increasing emission mass flux of the harmful gases. Therefore, this study aims at investigating the effect of ceiling fans on the dairy cows, air velocity profiles, and the distribution of gaseous concentrations throughout a naturally ventilated dairy barn. Three air velocity measurements campaigns, with two repetitions each, were carried out during summer season 2010. The air velocity was measured inside the barn using ultrasonic anemometers. The air temperature and humidity were measured using temperature-humidity sensors. The climatic data were recorded by weather station. The concentrations of CO2, NH3, CH4, and N2O were measured using a multi-gas monitor. The heat stress was estimated by determining the Temperature-Humidity Index (THI). A thermal infrared imaging camera was used to investigate the heat relief from the cows and freestalls under 2 conditions, which were: ceiling fans on and ceiling fans off. The results showed that the implementation of ceiling fans reduced the THI from 79 (significant stress) to 68 (no stress). The average air velocities were 0.98 and 0.59 m s-1 as the ceiling fans were “on” and “off”, respectively. It was concluded that the ceiling fans have cooling effect, alleviate the heat stress, and enhance the air movement and distribution throughout the barn. However, the ceiling fans indirectly increase the ventilation rates in higher potential then the disguised decrease of the gaseous concentrations, which ultimately results in increasing the gaseous emissions. 1Assistant Professor, Depart. of Agric. Eng., Faculty of Agriculture, Cairo University, Egypt 2Research Scientist, Leibniz Institute for Agric. Eng. Potsdam-Bornim (ATB), Potsdam, Germany Therefore, a balance must be achieved among the different contradictions: air velocity optimization, heat stress alleviation, air distribution enhancement, and gaseous emissions reduction.

Constructed wetlands support bats in agricultural landscapes

Bats are known to use aquatic habitats as foraging habitats. Agricultural intensification is perceived to be a main reason for the loss of wetlands. However, artificial wetland creation (i.e. the construction of retention-ponds) in the agricultural landscape aiming at water or nutrient retention has recently gained importance. We evaluated to what extent bats use these artificial wetlands as foraging habitats in an agricultural landscape.Bat activity and prey density were compared in matched pairs at retention-ponds and neighbouring vineyard sites using stationary bat-detectors and sticky-traps, respectively. To examine if bat activity is related to the number of bat individuals, a thermal infrared imaging camera was used. Pipistrellus pipistrellus, the dominant species, served as an example to assess habitat selection between retention-ponds and vineyards. This was performed by relating foraging activity to the available area available within the potential home-range.Total bat activity and nocturnal prey density were significantly higher above the retention-ponds than above vineyards. High differences of activity levels between the ponds and the respective vineyard sites were found for Pipistrellus spp. (P. pipistrellus and P. nathusii) and Myotis spp. (M. daubentonii and M. mystacinus), being about 180 times and 50 times higher above the retention-ponds, respectively. A significant correlation was found between recorded bat activity and the maximum number of bat individuals observed with a thermal infrared imaging camera. When relating foraging activity to habitat availability within the assumed home-range of P. pipistrellus, retention-ponds had on average a higher importance as a foraging habitat than the complete vineyard area although they covered less than 0.1% of its area.This study indicates that artificial wetlands such as retention-ponds provide foraging habitats for bats. Therefore, creation of wetlands in intensively used agricultural landscapes benefits bats.

Fault Detection on Transmission Lines Using a Microphone Array and an Infrared Thermal Imaging Camera

This paper proposes a hierarchical fault detection method for transmission lines using a microphone array to detect the location of a fault and thermal imaging and charge coupled device (CCD) cameras to verify the fault and store the image, respectively. There are partial arc discharges on faulty insulators which generate specific patterns of sound. By detecting these patterns using the microphone array, the location of the faulty insulator can be estimated. A sixth-order bandpass filter and an autocorrelation scheme were applied to remove the noise signals caused by the wind, bird chirpings, or other external influences. When a mobile robot carries the thermal CCD cameras to the possible location of the fault, the faulty insulators or power transmission wires can be detected by the thermal images. The CCD camera then captures an image of the faulty insulator for the record. This detection scheme has been proved to be effective through experimentation. As a result of this research, it will be possible to use a mobile robot with integrated sensors to detect faulty insulators instead of using a human being.

Maximum temperatures of 89°C recorded during the mechanical preparation of 35 femoral heads for resurfacing

Background and purpose We noticed that our instruments were often too hot to touch after preparing the femoral head for resurfacing, and questioned whether the heat generated could exceed temperatures known to cause osteonecrosis.Patients and methods Using an infra-red thermal imaging camera, we measured real-time femoral head temperatures during femoral head reaming in 35 patients undergoing resurfacing hip arthroplasty. 7 patients received an ASR, 8 received a Cormet, and 20 received a Birmingham resurfacing arthroplasty.Results The maximum temperature recorded was 89°C. The temperature exceeded 47°C in 28 patients and 70°C in 11. The mean duration of most stages of head preparation was less than 1 min. The mean time exceeded 1 min only on peripheral head reaming of the ASR system. At temperatures lower than 47°C, only 2 femoral heads were exposed long enough to cause osteonecrosis. The highest mean maximum temperatures recorded were 54°C when the proximal femoral head was resected with an oscillating saw and 47°C during peripheral reaming with the crown drill. The modified new Birmingham resurfacing proximal femoral head reamer substantially reduced the maximum temperatures generated. Lavage reduced temperatures to a mean of 18°C.Interpretation 11 patients were subjected to temperatures sufficient to cause osteonecrosis secondary to thermal insult, regardless of the duration of reaming. In 2 cases only, the length of reaming was long enough to induce damage at lower temperatures. Lavage and sharp instruments should reduce the risk of thermal insult during hip resurfacing.