In vivo dynamic thermal imaging of skin radiofrequency treatment

In recent years, popularity of radiofrequency (RF) has increased significantly. They are characterized by a low risk of complications and relatively high effectiveness. RF use high‐frequency currents causing oscillating motion of ions resulting in temperature rise stimulating skin regeneration processes. The aim of this work was the thermographic evaluation of the skin exposed to RF of different intensity. The dynamic thermal imaging was used to study the temperature of the skin exposed to RF. The research was carried out in two locations with different adipose tissue content: abdomen (ROI1) and forearm (ROI2). In the ROI1 area, RF was applied at nominal power range from 250 to 1750 W, while in ROI2 area: from 250 to 1000 W. The obtained thermographic data were fitted to exponential functions. A clear dependence of obtained thermokinetic parameters with the anatomical location of exposure to RF was demonstrated. Thicker layer of adipose tissue directly under the skin resulted in obtaining higher maximum temperatures of the skin surface during the procedure (maximum obtained temperature equaled 40.8°C). The temperature of the skin under the head of the device does not translate to subjective patient experiences. In anatomic locations filled with less adipose tissue mass, tolerance to RF is much lower. The dynamics of skin temperature changes, after the RF treatment, can be described by means of a single exponential function where the key parameter is the time constant t₁ defining the dynamics of skin temperature changes. The depth of the RF influence is slightly correlated with the RF power.     

Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously “yielded” samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the material.     

红外热成像技术在皮瓣外科中的应用进展

皮瓣外科手术中,皮瓣的穿支血管定位以及血运情况是临床医生最为关注的问题.近年来,红外热成像技术(IRT)作为一种便携、无创、快速、经济的探测手段逐渐应用于皮瓣外科中,其可以通过探测人体发出的红外辐射,精确地描绘组织表面的温度分布.本文综述IRT在皮瓣外科领域的应用方向,包括穿支血管探测以及血运监测两大方面,并探讨其潜在的应用价值,为临床医生提高皮瓣手术的预后提供参考和帮助.     

Response of the RIF-1 tumour to superficial or interstitial heating (46–50°C) using an Nd-YAG laser

The response of the RIF-1 tumour in C3H mice to 1064 nm near infra-red radiation from an Nd-YAG laser was investigated. Tumours in the right hind leg of mice were heated, in groups of 10, to 46, 48 or 50°C (at a feedback thermocouple) for 30 min. Superficial or interstitial treatment was effected by a 600 μm quartz fibre terminating in a microlens or cylindrical diffuser, respectively. Three thermocouples were inserted in each tumour for temperature measurement. The feedback thermocouple was connected to the laser and controlled power output during heating. Our experiments indicated that superficial heating (employing a feedback thermocouple at the base) resulted in greater tumour growth delay and control at 60 days compared to interstitial treatment, where the feedback thermocouple was located above the diffuser. A mean temperature gradient of approximately 13 degrees was observed from the surface to the base of tumours when heated superficially, resulting in extensive skin necrosis within 48h post-treatment. Superficial heating to a base temperature of 50°C resulted in 50% tumour control at 60 days. In contrast, only minor differences in temperature were measured above and below the inserted cylindrical diffuser during interstitial treatment, resulting in reduced skin necrosis at 48h and no long-term tumour control. It appears from our study that use of a single, defocused beam (superficial delivery) of 1064 nm radiation results in effective but non-uniform heating of the RIF-1 tumour, and may require surface cooling to limit skin temperatures. Use of a cylindrical fibre tip (interstitial delivery) will require insertion of multiple fibres in the tumour mass to effectively heat tumours larger than 1 cm.     

红外热像技术在糖尿病方面的应用研究

目的 基于生物传热理论，研究红外热像图在糖尿病研究中的应用。方法 采用温度负荷方法，将人体内代谢系统的功能活动诱发到体表，利用手背面摄取红外热像图，然后通过根据基本原理编写的程序分析，得到红外热像图检测结果，最后将红外热像图的分析结果与临床医生的综合诊断结果相对照。结果 对2042例临床数据进行统计和分析，显示出糖尿病患者和健康人的代谢功能有显著差异。结论 本文所采用的方法对糖尿病的代谢功能测定具有积极意义。     

B16 melanoma in hairless mice: a model for thermographic research

Little is understood concerning the mechanism of tumor-induced thermographic abnormalities observed in man. An ideal animal model is lacking. In an effort to create such a model we have worked with hairless mice, subcutaneously inoculated with B16 melanoma cells. This report documents the progress of that work and the subsequent development of a totally satisfactory system for the study of such tumors in a hairless animal.     

Thermography – a valuable tool to test hydrocephalus shunt patency

Summary Introduction. Shunt-function in hydrocephalic patients is verified by clinical examination and repeated cranial computed tomography (CCT) in most cases. Because of the disadvantages of multiple radiation especially in children it was our aim to introduce video-thermography as a simple and non-invasive methodology to evaluate shunt function. Methods. 54 patients treated with shunts for hydrocephalus were tested. A ventriculo-peritoneal shunt had been implanted in 38 patients, a ventriculo-atrial shunt in 16 patients. Recent CCT-scans were available for all patients and served as control. None of the patients presented with clinical signs of shunt-dysfunction. The temperature of the skin covering the drainage catheter distal to the valve was recorded real-time by a calibrated infrared camera. After cooling the skin area downstream of the valve for exactly 1 min with an ice pack, changes of the skin temperature in the area downstream were registered by a thermocamera. The signals were transferred to a video screen and recorded on videotape. By off-line analysis of the obtained pseudo colour images variations of 0.1 °C in skin temperature could be measured. Results. Temperature distribution of the area under investigation revealed a significant reduction of the skin temperature according to the location of the downstream catheter segment in 48 patients after cooling. In 6 patients skin temperature remained constant, although clinical evaluation and CCT-scan showed no signs of shunt dysfunction. Shunt patency could be verified in more than 85% of the patients by thermal imaging. Conclusion. Infrared-thermography is a valuable and promising tool for replacing CCT-scanning as a screening method to test shunt function in hydrocephalic patients.     

Effects of mechanical irritation on the autonomic part of the median nerve

The diagnosis of median nerve compression is generally based upon a prolonged nerve conduction velocity although this frequently is preceded by clinical symptoms for years. The present study was designed to identify indicators for early decompression of the median nerve in patients exhibiting symptoms compatible with carpal tunnel syndrome (CTS). Microvascular perfusion in finger tip skin and skin temperature were studied during dorsiflexion of the hand prior to and following a manual exercise test in control subjects and in patients with clinical symptoms and signs of CTS. Evaluation of the microcirculation was performed using photoplethysmography (PPG) and laser Doppler fluxmetry (LDF). Fingertip skin temperature was measured by thermography and was significantly reduced in patients after exercise ( P  < 0.001), whereas no significant change occurred in control subjects. During increasing degrees of dorsiflexion (0–75°) and after manual exercise, fingertip skin perfusion remained unchanged in both patients and control subjects. In conclusion, patients with low-grade CTS experience skin temperature reduction, presumably caused by increased sweating as opposed to a generally suspected vasoconstriction. These autonomic median nerve dysfunctions provide the physiological basis for the use of thermography in confirming low-grade CTS.     

The Disappearance of the "Cold Patch" in Recovered Migraine Patients: Thermographic Findings

In a previous paper we suggested that the vascular cold patch may be a useful prognostic index to followup migraine patients. Considerable criticism against our contention has been raised by Swerdlow and Dieter (Headache 29:562-568, 1989, ref. 1), who claim that the cold patch constitutes a "fixed geography" of the vasculature of migraine patients. In the present paper we replicate and extend our previous findings reporting the results of facial thermography in a sample of 246 consecutive migraine patients. Of these the 206 exhibiting a typical cold patch or a significant asymmetry in the forehead thermal dissipation were admitted to prophylactic treatment (beta blocker or calcium channel blocker). The thermography was performed at entry in the study and after six months of active treatment. The clinical outcome was compared to the thermographic findings. The patients were subdivided in three classes on the basis of the clinical outcome. Among the 136 patients who experienced complete or substantial relief from headache the cold patch disappeared or markedly improved in 85% of the cases. In the 46 patients with partial relief the thermogram showed an improved pattern in 48% of cases, most of the time of smaller extent than in the previous class. In 24 patients we observed no clinical improvement. Among these the thermogram remained unchanged in 85% of cases. Taken together these findings corroborate our previous suggestion that thermography is useful to monitor the clinical course of the disease. One additional suggestion from the present data is that thermography closely parallels the clinical course so as to represent a useful criterion for the decision of discontinuing the therapy.