Ultrasound monitoring of temperature and coagulation change during tumor treatment with microwave ablation

Microwave ablation therapy has become an important method for tumor treatment in recent years. The temperature and the coagulation region need real-time noninvasive monitoring to ensure the safety and effective-ness during the treatment. The authors reviewed the ultrasonic monitoring methods for tumor microwave ablation therapy both at home and abroad. In addition, the authors also prospected this technique in the future.     

Numerical study to establish relationship between coagulation volume and target tip temperature during temperature-controlled radiofrequency ablation

The present study aims at proposing a relationship between the coagulation volume and the target tip temperature in different tissues (viz., liver, lung, kidney, and breast) during temperature-controlled radiofrequency ablation (RFA). A 20-min RFA has been modelled using commercially available monopolar multi-tine electrode subjected to different target tip temperatures that varied from 70°C to 100°C with an increment of 10°C. A closed-loop feedback proportional-integral-derivative (PID) controller has been employed within the finite element model to perform temperature-controlled RFA. The coagulation necrosis has been attained by solving the coupled electric field distribution, the Pennes bioheat and the first-order Arrhenius rate equations within the three-dimensional finite element model of different tissues. The computational study considers temperature-dependent electrical and thermal conductivities along with the non-linear piecewise model of blood perfusion. The comparison between coagulation volume obtained from the numerical and in vitro experimental studies has been done to evaluate the aptness of the numerical models. In the present study, a total of 20 numerical simulations have been performed along with 12 experiments on tissue-mimicking phantom gel using RFA device. The study revealed a strong dependence of the coagulation volume on the pre-set target tip temperature and ablation time during RFA application. Further, the effect of target tip temperature on the applied input voltage has been studied in different tissues. Based on the results attained from the numerical study, statistical correlations between the coagulation volume and treatment time have been developed at different target tip temperatures for each tissue.     

The effects of fat layer on temperature distribution during microwave atrial fibrillation catheter ablation

Abstract

To investigate the effects of fat layer on the temperature distribution during microwave atrial fibrillation catheter ablation in the conditions of different ablation time; 3D finite element models (fat layer and no fat layer) were built, and temperature distribution was obtained based on coupled electromagnetic-thermal analysis at 2.45?GHz and 30?W of microwave power. Results shown: in the endocardial ablation, the existence of the fat layer did not affect the shape of the 50?°C contour before 30?s. The increase speed of depth became quite slowly in the model with fat layer after 30?s. When ablation depth needed fixed, there are no significant effect on effectively ablation depth whether fat layer over or not. However, the existence of fat layer makes the temperature lower in the myocardium, and maximum temperature point closer to the myocardium surface. What is more, in the model with fat layer, effective ablation reach lower maximum temperature and the shallower depth of 50?°C contour. But there are larger ablation axial length and transverse width. In this case, doctor should ensure safety of normal cardiac tissue around the target tissue. In the epicardial ablation, the existence of fat layer seriously affects result of the microwave ablation. The epicardial ablation needs more heating time to create lesion. But epicardial ablation can be better controlled in the shape of effective ablation area because of the slowly increase of target variables after the appearing of 50?°C contour. Doctor can choose endocardial or epicardial ablation in different case of clinic requirement.     

Resection of meningiomas with implantable microwave coagulation

Implantable microwave coagulation was used to perform resection on 62 patients that had intracranial meningiomas. When 20–60 W microwave power was applied for 15 s, the temperature at the center of the tumor tissue was 43–63°C; 30 mm from the center, the temperature was under 40°C. Histological changes in the center of the tumor showed coagulative necrosis, diminished nuclei, and obliterated blood vessels. The changes at 10–20 mm from the center of the tumor showed coagulative necrosis and degeneration and, 30–50 mm from the center of the tumor, showed normal cell morphology after microwave coagulation. The thermal field in brain tumor has an effective diameter of about 40 mm. No side effects on the normal brain tissues were observed. The amount of blood loss during the operation was minimal while the meningioma was coagulated, especially when the meningioma was located at the skull base or in the parasagittal or cerebral convexity region. After microwave coagulation, the entire tumor could easily be removed. Among the 62 surgically treated cases, gross total tumor excision was 85%. No postoperative complications occurred after microwave coagulation, and there was no operative mortality in the series. We believe that this new technique has the advantage of simplicity, less blood loss, and smooth postoperative procedures. Hemostatic effects during the operation are satisfactory, and blood transfusion can be reduced by 50–60%. © 1996 Wiley-Liss, Inc.     

Brain temperature measurements in rats: a comparison of microwave and ambient temperature exposures

In an effort to understand microwave heating better, regional brain and core temperatures of rats exposed to microwave radiation (2450 MHz) or elevated air temperatures were measured in two studies. In general, we have found no substantial evidence for temperature differentials, or "hot spots," in the brain of these animals. In the first study, after a 30-min exposure, no temperature differences between brain regions either after microwave or ambient air exposure were found. However, a highly significant correlation between brain and core temperatures was found and this correlation was the same for both microwave and ambient air heating. In the second study, time-temperature profiles were measured in rats exposed to either 30 mW/cm2 or 36.2 degrees C. In this study, the 30-min exposure period was divided into seven intervals and the change in temperature during each period was analyzed. Only the cortex showed significantly different heating rates between the air heating and microwave heating; however, this difference disappeared after the initial 5 min of exposure.     

超声造影引导下行微波消融术治疗肝癌的临床效果分析

目的：评估超声造影（CEUS）gl导下微波消融（MwA）治疗肝癌的有效性及应用价值。方法：108例肝癌患者,共147个病灶经MWA治疗。根据患者在做常规超声检查时,是否有扫查不清晰的结节或其他影像学检查提示可能存在多发结节等,分成CEUS族和对照组。CEUS组41名患者,年龄（57．9±7．8）岁,共57个病灶,平均直径（2．4±1．5）cm,经超声造影引导下行微波消融治疗。对照组67名患者,年龄（55．5±8．9）岁,共90个病灶,平均直径（2．6±1．7）cm,常规超声引导下同种条件行微波消融治疗。治疗后对两组患者进行6～12个月随访。结果：CEUS组的57个病灶均清晰显示其位置、数目、大小、边界、形态,完全消融的结节为55个,未完全消融的结节为2个。对照组67名患者的90个病灶,完全消融的病灶78个;未完全消融的结节12个。CEUS组完全消融率高于病例对照组（96．49％VS86．67％;P〈0．05）。随访6～12个月后发现,CEUS组完全消融率高于病例对照组（P〈0．05）,差异有统计学意义。结论：CEUS能更好的显示病灶的位置、数目、大小,更精确显示病灶边界、范围,造影引导下MWA是一种有效提高完全消融效率的方法,具有较大应用价值。     

Diffuse reflectance spectroscopy as a monitoring tool for gastric mucosal devitalization treatments with argon plasma coagulation

Electrosurgery with argon plasma coagulation is a widespread technique used in various medical fields for applications which range from hemostasis to devitalization processes. Developing tools which provide feedback concerning tissue condition during these surgeries is fundamental for improving the safety and success of this treatment. We present here a method based on diffuse reflectance spectroscopy to monitor gastric mucosal devitalization treatments. The analysis of the diffusely reflected spectra of the tissue allows us to differentiate between ablation states by using linear discriminant analysis (LDA) as a classification algorithm. An ex vivo pilot study on several swine stomachs showed promising results, with 97.8% of correctly classified ablation states on a new unseen stomach, encouraging further tests with human tissue.     

超声造影引导下行微波消融术治疗肝癌的临床效果分析*

摘要目的：评估超声造影(CEUS)引导下微波消融(MWA)治疗肝癌的有效性及应用价值。方法：108 例肝癌患者,共147个病灶经 MWA治疗。根据患者在做常规超声检查时,是否有扫查不清晰的结节或其他影像学检查提示可能存在多发结节等,分成CEUS 族和对照组。CEUS组41 名患者,年龄(57.9± 7.8）岁,共57 个病灶,平均直径（2.4± 1.5）cm,经超声造影引导下行微波消融治疗。 对照组67 名患者,年龄（55.5± 8.9）岁,共90 个病灶,平均直径（2.6± 1.7）cm,常规超声引导下同种条件行微波消融治疗。治疗后 对两组患者进行6～12 个月随访。结果：CEUS组的57 个病灶均清晰显示其位置、数目、大小、边界、形态,完全消融的结节为55 个,未完全消融的结节为2个。对照组67 名患者的90 个病灶,完全消融的病灶78 个;未完全消融的结节12 个。CEUS组完全消 融率高于病例对照组(96.49 %VS 86.67 %;P< 0.05）。随访6～12 个月后发现,CEUS 组完全消融率高于病例对照组(P< 0.05）,差 异有统计学意义。结论：CEUS能更好的显示病灶的位置、数目、大小,更精确显示病灶边界、范围,造影引导下MWA 是一种有效 提高完全消融效率的方法,具有较大应用价值。     

Comparison of percutaneous cryoablation with microwave ablation in a porcine liver model

We compared imaging and pathological changes between argon–helium cryosurgical (AH) and microwave (MW) ablation in a porcine liver model. Immediately after ablation, computed tomography (CT) imaging showed that the area affected by MW ablation was considerably greater than that affected by AH ablation; moreover, the surface area of necrotic tissue was considerably greater in the AH group, whereas the depth of the necrotic area was similar. Seven days after ablation, the affected area had not changed much in the AH group, but it had significantly increased in the MW group; similarly, the surface and depth of the necrotic areas had not changed much in the AH group, but they had increased significantly in the MW group. The pathological findings showed similar definitive areas for both groups at both time points. The findings indicated that long time after both therapies, complete tissue necrosis can be achieved, but the extent and depth of necrosis differ: necrosis foci after AH ablation could be predicted by ice ball under CT image, and necrosis foci after MW ablation will increase obviously. MW ablation might therefore be suitable for tumors with a larger volume and simple anatomical structures, and AH ablation might be suitable for tumors with complex anatomical structures or those located near important organs. These two methods could therefore be used in combination in clinical settings, but details of the procedure need to be studied.     

Comparison of peri-procedural anticoagulation with rivaroxaban and apixaban during radiofrequency ablation of atrial fibrillation

IntroductionProspective studies on rivaroxaban and apixaban have shown the safety and efficacy of direct anticoagulation agents (DOAC)s used peri-procedurally during radiofrequency ablation (RFA) of atrial fibrillation (AF). Studies comparing the two agents have not been performed.MethodsConsecutive patients from a prospective registry who underwent RFA of AF between April 2012 and March 2015 and were on apixaban or rivaroxaban were studied. Clinical variables and outcomes were noted.ResultsThere were a total of 358 patients (n = 56 on apixaban and n = 302 on rivaroxaban). There were no differences in baseline characteristics between both groups. The last dose of rivaroxaban was administered the night before the procedure in 96% of patients. In patients on apixaban, 48% of patients whose procedure was in the afternoon took the medication on the morning of the procedure. TIA/CVA occurred in 2 patients (0.6%) in rivaroxaban group with none in apixaban group (p = 0.4). There was no difference in the rate of pericardial effusion between apixaban and rivaroxaban groups [1.7% vs 0.6% (p = 0.4)]. Five percent of patients in both groups had groin complications (p = 0.9). In apixaban group, all groin complications were small hematomas except one patient who had a pseudoaneurysm (1.6%). One pseudo-aneurysm, 1 fistula and 3 large hematomas were noted in patients on rivaroxaban (1.7%) with the rest being small hematomas. DOACs were restarted post procedure typically 4 h post hemostasis.ConclusionsPeri-procedural uninterrupted use of apixaban and rivaroxaban during AF RFA is safe and there are no major differences between both groups.     

Concentric photothermal coagulation with basket‐integrated optical device for treatment of tracheal stenosis

A basket‐integrated optical device is developed to consistently treat tubular tissue by centering an optical diffuser in the lumen. Four nitinol arms in conjunction with the optical diffusing applicator are deployed to induce homogeneous circumferential light emission and concentric photothermal coagulation on tracheal tissue. A 1470‐nm laser light is employed for the tissue testing at various irradiation conditions and evaluated in terms of thermal gradient and temperature evolution. Preliminary experiments on liver tissue demonstrate the concentric development of the radial thermal coagulation in the tissue (eccentric ratio = ~5.5%). The interstitial tissue temperature increases with the total amount of energy delivery (around 65°C). Ex vivo trachea testing yields up to 16.5% tissue shrinkage due to dehydration as well as uniform ablation of the cilia and goblet cells in a mucosa layer under 7‐W irradiation for 10 s. The proposed optical device may be a feasible therapeutic method to entail the circumferential coagulation in the tubular tissues in a reliable manner.      

Effects of microwave exposure and temperature on survival of mice infected with Streptococcus pneumoniae

Female CD-1 mice were injected with an LD₅₀ dose of Streptococcus pneumoniae and then exposed to 2.45 GHz (CW) microwave radiation at an incident power density of 10 mW/cm² (SAR = 6.8 W/kg), 4 h/d for 5 d at ambient temperatures of 19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C. Four groups of 25 animals were exposed at each temperature with an equal number of animals concurrently sham-exposed. Survival was observed for a 10-d period after infection. Survival of the sham-exposed animals increased as ambient temperature increased from 19 °C–34 °C. At ambient temperatures at or above 37 °C the heat induced in the body exceeded the thermoregulatory capacity of the animals and deaths from hyperthermia occurred. Survival of the microwave-exposed animals was significantly greater than the shams (～20%) at each ambient temperature below 34 °C. Based on an analysis of the data it appears that the hyperthermia induced by microwave exposure may be more effective in increasing survival in infected mice than hyperthermia produced by conventional methods (ie, high ambient temperature). Microwave radiation may be beneficial to infected animals at low and moderate ambient temperatures, but it is detrimental when combined with high ambient temperatures.     

超声造影在甲状腺结节鉴别诊断及良性结节微波消融治疗中的应用价值

摘要 目的：研究超声造影在甲状腺结节鉴别诊断及良性结节微波消融治疗中的应用价值。方法：选取2015年1月～2018年2月我院收治的甲状腺结节患者100例作为研究对象,所有纳入对象均进行超声造影检查,分析甲状腺结节的超声造影特征,并与病理诊断结果进行对照。此外,将甲状腺良性结节患者以随机抽签法分成超声造影组31例和常规超声组30例。超声造影组微波消融治疗前后均予以超声造影配合,常规超声组微波消融治疗前后均予以常规超声配合。比较两组治疗前后甲状腺结节造影情况以及术后1年结节复发情况。结果：甲状腺恶性结节增强强度为低增强、增强模式为不均匀、无环绕增强占比均高于良性结节（均P＜0.05）。以病理诊断为金标准,超声造影诊断恶性甲状腺结节的灵敏度为92.31%、特异度为78.69%、准确度为84.00%。治疗后超声造影组甲状腺结节最长径、体积均低于常规超声组（均P＜0.05）。超声造影组术后1年结节复发率为0.00%,低于常规超声组的16.67%（P＜0.05）。结论：超声造影应用于甲状腺结节鉴别诊断的价值较高,且结合微波消融治疗良性结节的效果明显,预后理想,值得临床推广应用。     

Responses of human skin temperature and thermal sensation to step change of air temperature

1. 1. The purpose of this paper is to clarify the non-linearity of the human physiological and psychological responses to step change of air temperature by impulse response analysis using Discrete Fourier Transformation.

2. 2. Experiments were conducted to investigate the effect of thermal transients on human responses.

3. 3. Experimental conditions were as follows: lowering air temperature from 30 to 20°C and raising air temperature from 20 to 30°C.

4. 4. The responses of local skin temperature on lowering air temperature from 30 to 20°C are not necessarily opposite to the responses found on raising air temperature from 20 to 30°C.

5. 5. From impulse response analysis using Discrete Fourier Transformation, skin temperature responses to the opposite air temperature change do not necessarily coincide with each other whenever the same temperature stimulus is occurred.

Effects of 2.45-GHz microwave and 100-MHz radiofrequency radiation on liposome permeability at the phase transition temperature

Large unilamellar dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) liposomes loaded with an aqueous chemotherapeutic drug, cytosine arabinofuranoside (ARA-C), were exposed for 30 min to 60 W/kg continuous-wave (CW) 100-MHz or 2.45-GHz radiation in vitro at temperatures between 37 degrees C and 43 degrees C. Liposomes were exposed in HEPES buffer or in HEPES buffer supplemented with 44% by volume fetal calf serum (FCS). Characteristic phase transition responses were detected in the range of 39 degrees C to 40 degrees C with the presence of FCS, increasing maximum % release of 3H-ARA-C by 20% relative to HEPES suspension. Neither frequency of electromagnetic radiation had any detectable effect on liposome permeability or the location of the phase transition in the presence or absence of FCS.     

Ultrasound evaluation of visceral fat and metabolic risk factors during early pregnancy

Objective: The objective was to study the relationships between ultrasound estimated visceral fat and metabolic risk factors during early pregnancy. Research Methods and Procedures: Thirty consecutive healthy pregnant women at 11 to 14 weeks of gestation were studied. Maximum subcutaneous fat thickness (SFT) and visceral fat thickness (VFT) were successfully measured by ultrasound. Fasting plasma glucose, insulin, triglycerides, total cholesterol, high‐density lipoprotein cholesterol (HDL‐C), and blood pressure were measured. Insulin resistance was calculated by using the homeostasis model assessment (HOMA). Results: VFT significantly correlated with diastolic blood pressure (r = 0.37, p = 0.04), glycemia (r = 0.37, p = 0.04), insulinemia (r = 0.59, p = 0.001) insulin sensitivity (HOMA; r = 0.59, p = 0.001), triglycerides (r = 0.58, p = 0.03), HDL‐C (r = ?0.39, p = 0.03), and total cholesterol/HDL‐C ratio (p = 0.002), whereas SFT was significantly correlated with only diastolic blood pressure (p = 0.03). VFT better significantly correlated with the metabolic risk factors than pre‐gestational BMI [r = 0.39, p = 0.03 for insulinemia, r = 0.42, p = 0.02 for insulin sensitivity (HOMA), and r = 0.49, p = 0.01 for triglycerides and not significant for the rest]. Discussion: Visceral fat thickness can be easily measured by ultrasound at early pregnancy and correlates better than BMI with metabolic risk factors.     

First Dutch experience with the endoscopic laser balloon ablation system for the treatment of atrial fibrillation

IntroductionThe endoscopic laser balloon ablation system (EAS) is a relatively novel technique to perform pulmonary vein isolation (PVI) in the treatment of atrial fibrillation (AF). The present study aimed to report the results of the first 50 patients treated in the Netherlands with the EAS in terms of procedural characteristics and AF-free survival.MethodsFifty patients successfully underwent EAS PVI. Median follow-up was 17 months. Mean age was 56 years, 82 % had paroxysmal AF.Results99 % of the pulmonary veins were successfully isolated with the EAS. Mean procedure time was 171 min and mean fluoroscopy time was 36 min. One procedure was complicated by a temporary phrenic nerve palsy (2 %). During follow-up, 58 % of patients remained free of AF without the use of antiarrhythmic drugs.ConclusionPVI with EAS is associated with a low risk of complications and a medium-term AF-free survival comparable with other PVI techniques.

Electronic supplementary material

The online version of this article (doi:10.1007/s12471-014-0624-y) contains supplementary material, which is available to authorized users.     

Destruction and injury of Escherichia coli during microwave heating under vacuum

AIMS: To study the effect of 2450 MHz microwave radiation under vacuum (vacuum microwave or VM) on survival and injury of Escherichia coli and to search for possible nonthermal effects associated with VM. METHODS AND RESULTS: Destruction kinetics of E. coli in peptone water were determined in a continuous-flow vacuum system, heated by convection heating in a water bath or with microwaves (VMs). Vacuum was used to control the boiling point of water and to maintain temperature in the bacterial suspensions at specified levels (49-64 degrees C). CONCLUSIONS: z-Value in the water bath treatment was 9.1 degrees C while for VM at 510 and 711 W it was 6.2 and 5.9 degrees C, suggesting that E. coli is more sensitive to temperature changes under microwave heating. Arrhenius calculations of the activation energies of the destruction reactions suggest that the mechanism of destruction in VM may be different from that of conventional heat. The number of injured micro-organisms showed no significant differences among treatments. SIGNIFICANCE AND IMPACT OF THE STUDY: The impact of temperature on E. coli destruction was different when microwaves were the medium of heat transfer, suggesting the existence of factors other than heat contributing to the lethal effect of VM.