Zhong-Shan Deng

Minimally invasive probe system capable of performing both cryosurgery and hyperthermia treatment on target tumor in deep tissues

Cryosurgery is a clinical therapy aiming at the destruction of diseased target tissues through a controlled deep freezing and subsequent rewarming. It has recently been realized that freezing immediately followed by a rapid and strong heating of the target tissues would significantly improve the treatment effect. However, most of the currently available cryoprobe systems are only capable of performing a single freezing function. To accommodate to the rapid growth of the combined freezing and heating therapy of tumor treatment, we have developed a new cryoprobe system with a powerful heating feature, which can be conveniently applied to destroy the tumor in deep tissue using a minimally invasive approach. Its operation performance will be characterized through a series of experimental tests in air, water, phantom gel, in vitro tissues and rabbits under anaesthesia. This system is perhaps the first one aiming at performing both cryosurgery and hyperthermia on target tumors. Therefore, it provides the clinicians with more choices and algorithms on treating a specific diseased tissue. Further, strain sensors and thermocouples were applied to simultaneously record the transient temperature and the thermal stress fields over the tissues subjected to freezing and strong heating. It was observed that a sudden change in the transient thermal stress was often induced when phase change occurs, which may imply that an evident thermal stress occurs at the liquid‐solid interface. This modifies the commonly accepted viewpoint that no stress should exist at the liquid‐like phase change interface. Further, implementations of this new system in clinical cryosurgery or hyperthermia are discussed. In addition to the applications in tumor treatment, the present system can also be very useful in fundamental research such as revealing the thermal stress mechanisms in tissues due to quick freezing and heating, which is hard to do otherwise. One interesting result presented in this paper is the experimental discovery of shock rings induced in the biomaterials around the probe, due to alternant freezing and heating by the present system.

Minimally invasive thermotherapy method for tumor treatment based on an exothermic chemical reaction

In tumor thermotherapy treatment, it is very difficult to achieve the objective of exactly killing the tumor while minimizing the injury of healthy tissues or organs surrounding the tumor. In this study, we describe a new minimally invasive thermotherapy protocol for tumor treatment using heat released from an exothermic chemical reaction, which can safely deliver a totally localized and uniform heating to exactly kill the tumor. Both in vitro and in vivo experiments were performed to test the feasibility of this thermotherapy method based on an exothermic chemical reaction. After injection of only a small amount of matched reactants into the target tissue by medical syringes, an exothermic reaction takes place, and then releases tremendous heat to elevate the temperature to its thermally lethal value. Compared with most of the currently existing thermotherapy strategies, this heating is highly localized, completely safe and uniform, which will remarkably reduce the thermal damage and mechanical trauma to the surrounding healthy tissues. This study opens the clinical possibilities for tumors to be treated in a minimally invasive way by a thermotherapy treatment based on an exothermic chemical reaction.

Thermally induced porous structures in printed gallium coating to make transparent conductive film

A directly printable gallium-based film with both optically transmissive and electrically conductive properties was proposed and demonstrated. The structures, electrical, and optical behaviors of the film printed on the substrate were experimentally investigated. It was disclosed that the porous structure induced inside the printed gallium film by thermal treatment is the main reason for the significant improvement of optical transmittance. A visible transmittance of 47% with a sheet resistance of 16.17 Ω/sq was obtained when the thermal treatment temperature and time are maintained at 400 °C and 40 min, respectively.

New Cryoprobe System With Powerful Heating Features and Its Performance Tests on Biomaterials

Cryosurgery is a clinical therapy aiming at destroying the target of diseased tissues through a controlled deep freezing and subsequent rewarming [1,2]. Applications of this treatment are quite wide in skin cancers, glaucoma, lung tumor etc. [3]-[10]. In contrast to the freezing therapy, heating of tumors has also long been proved to be an effective way of selectively killing the cells of cancerous tissues [11]-[13]. Clinical tests showed that heating the tumor to above a critical minimum temperature such as 42–43 °C for an extended period could effectively destroy the target. It was recently realized that freezing immediately followed by a rapid and strong heating of the target tissues would significantly improve the treatment effect [14]-[16]. Therefore, an apparatus thus developed will be of great importance in cancer clinics. But until now, most of the currently available cryoprobe systems are only capable of performing a single freezing function, in which the treated tissue is often let to naturally re-warm by simply switching off the apparatus. The first one and only commercially available cryoprobe system aiming at both freezing and heating therapy is perhaps Endocare Corporation’s Ar-He Cryoprobe system [14]. However, the highest tissue temperature for this system to achieve is about 0–20 °C [17], which is not high enough to thermally destroy the target tissues. Presently, there is a strong lack of freezing applicators with powerful heating functions for hyperthermia purposes. Without strong enough heating, tumors may still have a chance to regenerate. This is perhaps one of the critical reasons to impede the widespread of cryosurgery in destroying pathological tissues.Copyright

NANO-CRYOSURGERY: A BASIC WAY TO ENHANCE FREEZING TREATMENT OF TUMOR

Cryosurgery is a minimally invasive clinical technique with controlled destruction of target tissues through a specifically administrated freezing procedure. This method has now been used in a wide variety of clinical situations such as treatment of skin cancers, glaucoma, lung and prostate tumor etc. However, there still exist many bottle necks to impede the success of a cryosurgery. A most critical factor has been that insufficient or inappropriate freezing will not completely destroy the target tumor tissues, which as a result may lead to tumor regenesis and thus failure of treatment. Meanwhile, the surrounding healthy tissues may suffer from serious freeze injury due to unavoidable release of a large amount of cold from the freezing probe. To resolve this difficulty, we proposed an innovative strategy, termed as nano-cryosurgery, to significantly improve freezing efficiency of a conventional cryosurgical procedure. The basic principle of this protocol is to inject functional solution with nano particles into the target tissues, which then serves as either to maximize the freezing heat transfer process, regulate freezing scale, modify ice-ball formation orientation or prevent the surrounding healthy tissues from being frozen. Meanwhile, introduction of nanoparticles during cryosurgery could also help better image the edge of a tumor as well as the margin of the iceball. Along this direction, several progresses have been made on mechanism interpretation, theoretical modeling, numerical prediction, conceptual experimental demonstration and treatment planning etc. in the authors’ lab. This study is dedicated to present a preliminary outline on the nano-cryosurgery by summing up the aspects as mentioned above. The evident merits and shortcomings of the nano cryosurgery will be illustrated. Some potential feasibility, versatile applications and possible challenges when nanotechnology meets cryosurgery will be pointed out. It is expected that the concepts of nano-cryosurgery may suggest new opportunities for realizing a highly safe, targeted and accurate freezing therapy in future tumor clinics.Copyright

Liquid metal bath as conformable soft electrodes for target tissue ablation in radio-frequency ablation therapy

Abstract Background: Radio-frequency ablation has been an important physical method for tumor hyperthermia therapy. The conventional rigid electrode boards are often uncomfortable and inconvenient for performing surgery on irregular tumors, especially for those tumors near the joints, such as ankles, knee-joints or other facets like finger joints. Material and methods: We proposed and demonstrated a highly conformable tumor ablation strategy through introducing liquid metal bath as conformable soft electrodes. Different heights of liquid metal bath electrodes were adopted to perform radio-frequency ablation on targeted tissues. Temperature and ablation area were measured to compare the ablation effect with plate metal electrodes. Results: The recorded temperature around the ablation electrode was almost twice as high as that with the plate electrode and the effective ablated area was 2–3 fold larger in all the mimicking situations of bone tumors, span-shaped or round-shaped tumors. Another unique feature of the liquid metal electrode therapy is that the incidence of heat injury was reduced, which is a severe accident that can occur during the treatment of irregular tumors with plate metal boards. Conclusions: The present method suggests a new way of using soft liquid metal bath electrodes for targeted minimally invasive tumor ablation in future clinical practice.

Feasibility study on using an infrared thermometer for evaluation and administration of cryosurgery

Successful performance of cryosurgery relies heavily on a quick, efficient, safe and economic imaging way to monitor the surgical advancement and then to evaluate the curative effect. However, there is currently a lack of such an imaging modality. As for the commonly adopted imaging devices such as X‐CT, MRI and PET, in addition their high cost and complexity in operation, they often induce additional scathe to the patients due to their potential radiation effects. Besides, in cryosurgery, the most important parameter – temperature – can not be directly detected by these methods. Considering the above factors, infrared thermography (IRT), a rather useful yet often neglected functional imaging technique in clinics, is proposed in this paper as an efficient tool for the quick evaluation and administration of a cryosurgical treatment of tumors. Based on skin surface temperature mapping, the degree of damage to the target tissue site caused by different freezing/heating protocols, as well as the states of blood circulation and metabolic heat generation within the treated region can possibly be identified. Further, through recording the temperature variation feature at the skin surface before and after cryosurgery, IRT would help to quickly evaluate the curative effect, which is very beneficial for later treatment planning. By detecting the surface infrared image and analyzing its digital values, the patients invisible focus and abnormal physiological states, e.g. inflammations or pneumothorax, often accompanied by cryosurgical output yet difficult to determine via conventional imaging, could also possibly be diagnosed. To test the above concepts, both typical animal and clinical experiments were performed to demonstrate the feasibility and advantages of IRT‐guided cryosurgery. This study may help push forward a novel, low‐cost and non‐contact way for an efficient performance of cryosurgery.

Art and Science Towards Noiseless Driving of Liquid Metal for Advanced Thermal Management of High Heat Flux Device

The room temperature liquid metal cooling is quickly emerging as a powerful way for the thermal management in many advanced high heat flux devices, spanning from electronics, optoelectronics, battery, to power system etc. Except for its pretty high conductivity that a metal coolant could offer, the unique merit lying behind this new generation cooling strategy is its drivability of the highly conductive coolant through the electromagnetic effect where no moving elements are involved and thus only very few energy consumption is needed. In addition, even waste heat could be strong enough to generate applicable electricity for such flow driving purpose. More directly, the temperature gradient intrinsically generated between the heat source and the sink has also been managed to drive the flow of the coolant and realize an automatic practical enough cooling in some situations. All these practices lead to a totally noiseless pumping of the heat delivery and a compact and reliable cooling modular can thus be possible. Starting from this basic point, we are dedicated here to present an overview on the art and science in developing the technical strategies for a smart driving of the liquid metal cooling of the target devices. Designing philosophy for an innovated thermal management will be discussed. Particularly, electromagnetic pumping, waste thermoelectricity driving, thermosyphon flow effect, etc. will be comparatively evaluated with each of the working performances interpreted. Power consumption rate and efficiency will be quantitatively digested. Typical application examples in the cooling of a series of device areas will be illustrated. Further improvement on the cooling solution along this category will be suggested. Challenging issues in pushing the new technology into large scale utilization will be raised. It is expected that such silent self-driving of the liquid metal coolant will find unique and important values in a wide variety of thermal management areas where reliability, compactness, low noise and energy saving are urgently requested.© 2015 ASME

Hybrid Mini/Micro-Channel Heat Sink Using Liquid Metal and Water as Coolants

The recent years have witnessed the tremendous development in electronics with high power density, such as highly integrated chips and high power LEDs. As a result, the continuous increase in power consumption of electronics is gradually leading to an urgent need for high performance cooling strategies. Among the existed cooling methods, liquid cooling has been proved to be a kind of effective cooling technology for the removal of a large amount of heat from high power devices. Traditional liquid cooling technique commonly refers to utilizing water as the coolant, which is low cost and owns a relatively higher specific heat capacity, however, lower convective coefficient. On the contrary, liquid metal owns much higher convective coefficient, however, lower specific heat capacity. In addition, the higher cost of liquid metal also limits its utilization with large quantity in electronic cooling areas. In this study, a hybrid mini/micro-channel heat sink, based on both of liquid metal and water, was demonstrated. The new system combines the advantages of the two coolants. Experimental studies were conducted to evaluate the capability of the cooling performances of the hybrid system under different operation conditions, including different flow rates, flow directions, pump failure and thermal shock. The experimental results indicate that the hybrid mini/micro channel heat sink owns better cooling performance than water-based heat sink.Copyright

Ultrasound Preprocessing to Improve Nanoparticles’ Performance in Enhancing Cryosurgery

Nanoparticles mediated cryosurgery was recently established as an efficient way to significantly improve the output of a conventional freezing therapy. To further improve this newly emerging nanomedicine way for ablating target tumor, here the ultrasound preprocessing was proposed for the first time to enhance the freezing strength to a better level on the tissues. In vitro experiments were carried out to evaluate the effects of a single ultrasound preprocessing, a single nanoparticle loading or their combination in enhancing the cryosurgery. Meanwhile, the mechanisms of the ultrasound preprocessing to improve nanoparticles’ mediated freezing capability were also theoretically interpreted. Experimental measurements demonstrate that, the ultrasound preprocessing on the target tissue site injected with nanoparticles not only evidently expended the freezing area, but also helps realize a much lower temperature scale and offers higher freezing rate during the nanocryosurgical process. Two main reasons to contribute to such effects were identified as the enhanced convective heat transfer in micro scale and the varied cellular impermeability caused by the ultrasound. The combined effect of ultrasound preprocessing and nanoparticles would be greater than the sum of their individual effects in mediating the nanocryosurgery. As a convinced approach, the present method opens a new way for the improved freezing ablation on tumor which can possibly be used in future clinics.Copyright