An analytical study on the thermal effects of cryosurgery on selective cell destruction

Nanoparticles in Cancer Diagnosis and Treatment

The use of tailored medication delivery in cancer treatment has the potential to increase efficacy while decreasing unfavourable side effects. For researchers looking to improve clinical outcomes, chemotherapy for cancer continues to be the most challenging topic. Cancer is one of the worst illnesses despite the limits of current cancer therapies. New anticancer medications are therefore required to treat cancer. Nanotechnology has revolutionized medical research with new and improved materials for biomedical applications, with a particular focus on therapy and diagnostics. In cancer research, the application of metal nanoparticles as substitute chemotherapy drugs is growing. Metals exhibit inherent or surface-induced anticancer properties, making metallic nanoparticles extremely useful. The development of metal nanoparticles is proceeding rapidly and in many directions, offering alternative therapeutic strategies and improving outcomes for many cancer treatments. This review aimed to present the most commonly used nanoparticles for cancer applications.

Nanoparticles for Cancer Therapy: Current Progress and Challenges

Cancer is one of the leading causes of death and morbidity with a complex pathophysiology. Traditional cancer therapies include chemotherapy, radiation therapy, targeted therapy, and immunotherapy. However, limitations such as lack of specificity, cytotoxicity, and multi-drug resistance pose a substantial challenge for favorable cancer treatment. The advent of nanotechnology has revolutionized the arena of cancer diagnosis and treatment. Nanoparticles (1-100 nm) can be used to treat cancer due to their specific advantages such as biocompatibility, reduced toxicity, more excellent stability, enhanced permeability and retention effect, and precise targeting. Nanoparticles are classified into several main categories. The nanoparticle drug delivery system is particular and utilizes tumor and tumor environment characteristics. Nanoparticles not only solve the limitations of conventional cancer treatment but also overcome multidrug resistance. Additionally, as new multidrug resistance mechanisms are unraveled and studied, nanoparticles are being investigated more vigorously. Various therapeutic implications of nanoformulations have created brand new perspectives for cancer treatment. However, most of the research is limited to in vivo and in vitro studies, and the number of approved nanodrugs has not much amplified over the years. This review discusses numerous types of nanoparticles, targeting mechanisms, and approved nanotherapeutics for oncological implications in cancer treatment. Further, we also summarize the current perspective, advantages, and challenges in clinical translation.

Hysteroscopic Access and Uterine Cavity Evaluation 12 Months Post-Endometrial Ablation with the Cerene® Cryotherapy Device

STUDY OBJECTIVE

To evaluate if physical access and the ability to systematically assess the post-ablation uterine cavity were preserved at 12 months after endometrial ablation with the Cerene® Cryotherapy Device (Channel Medsystems®, Emeryville, CA).

DESIGN

A prospective, multi-center, single-arm study.

SETTING

In the clinic at 8 US sites and outpatient hospital setting at 2 sites in Canada and 1 site in Mexico.

PATIENTS OR PARTICIPANTS

230 of 242 subjects post-ablation continued in the study at the Month 12 visit. 223 subjects were available for a diagnostic hysteroscopic evaluation.

INTERVENTIONS

Subjects who had previously been treated with a 2.5-minute cryoablation of the endometrium utilizing the Cerene® Device underwent a diagnostic hysteroscopy at the Month 12 follow-up visit.

MEASUREMENTS AND MAIN RESULTS

The uterine cavity was accessible in 220 of 223 subjects (98.7%) and not accessible in 3 (1.3%), due to pain (n=2) and cervical stenosis (n=1). Visualization of the uterine cavity was possible in 204 of 220 subjects (92.7%) with one or both tubal ostia identified in 89.2% (182/204) of subjects. Both tubal ostia were visible in 160 of 204 subjects (78.4%) and one ostium in 22 of 204 subjects (10.8%). The cavity was not visualized in the remaining 16 of 220 subjects (7.2%) due to intrauterine adhesions (n=14), technical difficulties (n=1), or menstruation (n=1). In 95.6% (195/204) of subjects where the cavity was visualized, the hysteroscopic view was judged adequate to evaluate the uterine cavity for pathologic change. No significant complications occurred during the hysteroscopic evaluations.

CONCLUSION

This is the largest study to date conducted to hysteroscopically evaluate the post-ablation uterine cavity. Uterine cavity assessment with in-office hysteroscopy one year after the use of the Cerene® Cryotherapy Device is attainable, enabling both diagnostic and therapeutic procedures within the endometrial cavity.

Nanoparticles: A New Approach to Upgrade Cancer Diagnosis and Treatment

Traditional cancer therapeutics have been criticized due to various adverse effects and insufficient damage to targeted tumors. The breakthrough of nanoparticles provides a novel approach for upgrading traditional treatments and diagnosis. Actually, nanoparticles can not only solve the shortcomings of traditional cancer diagnosis and treatment, but also create brand-new perspectives and cutting-edge devices for tumor diagnosis and treatment. However, most of the research about nanoparticles stays in vivo and in vitro stage, and only few clinical researches about nanoparticles have been reported. In this review, we first summarize the current applications of nanoparticles in cancer diagnosis and treatment. After that, we propose the challenges that hinder the clinical applications of NPs and provide feasible solutions in combination with the updated literature in the last two years. At the end, we will provide our opinions on the future developments of NPs in tumor diagnosis and treatment.

Optimizing the spray parameters of a cryospray process

Smaller spray zone of single-hole nozzle (SHN) constrains cryospray as a treatment method suitable for lesions having diameter larger than 15 mm on the skin surface. The present study is an attempt to resolve this issue, through the improvement in conventional technique of spraying liquid nitrogen on cancerous lesion. A multi-hole nozzle (MHN) with 5 holes is fabricated to demarcate the variation in outcome when cryogen is sprayed through customised MHN instead of conventional SHN. Special emphasis is placed on reducing the number of sitting required for completion of treatment and increasing the feasibility of cryospray process for larger lesions. Commercial SHN having a hole diameter of 0.8 mm is selected to compare results with the customised MHN having 5 holes of 0.8 mm diameter (4 holes are arranged in a circle of radius 2 mm around the central hole). Single freeze-thaw cycle is carried out to spray liquid nitrogen on tissue mimicking gel. Temperature profile accessed through infrared images advocates that lethal area formed through application of MHN is twice larger than the lethal area formed through the application of SHN on the surface of gel for same spraying distance (z). Thermocouples placed at various locations strengthen the fact that higher cooling rate (CR) corresponding to MHN ensures 15 mm spread of necrotic zone from the centre of spray (CS) and up to a depth of 2 mm from the gel surface while in case of SHN, it is limited to the vicinity of CS. On the basis of observations made through thermal images and digital images, it can be said that the ratio of lateral spread to penetration depth of ice ball remains almost same for SHN and MHN. However, the lateral spread of ice ball formed through the application of MHN is twice larger than SHN while the axial depth of ice ball does not record such increment. This reflects that MHN provides more destruction to superficial skin than SHN. Among the three spraying distances selected (i.e. z = 13 mm, 18 mm and 23 mm), the most optimised spraying distance (z) for MHN is also explored in this study. It has been found that cryoablation is not inversely proportional to the spraying distance. Spraying distance of z = 18 mm provided the most optimised result in terms of cryoablation.

A Prospective, Multicenter, Clinical Trial Evaluating the Safety and Effectiveness of the Cerene Device to Treat Heavy Menstrual Bleeding

STUDY OBJECTIVE

To evaluate the safety and effectiveness of a novel cryoablation device (Cerene Cryotherapy Device, Channel Medsystems, Emeryville, CA) in premenopausal women with heavy menstrual bleeding owing to benign causes.

DESIGN

A prospective, multi-center, single-arm, open label, non-randomized study.

SETTING

At 11 academic and private practices in North America: 8 clinic sites in the United States, and 3 outpatient hospital sites (1 in Mexico and 2 in Canada).

PATIENTS

A total of 242 subjects comprise the intent-to-treat population. Subject demographics were similar to other published endometrial ablation studies performed.

INTERVENTIONS

Subjects were treated with a single-use disposable cryoablation device (Cerene) which delivers a 2.5-minute treatment to the endometrium. Analgesia and local anesthesia were administered per investigator discretion; intravenous sedation was used in only 3% of subjects and no general anesthesia was used.

MEASUREMENTS AND MAIN RESULTS

There were no device or procedure-related serious adverse events, nor unanticipated adverse device effects. Cerene cryoablation was effective in reducing menstrual blood loss, which was measured by pictorial blood loss assessment chart (PBLAC) score. Mean score dropped from 360.6 at pretreatment (±332.1) to 51 at 12 months posttreatment (±64.1), with 81% of 230 evaluable subjects reporting a PBLAC score of ≤75 and 85% of evaluable subjects reporting a PBLAC score of ≤ 100. The median pain rating was ≤2 (mild) throughout the treatment. Of 223 subjects that underwent hysteroscopic evaluation at 12 months, the uterine cavity was visualized in 220 subjects. Quality of life improved with 90% of reporting subjects indicating satisfied or very satisfied at month 12.

CONCLUSION

This study demonstrated that Cerene cryoablation is safe and effective, offering the benefits of reduced menstrual blood loss with limited use of pain medication, high patient tolerability, quality of life improvement, and preserved access to the uterine cavity.

Role of Nanofluids in Drug Delivery and Biomedical Technology: Methods and Applications

Recently, suspensions of several nanoparticles or nanocomposites have attained a vast field of application in biomedical research works in some specified conditions and clinical trials. These valuable suspensions, which allow the nanoparticles to disperse and act in homogenous and stable media, are named as nanofluids. Several studies have introduced the advantages of nanofluids in biomedical approaches in different fields. Few review articles have been reported for presenting an overview of the wide biomedical applications of nanofluids, such as diagnosis and therapy. The review is focused on nanosuspensions, as the nanofluids with solid particles. Major applications are focused on nanosuspension, which is the main type of nanofluids. So, concise content about major biomedical applications of nanofluids in drug delivery systems, imaging, and antibacterial activities is presented in this paper. For example, applying magnetic nanofluid systems is an important route for targeted drug delivery, hyperthermia, and differential diagnosis. Also, nanofluids could be used as a potential antibacterial agent to overcome antibiotic resistance. This study could be useful for presenting the novel and applicable methods for success in current medical practice.

A study of heat transfer during cryosurgery of lung cancer

In this study, a mathematical model describing two-dimensional bio-heat transfer during cryosurgery of lung cancer is developed. The lung tissue is cooled by a cryoprobe by imposing its surface at a constant temperature or a constant heat flux or a constant heat transfer coefficient. The freezing starts and the domain is distributed into three stages namely: unfrozen, mushy and frozen regions. In stage I where the only unfrozen region is formed, our problem is an initial-boundary value problem of the hyperbolic partial differential equation. In stage II where mushy and unfrozen regions are formed, our problem is a moving boundary value problem of parabolic partial differential equations and in stage III where frozen, mushy, and unfrozen regions are formed, our problem is a moving boundary value problem of parabolic partial differential equations. The solution consists of the three-step procedure: (i) transformation of problem in non-dimensional form, (ii) by using finite differences, the problem converted into ordinary matrix differential equation and moving boundary problem of ordinary matrix differential equations, (iii) applying Legendre wavelet Galerkin method the problem is transferred into the generalized system of Sylvester equations which are solved by applying Bartels-Stewart algorithm of generalized inverse. The complete analysis is presented in the non-dimensional form. The consequence of the imposition of boundary conditions on moving layer thickness and temperature distribution are studied in detail. The consequence of Stefan number, Kirchoff number and Biot number on moving layer thickness are also studied in specific.

Generalized solution and estimation method for cooling performance of downscaled cryoprobe

In cryosurgery, downscaling of cryoprobes is important to minimize surgical invasion. In this study, a set of analytical solutions to the freezing phenomenon around a cryoprobe in a dimensionless form is derived and the general trend is discussed to clarify the relationship between the freezing ability of a biological tissue and the cooling power of a cryoprobe. A one-dimensional axisymmetric model in the steady-state condition is considered. The relationship between the size of the frozen region, fluid temperature in the cryoprobe, and heat transfer coefficient on the wall of the cryoprobe in the dimensional form is derived under the condition mentioned above. The fluid temperature and heat transfer coefficient are eliminated from the solutions by introducing the steady-state cryoprobe surface temperature. This transformation indicates that the steady-state surface temperature directly affects the size of the frozen region and combination of fluid temperature and heat transfer coefficient occurs, which has the same cooling effect. The derived solutions are transformed into a dimensionless form using the characteristic length of bioheat transfer and normalizing the temperature distribution in an unfrozen tissue. The applicability of these analytical solutions is evaluated by comparing them with numerical simulation results from existing studies. The dimensionless solutions describe the general trend of the relationship between the frozen region and the cooling power of a cryoprobe, which is independent of the type of organ, fluid temperature, and heat transfer coefficient. Finally, the concept of freezing limit is established using the derived solutions. The freezing limit describes the minimum requirements to freeze a tissue, and it can be used as guideline to design future downscaled cryoprobes with a suitable cooling mechanism.

Numerical Simulation of the Heat Transfer in the Cryoprobe of an Innovative Apparatus for Cryosurgery

Cryosurgery is a rapidly developing discipline, alternative to conventional surgical techniques, used to destroy cancer cells by the action of low temperatures. Currently, the refrigeration is obtained via the adiabatic expansion of gases in probes used for surgeries, with the need of inherently dangerous pressurized vessels. The proposed innovative prototypal apparatus aims to reach the cryosurgical temperatures exploiting a closed-loop refrigeration system, avoiding the hazardous presence of pressurized vessels in the operating room. This study preliminarily examines the technical feasibility of the cryoablation with this machine focusing the attention on the cryoprobe design. Cryoprobe geometry and materials are assessed and the related heat transfer taking place during the cryoablation process is simulated with the aid of the computational fluid dynamics software ANSYS®Fluent. Parametric analyses are carried out varying the length of the collecting tubes and the inlet velocity of the cold carrier fluid in the cryoprobe. The values obtained for physical quantities such as the temperature reached in the treated tissue, the width of the obtained cold front, and the maximum pressure required for the cold carrier fluid are calculated and discussed in order to prove the effectiveness of the experimental apparatus and develop the machine further.

A study of cryosurgery of lung cancer using Modified Legendre wavelet Galerkin method

In this paper, we have developed a new mathematical model describing bio-heat transfer during cryosurgery of lung cancer. The lung tissue cooled by a flat probe whose temperature decreases linearly with time. The freezing process occurs in three stages and the whole region is divided into solid, mushy and liquid region. The heat released in the mushy region is considered as discontinuous heat generation. The model is an initial-boundary value problem of the hyperbolic partial differential equation in stage 1 and moving boundary value problem of parabolic partial differential equations in stage 2 and 3. The method of the solution consists of four-step procedure as transformation of problem in dimensionless form, the problem of hyperbolic partial differential equation converted into ordinary matrix differential equation and the moving boundary problem of parabolic partial differential equations converted into moving boundary problem of ordinary matrix differential equations by using finite differences in space, transferring the problem into the generalized system of Sylvester equations by using Legendre wavelet Galerkin method and the solution of the generalized system of Sylvester equation are solved by using Bartels-Stewart algorithm of generalized inverse. The whole analysis is presented in dimensionless form. The effect of cryoprobe rate on temperature distribution and the effect of Stefan number on moving layer thickness is discussed in detail.

Simulation and evaluation of freeze-thaw cryoablation scenarios for the treatment of cardiac arrhythmias

Background

Cardiac cryoablation is a minimally invasive procedure to treat cardiac arrhythmias by cooling cardiac tissues responsible for the cardiac arrhythmia to freezing temperatures. Although cardiac cryoablation offers a gentler treatment than radiofrequency ablation, longer interventions and higher recurrence rates reduce the clinical acceptance of this technique. Computer models of ablation scenarios allow for a closer examination of temperature distributions in the myocardium and evaluation of specific effects of applied freeze-thaw protocols in a controlled environment.

Methods

In this work multiple intervention scenarios with two freeze-thaw cycles were simulated with varying durations and starting times of the interim thawing phase using a finite element model verified by in-vivo measurements and data from literature. To evaluate the effects of different protocols, transmural temperature distributions and iceball dimensions were compared over time. Cryoadhesion durations of the applicator were estimated in the interim thawing phase with varying thawing phase starting times. In addition, the increase of cooling rates was compared between the freezing phases, and the thawing rates of interim thawing phases were analyzed over transmural depth.

Results

It could be shown that the increase of cooling rate, the regions undergoing additional phase changes and depths of selected temperatures depend on the chosen ablation protocol. Only small differences of the estimated cryoadhesion duration were found for ablation scenarios with interim thawing phase start after 90 s freezing.

Conclusions

By the presented model a quantification of effects responsible for cell death is possible, allowing for the analysis and optimization of cryoablation scenarios which contribute to a higher clinical acceptance of cardiac cryoablation.

Development of a closed-loop J-T cryoablation device with a long cooling area and multiple expansion parts

Cryoablation is a surgical procedure used to freeze defective cells by inserting a low temperature probe into a human body to destroy malignant tissues. Miniaturized Joule-Thomson (J-T) refrigerators are often used to minimize the volume of the cooling device and reduce the destruction zone of normal tissue. The cooling effects of the existing probes are not uniformly generated along the longitudinal direction of the probe, which makes their applications less effective in surgeries of incompetent great saphenous veins (GSVs), where the target cells are distributed over a broad range. Long uniform refrigeration is required across the entire area of the probe to apply the same cooling effects. In this paper, a closed-loop J-T cryoablation probe was designed and fabricated to provide uniform refrigeration over a large area, with multiple expansion parts. Using flow boiling heat transfer, uniform cooling of a 200 mm-long and 0.3 mm thickness piece of target tissue was possible and simulated in a gelatin solution. The developed probe produced a greater than 53 K min(-1) cooling rate and the cooling temperature was below 253 K to satisfy the required cell death conditions.

Studying the performance of bifurcate cryoprobes based on shape factor of cryoablative zones

Conventional cryosurgical process employs extremely low temperatures to kill tumor cells within a closely defined region. However, its efficacy can be markedly compromised if the same treatment method is administrated for highly irregularly shaped tumors. Inadequate controls of freezing may induce tumor recurrence or undesirable over-freezing of surrounding healthy tissue. To address the cryosurgical complexity of irregularly shaped tumors, an analytical treatment on irregularly-shaped tumors has been performed and the degree of tumor irregularities is quantified. A novel cryoprobe coined the bifurcate cryoprobe with the capability to generate irregularly shaped cryo-lesions is proposed. The bifurcate cryoprobe, incorporating shape memory alloy functionality, enables the cryoprobe to regulate its physical configuration. To evaluate the probe's performance, a bioheat transfer model has been developed and validated with in vitro data. We compared the ablative cryo-lesions induced by different bifurcate cryoprobes with those produced by conventional cryoprobes. Key results have indicated that the proposed bifurcate cryoprobes were able to significantly promote targeted tissue destruction while catering to the shape profiles of solid tumors. This study forms an on-going framework to provide clinicians with alternative versatile devices for the treatment of complex tumors.

Anatomical model-based finite element analysis of the combined cryosurgical and hyperthermic ablation for knee bone tumor

This paper is aimed at investigating the capacity of using combined cryosurgical and hyperthermic modality for treating knee bone tumor with complex shape. An anatomical model for human knee was constructed and a three-dimensional (3D) finite element analysis was developed to determine temperature distribution of the tissues subject to single freezing (SF), single heating (SH) and alternate freezing-heating (AFH), respectively. The heat fluxes of the probes wall and the ablation volume are particularly tracked to comparatively evaluate the ablation ability of different probe configurations with varied diameter, number and active working length. As example, an effective conformal treatment strategy via one time's insertion while cyclic freezing-heating using multiple probes is designed for a predefined knee bone tumor ablation. Both SF and SH could create large enough ablation volume, while it is hard for them to perform a conformal treatment on irregular and slender knee tumor. As an alternative, AFH could form a flexible and controlled shape and volume of the ablation by changing the size and number of the probes and adjusting their insertion depth. In addition, a thermal protection method is considered to reduce cryoinjury of the health tissue.

A study on the effect of metabolic heat generation on biological tissue freezing

The effect of metabolic heat generation on the freezing of biological tissue has been studied. Quasi-steady approximation is used to solve the Pennes bioheat equation in tissues. Temperature profile and motion of freezing interfaces are obtained for different values of metabolic heat generation. It is observed that metabolism has a significant effect on freezing of biological tissues during cryosurgery.

3D simulation of platelet aggregation in cryosurgery

In cryosurgery for cancer treatment, cells are injured not only by freezing but also by vascular stasis. The vascular stasis caused by thrombosis necrotizes the surrounding non-targeted cells due to the lack of oxygen and nourishment. Inhibition of thrombus formation, which is the former phase of the vascular stasis, is required to prevent damaging normal cells around a tumorDForegoing studies simulated platelet aggregation based on distance between platelets. However, in cryosurgery, temperature dependency of blood-clotting factors' activity is required to be considered. The authors constructed a three-dimensional model consisting of vascular and extra- vascular tissues, and simulated heat transform and platelet aggregation. Heat transform was analyzed by boundary fitted coordinates method, and platelet aggregation was analyzed by particle method. The probability of bonding between platelets is derived from chemical reaction kinetics. The results showed larger size of simulated thrombus on higher temperature. The simulation with varied temperature around destructed area showed platelet aggregation depending on temperature.

Synergistic effects of cryolipolysis and shock waves for noninvasive body contouring

BACKGROUND

Excess body fat, localized adiposity, and cellulite represent important social problems. To date, techniques using radiofrequencies, cavitation and noncavitation ultrasound, and carbon dioxide have been studied as treatments for noninvasive body contouring. Ice-Shock Lipolysis is a new noninvasive procedure for reducing subcutaneous fat volume and fibrous cellulite in areas that normally would be treated by liposuction. It uses a combination of acoustic waves and cryolipolysis. Shock waves, used normally in the treatment of renal calculi and musculoskeletal disorders, are focused on the collagen structure of cellulite-afflicted skin. When used on the skin and underlying fat, they cause a remodeling of the collagen fibers, improving the orange-peel appearance typical of the condition. Cryolipolysis, on the other hand, is a noninvasive method used for the localized destruction of subcutaneous adipocytes, with no effects on lipid or liver marker levels in the bloodstream. The combination of the two procedures causes the programmed death and slow resorption of destroyed adipocytes.

METHODS

In this study, 50 patients with localized fat and cellulite were treated with a selective protocol for the simultaneous use of two transducers: a Freezing Probe for localized fatty tissue and a Shock Probe for fibrous cellulite.

RESULTS

The procedure significantly reduced the circumference in the treated areas, significantly diminishing fat thickness. The mean reduction in fat thickness after treatments was 3.02 cm. Circumference was reduced by a mean of 4.45 cm. Weight was unchanged during the treatment, and no adverse effects were observed. Histologic and immunohistochemical analysis confirmed a gradual reduction of fat tissue by programmed cell death. Moreover, the reduction in fat thickness was accompanied by a significant improvement in microcirculation, and thus, the cellulite. The safety of the method also has been highlighted because it is accompanied by no significant increase in serum liver enzymes or serum lipids.

CONCLUSION

The study aimed to observe the effects of the new technique in the treatment of localized fat associated with cellulite in order to assess adipose tissue alterations, cellular apoptosis, and levels of serum lipid or liver markers. The findings show that the action of Ice-Shock Lipolysis is a safe, effective, and well-tolerated noninvasive procedure for body contouring. In particular, the authors believe that this could be an ideal alternative to liposuction for patients who require only small or moderate amounts of adipose tissue and cellulite removal or are not suitable candidates for surgical approaches to body contouring.

Cortical bone drilling and thermal osteonecrosis

BACKGROUND

Bone drilling is a common step in operative fracture treatment and reconstructive surgery. During drilling elevated bone temperature is generated. Temperatures above 47°C cause thermal osteonecrosis which contributes to screw loosening and subsequently implant failures and refractures.

METHODS

The current literature on bone drilling and thermal osteonecrosis is reviewed. The methodologies involved in the experimental and clinical studies are described and compared.

FINDINGS

Areas which require further investigation are highlighted and the potential use of more precise experimental setup and future technologies are addressed.

INTERPRETATION

Important drill and drilling parameters that could cause increase in bone temperature and hence thermal osteonecrosis are reviewed and discussed: drilling speed, drill feed rate, cooling, drill diameter, drill point angle, drill material and wearing, drilling depth, pre-drilling, drill geometry and bone cortical thickness. Experimental methods of temperature measurement during bone drilling are defined and thermal osteonecrosis is discussed with its pathophysiology, significance in bone surgery and methods for its minimization.

NONLINEAR DYNAMICS OF CELL CYCLES WITH STOCHASTIC MATHEMATICAL MODELS

Cell cycles are fundamental components of all living organisms and their systematic studies extend our knowledge about the interconnection between regulatory, metabolic, and signaling networks, and therefore open new opportunities for our ultimate efficient control of cellular processes for disease treatments, as well as for a wide variety of biomedical and biotechnological applications. In the study of cell cycles, nonlinear phenomena play a paramount role, in particular in those cases where the cellular dynamics is in the focus of attention. Quantification of this dynamics is a challenging task due to a wide range of parameters that require estimations and the presence of many stochastic effects. Based on the originally deterministic model, in this paper we develop a hierarchy of models that allow us to describe the nonlinear dynamics accounting for special events of cell cycles. First, we develop a model that takes into account fluctuations of relative concentrations of proteins during special events of cell cycles. Such fluctuations are induced by varying rates of relative concentrations of proteins and/or by relative concentrations of proteins themselves. As such fluctuations may be responsible for qualitative changes in the cell, we develop a new model that accounts for the effect of cellular dynamics on the cell cycle. Finally, we analyze numerically nonlinear effects in the cell cycle by constructing phase portraits based on the newly developed model and carry out a parametric sensitivity analysis in order to identify parameters for an efficient cell cycle control. The results of computational experiments demonstrate that the metabolic events in gene regulatory networks can qualitatively influence the dynamics of the cell cycle.

Interventional radiological treatment of hepatocellular carcinoma

BACKGROUND

Locoregional treatments of hepatocellular carcinoma (HCC) have evolved over the past 20 years. Interventional radiologists have developed an important role in the palliative and curative treatment of the disease. This review summarizes commonly used interventional radiological treatment protocols to assist practitioners in understanding the techniques used to treat HCC.

METHODS

Various searches were performed to evaluate recent publications regarding systemic treatments of HCC as well as transplant/surgery, chemoembolization, yttrium-90 radioembolization, percutaneous radiofrequency ablation (RFA), cryoablation, and percutaneous ethanol injection (PEI).

RESULTS

No standard for chemoembolization was found. Two studies evaluating survival with chemoembolization vs medical therapy found benefits with the former. PEI offers favorable outcomes in small HCC but has increased recurrence and decreased long-term survival compared with RFA. Local recurrence, response rates, and mortality from RFA rival surgical resection in HCC less than 3 cm. Cryoablation appears to be effective, and yttrium-90 radioembolization is an additional tool.

CONCLUSIONS

Chemoembolization improves survival and offers improved tumor response compared to systemic treatment. More studies are needed to standardize chemoembolization preparations and techniques. RFA provides better results than PEI but has not been compared with cryoablation. Radioembolization appears to be as effective as chemoembolization, but the preprocedure evaluation and costs may limit its use.

Cell accelerated cryoablation simulation

Tumor cryoablation is a clinical procedure where supercooled probes are used to destroy cancerous lesions. Cryoablation is a safe and effective palliative treatment for skeletal metastases, providing immediate and long term pain relief, increasing mobility and improving quality of life. Ideally, lesions are encompassed by an ice ball and frozen to a sufficiently low temperature to ensure cell death. "Lethal ice" is the term used to describe regions within the ice ball where cell death occurs. Failure to achieve lethal ice in all portions of a lesion may explain the high recurrence rate currently observed. Tracking growth of lethal ice is critical to success of percutaneous ablations, however, no practical methods currently exist for non-invasive temperature monitoring. Physicians lack planning tools which provide accurate estimation of the ice formation. Simulation of ice formation, while possible, is computationally demanding and too time consuming to be of clinical utility. We developed the computational framework for the simulation, acceleration strategies for multicore Intel x86 and IBM Cell architectures, and performed preliminary validation of the simulation. Our results demonstrate that the streaming SIMD implementation has better performance and scalability. Both accelerated and non-accelerated algorithms demonstrate good agreement between simulation and manually identified ice ball boundaries in phantom and patient images. Our results show promise for the development of novel cryoablation planning tools with real-time monitoring capability for clinical use.

Cell death along single microfluidic channel after freeze-thaw treatments

Cryotherapy is a prospective green method for malignant tumor treatment. At low temperature, the cell viability relates with the cooling rate, temperature threshold, freezing interface, as well as ice formation. In clinical applications, the growth of ice ball must reach a suitable size as cells could not be all killed at the ice periphery. The cell death ratio at the ice periphery is important for the control of the freezing destruction. The mechanisms of cryoinjury around the ice periphery need thorough understanding. In this paper, a primary freeze-thaw control was carried out in a cell culture microchip. A series of directional freezing processes and cell responses was tested and discussed. The temperature in the microchip was manipulated by a thermoelectric cooler. The necrotic and apoptotic cells under different cryotreatment (duration of the freezing process, freeze-thaw cycle, postculture, etc.) were stained and distinguished by propidium iodide and fluorescein isothiocyanate (FITC)-Annexin V. The location of the ice front was recorded and a cell death boundary which was different from the ice front was observed. By controlling the cooling process in a microfluidic channel, it is possible to recreate a sketch of biological effect during the process of simulated cryosurgery.

Multi-scale heat and mass transfer modelling of cell and tissue cryopreservation

Cells and tissues undergo complex physical processes during cryopreservation. Understanding the underlying physical phenomena is critical to improve current cryopreservation methods and to develop new techniques. Here, we describe multi-scale approaches for modelling cell and tissue cryopreservation including heat transfer at macroscale level, crystallization, cell volume change and mass transport across cell membranes at microscale level. These multi-scale approaches allow us to study cell and tissue cryopreservation.

Experimental study of the safety of pancreas cryosurgery: the comparison of 2 different techniques of cryosurgery

OBJECTIVES

To test the feasibility of cryosurgery for pancreatic carcinoma and to observe the consequence of cryosurgery by 2 different techniques.

METHODS

Twelve healthy pigs underwent laparotomy, during which, chop amputation of common bile duct and duodenum were performed, meanwhile other intra-abdominal organs with the pancreas were isolated. Two different techniques of cryosurgery were performed on the pancreas. Group A (n = 6) accepted the mild hypothermic cryosurgery with liquid nitrogen superficial refrigeration, and group B (n = 6) were performed with the deep hypothermic cryosurgery at -170 degrees C with LCS2000 cryogenic surgical system. All the animals' digestive tract was reconstructed with cholecystojejunostomy and gastroenterostomy, respectively.

RESULTS

Acute necrotizing pancreatitis occurred on all animals in group A, of which 5 of the 6 died within 1 week, whereas only 1 of the 6 reported a 4-week survival. All animals in group B survived during the observation, in which only a transient increment and a gradual correction of pancreatic amylase level were recorded. Small pancreatic pseudocyst occurred in 1 case.

CONCLUSIONS

Mild hypothermic cryosurgery with liquid nitrogen superficial refrigeration might lead to pancreatic injury and induce acute pancreatitis, yet deep hypothermic cryosurgery with adequate time showed a promising effect in destroying pancreatic tissue and preventing acute pancreatitis.

Cryosurgery: early ultrastructural changes in liver tissue in vivo

BACKGROUND

Experimental observations with regard to freezing in vitro cell lines and fluid systems led to the application of low temperatures to in vivo biological systems. For the first time, this report describes the cryosurgical response of liver parenchyma and the early ultrastructural cellular changes in liver tissue, i.e., cryosurgery, in vivo.

MATERIALS AND METHODS

Forty-eight animals were used for the experiment. The dogs were divided into four groups. In group A, the liver tissue was frozen to -80 degrees C and in group B, to -180 degrees C. Temperatures of -80 degrees C and -180 degrees C in contact with liver tissue was selected for cryosurgical exposure. For transmission electron microscopy, the specimens were taken immediately and 1 h after the finishing of the freeze-thaw cycles intraoperatively. Further, the next specimens were taken in 24 h, this time also intraoperatively.

RESULTS

The electronic microscopic analysis showed that, after local cryodestruction at temperatures of -80 degrees C and -180 degrees C, similar processes occurred within the liver tissue in the early postcryosurgical phase-immediately and 1 h after cryosurgical session. The hepatocytes in the center of the cryozone changed upon thawing. Ultrastructural changes in the hepatic cells, where the first signs of dystrophic processes had been noticed, were increased.

CONCLUSIONS

Our new insights prove on the cell level that suddenly and progressively damaged liver cells in the postcryosurgical zone lead to aseptic cryoaponecrosis and then to aseptic cryoapoptosis of vital normal tissue. The vascular capillary changes and circulatory stagnation demonstrate together with cryoaponecrosis and cryoapoptosis the anti-angiogenesis mechanisms, which are some of the main mechanisms of biological tissue injury following the low temperature exposure.