A novel approach to improve the efficacy of tumour ablation during cryosurgery (original) (raw)
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A numerical study on optimising the cryosurgical process for effective tumour necrosis
Heat and Mass Transfer, 2016
the results presented in the study help in optimising the layer thickness at the tumour interface, the identification of an appropriate substance for making the layer and the use of gap to evaluate the most optimal configuration for freezing the tumours effectively. List of symbols c Specific heat (J/kg K) H Specific total enthalpy (J/kg) h Specific sensible enthalpy (J/kg) k Thermal conductivity (W/m K) L Specific latent heat of fusion (J/kg) Q m Metabolic heat generation (W/m 3) T Temperature (°C) t Time (s) m b Blood perfusion rate (kg blood per m 3 of tissue per second) Subscripts b Blood f Frozen tissue l Point at which freezing starts s Point at which freezing ends u Unfrozen tissue * A. Thirugnanam
Validation of a low-cost, carbon dioxide-based cryoablation system for percutaneous tumor ablation
PLOS ONE
Breast cancer rates are rising in low-and middle-income countries (LMICs), yet there is a lack of accessible and cost-effective treatment. As a result, the cancer burden and death rates are highest in LMICs. In an effort to meet this need, our work presents the design and feasibility of a low-cost cryoablation system using widely-available carbon dioxide as the only consumable. This system uses an 8-gauge outer-diameter needle and Joule-Thomson expansion to percutaneously necrose tissue with cryoablation. Bench top experiments characterized temperature dynamics in ultrasound gel demonstrated that isotherms greater than 2 cm were formed. Further, this system was applied to mammary tumors in an in vivo rat model and necrosis was verified by histopathology. Finally, freezing capacity under a large heat load was assessed with an in vivo porcine study, where volumes of necrosis greater than 1.5 cm in diameter confirmed by histopathology were induced in a highly perfused liver after two 7-minute freeze cycles. These results demonstrate the feasibility of a carbon-dioxide based cryoablation system for improving solid tumor treatment options in resource-constrained environments.
2015
The complete necrosis of malignant biological tissue can be achieved, when the optimal parameters (generation of ice ball around the cryoprobe, ablation ratio, cooling power requirement) are known to the cryosurgeon. In this study the optimal parameters(volume of ice ball around the cryoprobe, ablation ratio, cooling power requirements)are predicted and compared to maximize the tissue necrosis. Surgical parameters like lethal zone, frozen zone and ablation ratio are studied for different placements of cryoprobes. The percentage increase in ice ball volume (obtained at the end of freezing cycle, i.e. 10 min considering with and without central cryoprobe configurations) decreases with increase in the number of offset cryoprobe at same opereating conditions. It was observed that with the increase in offset cryoprobes, there was no remarkable growth on ablation ratio at the end of freezing process. However, the less number of offset cryoprobes resulted in effective ablation during the e...
Godunov Method for Multiprobe Cryosurgery Simulation with Complex-Shaped Tumors
The 7th SEAMS-UGM 2015 International Conference on Mathematics and Its Applications
Cryosurgery is a technique to eradicate abnormal biological tissues by freezing. The objective of cryosurgery is to maximize cryoinjury of tumor tissues while at the same time minimizing cryoinjury to the surrounding healthy tissues. The location and number of cryoprobes are important factors to obtain optimal cryosurgery in complex-shaped tumors. This paper presents multiprobe cryosurgery simulation with optimal cryoprobes location in target region. Bubble packing method is used to obtain optimal cryoprobes layout. We consider mathematical model of freezing by bioheat transfer equation in solid (frozen tissue), liquid (unfrozen tissue), and mushy region. This model is referred to as Stefan problem where the location of moving solid-mushy or mushy-liquid interface is not known and it is as part of the solution. We reformulate the bioheat equations into enthalpy (energy) equation which can resolve the moving boundary between two phases. The first-order of Godunov method is adopted to obtain numerical solution of the phase change problem. For demonstration purposes, multiprobe cryosurgery for lung cancer case with complex geometry is simulated and interpreted. The numerical simulation shows that the nine cryoprobes layout has the smallest total defect in this case. The numerical results provide an important information for cryosurgeon before conducting effective cryosurgery protocol.
Cryotherapy – a mature ablation technique
HPB, 2006
This article discusses the use of cryotherapy for the treatment of hepatic tumours, from its early origins to the present day. Results of therapy, preoperative assessment, safety, and the pros and cons of its use are described.
Confinement of Freezing Front by Laser Irradiation During Cryosurgery
Heat Transfer: Volume 1, 2005
A new methodology to control the freezing front propagation during cryosurgical procedures is studied through the use of numerical techniques. Laser irradiation of a target tissue is explored as a new methodology for localizing heat generation and, thus, confining more accurately the desired cryoinjury region and to protect a thicker superficial layer of tissue. In addition to the irradiation of laser energy, the use of dyes is proposed as a means of localizing heat absorption and increasing the thickness of the protected region.
Tumour ablation: technical aspects
Cancer Imaging, 2009
Image-guided percutaneous radiofrequency ablation (RFA) is a minimally invasive, relatively low-risk procedure for tumour treatment. Local recurrence and survival rates depend on the rate of complete ablation of the entire tumour including a sufficient margin of surrounding healthy tissue. Currently a variety of different RFA devices are available. The interventionalist must be able to predict the configuration and extent of the resulting ablation necrosis. Accurate planning and execution of RFA according to the size and geometry of the tumour is essential. In order to minimize complications, individualized treatment strategies may be necessary for tumours close to vital structures. This review examines the state-of-the art of different device technologies, approaches, and treatment strategies for percutaneous RFA of liver tumours.
Cryobiology, 2001
The goal of this study was to estimate the three-dimensional (3D) temperature distribution in liver cryolesions and assess the margin of the transition zone between the tumoricidal core of the lesion and the surrounding unfrozen tissue, using criteria proposed in the literature. Local recurrences after liver tumor cryoablation are frequent. Temperatures below Ϫ40°C and a 1-cm zone of normal tissue included in the cryolesion are considered necessary for adequate ablation. The 3D temperature distribution in 10 pig cryolesions was estimated by numerical solution of a simplified bioheat equation using magnetic resonance imaging data to establish cryolesion border conditions. Volumes encompassed by the Ϫ20, Ϫ40, and Ϫ60°C isotherms were estimated. The shortest distance from every voxel on the Ϫ40°C isotherm to the cryolesion edge was calculated and the mean and the maximal of these distances were defined for each cryolesion. Median cryolesion volumes with temperatures of Ϫ20, Ϫ40, and Ϫ60°C or colder were 53, 26, and 14% of the total cryolesion volume, respectively. The median cryolesion volume was 12.3 cm 3. The median of the mean distances calculated between the Ϫ40°C isotherm and the cryolesion edge was 4.1 mm and increased with increasing cryolesion volume. The median of the largest of these distances calculated for each cryolesion was 8.1 mm. Temperatures claimed to be adequate for tumor destruction were obtained only in parts of the cryolesion. The adequacy of a 1-cm zone of normal liver tissue included in the cryolesion to ensure tumor ablation is questioned.
OMICS: A Journal of Integrative Biology, 2015
Cryosurgery is a widely regarded minimally invasive surgery for treatment of various types of cancers. It involves destruction of cancer cells within a limited spatial domain by exposing them to very low temperatures while minimizing injury to surrounding peripheral healthy tissues. Surprisingly, despite increasing demands for cryosurgery, there has been limited innovation in the design of cryoprobes, particularly in solid tumors (e.g., breast, prostate, and lung cancers). For advances in cancer therapeutics, integrative biology research can illuminate the mechanistic interface between a surgical cryoprobe and its tissue site of action. Here, we describe the design and development of three novel low pressure liquid nitrogen (LN2) cryoprobes with different physical dimensions and the parameters that determine their effectiveness experimentally, using water and biogel as the phase changing mediums. Smaller diameter low pressure probes produced lesser cryogenic injury. Vapor Separator is found to be an effective means (particularly for smaller diameter probes) to remove the vapor lock in the LN2 low pressure cryoprobes and also to reduce the precooling time. The low pressure LN2 cryoprobes produced lower probe temperatures and consequently larger and faster iceball growth for low cooling loads. Additionally, a numerical code was written in MATLAB based on the Enthalpy method to simulate the bio-heat transfer in a cryosurgical process. The numerical code is validated by analytical solution, laboratory experiments, and data from an in vivo cryosurgery. The developed numerical code is presented herein to illustrate that LN2 cryoprobes capable of producing lower probe temperatures produce more efficient cryosurgical operation by reducing the buffer zone and duration of surgery.This is the first report, to the best of our knowledge, on design of the next generation of LN2 surgical cryoprobes. These new surgical cryoprobes offer potentials for future preclinical and clinical testing in solid cancers.