A computational framework to simulate the thermochemical process during thermochemical ablation of biological tissues
- Authors: Mak, Nguoy , Ooi, Ean H. , Lau, Ee , Ooi, Ean Tat , Pamidi, N. , Foo, Ji , Mohd Ali, Ahmad
- Date: 2022
- Type: Text , Journal article
- Relation: Computers in Biology and Medicine Vol. 145, no. (2022), p.
- Full Text: false
- Reviewed:
- Description: Thermochemical ablation (TCA) is a thermal ablation therapy that utilises heat released from acid-base neutralisation reaction to destroy tumours. This procedure is a promising low-cost solution to existing thermal ablation treatments such as radiofrequency ablation (RFA) and microwave ablation (MWA). Studies have demonstrated that TCA can produce thermal damage that is on par with RFA and MWA when employed properly. Nevertheless, TCA remains a concept that is tested only in a few animal trials due to the risks involved as the result of uncontrolled infusion and incomplete acid-base reaction. In this study, a computational framework that simulates the thermochemical process of TCA is developed. The proposed framework consists of three physics, namely chemical flow, neutralisation reaction and heat transfer. An important parameter in the TCA framework is the neutralisation reaction rate constant, which has values in the order of 108 m3/(mol
How does saline backflow affect the treatment of saline-infused radiofrequency ablation?
- Authors: Kho, Antony , Ooi, Ean H. , Foo, Ji , Ooi, Ean Tat
- Date: 2021
- Type: Text , Journal article
- Relation: Computer Methods and Programs in Biomedicine Vol. 211, no. (2021), p.
- Full Text: false
- Reviewed:
- Description: Background and objective: Saline infusion is applied together with radiofrequency ablation (RFA) to enlarge the ablation zone. However, one of the issues with saline-infused RFA is backflow, which spreads saline along the insertion track. This raises the concern of not only thermally ablating the tissue within the backflow region, but also the loss of saline from the targeted tissue, which may affect the treatment efficacy. Methods: In the present study, 2D axisymmetric models were developed to investigate how saline backflow influence saline-infused RFA and whether the aforementioned concerns are warranted. Saline-infused RFA was described using the dual porosity-Joule heating model. The hydrodynamics of backflow was described using Poiseuille law by assuming the flow to be similar to that in a thin annulus. Backflow lengths of 3, 4.5, 6 and 9 cm were considered. Results: Results showed that there is no concern of thermally ablating the tissue in the backflow region. This is due to the Joule heating being inversely proportional to distance from the electrode to the fourth power. Results also indicated that larger backflow lengths led to larger growth of thermal damage along the backflow region and greater decrease in coagulation volume. Hence, backflow needs to be controlled to ensure an effective treatment of saline-infused RFA. Conclusions: There is no risk of ablating tissues around the needle insertion track due to backflow. Instead, the risk of underablation as a result of the loss of saline due to backflow was found to be of greater concern. © 2021 Elsevier B.V.
Unidirectional ablation minimizes unwanted thermal damage and promotes better thermal ablation efficacy in time-based switching bipolar radiofrequency ablation
- Authors: Ooi, Ean H. , Ooi, Ean Tat
- Date: 2021
- Type: Text , Journal article
- Relation: Computers in Biology and Medicine Vol. 137, no. (2021), p.
- Full Text: false
- Reviewed:
- Description: Switching bipolar radiofrequency ablation (bRFA) is a thermal treatment modality used for liver cancer treatment that is capable of producing larger, more confluent and more regular thermal coagulation. When implemented in the no-touch mode, switching bRFA can prevent tumour track seeding; a medical phenomenon defined by the deposition of cancer cells along the insertion track. Nevertheless, the no-touch mode was found to yield significant unwanted thermal damage as a result of the electrodes’ position outside the tumour. It is postulated that the unwanted thermal damage can be minimized if ablation can be directed such that it focuses only within the tumour domain. As it turns out, this can be achieved by partially insulating the active tip of the RF electrodes such that electric current flows in and out of the tissue only through the non-insulated section of the electrode. This concept is known as unidirectional ablation and has been shown to produce the desired effect in monopolar RFA. In this paper, computational models based on a well-established mathematical framework for modelling RFA was developed to investigate if unidirectional ablation can minimize unwanted thermal damage during time-based switching bRFA. From the numerical results, unidirectional ablation was shown to produce treatment efficacy of nearly 100%, while at the same time, minimizing the amount of unwanted thermal damage. Nevertheless, this effect was observed only when the switch interval of the time-based protocol was set to 50 s. An extended switch interval negated the benefits of unidirectional ablation. © 2021 Elsevier Ltd