Evaluating the Impact of Cryoprobe Tip Structure for Effective Cryoablation of Breast Cancer

This study aims to analyze the impact of the structure of a cryoprobe tip on the transient thermal phenomenon that takes place during cryoablation of breast cancer. A 2D axisymmetric breast model with an embedded tumor has been constructed using COMSOL Multiphysics® interface. Three different tip structures (conical, spherical, cylindrical) have been considered for the experimentation to determine the optimal shape which not only destroys a greater fraction of tumor volume with great rapidity but also ensures minimal damage to the neighboring healthy tissues. Fine triangular meshes have been generated all over the experimentation domain. The simulation has been performed for a duration of 200s employing Pennes bioheat equation with relevant thermo-physical properties of tissue layers and appropriate boundary conditions as well as initial conditions for each of the structure. From the result illustrated via the frozen fraction vs time plot, it can be deduced that despite having nearly same and comparable dimensions, the cylindrical probe tip, outperforms the conical and spherical tips by a margin of 13.57% and 7.44%, respectively in terms of destroying the tumor tissue volume. Therefore, the result shows that the probe tip with a greater surface area demonstrates better cryogenic activity which is in conformity with the expectation. In conclusion, the study delivers a significant insight for manufacturing especially engineered cryoprobe tip with adequate proof of concept and ushers a new pathway for enhancing the net efficacy of the cryosurgical intervention for the treatment of breast cancer. Still, the study offers scopes for further optimization to make it more realistic, effective and clinically relevant.

I. Introduction

Being the primary cause of mortality among women, breast cancer has lately emerged as a public health concern in the globe landscape. In 2020, around 2.3 million new breast cancer cases were identified while approximately 685,000 deaths were reported [1]. However, despite the gradual rise in the incidence rate of breast cancer, the mortality rate seems to be decreasing. About 40% mortality rate has dropped in high income countries from 1980s to 2020 [1]. This can be attributed to the availability of advanced medical treatments namely chemotherapy, cryosurgery, hormonal therapy, radiation therapy, biopsy or lumpectomy, mastectomy etc. [2]. These methods are adopted depending on the type and stage of the cancer. Surgeries like, lumpectomy and mastectomy are invasive while chemotherapy and hormonal therapy have many devastating side-effects including hair loss, destruction of the blood forming bone marrow cells, reproductive cells, gastrointestinal cells, damage of lungs, kidneys, heart, bladder, nervous system etc. [3]. Cryosurgery is a minimally invasive method that stands against most of the adversaries of the aforementioned methods and enables the destruction of the cancer cells (tumor) at an early stage of the cancer [2]. In this procedure, a hollow needle is inserted in the region of interest and cooled upto - or lower through the flow of argon gas or any medical grade cryogenic agent. After some time, ice ball forms at the tip of the needles, freezes and effectively destroys the tissues at the contact site. Cryoprobe is the apparatus that is used for releasing the cryogenic agent at the surgical site. Although higher surface area of the probe tip increases the effectiveness of the cryoablation procedure [4], if it is attained by using a larger probe tip with blunt outer surface, it destroys the nearby healthy tissues. To prevent this, the internal surgical site of the breast is monitored by the physicians using ultrasound images during cryosurgery [5]. Moreover, the tip of the probe to be used is manufactured with a minuscule dimension so that the number of the destroyed healthy cells can be kept as minimum as possible. Thus, it has almost negligible side-effects compared to the other methods.