Bio-heat Transfer Modeling of High-Intensity Focused Ultrasound Waves in an Ex-Vivo Setup for Choroidal Tumor Treatment

High-intensity focused ultrasound (HIFU) has gained growing research interest among scholars in the past decade. Several HIFU treatments have gained clinical acceptance. This technology employs the concepts of piezoelectricity and offers the promise of non-invasive focal therapy. HIFU applications in ophthalmology have not been investigated extensively, although being among the first therapeutic applications to be investigated by researchers historically. This might be due to the lack of high-intensity and high-frequency ultrasound probes to satisfy the requirements of ophthalmic disease treatment. Fast development,deployment and utilization of laser therapy in ophthalmology would be another reason for lack of interest in investigating HIFU therapy in the eye. However, laser therapy has two important limitations. Laser would not pass through opaque cancerous tissue and it would not penetrate deep enough for thermal ablation in chorioretinal and chorio-scleral regions. However, HIFU can overcome both challenges and provide a non-invasive thermal ablation. Thus, recently HIFU demonstrated promising results in the treatment of glaucoma through selectively ablating parts of the ciliary body. The main objective of the present study is to investigate the temperature increment due to the utilization of HIFU for choroidal tumor ablation thorough a multiphysics simulation. The numerical model was developed in COMSOL Multiphysics® software based on different tissues of human eye mechanical properties, available in the literature. The model is capable of capturing physics involved in HIFU treatment. The results showed that increasing the frequency of the transducer makes the focal region finer. Thus with high frequency focused ultrasound, thermal ablation of choroidal tumors could be possible. The results also showed a very steep temperature profile in the vicinity of the focal region which endorses the non-invasive feature of the proposed focal therapy.

Keywords:

High intensity focused ultrasound , Ocular tumor , Tumor ablation , Bio-heat transfer , Finite element method