Cancer ablation by high intensity focused ultrasound
Siu, Jun Yang
Date of Issue2016
School of Mechanical and Aerospace Engineering
High Intensity Focused Ultrasound (HIFU) is a promising non-invasive clinical tool in the field of clinical studies. This technique allows a precise generation of small shaped lesions within a localised tissue target upon ablation. The main mechanism of HIFU includes thermal and mechanical effects in which operating parameters play an important role during the treatment. Due to the variance of HIFU parameters during ablation, it results in different characteristics of lesion growth sizes. An increase in duty cycle and ablation time sees an increase in lesion size while a change in pulse repetitive frequency shows no significant trend in the lesions growth size. In addition with a vessel with different flow rates through the area of ablation, a faster flow rate would enhance heat dissipation of the thermal effects during the process thus generating smaller lesions. With the concept of heat dissipation, a vessel with bigger inner diameter also yield a smaller lesion. Mechanical effects of HIFU, also known as cavitations (both stable and inertia), is in the form of microbubbles. Due to high acoustic and pressure, these microbubbles coalesce and collapse in a random manner during the ablation, producing shockwaves that damages the tissue cells within the localised area of treatment. These microbubble activities are measured by a passive cavitation detector (PCD). Interchanging parameters yield different characteristics of microbubble activities. Due to the primary concerns of the safety of patients using HIFU as a clincal treatment for the removal of tumors, in-depth understanding and real time feedback monitoring of the lesion and bubble cavitation activities present at the localised area of treatment is vital as it enhances the efficacy and efficiency of HIFU therapy.
Final Year Project (FYP)
Nanyang Technological University