Dual-modality image guided high intensity focused ultrasound device design for prostate cancer : a numerical study

摘要

In this study we established the feasibility of designing a multi-element high intensity focusedultrasound (HIFU) device for Magnetic Resonance and an ultrasound imaging-guided transrectaltreatment of prostate cancer. An initial geometry was specified based on a clinical transrectalHIFU device with a central open space to lodge an independent ultrasound imaging probefor guidance. A parametric study was performed to determine the optimal focal length (L ),operating frequency (j), element size (a) and central opening radius (r) of a device that would becapable of treating cancerous tissue within the prostate, spare the surrounding organs andminimize the number of elements. Images from the Visible Human Project were used todetermine the organ sizes and treatment locations for simulation. Six virtual ellipsoidal tumorswere located throughout a simulated prostate and their lateral and axial limit locations wereselected as test locations. Using Tesla 1060(NVIDIA) graphics processors, the Bio-Heat TransferEquation was implemented to simulate the heating produced during treatment at the testlocations. L, f a and r were varied from 45 to 75mm, 2.25 to 3.00MHz, 1.5 to 8 times A,where A= f speed of sound , and 9 to 12.5mm respectively. Results indicated that a combination ofL,f, a and r of 68mm, 2.75MHz, 2.05A. and 9mm respectively could safely ablate tumors withinthe prostate and spare the surrounding organs. The number of therapeutic elements required forthis device was 761.