in this study we established the feasibility of designing a multi-element high intensity focused ultrasound (hifu) device for magnetic resonance and an ultrasound imaging-guided transrectal treatment of prostate cancer. an initial geometry was specified based on a clinical transrectal hifu device with a central open space to lodge an independent ultrasound imaging probe for 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 be capable of treating cancerous tissue within the prostate, spare the surrounding organs and minimize the number of elements. images from the visible human project were used to determine the organ sizes and treatment locations for simulation. six virtual ellipsoidal tumors were located throughout a simulated prostate and their lateral and axial limit locations were selected as test locations. using tesla 1060(nvidia) graphics processors, the bio-heat transfer equation was implemented to simulate the heating produced during treatment at the test locations. 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 of l,f, a and r of 68mm, 2.75mhz, 2.05a. and 9mm respectively could safely ablate tumors within the prostate and spare the surrounding organs. the number of therapeutic elements required for this device was 761.