Development of electronic array drivers for high intensity focused ultrasound applications

High intensity focused ultrasound (HIFU) have been used in thermal ablation of unwanted tissue, coagulation of blood, and drug delivery applications for some decades. In the last decade, HIFU has been associated with cancer treatment because it can actually burn the particular tissue without harming the tissues around. HIFU treatments are typically done with ultrasonic transducer arrays which allow electronic focusing and scanning, rather than fixed focus single element transducers. Therefore, an essential part of a HIFU system is an electronic driving circuitry that can drive each transducer array element independently, can deliver enough electrical power, and provide sufficient phase resolution to allow for focusing and steering capability. HIFU treatments also require image guidance and currently ultrasound and magnetic resonance imaging are the only imaging methods used for HIFU guidance. Because of the higher image quality and thermal imaging capability, MRI guidance is the preferred method. Aside from being expensive MRI guidance also puts MR compatibility constraint on the HIFU transducer and its driving electronics. MR guidance provides close to real-time feedback on the location of the focal spot and on the progress of the thermal treatment. This feedback is then used to control the electronic driving circuitry. Hence, the driver has to allow for the fast update of the driving parameters. In this thesis we developed a MR compatible, PWM based, easily programmable, low cost and portable 64 channels HIFU driver with high power capability, 7.50 phase resolution and 256 level amplitude resolutions. This driver is used with a 64 element MR compatible transducer array and is shown to operate as desired under MR guidance.