Portable device for recurrent test of ultrasonic transducers acoustic pressure

Abstract

The transducer is the main component of ultrasound devices that consists of piezoelectric elements responsible for converting mechanical energy into electrical energy and vice versa. The variety in shape, size and frequency of transducers allows its use for various clinical applications in imaging or therapy methods. The transducer is one of the most exposed parts to mechanical impact, misuse and heating. Thus, it is one of the most frequently replaced components and often associated with poor quality images in defective diagnostic device. A damaged piezoelectric element can generate artifacts in B-mode images and/or side lobes that cause errors in the Doppler calculation of blood velocity. In addition, an uncalibrated transducer - operating at unspecified acoustic intensity ranges - can either be ineffective in therapeutic treatments as cause damage to biological tissue in therapy or diagnosis. Alarmingly, the calibration of this component is only required during the manufacturing process. One reason for the lack of predictive evaluation of the ultrasound equipment is that national or international regulatory agencies do not establish mandatory assessments of the equipment quality, although recommended by standards. Therefore, users only evaluate the transducers when image artifacts prevent diagnosing or when observing apparent therapy ineffectiveness. In this study, a magnetic sensor-based device dedicated to measure the acoustic radiation force (ARF) will be designed for the recurrent tests of ultrasound imaging and therapy transducers. The proposed device is composed of: a support to fit different types of transducers, an acoustic coupling material with magnetic particles, sensors (magnetic field, temperature and pressure), and an electronic circuit for control, acquisition, processing and signal communication. The ARF produced by the transducer will shift the magnetic particles dispersed in the coupling material and so generate static and dynamic components of the magnetic field measured by the sensor. The main challenges of this research are: 1 - develop gelatin-based magnetized materials that generate oscillating magnetic field due to the action of acoustic waves; 2 - develop a robust electrical shielded assembly with active cancellation of the electromagnetic noise allowing its use in different environments; 3 - develop a fastening system with pressure sensors to avoid poor positioning of the transducer. The device will be designed to be: easy to use by medical professionals, robust to be operated in offices, hospitals and clinics, with costs that encourage purchasing it together with the ultrasound device. The device will alert the healthcare professional when the transducer or equipment presents the first signs of malfunction. Therefore, the maintenance or replacement can be scheduled in advance ensuring the effective diagnosis and therapy for patients, reducing costs and administrative impacts due to the rescheduling of exams, extending patient hospitalization, inconvenience for patients and loss of productivity. (AU)