Cavitation detection in cardiac sonothrombolysis: investigation of alternatives

Abstract

Most deaths from acute myocardial infarction occur outside the hospital environment. In this context, a recent proposal called cardiac sonothrombolysis with microbubbles has the potential to promote significant improvements in patient care. However, it is especially important that the main phenomenon involved in thrombolysis - cavitation of microbubbles - is controlled to avoid harm to the patient. Ultrasound is considered very promising in the treatment of acute and chronic thrombosis, as it can be applied externally, is not ionizing, and can be reapplied several times. Ultrasound cavitation creates shear forces capable of dissolving microvascular and epicardial thrombi and may benefit patients with acute and chronic diseases. Significant improvements in epicardial coronary circulation and microcirculation have been observed. Thus, the development of a portable, simpler, and easier to use equipment for sonothrombolysis can expand access to this procedure and is the subject of ongoing research. The prototype of this research will not have the B-mode ultrasound display, as it is intended for emergency care without the need for an imaging specialist. However, a simple replication of the protocol clinically tested on a portable equipment may not be the most efficient and the safest. Among the various difficulties of the development of the prototype, some can be anticipated: a) occurrence of regions with intensities above the desired one so that it can cause damage; b) underexposed regions due to attenuations; c) unwanted heating; d) subset of ineffective transducers for certain foci, wasting energy. The objective of this proposal is to investigate efficient safety mechanisms, especially alternative detection of cavitation and the feedback control of pressure intensities, aiming at safer equipment for the patient. The methodology will consist of theoretical studies and simulation of cavitation and its detection via conventional transducers for sonothrombolysis. It is also intended to perform conceptual evaluations in acoustic tank. Evaluation in animals or patients is not part of the scope of this project. (AU)