Bubbles and ultrasound

摘要

Ultrasonic imaging is becoming the most popular medical imaging modality. Taking into account all hospital expenses, the costs of ultrasound and of X-ray examinations are roughly the same, whereas MRI and CT scans are approximately three times as expensive. A basic B-mode ultrasound scan typically shows contrast at regions of differing acoustic impedance. However, blood is a poor scatterer of ultrasound waves at clinical diagnostic frequencies, and thus techniques to enhance contrast have naturally emerged over the last few decades. The development of ultrasound contrasts agents, microscopically small bubbles with resonance frequencies in the clinical diagnostic range, has extended the functionality of standard sonography to perfusion assessment and even to molecular imaging.