ABSTRACT
Clinical ultrasound (US) or sonography is an imaging modality using high frequency sound waves typically between 1 and 20 MHz. US pulses are created in transducers, often piezo-electrical crystal, which converts changes of thickness of the crystal into sound waves by alternating applying voltage. In brachytherapy, transrectal ultrasound (TRUS) probes are commonly used. They can be used for prostate and anal cancers, as well as, with some restrictions, for gynecological brachytherapy treatments. US is extensively used for diagnostic purposes in oncology. The high image resolution and good soft-tissue contrast allow for assessment of different oncologic sites such as abdominal or pelvic tumors, breast cancer, or various lymph node regions. For selected indications, US is considered equal or even superior to computed tomography (CT) or magnetic resonance imaging (MRI). The ultrasound contrast agents (UCA) used in contrast-enhanced ultrasound (CEUS) imaging consist of small bubbles of gas encapsulated in biocompatible shell, which resonate when excited by US waves at certain frequencies.
