Ultrasound imaging uses a transducer or probe to generate sound waves and produce pictures of the body’s internal structures. It does not use ionizing radiation, has no known harmful effects, and provides a clear picture of soft tissues that don’t show up well on x-ray images. Ultrasound is often used to help diagnose unexplained pain, swelling and infection. It may also be used to provide imaging guidance to needle biopsies or to see and evaluate conditions related to blood flow. It’s also the preferred imaging method for monitoring a pregnant woman and her unborn child.
Advantages
- ultrasound uses non-ionizing sound waves and has not been associated with carcinogenesis – this is particularly important for the evaluation of the fetal and gonads
- in most centers, ultrasound is more readily available than more advanced cross-sectional modalities such as CT or MRI
- ultrasound examination is less expensive to perform than CT or MRI
- ultrasound is straightforward to perform portably, unlike CT/MRI
- there are few (if any) contraindications to the use of ultrasound, compared with MRI or contrast-enhanced CT
- the real-time nature of ultrasound imaging is useful for the evaluation of physiology as well as anatomy (e.g. fetal heart rate)
- Doppler evaluation of organs and vessels adds a dimension of physiologic data, not available on other modalities (with the exception of some MRI sequences)
- ultrasound images may not be as adversely affected by metallic objects, as opposed to CT or MRI
- an ultrasound exam can easily be extended to cover another organ system or evaluate the contra lateral extremity
Disadvantages
- training is required to accurately and efficiently conduct an ultrasound exam and there is non-uniformity in the quality of examinations (“operator dependence”)
- ultrasound is not capable of evaluating the internal structure of tissue types with high acoustical impedance (e.g. bone, air). It is also limited in evaluating structures encased in bone (e.g. cerebral parenchyma inside the calvarias)
- the high frequencies of ultrasound result in a potential risk of thermal heating or mechanical injury to tissue at a microscopic level, this is of most concern in fetal imaging
- ultrasound has its own set of unique artifacts (US artifacts), which can potentially degrade image quality or lead to misinterpretation
- some ultrasound exams may be limited by abnormally large body habitués
