Ultrasound vs. X-rays, what are the differences?

Both ultrasound and X-rays are used in medical diagnosis. We look at the differences in their physical properties and the applications differences between the two as applied in medical diagnosis.

Table 1: Physical Property differences between Ultrasound and X-rays

Property	Ultrasound	X-rays
Wave type	Longitudinal	Electromagnetic
Transmission requirement of medium	Elastic	No medium is required
Velocity	It depends upon the medium through which it propagates	Constant
Generation	Stressing the medium	Accelerating the electric charge
Similar waves	Acoustic, seismic	Radio, light

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Table 2: Application differences between Ultrasound and X-rays in medical diagnosis

Ultrasound	X -rays
It uses sonic energy and it needs a medium for propagation.	It uses electromagnetic energy and it needs no medium.
It is non-invasive and it has no long-term side effects.	Though non-invasive the body is invaded by ionizing radiation which has harmful effects.
Imaging is obtained from the echoes which are reflected beams from the targets.	Imaging is obtained from the radiation that leaves the body.
It is a real time imaging. It is highly operator dependent.	It is not a real-time imaging.
Ultrasound cannot penetrate bones. Sonography of the brain is almost impossible. It images only muscles, soft tissues and bone surface.	X-rays show up well the high density parts such as bones and air cavities.
Depth penetration is limited. The quality of the image decreases in case of obese patient.	There is no penetration problem, since imaging is obtained from the radiation leaving the body.
Performs poorly when there is a gas between the transmitter and the organ.	X-rays have no such a problem.
Displacement of structure and valves as well as blood flow can be imaged.	It is not possible to do imaging in cases like these.