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 |
You can also read: CAT scan
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. |
You can also read: The Introduction to Biomedical Instrumentation
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