X-rays and ultrasound are both medical imaging techniques used to visualize the inside of the human body, but they work on different principles and have distinct applications.

X-ray (Radiography):

Principle: X-ray imaging relies on the interaction of high-energy X-ray photons with the body's tissues. When X-rays pass through the body, they are absorbed differently by different tissues, creating a shadow image on a detector.

Use: X-rays are commonly used to visualize bones and dense structures like teeth, as well as to detect various medical conditions such as fractures, tumors, infections, and lung issues. They are also used in some interventional procedures, like angiography, to visualize blood vessels.

Safety: X-rays involve exposure to ionizing radiation, which can potentially damage cells and increase the risk of cancer if used excessively. Therefore, their use is controlled and monitored to minimize radiation exposure.

Ultrasound (Ultrasonography):

Principle: Ultrasound imaging utilizes high-frequency sound waves (ultrasound) that are emitted by a transducer and bounce back (echo) when they encounter different tissues in the body. The returning echoes are processed to create an image.

Use: Ultrasound is versatile and is commonly used for imaging various soft tissues, including muscles, organs (such as the liver, kidneys, and heart), blood vessels, and the developing fetus during pregnancy. It is also used for real-time guidance during procedures like biopsies or catheter placement.

Safety: Ultrasound is considered a safe imaging modality because it does not involve ionizing radiation. It is non-invasive and can be used during pregnancy without known harmful effects to the fetus.