X-RAYS AND ULTRASOUNDS
WHAT IS AN X-RAY?
X-rays are a type of radiation called electromagnetic waves that produce images (radiographs) in shades of black and white by passing high frequency radiations through the body. An x-ray is usually taken for medical diagnosis.
HOW IS THE RADIOGRAPH FORMED?
When the radiations are passes through our body, less dense tissues and organs such as our skin, blood, muscles, etc. do not absorb any of the radiations and let them pass through, and the dense elements such as our bones absorb most of the radiations.
The places where the rays have been absorbed give us a white image and the places where the rays pass through give rise to the black parts of the radiograph. Now obviously, we cannot use any normal paper to get the radiograph.
What is so special about the radiographic film used?
The film consists of a silver halide, preferably silver iodide or silver bromide, as these have the tendency to show multiple crystalline defects and thus have free electrons or cations to move through the film.
In the normal state, silver halides have very low photo sensitivity, however, when irradiated by the radiations in the presence of a reducing agent containing sulphur, silver sulphide is formed, called sensitivity peak, which is the site where electrons get trapped and hence the image is produced.
ULTRASOUNDS
The device that we see radiologists holding is called a transducer. The transducer passes ultrasonic waves of frequencies between 2- 18 MHz, and these waves pass completely through soft tissues, blood, and other thin material, but are reflected back by denser material like bones, gall stones, kidney stones, etc.
This reflecting back of waves gives rise to the different shades of gray we see on a sonograph. When the sound waves reflect back, the vibrations are produced on the transducer, which converts the vibrations into electrical pulses, which travel through the ultrasound scanner, and are transformed into a digital image.
DIFFERENCES BETWEEN X-RAYS AND ULTRASOUNDS
コメント