- produce images (usually 2D still images, but in some cases moving or 3D images).
The main purpose of these techniques is to investigate the appearance of internal organs. which would not be possible without opening the body surgically.
One advantage - non invasive (i.e do not involve penetration of the patients body.) as a result of this nopain or discomfort is caused.
-uses a transducer to procude a beam of high-frequency sound waves. these sound waves can penetrate some soft tissues and are partialy reflected from surfaces. the practitioner places the transducer on the part of the body which is to be scanned. an oily gel is used to ensure there is good contact between this and the skin. alongside the transducer is a reciever which can pick up the soundwaves. computer technology is used to process the image of the tissues.
-used to observe foetal development whilst in the womb, can also be used to monitor internal organs such as appendix.
disadvantage is that the image produces is of poor 2D quality and show less detail, the technique does not penetrate bone and so cannot be used to scan the brain or internal organs.
advantage is that is carries a low risk of harm, produces a real moving image (which is important in studying the health of a foetus), relatively inexpensive.
- type of electromagnetic radiation. which have a very short wavelength. this short wavelength enables them to penetrate some materials that light and radioaves cannot be passed through, they can pass through soft tissue however, cannot pass through thick bone or metal.
- an x-ray machine produces an invisible beam which is emmitted to a specific part of the patient's body. underneath the wrist is placed a sheet of photographic paper in a envelope (to prevent it from being exposed to light), the X-Rays pass through the patient's wrist and the envlope and cause a change in the photographic paper. More X-Rays pass through the soft tissue than bone and so a kind of shadow is formed on the paper where the bone is. the paper is then developed like a normal photographic negative, producing an X-Ray. the negative shows bones as light and soft tissue as dark, this is beacsue denser tissues such as bones and heart muscles absorb more of the radiation than soft tissues do. A practitioner holds up the negative to an illuminated panel to examine the image.
-advantage is that it is quick and easy to use. negatives can be developed while the patient waits. some x-ray machine's are small enough to use in a dentist surgery. compared with other imaging techniques it is very cheap.
-disadvantage is exposure to radiation can cause cancer.
- As well as imaging bone to diagnose fractures, X-rays can be used to examine softer tissue structures. abnormalities of the heart and lungs often show up as a shoadow on an x-ray. However, hollow or fluid filled organs such as those of the digestive tract are more difficult to image.
- The method of contrast x-rays uses a contrast medium which is put into the patients digestive tract. This a liquid containing barium (also called a barium meal) is made up of metal salts that are opaque to x-rays. There are two ways this can get into the digestive system.