Many people can’t tell the difference between X-rays, CT, ultrasound, and MRI, which are commonly used imaging tests. Now, we compare the body to food and tell you how these tests play different roles.
1, X-ray: like flattening the bread to see
X-rays will pass through the body, encountering the obscured parts, the negative will not be exposed, and this part is white after the film is washed. The biggest disadvantage of X-rays is that they are subject to overlapping and hidden images of deep and shallow tissues, some parts will not be visible, and sometimes need to take X-rays from multiple angles.
2, CT: like a slice of bread to see
CT examination principle is that the X-ray will be layered through the body, after the computer calculates the secondary imaging, like a piece of bread cut into slices to see. The advantage is that you can see in layers, after the calculation can show more information about the tissue.
3.B ultrasound: like picking a watermelon before knocking
The principle of ultrasound is to use ultrasound to penetrate the body, when the sound waves encounter human tissue will produce reflected waves, through the calculation of reflected waves imaging. Just like picking a watermelon, while knocking to show the condition of the lesion.
4, MRI: shake and then look
MRI machine uses a more powerful magnetic field, so that all the water molecules in the human body magnetic field of the same direction of magnetic lines, when the magnetic field of the MRI machine suddenly disappears, the body of water molecules in the direction of magnetic lines, suddenly returned to the original random arrangement of the state. Simply put, it is equivalent to shaking your hand to make the water molecules vibrate, then calm down and feel the vibration inside. Therefore, MRI is also jokingly referred to as a shake and see examination.
What kind of tests are used for each of the four imaging modalities?
Doctors often prescribe a variety of imaging tests: ultrasound, CT, and MRI. …… Many patients may question their doctor’s intention to prescribe high-cost tests. In fact, doctors choose different imaging examinations according to different conditions.
1, traumatic bone – a rough look at the X-ray, a closer look at the CT
A variety of trauma, if you suspect that the injury to the bone, the priority choice of X-ray photos, the results of the examination is fast and easy to obtain. If you want to further observation, you can choose CT. ultrasound, nuclear magnetic for the bone cortex medulla, etc. do not see very clear, generally do not choose.
2.Cervical spine and lumbar spine – the best choice of MRI, the second choice of CT
For cervical spondylosis, lumbar disc herniation and other intervertebral disc diseases that require observation of the intervertebral disc and the corresponding nerve roots, the best choice is MRI for better observation of these soft tissues. Similarly, for joint, muscle and fat tissue examination, MRI is also preferred.
3, chest – a cursory look at the X-ray film, a closer look at the CT
X-ray chest film can roughly examine the heart, aorta, lungs, pleura, ribs, etc. It can check for increased lung texture, calcified lung spots, calcified aortic nodes, etc. CT chest examination shows clearer structures, and is more sensitive to detecting chest lesions and more accurate in showing lesions than conventional X-ray chest films, especially for early lung cancer diagnosis. However, the radiation dose of CT examination is higher than that of X-ray. The application of MRI for the diagnosis of lung diseases is very limited.
4.Abdominal pelvis – except for intestines, general ultrasound can be investigated
The abdominal organs are more affected by breathing, which in turn affects CT and MRI imaging, while ultrasound will not be affected by this. At the same time, ultrasound is more accurate in diagnosing the liver, spleen, pancreas, kidneys, pelvic organs, etc. However, ultrasound is greatly disturbed by gas, and the diagnostic accuracy of ultrasound will be reduced for organs containing more gas, such as the intestines.
5.Heart – exclude coronary heart disease with CT, see the heart function with ultrasound
Routine examination of heart structure and function, the information provided by cardiac ultrasound has been more than adequate, and simple and easy. With CT can check the coronary arteries, but coronary CT examination radiation is large, not suitable as a routine physical examination. Although MRI is free of electromagnetic radiation, it is not as good as CT for coronary artery observation, and cardiac MRI is the “gold standard” for evaluating the structure and function of the heart.