How to choose radiology examination?

Most patients who visit hospitals will go to the radiology department for examinations. However, many people have never figured out the differences between the examination items. What are the differences between X-rays, CT scans, and MRIs? How should we choose?

First of all, we need to know that the hospital's radiology department consists of three parts: DR (digital radiography machine), CT (computer tomography), and MRI (magnetic resonance imaging).

DR examination is an X-ray examination. Thicker tissues such as bones and calcifications absorb more X-rays, and less X-rays penetrate the human body, thus forming a white image. Loose organs such as the respiratory tract and gastrointestinal tract absorb less X-rays and appear black in the image.

CT is essentially similar to DR, both of which are branches of X-ray examination. It can perform tomographic scans of human body parts and produce secondary images after computer processing, just like cutting a piece of bread into slices.

Magnetic resonance imaging (MRI) places the human body in a special magnetic field and uses radio frequency pulses to excite the hydrogen nuclei in the body, causing the hydrogen nuclei to resonate. Images are obtained through computer processing, and the differences between normal tissues and diseased areas can be observed after imaging.

The above three imaging examinations each have their own advantages. Doctors will consider the most suitable disease examination, as well as the economic burden, the difficulty of the examination, and the length of the examination time. Sometimes multiple examinations are supplemented.

1. Central nervous system

[Cerebral hemorrhage] CT is the first choice. Bleeding can be clearly shown on CT, and the examination speed is fast.

[Cerebral infarction] CT is generally the first choice to save time, but CT is not as sensitive as MRI, which can reflect cerebral infarction several hours after the onset. If the condition allows, MRI is recommended.

[Encephalitis, meningitis, brain tumors, spinal cord lesions] For these inflammatory or tumor diseases, MRI is better than CT.

2. Skeletal and muscular system

[Fracture] If the fracture is caused by trauma or a fracture is suspected, the first choice is X-ray, which is convenient and relatively low in cost. If a clear diagnosis cannot be made, CT scan can be chosen.

[Joints] CT or MRI is the first choice for bone degeneration (aging) of joints and spine. However, MRI is the first choice for arthritis, joint muscle, ligament injury, etc.

[Bone tumors] If bone lesions are suspected, X-rays are the first choice, as they are convenient and economical. If you want to further observe the invasion of soft tissues and surrounding structures, you can choose magnetic resonance imaging.

3. Respiratory system

CT can be used to rule out early lung tumors or if abnormalities are found that require further diagnosis.

Chest X-rays during routine physical examinations are of little significance for early screening of lung cancer. The internationally recognized most effective way to screen lung cancer is low-dose spiral CT.

4. Head and Neck

【Ear】CT is the first choice for the middle ear and mastoid. MRI is the first choice for the inner ear.

[Cervical spine] Magnetic resonance imaging is preferred. CT can be used as a powerful supplement to observe bone hyperplasia and intervertebral foraminal stenosis.

[Thyroid gland] Ultrasound and ultrasound-guided puncture are the first choice. If you want to see whether there is tumor invasion or metastasis, CT and MRI can be performed.