Common imaging examinations mainly include five categories: X-ray, CT, MRI, ultrasound and nuclear medicine examinations. Each technology has its own advantages and applicable scenarios.X-rays and CT are fast and low-cost, and are suitable for bone and lung examinations; MRI provides high-resolution soft tissue imaging and is often used for nerve and joint diseases; ultrasound is radiation-free and real-time dynamic, and is widely used in obstetrics and gynecology and cardiovascular fields; nuclear medicine (such as PET-CT) focuses on functional metabolic assessment. The following will analyze its principles, applications and precautions in layers.

X-ray examination is the cornerstone of imaging, which uses electromagnetic waves to penetrate the human body to form images.Mainly used for preliminary screening of fractures, pneumonia and digestive tract diseases, such as chest X-ray and barium meal angiography. Its advantages are easy operation and low price, but the soft tissue contrast is poor. Digital DR (direct digital radiography) is gradually replacing traditional film, with lower radiation levels. It should be noted that pregnant women need to choose carefully to avoid the risk of embryo exposure.

CT (computed tomography) reconstructs tomographic images through multi-angle X-ray projection.It is widely used in emergency situations such as cerebral hemorrhage, pulmonary embolism and tumor staging. High-resolution CT can detect millimeter-level lesions, and enhanced scanning can also observe vascular abnormalities. However, the radiation dose of CT is relatively high, and children and those who have undergone multiple examinations need to weigh the pros and cons. In recent years, low-dose CT has shown significant value in lung cancer screening. For example, the Revolution series equipment of the American company GE can reduce radiation dose by 50%.

MRI (magnetic resonance imaging) uses magnetic fields and radiofrequency pulses to create three-dimensional images.It has excellent effects on the brain, spinal cord, muscles, ligaments and pelvic organs, such as diagnosing cerebral infarction and meniscus injury. The lack of ionizing radiation is its biggest advantage, but the examination is time-consuming, expensive, and may be limited for those with metal implants in the body. Siemens' MAGNETOM series and Philips' Ingenia MRI are widely used in clinical settings to support functional imaging such as diffusion-weighted imaging (DWI).

Taken together, imaging examinations need to be selected individually based on disease characteristics.X-ray and CT are suitable for rapid screening, MRI is good at soft tissue analysis, and ultrasound and nuclear medicine are irreplaceable in dynamic observation and metabolic assessment. With the development of AI-assisted diagnosis (such as United Imaging Medical’s uAI system), the efficiency and accuracy of image interpretation continues to improve. Patients should follow the doctor's advice and choose the most appropriate solution based on their own circumstances to avoid unnecessary repeated examinations.

Quote sources:1. "Medical Imaging" (People's Health Publishing House, 8th Edition) 2. "Expert Consensus on CT Examination Technology" by the Radiology Branch of the Chinese Medical Association 3. For equipment data, please refer to the technical parameters disclosed on the official websites of GE Healthcare and Siemens Healthcare