Magnetic Resonance Imaging (MRI):
Basic Information: Magnetic Resonance Imaging (MRI), following CT, represents another major advancement in medical imaging. Since its introduction in the 1980s, it has developed at an extremely rapid pace. Its fundamental principle involves placing the human body within a specialized magnetic field. Radiofrequency pulses excite hydrogen nuclei within the body, causing them to resonate and absorb energy.
After the radiofrequency pulses cease, the hydrogen nuclei emit radio signals at specific frequencies, releasing the absorbed energy. These signals are captured by external receivers and processed by computers to generate images—this process is known as magnetic resonance imaging.high information content, multi-planar imaging capability, and exceptional soft tissue resolution. Since its inception, it has garnered significant attention from scholars across various fields. Rapid advancements have been made in equipment refinement, software updates and upgrades, and research into its diagnostic applications for organs throughout the body. Now mature, it is widely used in clinical disease diagnosis and has become an indispensable examination method for certain pathologies.
Magnetic resonance is a physical phenomenon widely applied as an analytical tool in physics, chemistry, and biology. Its use in medical diagnostics only began in 1973. To avoid confusion with radiographic imaging in nuclear medicine, it is termed Magnetic Resonance Imaging (MRI).
MR is a biomagnetic spin imaging technique that utilizes the characteristics of atomic nuclear spin motion. Within an applied magnetic field, radiofrequency pulses excite the nuclei to generate signals. These signals are detected by sensors and transmitted to a computer, where processing converts them into images displayed on a screen.The information provided by MR not only surpasses that of many other imaging techniques in medical imaging but also differs fundamentally from existing methods. Consequently, it holds significant potential advantages for disease diagnosis. It can directly produce cross-sectional, sagittal, coronal, and various oblique plane tomographic images without generating the artifacts seen in CT scans; it requires no contrast agent injection; and it involves no ionizing radiation, posing no adverse effects on the body.
MRI is highly effective for detecting common cranial diseases such as intracerebral hematomas, extracerebral hematomas, brain tumors, intracranial aneurysms, arteriovenous malformations, cerebral ischemia, intraspinal tumors, syringomyelia, and hydrocephalus. It is also highly effective for diagnosing conditions like lumbar disc herniation and primary liver cancer.
Essential Components of MRI Equipment:
1. Magnet: Beyond the aforementioned types, barrel-shaped closed magnets and open magnets exist; the latter enables interventional procedures.
2. Gradient Fields: Designed for spatial encoding; software functionality depends on their intensity and rate of change.
3. RF Coils: Multiple types transmit and receive radiofrequency pulses.
4. Acquisition System: Programs and imaging processes.
5. Computer: Requires large capacity, fast processing, comprehensive functionality, and user-friendly operation.
Indications for Examination:
1. Neurological Disorders: Cerebral infarction, brain tumors, inflammation, degenerative diseases, congenital anomalies, etc.
2. Spinal Disorders: Lumbar disc herniation, spinal stenosis, spinal cord tumors, etc.
3. Radiation-Induced Diseases: Radiation-induced brain lesions, spinal cord lesions, etc.
4. Interventional Procedures: Percutaneous spinal injections, spinal cord shunts, etc.
5. Computational Requirements: Large capacity, fast processing, comprehensive functionality, and user-friendly operation.5. Computer: Requires high capacity, fast processing, comprehensive functionality, and user-friendly operation.
Indications for Examination
1. Neurological disorders: Cerebral infarction, brain tumors, inflammation, degenerative diseases, congenital anomalies, trauma, etc. This was the earliest application in human systems, with extensive accumulated experience. It provides accurate and timely localization and characterization of lesions, enabling detection of early-stage abnormalities.
2. Cardiovascular System: Used for diagnosing heart disease, cardiomyopathy, pericardial tumors, pericardial effusion, as well as mural thrombi and endocardial flaps.
4. Abdominal Organs: Diagnosis and differential diagnosis of liver cancer, hepatic hemangiomas, and liver cysts; diagnosis and differential diagnosis of intra-abdominal masses, particularly retroperitoneal lesions.
5. Pelvic Organs: Diagnosis and localization of uterine fibroids, other uterine tumors, ovarian tumors, and pelvic masses; detection of rectal, prostate, and bladder tumors.
6. Bones and joints: Diagnosis and extent of bone infections, tumors, and trauma, with particular value for subtle changes like bone contusions. High diagnostic value for intra-articular lesions (cartilage, ligaments, menisci, synovium, bursae) and bone marrow disorders.
7. Systemic Soft Tissue Lesions: Accurate localization and characterization of tumors, infections, and degenerative lesions originating from nerves, blood vessels, lymphatics, muscles, or connective tissue.
Examination Precautions
1. Individuals with implanted cardiac pacemakers or neurostimulators are prohibited from undergoing the examination.
2. Individuals with intracranial silver clips or metallic foreign bodies within the eyeball are prohibited from undergoing the examination.
3. Electrocardiographic monitors are not permitted in the MRI examination room. Individuals who have undergone arterial bypass surgery or cardiac surgery with artificial heart valves are prohibited from undergoing the examination.
4. Patients with critical conditions: including coma, agitation, arrhythmia, respiratory failure, uncontrolled bleeding, or incontinence following trauma or accidents.
5. Individuals with metallic objects in the examination area (e.g., internal fixation pins) cannot undergo the scan.
6. Pregnant women should exercise caution with this examination. Inform the examining physician if pregnancy is possible.
7. Please bring medical records, X-ray films, CT scans, previous MRI images, and other relevant materials to the MRI room for reference.