Magnetic Resonance Imaging (MRI) [Neurosurgery Wiki]

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====== Magnetic Resonance Imaging (MRI) ======

Magnetic Resonance Imaging (MRI) is a **non-invasive medical imaging technique** that provides high-resolution images of internal body structures, especially **soft tissues** such as the [[brain]], [[spinal cord]], [[muscle]]s, and internal organs.

===== Physical Principles =====

MRI is based on the following components:
  * A **strong magnetic field** aligns hydrogen nuclei (protons) in the body.
  * **Radiofrequency (RF) pulses** disturb this alignment.
  * As protons return to their original alignment, they emit signals.
  * These signals are detected and processed into detailed images.

===== Advantages =====
  * No ionizing radiation.
  * Excellent soft tissue contrast.
  * Multiplanar capabilities (axial, sagittal, coronal, oblique).
  * Functional and contrast-enhanced imaging options.

===== Common Clinical Uses =====
  * **Neurology**: stroke, tumors, multiple sclerosis, epilepsy, trauma
  * **Spine**: disc herniation, myelopathy, spinal tumors
  * **Musculoskeletal**: ligament/tendon injuries, joint disorders
  * **Cardiology**: myocardial viability, congenital heart disease
  * **Oncology**: tumor detection, staging, and follow-up
  * **Abdominal imaging**: liver, kidneys, uterus, prostate, pancreas

===== Contrast Agents =====
  * Gadolinium-based agents are used to enhance vascular structures and highlight pathology.
  * Usually safe, but used cautiously in patients with severe renal impairment (due to risk of nephrogenic systemic fibrosis).

===== Limitations and Contraindications =====
  * **Metallic implants**, **pacemakers**, or **ferromagnetic fragments** may pose risks.
  * **Claustrophobia** may require sedation or use of open MRI systems.
  * Long acquisition times compared to CT.

===== Variants =====
  * [[fMRI]] (Functional MRI)
  * [[MR angiography]] (MRA)
  * [[Diffusion-weighted imaging]] (DWI)
  * [[Perfusion MRI]]
  * [[MR spectroscopy]] (MRS)

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**See also:**  
  * [[Computed Tomography (CT)]]  
  * [[Positron Emission Tomography (PET)]]  
  * [[Neuroimaging techniques]]