MAGNETIC RESONANCE IMAGING 2

MAGNETIC RESONANCE IMAGING – Definition, Purpose, Principle, Instruction, Preparation of the Client, MRI Equipment, Procedure, After Care, Advantages of MRI, Disadvantages and Contraindications

Magnetic resonance imaging is also called as nuclear magnetic resonance; this technique was independently discovered by Felix Bloch and Purcell in 1952. He explained that when the nuclear energy is exposed to a magnetic field, it behaves like a magnet. This nuclear magnetism with its magnetic field helps the nuclear energy to act as a small magnet

DEFINITION

  • Magnetic resonance imaging (MRI) is a noninvasive diagnostic test with a powerful magnetic field to obtain images of different areas of the body
  • Magnetic resonance imaging or MRI uses a powerful magnetic field and radiofrequency waves to produce computerized images of internal organs and tissues

PURPOSE

  • To produce tissue analysis and images not readily seen on standard X-ray
  • To detect tiny lesions of multiple sclerosis on brain and spinal cord
  • To detect slipped disc in the spinal cord
  • To get a clear image of internal structures in response to the magnetic field, created by harmless, low energy radiowaves
  • To detect, localize and stage malignancies of the CNS, spine, head and neck and musculoskeletal system

PRINCIPLE

  • MRI does not employ ionizing radiations, so it is free from radiations where as CT scan is by X-ray
  • The picture from an MRI are opposite of the CT scan. In MRI the bones appear black whereas in CT scan bones appear white
  • MRI is used to study the tissue metabolism by spectroscopy where as CT not
  • MRI is used to obtain sectional views in any plane unlike CT scan which is more or less restricted to cross-sectional imaging
  • MRI detects water because it focuses on the behavior of hydrogen atom in water molecule. This allows MRI to distinguish between water proof and water rich tissues
  • MRI gives early warning of myocardial infarction or stroke with the help of sodium or phosphorus ions

INSTRUCTIONS

  • The client informed that it is painless noninvasive procedure and he will hear a lot of noises during the procedure
  • All jewelry, eye glasses and hair pins/clips or any other metal objects should be removed
  • Carefully question and screen for the presence of any metal implantation
  • Consent for contrast and general anesthesia to be taken
  • Patient should wear only cotton dress
  • No dietary restriction for MRI even for contrast, unless anesthesia is planned
  • Extra blanket may be provided as the client is in the air conditioned for more than 45 minutes

PREPARATION OF THE CLIENT

  • Explain the procedure to the patient in a simple language
  • Remove all metal objects, clips and jewelry from the patient’s body
  • Give information about actual procedure, staff involved, duration and sensation to be experienced and probable outcome
  • The patient is assured the investigation is safe and painless
  • Psychological support and assistance to be given for claustrophobia

MRI EQUIPMENT

  • Magnet
  • Radiofrequency (RF) coils (transmitter/receiver)
  • Gradient coils
  • Computer
  • Display unit
  • Digital storage facilities

PROCEDURE

  • After removing all metal objects, the client lies on a padded stretcher that slides into tunnel like chamber
  • Place the head in a plastic helmet like structure
  • Place the arms at the side of the X-ray table is the rolled several feet into the scanner
  • The patient is placed in a strong magnetic field up to 40,000 times stronger than the earth’s magnetic field and is then subjected to precise, computer programmed bursts of radiofrequency waves
  • The client feels nothing and hears only loud noises caused by the pulsating radiofrequency waves the resemble a Jackhammer or drill which lasts about a few minutes

AFTER CARE

  • Ask the patient to get up slowly, it the client may feel dizzy provide bed rest
  • Check the vital signs and record it
  • Assess the allergic reactions if dye administered
  • For clients who had MRI under general anesthesia kept fasting for 3-4 hours and IV fluids to be given

ADVANTAGES OF MRI

  • Does not expose the client to radiation because it is non-ionizing radiation
  • Results are obtained rapidly
  • Multisectional imaging
  • It is safe even contrast dye is used
  • Cost affordable when comparing with other invasive surgical procedures
  • Provides tissue characterization and blood flow
  • Provides clear images of moving organs
  • Helps to detect disorders that cause loss of myelin from nerve such as multiple sclerosis

DISADVANTAGES

  • Long imaging time
  • Many protocol options
  • Correct choice of machine parameters essential
  • Poor bone and calcium detail
  • Not available in all areas
  • Difficult to manage and monitor patients who are critically ill

CONTRAINDICATIONS

  • Clients with pacemaker are contraindicated
  • Cannot use in clients who are extremely obese
  • Cannot use in clients with metal implants
MAGNETIC RESONANCE IMAGING – Definition, Purpose, Principle, Instruction, Preparation of the Client, MRI Equipment, Procedure, After Care, Advantages of MRI, Disadvantages and Contraindications
MAGNETIC RESONANCE IMAGING – Definition, Purpose, Principle, Instruction, Preparation of the Client, MRI Equipment, Procedure, After Care, Advantages of MRI, Disadvantages and Contraindications

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