MRI Flashcards
(15 cards)
What is MRI
MRI is an interaction between an external magnetic field, radio waves and hydrogen nuclei in the body
Define Longitudinal Magnetisation
When the net magnetisation is parallel to the Z axis of the external magnetic field at equilibrium
What is Resonance
Additional energy in the form of a radio wave is applied which causes the magnetic vector to be deflected
What is the LARMOR equation
The radio frequency that causes the hydrogen nuclei to resonate and is dependent on the element and the strentgh of the magnetic field
Describe how MRI images are obtained
- Placing the patient in a powerful, highly uniform, static magnetic field
- Magnetised protons within the patient align like small magnets in this field
- RF pulses are then applied which result in state of excitation
- As the nuclei returns from excitation, an analogue signal induced in the receiver coil of the instrument by the nuclear magnetisation can then be transformed into digital images
State the key components of the MR system
- Large Magnet
- Gradients
- RF Subsystem
- Computer
- Table and Ancillary Equipment
- Coils
What is the function of the coils in the MR system
- Pick up signals coming from the patient
What are specific body part coils used for?
Transmit RF pulses or receive the MR signal coming back from the patient
Do coils transmit only or receive only?
Coils can both transmit only and receive only
What are clinical applications of MRI
- CNS for Brain and Spine
- Musculoskeletal and Sport Injuries
- Oncology
- Cardiology
- Abdomen and Pelvis
What should policies and procedures should radiographers know?
- Local Rules
- Controlled Areas
- Authorisation
State what safety issues the radiographer should be aware of before starting the scan?
- Pacemakers
- Implants
- Claustrophobia
- Screening prior to Scanning
- Biological Effect
- Projectile Effect
Define MR Safe
Means that the device posses no risk to the patient in the MR environment as image quality may be affected
Define MR Conditional
Means that the device poses no additional risk to the patient when introduced to the MR environment under specified conditions
Define MR Unsafe
Means that the device may not be introduced into MR environment as it posses significant risk to the patient and/or staff
