Magnetic Resonance Imaging (MRI) Flashcards
A moving electric field will set up a magnetic field around it
electro-magnetic induction
Charged subatomic particles (i.e. protons) will have a spin or wobble which create a
magnetic dipole moment
A magnetic field can cause a change in the direction of ___________.
the spin of hydrogen nuclei
Relaxation of the hydrogen molecules upon turning off magnetic fields will produce _______.
RF waves
the time that it takes the nuclei to recover from longitudinal magnetism
T1
the time that it takes to recover from transverse magnetization
T2
__________ are given off are recorded and analyzed by a computer to produce MR image
RF signals
A circular main magnet produces a strong homogeneous field of _______Tesla with super-conducting coils, cooled with liquid helium
.5 -3 Tesla
___ sets of gradient coils installed inside the bore of the main magnet produce magnetic field gradients in 3 dimensions (x, y and z, which is in the direction of the main magnet)
3
it improves the visibility of inflammation, tumors, blood vessels and, for some organs, blood supply.
Gadolinium contrast
weighted images display the tumor and edema as a low signal or dark area
T1
weighted images display the tumor and edema as a high signal or bright area
T2, T2 = H2O (water (ie. eyes) shows up bright in these datasets)
locations with large amounts of free water, produce a ____ signal, whereas bone emits a very ____ signal.
strong, weak
Different _____ create images with different contrast that are useful for viewing different anatomy.
pulse sequences
higher field strength =
larger field of view (FOV) =
greater distance from center =
increased geometric distortion
imaging for accurate positioning prior to treatment
Interfractional imaging
real-time images throughout an entire treatment and automatic beam off when target moves out treatment field
Intrafractional treatment
Dose prediction based on treatment plan and tumor location. Plan adaptation tools will reoptimize the plan based on tumor and critical structure location
Adaptive optimization
The vendor with this patent and currently the only MRI combined Treatment Machine is
ViewRay.
both currently testing a linear accelerator that is specifically designed to interface with an MRI unit with no interference.
ViewRay and Elekta/Philips
These 3 sets of ___________ are what turn on and off when patients hear load banging noises
gradient coils
