MRI - PRELIM L2 Flashcards
The dense, central core of an atom, containing nearly all
of its mass.
Atomic Nucleus
Fill in the blanks with their corresponding charges:
Protons:
Neutrons:
Electrons:
Protons: Positive Electric Charge
Neutrons: Neutral Charges
Electrons: Negative Electric Charges
The Nucleus is made up of ______ and ______, held together by the ______
- Protons
- Neutrons
- Strong Nuclear Force
Electrons orbit the nucleus in regions called _______
Electron Shells / Orbitals
Many of the electron spins align in the same direction, creating a stronger overall magnetic field such as in magnetic materials like _____
Iron
TRUE OR FALSE
Electrons balance the positive charge of protons, keeping the atom electrically neutral
TRUE
In most materials, the magnetic fields of individual atoms cancel out because they point in _________
Random Directions
This comes from the motion of charged particles
(especially electrons) inside atoms.
Magnetism
Electrons have a property called _______ which generates tiny magnetic fields
Spin
The proton has a spin of
1/2
Proton Spin is a _______ that does not correspond to literal spinning in space but rather to a form of _______
- Quantum Mechanical Property
- Intrinsic Angular Momentum
Refers to a fundamental property of protons (and other elementary
particles) related to their intrinsic angular momentum
Proton Spin
It provides a mathematical way to determine the frequency at which a charged particle precesses in a magnetic field
Larmor Relationship
TRUE OR FALSE
When subjected to a strong magnetic field, electrons in the body align and then release energy when they return to their original alignment, which is detected to form images.
FALSE
When subjected to a strong magnetic field, PROTONS in the body align and then release energy when they return to their original alignment, which is detected to form images.
The time it takes for protons to return to their original alignment
with the magnetic field after being disturbed by an RF pulse by the
interaction energy with their surrounding environment
T1 Relaxation Time
The motion of protons as they wobble around the magnetic field after being disturbed by the RF pulse.
Precession
The wave character of
electromagnetic radiation but it is basically equivalent to the
wavelength since the wavelength is just the speed divided by the frequency and the speed of light is a constant.
Radiofrequency
Motion of nuclear spins in a magnetic field when there is no external influence, such as a radiofrequency (RF) pulse, acting on them
Free Precession
Frequency of precession is called as ________
Larmor Frequency
The uniformity and synchronization of the precessional
motion of protons (or other nuclei) in response to an applied magnetic field
Phase Coherent
MRI images are made with RF in the range from _________
Approximately 10 to 300 MHz
After the protons align with the magnetic field, short RF pulse (a burst of electromagnetic energy) is applied at a specific frequency, this is hence the ________
Larmor Frequency
When all protons are precessing in phase, the signal they emit is _______ and ______ to detect.
Stronger and Easier
The time constant that describes when a signal decreases with
time as the proton spins begin to lose phase coherence or diphase
Relaxation Time
The Relaxation Time is the period it takes for protons to return to their _______ after being disturbed by an RF pulse
Equilibrium State
The time it takes for protons to lose phase coherence in the transverse plane after the RF pulse is turned off.
T2 Relaxation Time
T1 is important for creating contrast between tissues in T1-weighted images, where tissues with a shorter T1 (like fat) show up _______ and tissues with Longer T1 (like Water) show up ______
Shorter T1 = Brighter
Longer T1 = Darker
T1 Relaxation Time may also be known as _______ or ______
- Spin-Lattice Relaxation Time
- Longitudinal Relaxation Time
T2 is crucial for creating contrast in T2-weighted images, where
tissues like water (which has a longer T2) appear _______, and tissues like fat (which have a shorter T2) appear _______
Shorter T2 = Darker
Longer T2 = Brighter
T2 Relaxation Time may be also called as _______ or _______
- Spin-Spin Relaxation Time
- Transverse Relaxation Time
RELAXATION SPEED
T1 is ________ than T2 whereas T2 is _______ than T1
- Generally Slower
- Generally Faster
T1 is important for showing ______ vs _____
Fat vs Water
Tissues like muscle (which has a relatively high _____ ) will appear _____.
- Proton Density
- Darker
The concentration of magnetic nuclei
(typically protons) that are available to contribute to the MR signal. Essentially, it refers to the number of protons in a given tissue volume that can be detected during an MRI scan
Spin Density
T2 is important for showing ______ or ______
Edema or Inflammation
Fat or bone (which has a _____ proton density) will appear _______
- Lower
- Darker
