prac qs Flashcards
The nucleus of an atom has a_____ charge
Positive.
Presence of proton
The electrons orbit the nucleus in regions called___
Electron shells or orbitals.
Most of the mass of an atom resides in the___
Nucleus.
If the atom has an equal number of protons and electrons, the atom is said to be electrically___
Neutral.
Magnetism comes from the motion of charged particles inside atoms. Electrons have the property of____
Spin.
When spins of the atoms cancel out each other, or when they are randomly aligned, their spin is directed at___
Random directions.
Some materials like _____ have electron spins align in the same direction, creating stronger overall magnetic field.
Iron.
____ refers to a fundamental property of protons related to their intrinsic angular momentum
Proton Spin.
The spin of an atom is a quantum mechanical property that corresponds to literal spinning in space (T or F)
F.
proton spin is a form of intrinsic angular momentum, not a literal, physical rotation.
A proton has a spin of ___
1/2.
MRI observes the spin of _____ molecules in the human body using the principle of proton spin
Hydrogen atoms. Hydrogen nuclei.
This describes the connection bet. The Larmor Frequency and magnetic field strength. A mathematical way to identify how a charged particle precesses in a magnetic field.
Larmor relationship.
Refers to the motion of protons as they wobble around the Bo (Magnetic field) after being disturbed by the RF pulse?
Precession.
This is known as the frequency of precession.
Larmor Frequency.
A proton, when aligned in a magnetic field, is disturbed by____. Then, the atom releases energy at the same frequency.
Radiofrequency Pulse.
MR images are made with RF in the range from approx.
10-300MHz.
After a short RF pulse is applied at a specific frequency, which is called ____, which depends on the strength of magnetic field. The RF pulse tips the protons out of alignment with the Bo (magnetic field)
Larmor frequency.
Refers to the uniformity and synchronization of the precessional motion of protons (or other nuclei) in response to an applied Bo
Phase Coherent.
When all protons are precessing in phase, the signal they emit is weaker and more difficult to detect. (T or F)
F.
It is stronger and easier to detect. Bo produced by spinning atoms can add up, amplifying overall signal.
This is the motion of nuclear spins in a Bo (magnetic field) when there is no external influence, such as RF pulse, acting on them
Free precession.
For the following numbers, answer if it is phase coherent or free precession: Spins initially start in sync but lose coherence over time?
Free precession.
Strong signal due to synchronized spins
Phase Coherent.
Signal diminishes as spins lose phase coherence (FID)
Free precession.
Spins are in sync, maintaining consistent phase.
Phase Coherent.
Occurs immediately after the RF pulse, while spins are aligned
Phase coherent.
Key for generating a strong initial signal
Phase coherent.
Occurs after the RF pulse ends, where spins precess naturally.
Free precession.
Key in measuring the decay of coherence and relaxation times (T2)
Free Precession.
Time constant that describes when a signal decreases with time as the proton spins begin to lose phase coherence or diphase?
Relaxation time.
Two main types of relaxation time?
T1 (longitudinal; Spin-lattice) and T2 (transverse; Spin-Spin).
It refers to the time it takes for protons to return to their equilibrium state after being disturbed by RF pulse.
Relaxation time.
Lattice refers to____
Interaction energy with the surrounding environment.
T1 relaxation time is also known as___
Longitudinal relaxation time or Spin-Lattice Relaxation time.
T1 is important for contrast between tissues in T1-weighted images. T1 short (fat) appears___. T1 long (water) appears___
Brighter and Darker, consecutively.
(So FaBulous: Short, Fat, Bright) (LeWD: Long, Water, Dark)
Other names for T2 relaxation time?
Transverse Relaxation Time. Spin-spin Relaxation Time.
T2 is crucial for creating contrast in T2-weighted images where Longer T2 (water) appears____ and shorter T2 (fat) appears___
Brighter and Darker, consecutively.
Reverse of LAST MNEMONICS in T1.
Time it takes for protons to lose phase coherence in the transverse plane after the RF pulse is turned off.
T2.
For the following numbers, identify if it is T1 or T2: Time for protons to lose coherence in transverse plane
T2.
In Process, this is the energy exchange with surrounding lattice (tissue environment)
T1.
Time for protons to realign in longitudinal plane or Bo (magnetic field)
T1.
Shorter ___ (Fat) tissues are brighter. (So FaBulous)
T1.
Tissues with longer___ (water) are brighter. Clue: (reverse of mnemonics: So FaBulous and LeWD)
T2.
Dephasing due to interactions between spins.
T2.
Generally faster
T2.
Generally slower
T1.
Important for showing fat vs water
T1.
Important for showing edema or inflammation
T2.
Term used to describe the concentration of magnetic nuclei (protons) available to contribute to the MR signal. Refers to the number of protons in a given tissue that can be detected.
Spin density.
Spin density is closely related to ___
Proton density.
(in MRI the signal is primarily generated by hydrogen nuclei)
This determines the energy levels of the nucleus in an external magnetic field, which can be detected and used to gather information about the environment around the nucleus
Nuclear Spin.
Spin density plays a significant role in the overall image contrast of _____
Proton density-weighted images (PD-weighted images).
Muscles, in the context of proton density has___. Fat and bone, on the other hand have____.
Muscle: high proton density and appears brighter.
(mas maraming available water)
Fat and Bone: Low proton density and appears darker. (mas kakaunti ang water)
Refers to the intrinsic angular momentum of an atomic nucleus. Describes a property of nucleons inside the nucleus
Nuclear Spin.
It influences the behaviour of nuclei in magnetic fields.
____ nuclei have zero nuclear spin while ___nuclei have spin value of 1/2, 1, 3/2
Even number and Odd number.
Examples are (carbon-12, oxygen-16; hydrogen-1, nitrogen-15)
Law of physic states that a spinning, charged mass induces a ___ about itself
Magnetic field (Bo).
The Bo is given a special name of _____ and its intensity is related to the mass, charge, and rate of spin of the nucleus
Nuclear Magnetic Moment (NMM).
This is the ratio of magnetic moment to the angular momentum of a particle; constant for a given nucleus (MHz/T)
Gyromagnetic Ratio.
Non-zero spin has a _____ number of nuclei
odd.
During precession, the ____ is directly proportional to the gyromagnetic ratio.
Frequency.
(remember the formula)
Formula for Gyromagnetic Ratio (Y)
Y= u/J (Parang YuJi**).
Where: Y is gyromagnetic ratio, u is magnetic moment of particle, J is the angular momentum or spin of the particle.
Hydrogen has a gyromagnetic ratio (MHz/T) of ____
42.6.
Measuring the action of individual nuclei is possible (T or F)
F.
Impossible, signal is a result of a bulk phenomenon from as many as 10^26 nuclei or (1000000000000000000000000000).
The aggregate of spins (the bulk of nuclei) is sometimes called an____ to emphasize the bulk of the signal-producing nuclear spins.
Ensemble of spins.
The signal from a spin ensemble accurately reflects the behaviour of each individual nuclei, and thus the ____ can be used
Net Magnetization (Mz) or M=∑▒〖*u〗.
The process by which atomic nuclei are exposed to a strong magnetic field and then to a pulse of RF energy. This causes the nuclei to absorb the energy and ‘resonate’ at a specific frequency
Resonance.
The specific frequency at which this energy is absorbed by the nuclei is called the ____, which depends on the strength of Bo and the type of nucleus.
Resonance Frequency.
EMR produced by oscillator is called a
RF emission.
RF oscillating electric field is positioned ____ degrees to an oscillating magnetic field
90.
The RF pulse not in tuned to the nuclei’s larmor frequency can be used to detect signal (T or F)
F.
It must TUNED. If RF pulse is not at a specific frequency of a nuclei, the nuclei do not absorb the energy and the Mz (net magnetization) is not rotated.
Formula for Larmor Frequency?
F=YBo or f=BoY (F*ck Boy).
F= frequency of precession (MHz), Y= gyromagnetic ratio (MHz/T), Bo= is the strength of the external magnetic field (T).
The frequency of precession of a nucleus can be calculated with the ____
Larmor frequency equation.
Is a quantity that has direction
Vector.
Cartesian coordinate system has a space of ____ drawn perpendicular to one another
X, Y, and Z.
The parameters that affects the amplitude of the MR signal might be the ______within the sample volume
Number of hydrogen nuclei.
(Recall Spin density/Proton density)
Hydrogen has how many gyromagnetic ratio (MHz/T)?
42.6.
Muscle has a relative spin density of___
90.
Air has a relative spin density of
<1.
Which has more spin density, muscle or bone?
Muscle (because of the presence of MORE hydrogen nuclei).
After RF pulse excites the H nuclei, the nuclei release energy as they return to low-energy state. This is called?
Relaxation.
The relaxation of H nuclei emit RF signals at the same frequency they absorbed when they were flipped. This is called____
Signal Emission.
T1 relaxation time is parallel to ___
Magnetic field (Bo).
T2 relaxation time represents the loss of net XY magnetization. Loss of phase coherence in a plane ___to Mo
perpendicular to or transverse.
When nuclei are disturbed by RF pulse, the net magnetization of the atom is rotated and changed in magnitude, the nuclei realigns with the external Bo and return to equilibrium. The regrowth of net magnetization is the ____ process and represents the spin’s return to equilibrium.
T1.
Signal detection happening in T1 is also similar in ___ but the plane is perpendicular to or transverse to Mo, which lies along the Z-axis
T2.
