physics quizzes Flashcards
When the RF pulse is applied the Net Magnetic Value Vector Flips into the ________plane
Transverse
Once the RF pulse is removed Mo realigns to Bo and the created transverse magentization decays.
true
The F.I.D. can be defined as. (Select all that apply)
A. Signal after the R.F. pulse is removed
B. Primary signal
C. Dephasing Hydrogen Protons
In order for resonance to occur the RF Pulse needs to match the exact precessional Frequency of Hydrogen Atoms
True
In the presence of a Magnetic Field a spinning proton
Precesses
This signal is the intial signal recieved after the 90 degree excitation pulse.
F.I.D.
Transverse Magnetization decreases after the intial excitation pulse is removed
True
When Hydrogen Atoms are termed In Phase it refers to the precessing magnetic moments being
On the same point in their Precessional Path
A moving charged particle induces a magnetic field in a plane parallel to its motion
False
A unit of electrical charge is measured in
Coulomb
Control of TE is exercised by control of
T2 relaxation time
Free Induction decay is ad RF wave that is emitted from the patient
True
In order for resonance to occur what has to happen
Precessional Frequency and RF pulse must match
T1 and T2 times occur at the same time
True
T1 is also termed
Longitudinal Relaxation
T2 is also termed
Transverse Relaxation
The Fourier Transform of the FID results in a nuclear magnetic spectrum which is in the frequency domain
True
The induced signal from the patient decreases with time as the proton spins relax
True
The time between the initial 90 degree pulse and the Peak signal is called
TE
The time from the initial 90 degree RF pulse to the next RF pulse is termed?
repition time
In phase is also called?
coherent
Phase is measured in____________
radians of degrees
—Frequency is the unit of occurrence or frequency and is measured as Hertz (Hz).
true
Hydrogen Nuclei start to Recover back to Bo or the Longitudinal Plane, they are now Out of Phase
true
—T1 recovery(spin lattice relaxation) is the relaxation time for 67% of the Net magnetization of the tissue to recover.
false
—The T2 relaxation time is the time it takes for tissue to decay in the transverse plane to 37% (or 63% to be lost)
true
The time from the initial 90 degree RF pulse to the next RF pulse is termed?
repition time
Know as the father of MRI
felix bloch
When the protons return to their “normal” state in the longitudinal plane (Z) after being excited by the RF pulse this is called.
equilibrium
The 90 degree RF pulse is also called the ______________.
flip angle
Number of Protons in the Nucleus is termed.
Atomic Number
In the presence of a Magnetic Field a spinning proton
precesses
At 1 Tesla the gyromagnetic ratio of hydrogen is
42.57 Mhz
A Vector is a quantity that has
magnitude and direction
When a patient is subjected to a strong magnetic field the patient becomes polarized and has
Net Magnetization
Precession Frequency depends on what factor(s)
Type of atoms nucleus.
Strength of Bo
Who is considered by most to be the father of MRI
Felix Bloch
Once the Hydrogen nuclei are subjected to a external magnetic field they start to__________.
Wobble
Line up with or against the field
Precess
A Magnetic Field is created when (select two)
A charged particle moves
Current is moving along a path of wire
Hydrogen contains its own large magnetic moment due to the odd number of Protons in the Nucleus
True
With no exposure to a Magnetic Field, Magnetic moments are randomly situated
True
Once a Magnetic Moment is exposed to an external Magnetic Field it will line up with or against the external field.
True
Spin up Nuclei contain energy that are
low
Spin down Nuclei contain energy that is
high
Net Magnetization Vector (N.M.V.) is the result of
A battle between Spin Up and Spin Down Nuclei
In order for resonance to occur the RF Pulse needs to match the exact precessional Frequency of Hydrogen Atoms
True
Once a Magnetic Moment is exposed to an external Magnetic Field it will line up with or against the external field.
true
This signal is the intial signal recieved after the 90 degree excitation pulse.
FID
When Hydrogen Atoms are termed In Phase it refers to the precessing magnetic moments being
On the same point in their Precessional Path
In order for resonance to occur the RF Pulse needs to match the exact precessional Frequency of Hydrogen Atoms
True
Precessional Frequency of any atom that meets the criteria for MRI, we must know what two things.
The gyro magnetic ratio of that atom at 1 T
Strength of Bo
The F.I.D. can be defined as
Signal after the R.F. pulse is removed
Primary signal
Dephasing Hydrogen Protons
Once the RF pulse is removed Mo realigns to Bo and creates magentization decays
True
