Chapter 9 Questions Flashcards
the magnetic property which results in a -1 susceptibility is
a. diamagnetic
b. paramagnetic
c. ferromagnetic
a. diamagnetic
an element which has unpaired electrons will have which of the following magnetic properties
a. diamagnetic
b. paramagnetic
c. ferromagnetic
b. paramagnetic
gadolinium is an example of an element which is
a. diamagnetic
b. paramagnetic
c. ferromagnetic
b. paramagnetic
when used as a mr contrast agent, gadolinium is injected
a. as an ionic compound
b. a chelate
c. a oxymethal compound
b. a chelate
the mass of an atom represents
a. the # of neutrons in the nucleus
b. the # of protons in the nucleus
c. the # of protons and neutrons in the nucleus
c. the # of protons and neutrons in the nucleus
the magnetic field of the hydrogen proton is known as
a. the magnetic moment
b. the gyromagnetic ratio
c. the dipole field
a. the magnetic moment
the spin value for hydrogen is
a. 1/3
b. 1/4
c. 2
d. 1/2
d. 1/2
when placed in an externally applied magnetic field, hydrogen protons will assume
a. 1 of 2 spin states
b. 1 of 3 spin states
c. a low energy spin state
a. 1 of 2 spin states
hydrogen protons in the low energy spin state are said to have their magnetic moment
a. aligned against the direction of the external magnetic field
b. perpendicular to the direction of the external magnetic field
c. aligned with the direction of the external magnetic field
c. aligned with the direction of the external magnetic field
which of the following external fields will result in the greatest energy difference between the high and low energy states
a. .5 T
b. 1.0 T
c. 1.5 T
d. 3.0 T
d. 3T
the human body is approximately 80%
a. water
b. fat
c. carbon
d. phosphorus
a. water
within a few seconds of being placed in a magnetic field, the hydrogen protons reach a condition known as
a. steady state
b. complete saturation
c. thermal equilibrium
c. thermal equilibrium
increasing the strength of the external magnetic field increases the number of protons in
a. high energy state
b. low energy state
c the tissues being imaged
b. low energy state
increasing the strength of the external magnetic field will result in
a. greater tissue magnetization
b. less spins the low energy state
c. shorter exam times
a. greater tissue magnetization
the gyromagnetic ratio for hydrogen is
a. 63.8 MHz/T
b. 42.6 MHz
c. 42.6 MHz/T
d. 63.8 MHz
c. 42.6 MHz/T
the resonant or precessional frequency of hydrogen when placed in an externally applied magnetic field can be calculated using
a. ernst angle equation
b. faradays law of induction
c. larmor equation
c. larmor equation
increasing B0 results in an increase in
a. gyromagnetic ratio
b. steady state
c. the resonant frequency
c. the resonant frequency
which of the following will exhibit the highest resonant frequency due to chemical shift
a. water based protons
b. fat based protons
a. water based protons
chemical shift at all field strengths is
a. 224 Hz
b. 448 Hz
c. 3.5 ppm
d. 42.6 ppm
c. 3.5 ppm
the process by which the magnetic field is made as homogeneous as possible is known as
a. shimming
b. ramping
c. shielding
a. shimming
at thermal equilibrium the individual magnetic moments of the hydrogen protons do not precess in phase primarily due to
a. the magnetic field strength utilized
b. the particular gyromagnetic ratio
c. inhomogeneities and chemical shift
c. inhomogeneities and chemical shift
when using 3D graphs to illustrate the oreitnation of the net magnetization vector of the tissues, magnetization along the direction of the externally applied magnetic field is said to be in the ______axis.
a. x
b. y
c. z
c. z
the only magnetization which can be detected or measured is
a transverse
b longitudinal
c out of phase
a transverse
B1 and B0 must be _____ to each other
a. parallel
b. perpendicular
c. anti-parallel
b. perpendicular
the frequency range of RF used in MRI at 1.5 T is close to that of
a. am radio
b. cell phones
c. FM radio
d. gamma rays
c. FM radio
in most clinical situations, the RF is tuned to the frequency of
a. water
b. fat
c. between water and fat
a. water
MR signals are created in the receiver coil according to
a. the larmor equation
b. the ernst angle equation
c. faradays law of induction
c. faradays law of induction
