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ARRT MRI registry review program
(400 Questions and Answers).
An RF pulse of what flip angle will maximize the component of the net magnetization projected into the transverse plane? a. 180 b. 120 c. 90 d. 45 - Correct answer c. T1 relaxation refers to ____ relaxation. a. spin-spin b. longitudinal c. phase d. transverse - Correct answer b. Which of the following statements is false? a. T1 relaxation refers to longitudinal recovery of magnetization while T relaxation refers to the transverse decay of magnetization b. T1 relaxation and T2 relaxation occur simultaneously c. echoes collected in the transverse plane demonstrate only T2 relaxation differences d. T2 relaxation occurs much more quickly than T1 relaxation - Correct answer c. If the precessional frequency of the patient's protons is approximately 21 MHz, what magnetic field strength is being experienced by the patients protons? - Correct answer Larmor frequency equation W0= B0 x Y 21= 42.6 x (X) 21/42.6 = .4929 (round) = 0.5T
Which of the following is the definition of T1 relaxation? a. the time is takes the net longitudinal magnetization of protons to grow 63% of its final amplitude b. the time at which is takes the transverse magnetization has decayed 63% of its full value - Correct answer a. Based on the graph of longitudinal relaxation shown above, which of the following would have the brightest signal intensity on T1 image? a. bone marrow b. intervertebral disk c. CSF d. muscle (post test 1; page 1) - Correct answer a. Based on the graph of longitudinal relaxation shown above, which of the following would have the shortest T1 relaxation time? a. bone marrow b. intervertebral disk c. CSF d. muscle (post test 1; page 1) - Correct answer a. The edema associated with pathology in the brain has a much longer T relaxation time than surrounding normal brain tissue. On a T2 image, what does this result in? a. isointense between edema and surrounding normal brain tissue b. a low signal intensity in the area of edema c. a signal void in the area of edema d. a high signal intensity in the area of edema - Correct answer d. Which of the following dephasing mechanisms affects the size of the resulting spin echo?
b. more protons align against the main magnetic field than with the main magnetic field c. equal numbers of protons align against the main magnetic field d. all of the protons line up perpendicular to the main magnetic field - Correct answer a. On a T2 image, CSF appears bright because it has a ____ relaxation time. a. long T b. short T2 - Correct answer a. The precessional frequency of the net magnetization of protons in a magnetic field is determined by which of the following? a. the T1 relaxation times of the protons b. the gyromagnetic ratio and field strength c. the repetition time and the echo time d. spin-lattice relaxation - Correct answer b. The RF pulse should be transmitted at a frequency of approximately ____ MHz in order to disturb protons experiencing a 4 T field. a. 190 b. 180 c. 170 d. 42.6 - Correct answer c. Referring to the figure below, if the main magnetic field is aligned along the z-axis, which of the following corresponds to the correct orientation of the transverse plane? a. y-z b. x-z c. x-y d. a plane that divides the patient's L/R side (post test 1; page 2) (standard x, y, z patient coordinates- horizontal) - Correct answer c.
Which of the following is NOT a requirement for magnetic resonance imaging? a. atomic nuclei with an odd number b. a strong magnetic field c. ionizing radiation d. RF energy - Correct answer c. Referring to the figure below, if the main magnetic field is aligned along the y-axis, which of the following corresponds to the correct orientation of the transverse plane? a. y-z b. x-z c. x-y d. a plane that divides the patient's L/R side (post test 1; page 2) (standard x, y, z patient coordinates- horizontal) - Correct answer b. What is the phenomenon called in which one proton transfers energy to another? a. precession b. rephasing c. spin-spin interactions d. echo time - Correct answer c. Which of the following parameters controls the amount of contrast seen in an image due to T2 relaxation? a. TR b. TE c. TI d. TM - Correct answer b. What is the time from the initial RF excitation pulse to the next RF excitation pulse for a given slice called? a. TE
a. one b. three c. five d. six - Correct answer a. Using a spin-echo pulse sequence which generates two echoes, imagine a hypothetical tissue in which protons never experience spin-spin interactions. How does the signal from the first echo compare to the signal from the second echo? a. its frequency is higher b. its frequency is lower c. its the same size d. it is smaller in size - Correct answer c. What is the time from the 180 RF pulse to the echo? a. TE b. TR c. 2.0 x TE d. 0.5 x TE - Correct answer d. TE/ TAU Which of the following dephasing mechanisms is NOT rephased by a 180 RF pulse? a. magnetic susceptibility b. phase effects of a chemical shift c. spin-spin interactions d. magnetic field inhomogeneities - Correct answer c. Which of the following parameters controls the amount of contrast seen in an image due to T2 relaxation? a. TI b. TR c. TM
d. TE - Correct answer d. The effect of an IV. administered paramagnetic contrast agent used in MRI is a shortening of a T1 relaxation time of the protons within any perfused tissue. A vascular lesion would appear ____ on a T1-W contrast-enhanced image as compared to its appearance on a T1-W unenhanced image. a. the same b. darker c. as a signal void d. brighter - Correct answer d. In a given MR system, the magnetization of protons within the patient precesses at 63.83MHz. Without the interference of any other system component, what is the expected result if the RF energy is applied at a frequency of 63.83 MHz? a. only the patient's protons in a sagittal slice will be disturbed by the external energy b. all of the patient's protons within range of the transmitting antenna will be disturbed by the external energy c. none of the patient's protons would be disturbed by the external energy d. only the patient's protons in a transverse slice will be disturbed by the external energy - Correct answer b. If the field strength experienced by a patient within an MR magnet is increased, the precessional frequency of the magnetization of the patient's protons will: a. increase b. reverse its spin direction c. remain unaffected d. decrease - Correct answer a. The energy used to form MR images is ____ the patient's tissues. a. attenuated by b. magnified by c. reflected off of d. released from - Correct answer d.
During a six minute scan, when is the data used to form the lower third of the image collected? a. during the first 2 minutes b. during the middle 2 minutes c. during the last 2 minutes d. throughout the entire scan - Correct answer d. Using a traditional pulse sequence, which of the following is FALSE regarding a single echo? a. it contains the anatomical information from a specific line of the resulting image b. it is decoded by Fourier Transform c. it is accumulated within the raw data file d. it represents the information acquired within the TR period for a single slice - Correct answer a. Along what direction are motion artifacts always seen? a. along the phase direction of the image b. along the frequency direction of the image - Correct answer a. Along what direction are chemical shift artifacts always seen? a. along the phase direction of the image b. along the frequency direction of the image - Correct answer b. In order to disturb the proton in a particular location of the body, what must the frequency of the RF energy be? a. 63 MHz b. matched to the precessional frequency of the patient's protons at that location c. matched to the precessional frequency of the patient's protons which are exposed to the main magnetic field - Correct answer b. Which physical gradient must be used for slice selection in order to produce a coronal image?
a. y b. x c. x and z together d. z - Correct answer a. Which physical gradient could be used for phase encoding in a sagittal image? a. x or y b. only the x c. y or z d. x or z - Correct answer c. A positive change in frequency by an equal negative change in frequency, both for the same duration, will ____ the net phase of stationary protons. a. triple b. double c. halve d. have no effect on - Correct answer d. 4th relationship Which of the following is a linearly varying magnetic field? a. radio frequency b. Fourier Transform c. a gradient d. raw data - Correct answer c. Which physical gradient must be used for slice selection in order to produce a sagittal image? a. y and z together b. y c. z d. x - Correct answer d.
The frequency encoding gradient must be turned on during which of the following events? a. phase encoding b. spin-spin interactions c. application of RF pulse d. readout of the echo - Correct answer d. Which of the following statements is FALSE? a. gradients are responsible for ensuring that all of the protons in the body simultaneously receive the RF energy b. gradients cause the precessional frequency of protons to vary with position c. gradients applied in an equal but opposite fashion can ensure that phase will not accumulate d. gradients linearly vary the magnetic field - Correct answer a. Decreasing the slice select gradient amplitude will have what affect on the resulting slice if the RF transmitter bandwidth is held constant? a. change the orientation of the slice b. change the angle of the slice c. increase slice thickness d. invert the phase and frequency directions - Correct answer c. If the z-gradient is applied, which of the following statements is TRUE regarding a patient's protons? a. those in the patient's left hand precess at a different frequency than those in the patient's right hand b. those in the patient's left ear precess at a different frequency than those of the patient's right knee c. those located anteriorly in the patient's head precess at a different frequency than those located more posteriorly in the patient's head - Correct answer b. On a coronal image, if frequency encoding is accomplished with the z- gradient, which physical gradient is used for phase encoding?
a. y b. y and z together c. x d. x and z together - Correct answer c. On a sagittal image, which logical gradient is assigned to the x-gradient? a. phase encoding b. the readout gradient c. frequency encoding d. slice select - Correct answer d. The phase encoding gradient must be turned on during which of the following events? a. prior to echo collection, but the exact timing isnt critical b. readout of the echo c. application of the RF energy d. frequency encoding - Correct answer a. What effect will an applied gradient have on a population of stationary in- phase protons within a 10cm sphere at the center of the magnet? a. it will have no net effect on the plane b. it will move the magnetization of protons into the longitudinal direction c. it will move the magnetization of protons into the transverse plane d. it will increase the phase dispersion - Correct answer d. Which of the following is contained within a single spin echo? a. the anatomical information from a specific line of the resulting image b. many frequencies c. the anatomical information from all of the images in the scan d. many phases - Correct answer b. If a population of protons moves through some distance during the time the echo is being sampled, what will be the appearance of the resulting image, provided that the gradients are operating properly for a simple spin echo pulse sequence?
- calculate nominal precessional frequency 42.56 MhZ x 0.2T = 8.512 MhZ/T
- effect of gradient shift 8.62 - 8.512 = 0.108 MhZ .108 MhZ = 42.56 MhZ/T = 0.0025 T x 1000 = 2.5 mT (larmor frequency)
- distance from center 7mT/m = 2.5 mT = 0.35 m x 100 = 35.71 cm Which of the following gradients is NOT balanced for phase? a. slice select b. frequency encoding c. readout d. phase encoding - Correct answer d. In a 1.0T MR system, which of the following statements is FALSE regarding the RF energy if no gradient is applied while a 42.56 MHz 90 RF pulse is being transmitted?
- it will be absorbed by all protons in the range of the transmitting antenna
- it will be absorbed by only the protons at the center of the magnet
- it will cause all protons in the range of the transmitting antenna to generate transverse magnetization a. 1 only b. 2 only c. 3 only d. 1, 2, and 3 - Correct answer b. Which of the following is TRUE regarding the Fourier Transform? a. it calculates the amount of energy absorption experienced by each tissue and generates the final image
b. it separates the phase and frequency components corresponding to each point of anatomy in the image plane c. it produces the RF energy for the 90 RF pulse - Correct answer b. Which of the following is NOT an essential part of localizing the MR signal generated during an MR study? a. moving the patient within the magnet to ensure only the center slice is imaged b. using the FT to separate the phase and frequency components corresponding to each point of anatomy in the image plane c. transmitting a selective range of radio frequencies d. applying linear gradients along the three dimensions of the magnet - Correct answer a. A given MR system claims its maximum gradient amplitude is 30 mT/meter. Imagine an ideal case in which the field strength at all points inside the magnet is 1.500T. If a pulse sequence drives the x-gradient to its maximum amplitude, the field strength at a point which is centered along the x- direction and displaced one meter toward the positive direction is ____ Tesla. a. 1. b. 1. c. 1. d. 1.500 - Correct answer d. If a population of protons moves through some distance during the time the 90 RF pulse is applied, what will be the appearance of the resulting image, providing that the gradients are operating properly for a simple spin-echo pulse sequence? a. artifacts will appear in the phase encoding direction b. artifacts will appear in the frequency encoding direction c. image is unaffected d. image will be inverted - Correct answer a. Which gradient will make the precessional frequency of the magnetization of protons in the patient's left eye different than that in the patient's right heel?
a. the superconducting windings must be maintained at a temperature approaching absolute zero b. there must be at least 25 turns of the superconducting windings c. the magnetized ceramic bricks must be oriented so that their magnetic fields face in the same direction d. the magnet room must have air conditioning - Correct answer a. If a voltage source was connected to a solenoid, so that the current flowed as in the diagram below, how would a magnetic field be generated? a. to the left b. no magnetic field would be generated c. in the same direction as the current is flowing d. to the right (post test 3; page 8) - Correct answer d. The purpose of the shims is to: a. keep RF energy used in scanning from interfering with the external enviroment b. contain the magnetic field c. linearly vary the magnetic field along the axis of the magnet d. make the main magnetic field more uniform - Correct answer d. The purpose of the magnetic shielding is to: a. linearly vary the magnetic field along b. keep the RF energy used in scanning from interfering with the external environment c. keep the stray radio signals in the environment from creating artifacts in the MR images d. keep the fringe field magnetic field closer to the magnet - Correct answer b. The correct location of the z-gradient coils in a superconductive MRI system is wrapped ____ a cylinder within the bore of the magnet. a. in a spiral fashion around b. completely around each end of
c. on the top and bottom of - Correct answer b. Which of the following is affected by the transmitter bandwidth? a. FOV of the image b. severity of chemical shift artifact in the image b. orientation of the image d. the slice thickness - Correct answer b. Which of the following MRI system components is responsible for the timing and correct performance of each component once the sequence has been started? a. MR controller b. pulse sequence controller c. host computer - Correct answer b. Which of the following describes the operational mechanism of an electromagnet? a. magnetized ceramic bricks are stacked together so that their magnetic fields point in the same direction, generating a strong magnetic field b. a population of small magnets wobbles at a specific frequency, generating a strong magnetic field c. a power supply is connected to the ends of a coil of long wire, generating a strong magnetic field - Correct answer c. Gradient rise time is defined as which of the following? a. the time required for a gradient to reach its specified amplitude, beginning from resting state b. the time a gradient maintains its maximum amplitude c. the time the current is applied to a gradient coil d. the time to install a gradient - Correct answer a. Which of the following describes the percentage of time that a gradient is applied to a specific amplitude? a. gradient rise time b. gradient amplitude
