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MRI magnetism
| Question | Answer |
|---|---|
| What type of magnet is used with most MRI systems currently manufactured? A. Resistive B. Superconducting C. Permanent D. Refrigerator | Superconducting |
| What element in the body is the principal nucleus utilized in clinical MR imaging? A. Calcium B. Oxygen C. Helium D. Hydrogen | Hydrogen |
| The precessional frequency of hydrogen, according to the Larmor equation, at 3Tesla is: A. 42.57 MHz B. 63.86 MHz C. 127.71 MHz D. 220 MHz | 127.21 |
| A system operating at 30,000 Gauss has a field strength of: A. 0.3 Tesla B. 1 Tesla C. 1.5 Tesla D. 3 Tesla | 3 tesla |
| The protons that align themselves with the direction of the static magnetic field (B0) exist in a ___________energy state than those anti-parallel to the magnetic field. A. Aliased B. Lower C. Higher D. Chemical Shifted | Lower |
| ___________ substances have strong magnetic properties and can be pulled into the magnetic field. A. Wooden B. Paramagnetic C. Diamagnetic D. Ferromagnetic | Ferromagnetic |
| All of the following are non-ferrous substances EXCEPT: A. Plastic B. Titanium C. Iron D. Copper | iron |
| The first documented human MR image was obtained on a 15 MHz RF system, what field strength did it operate at? A. 0.352 Tesla B. 0.714 Tesla C. 1.264 Tesla D. 1.503 Tesla | .352 tesla |
| What is defined as the excess number of hydrogen protons aligned with the static magnetic field direction (B0)? A. Transverse magnetization B. TE C. Gyromagnetic ratio D. Longitudinal magnetization | Longitudinal magnetization |
| The energy used to form MRI images is ____________ the patient's tissues. A. Attenuated by B. Emitted from C. Amplified from D. Reflected off | Emitted from |
| The extent to which a material or tissue becomes magnetized in an external magnetic field is called: A. Magnetic inversion B. Contrast to noise ratio C. Tau time D. Magnetic susceptibility | Magnetic susceptibility |
| If the RF energy transmitted is __ MHz, the slice through the patient would be in a magnetic field of .995T. A. 42.36 B. 42.57 C. 63.86 D. 95.5 | 42.36 |
| _________ magnets can be “shut off” the quickest in case of an emergency. A. Permanent B. Superconducting C. Resistive D. Refrigerator | Resistive |
| The _________ is defined as the resonant frequency, and is equal to the product of the magnetic field and the gyromagnetic ratio. A. RF excitation pulse B. Precessional frequency C. Inversion recovery D. Presaturation pulse | Precessional frequency |
| ______________ is the term used to describe the degree of magnetization of an object. A. Susceptibility B. Fourier transform C. Radiofrequency D. Gradient | Susceptibility |
| A magnetic vector possesses attributes of both __________ and _____________. A. Strength; magnitude B. Direction; purpose C. Magnitude; direction D. Strength; flow | Magnitude and direction |
| Hydrogen is used in MR imaging because: A. It has an even atomic mass number B. Of its abundance in the body C. Of its detectability in the presence of ionizing radiation D. None of the above | Of its abundance in the body |
| Calculate the Larmor frequency for H at 0.5Tesla. A. 42.57 Mhz B. 63.86 Mhz C. 127 Mhz D. 21.28 Mhz | 21.28 |
| Hydrogen protons in the anti-parallel state are referred to as: A. Spin down B. Low energy spins C. High energy spins D. Both A and B E. Both A and C | D. Both A and C |
| Immediately following the application of the 90° RF pulse, the transverse magnetization is: A. Eliminated B. The same as longitudinal magnetization C. Non-zero D. Zero | Non-zero |
| In one T2 relaxation time: A. 63% of the transverse magnetization has decayed B. 63% of the longitudinal magnetization has decayed C. 37% of the longitudinal magnetization has decayed D. None of the above | 63% of the transverse magnetization has decayed |
| In one T1 relaxation time: A. 67% of the longitudinal magnetization has decayed B. 67% of the transverse magnetization has decayed C. 63% of the transverse magnetization has recovered D. 63% of the longitudinal magnetization has recovered | 63% of the longitudinal magnetization has recovered |
| A Free Induction Decay (FID) is produced from a: A. Flip angle B. Shim coil eddy current C. Image archive data cleanse D. RF pulse | RF pulse |
| When thermal equilibrium is reached: A. There are more hydrogen protons in the low energy state B. There are more hydrogen protons in the high energy state C. The low and high energy protons completely cancel each other out | There are more hydrogen protons in the low energy state |
| At 1.5 Tesla, the chemical shift between fat and water is: A. 63.86 Hz B. 100 Hz C. 220 Hz D. 440 Hz | 220 Hz (The chemical shift is approx 3.5 parts per million ) |
| Which of the following most accurately defines what Image 59 is? A. Metabolites detected in the VOI sampled B. Free Induction decay. FID C The decaying, oscillating signal induced after 90º pulse | Free induction decay. FID |
| Which of the following most accurately defines what image 59 is? | The decaying, oscillating signal induced after 90 degree pulse |
| Image 60 represents the | Larmor equation |
| Image 51 represents | T1 recovery |
| Image 62 represents | T2 decay |
| Image 82 was acquired at what field strength | 1.5 Tesla |
| Aside from the center of frequency, what other indicator in image 82 signifies it was acquired at 1.5 Tesla? | The chemical shift between fat and water is 220 Hz |
| Image 91 was acquired at what field strength? | 1.5 Tesla. Center frequency (resonance frequency) at 1.5 Tesla is -63.86 MHz |
| Image 92 was acquired at what field strength? | 1 Tesla Center Frequency (resonance frequency) for 1 Tesla is -42.57 MHz |
| The net magnetization vector (NMV), when aligned with the magnetic field direction, is aligned __________. A. Along the transverse axis B. Along the longitudinal axis C. 90º perpendicular to the direction of the magnetic field D. Both A & C | Along the longitudinal axis |
| The fringe magnetic field: A. Is eliminated by magnetic shielding B. Is eliminated by shimming C. Poses no safety risks if the MRI machine is not scanning D. Can cause nearby medical devices to malfunction | Can cause nearby medical devices to malfunction |
| ____________ states that a changing magnetic field will induce a voltage. A. Maxwell's equations B. Bloch equations C. Gilbert's law of relativity D. Faraday’s law of induction | Faradays Law of Induction |
| What has a higher precessional frequency? A. Grey matter B. Bone C. Fat D. Water | Water |
| A FID is produced from: A. A gradient B. An RF pulse C. T2 decay D. T1 recovery | An RF pulse |
| How many radiofrequency pulses produce a FID? A. 1 B. 2 C. 3 D. None | 1 |
| How well a material attracts the imaginary lines of the magnetic field is defined as: A. Magnetic susceptibility B. Magnetic permeability C. Magnetohydrodynamic effect D. Magnetic resonance | Magnetic permeability |
| _____________ occurs after initial RF application, causing phase differences to appear between precessing spins, resulting in decay of transverse magnetization. A. Weighting B. Precession C. Recovery D. Dephasing | Dephasing |
| The difference in chemical shift is approximately ______ parts-per-million A. 1.5 B. 2.5 C. 3.5 D. 4.5 | 3.5 |
| At 1 Tesla the frequency difference between that of fat and water is approximately: A. 36 Hz B. 42.57 MHz C. 63.86 MHz D. 147 Hz | 147Hz |
| All of the following are non-ferrous substances EXCEPT: A. Plastic B. Titanium C. Iron D. Copper | iron |
| Aside from the center frequency, what other indicator in Image 82 signifies it was acquired at 1.5 Tesla? A. The chemical shift between fat and water is 147 Hz B. The chemical shift between fat and water is 220 Hz | B. The chemical shift between fat and water is 220 Hz |
| The force that an object can be attracted to the magnetic field is reliant upon: A. The field strength (Tesla) of the MR system B. The mass of the projectile C. The specific ferromagnetic nature/properties of the material D. All of the above | D. All of the above |
| Force on an object in an magnetic environment depends on: I. Mass of the object II. Strength of the magnetic field III. Strength of the RF field IV. Ferromagnetic properties of the object C. I, II, and III D. I, II, and IV E. I, II, III and IV | D. I, II, and IV |
| Immediately following the application of the 90° RF pulse, the precessing protons: A. Begin to precess in phase B. Tip into the transverse plane C. All move into a high energy state D. Both A and B | D. Both A and B |
| All of the following are TRUE except: A.RF converts FID into an echo B. Magnetic field gradients are static C. The RF field oscillates at the Faraday frequency D. The resonance frequency in a 1.5 Tesla magnet is 63.86 Mhz | A.RF converts FID into an echo |
Created by:
zach1710