ABSTRACT
MR signal b. The signal recorded in a 1.5 T magnet will be proportionally
higher than in a 3.0 T magnet c. MR signal strength is inversely proportional to proton density d. RF transmitter/receiver coils need to be able to perform both
functions simultaneously e. Most signals from the body are received from water protons
4. The MR signal: a. In the plane running transverse to the static magnetic field, there
is no MR signal at rest b. Application of RF energy causes the hydrogen protons to
precess in phase c. A 908 pulse requires more energy than a 1808 pulse d. Following an RF pulse, the phase coherent protons will remain
in this state indefinitely e. Depends only on the proton density of the material
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5. of precession of the
b. Photons with twice the Larmor frequency have the correct
energy to tip all the ‘spin up’ protons to ‘spin down’ c. Photons in a 1808 RF pulse have twice the energy of photons
for a 908 RF pulse d. An initial 908 RF pulse reduces mz (the net magnetic vector in
the z-axis) to approximately 0 e. As the magnetic vector returns to its equilibrium position along z,
a signal is produced which is received by an RF coil to form the picture
6. Concerning T1: a. It is the time taken for transverse recovery to reach 37% of the
maximum value b. T1 is increased with greater field strength c. Fat andmelanin bothproduce ahigh signal on aT1-weighted image d. A short time to echo (TE) and short time to repeat (TR) will
give a T1-weighted image e. T1 is always longer than T2
7. Concerning T2: a. T2 decay is longitudinal relaxation b. A long TR and long TE will give a T2-weighted image c. Cerebrospinal fluid (CSF) and flowing blood will produce high
signal on a T2-weighted image d. The T2 of grey matter is longer than that of white matter e. Spin-spin relaxation occurs because the neighbouring protons
exert a tiny magnetic field of their own which can alter the rate of precession
8. T2 decay: a. Occurs due to spin-lattice relaxation b. Is referred to as T2 when an initial 1808 pulse is used in spin-echo
(SE) sequencing c. T2 relaxation time increases with an increase in magnet strength d. Is affected by magnetic field inhomogeneities e. When 63% of the transverse signal is lost, this is referred to
as time T2
9. T1 and T2 recovery: a. Free induction decay (FID) is also known as spin-lattice
relaxation b. T2 always has a longer decay time than T2 c. T1 time is the time for 63% recovery of mz d. Fat and large molecules shorten the T1 time of tissues e. Local field variation is fastest in free fluids such as water,
giving a short T2
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10. dephasing effect of field
inhomogeneities with a second 908 pulse c. The rephasing pulse in SE sequencing also removes the need for
ultrafast switching of coils from transmit to receive d. With improvements in magnet technology, field inhomogeneities
will probably become a thing of the past, negating the need for the formation of spin-echoes in MR
e. The longer the TE, the smaller the subsequent MR signal
11. Regarding the SE sequence: a. The SE sequence allows the T2 effect of a specific tissue to be
measured b. The presence of the patient adversely affects the magnetic field c. Following rephasing, the MR signal is equal to that immediately
after the initial 908 pulse d. Immediately following a single 908 pulse, all of the dipoles are in
phase e. The 1808 rephasing pulse is applied at TE/2 after the initial RF
excitation
12. Weighted images: a. A T1-weighted image would have a TR of 1000 ms and a TE of
100 ms b. A T2-weighted image might have a TR of 400 ms and a TE of
15 ms c. Water and fluids such as CSF appear bright on T2 d. Cortical bone appears white on proton density weighted images e. Short tau inversion recovery (STIR) is a type of fat suppression
13. Imaging with MR: a. Signal strength depends only on the proton density
of the material b. A short TE and a long TR will give a T1-weighted image c. A T1-weighted image will show water as high signal d. Most soft tissues show as high signal on proton density (PD)
weighted images e. If TE is longer than TR, the image is weighted towards PD
14. Spatial encoding in MR: a. Slice selection must always be applied to the z-axis b. In a standard SE sequence, frequency encoding is applied
during signal acquisition c. In a standard SE sequence all of the information for a single slice is
obtained within one TR d. The steeper the slice selection gradient, the thinner the slice e. In a standard SE sequence the image can be built up line by line
during acquisition
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15. with the initial RF
b. A row of phase encoding data in K-space takes less time to acquire
than a column of frequency encoding data c. The centre of a K-space contains the data relating to high
spatial resolution d. Slice thickness can be reduced by decreasing the RF bandwidth
for each slice (assuming the gradient remains the same) e. RF excitation outside the field of view (FOV) can result in
aliasing artefacts
16. Pulse sequences in MR: a. Within a single TR, following collection of PD-weighted data
the echo can be re-sampled after another TE to provide T2-weighted data
b. Inversion recovery is used to accentuate subtle differences in T1 weighting between tissues
c. STIR sequencing is used to enhance tissue boundaries d. Gradient echo sequences achieve equivalent rephasing when
compared to the 1808 pulse of SE e. Echo-planar imaging (EPI) provides highly detailed images
17. Regarding imaging techniques and pulse sequences: a. Gradient recalled echo (GRE) sequences are used for their
speed of acquisition b. Fast SE involves simultaneously recording multiple frequency
encoding echoes which results in the acquisition time being shortened by a factor of 16 or more
c. STIR sequences are used to suppress the signal from fat d. Multi-slice imaging is not possible in MR e. In diffusion-weighted images, tissue oedema produces a high
signal
18. Other sequences and techniques: a. A reduced tip angle can be used to decrease the scan time at the
expense of signal strength b. Fast (turbo) spin-echo (FSE) techniques use several refocusing
1808 RF pulses to rephase and produce extra echoes at different phase gradients for each excitation
c. Multi-sliceMR techniques use several rows of detectors within the path of the beam
d. In MR angiography flowing blood normally appears dark e. Gadolinium produces a bright area of uptake on T2-weighted
images
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19. flowing blood shows as high
signal because its movement prevents longitudinal relaxation c. Restricted diffusion shows as high signal and is abnormal in
diffusion-weighted images of stroke d. Deoxygenated haemoglobin is paramagnetic; this is the basis for
functional MRI e. Chemical shift imaging utilizes the subtle Larmor frequency
differences for hydrogen contained in molecules to distinguish those molecules
20. Concerning MR angiography: a. On a SE sequence, slow flowing blood appears dark
(flow void) b. In GRE flowing blood appears bright only after administration
of intravenous gadolinium c. Pulsatile movement artefact is most apparent in the phase-
encoding direction d. Vessel calcification will produce a high signal which can mask a
stenosis e. Turbulent flow shows high signal on an SE sequence
21. Artefacts in MRI: a. Patient movement creates artefacts most commonly in the
frequency encoded direction b. Flowing blood can appear bright in GE sequences c. Ferromagnetic foreign bodies appear as a high signal artefact d. Chemical shift artefact can be reduced through use of a steeper
frequency encoding gradient e. Image wrap-around occurs only when using a magnet of less
than 2 T
22. Regarding MRI artefacts: a. Chemical shift is displaced in the frequency encoding
direction b. Chemical shift is more apparent at lower static field strengths c. Ferrous metal implants cause streak artefact d. Cardiac motion artefact can be reduced by triggering the pulse
sequence with the electrocardiogram (ECG) e. Aliasing occurs if the FOV is too large
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23. chemical diffusion and
oedema b. Chemical shift artefacts are in the phase encoding direction c. Aliasing may be apparent in the phase encoding direction as part
of the image being wrapped to the wrong side d. Motion artefact occurs because the phase encoding steps are
spread over time and therefore any movement can cause a misregistration of position
e. Ferrous metallic objects can cause localized distortion and degradation of the image
24. Image quality in MR: a. Spatial resolution is better with smaller coils b. Surface coils improve signal to noise ratio (SNR) of near surface
tissues c. SNR decreases as voxel volume increases d. T2 imaging always provides the best degree of tissue contrast e. For quality assurance purposes, magnetic field homogeneity
should be tested daily
25. Concerning MRI image quality: a. Spatial resolution is reduced when using a thinner slice b. The majority of noise in an MR image is due to external RF
interference c. Gadolinium nuclei emit the high signal seen on contrast-enhanced
MR images d. Signal strength is increased by using a greater static field e. Some clinical sequences use simultaneous T1 and T2 weighting
26. Image quality and noise: a. Noise in MR is predominantly due to quantum mottle b. Noise is most apparent in areas of high signal such as fluid filled
areas on T2 c. Decreasing the voxel size improves the SNR and resolution at the
expense of scan time d. Increasing TR and/or decreasing TE would increase the signal e. Increasing the number of excitations (Nex) would increase the
SNR at the expense of scan time
27. Magnetic equipment in MRI: a. The main system magnet must be a superconducting
electromagnet b. Superconductivity requires cooling to near 08C c. Resistive electromagnets should ideally not be switched off d. Gradients for spatial encoding are provided by altering the main
magnet e. The main magnetic field is normally defined to be along the
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28. scanner: the electrical mains
b. Quenching of the system may occur spontaneously if the
operating temperature is not maintained c. A Faraday cage minimizes the effect of the scanner magnetic
field beyond the boundary of the scanner room d. The field strength at 2 m from the centre of the magnet is 25%
of the strength at 1 m from the centre of the magnet e. The use of surface coils gives greater image uniformity than
body coils
29. Different types of magnets and coils: a. A 0.5 T superconducting magnet produces a greater field
strength than a 0.5 T resistive magnet b. A paramagnetic MR system uses a conductive magnet c. A permanent magnet may be rapidly shut down in an emergency d. Shim coils are coils that are fine tuned to make the main
magnetic field as uniform as possible e. Surface coils are placed directly on the patient
30. RF coils in MRI: a. Separate send and receive coils are needed b. The loud bangs heard during imaging occur when switching from
transmit to receive c. Surface coils are commonly used for whole body imaging d. Phased array coils can allow faster imaging e. RF signal is amplified before transmission
31. Equipment safety in MRI: a. The torque effect is greater for rod-shaped objects b. Noise levels commonly exceed 90 dB c. The fringe field is well contained around an electromagnet d. Induced heating is the primary concern when using
gradient fields e. A magnet quench can cause oxygen levels to drop in the scan room
32. Concerning safety and MRI: a. The Medicines and Healthcare products Regulatory Agency
(MHRA) publishes guidelines on safe MRI practice b. A patient with a cardiac pacemaker should not be in an area
where stray fields may be greater than 5 mT c. Ethics approval is not required for medical research scans
under 2 T d. The presence of metallic dentition is a contraindication to
MRI scanning e. Previous allergic reaction to iodinated intravenous contrast
agents is a relative contraindication to administering gadolinium
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33. are safe for MRI as joint prostheses and
past eye injury foreign bodies are not a risk to the patient as they are firmly fixed in place
c. Patient screening should be performed as soon as the patient enters the controlled area
d. Pregnant patients should not be exposed to field strengths above 2.5 T
e. Specific absorption ratio (SAR) is the amount of ionizing radiation absorbed per mass of tissue expressed as watts per kg during the MR scan
34. Safety in MRI: a. Public access to areas where field strength is greater than 0.5 mT
is restricted b. A patient with a pacemaker can have parts of their body other
than the thorax imaged safely c. Routine whole body clinical scanning is limited to 4 T d. Torque force on joint replacements is of particular concern e. Varying gradient fields can cause nerve stimulation
35. Regarding the effects of MRI scanning: a. RF fields can cause peripheral nerve stimulation b. Equipment leads exposed to the gradient field can cause skin burns
if inappropriately positioned c. Intraorbital metal fragments are of concern primarily because they
can become overheated and cause thermal damage to the retina d. Staff with body piercings must wear lead-lined undergarments
when approaching the magnet e. With a SAR of 1.0, the patient’s body temperature will rise by
more than 0.58C if they are scanned for 30 min
36. Emergencies in MR: a. In the event of a cardiopulmonary arrest, the resuscitation team
should never enter the scan room while the magnet is energized b. The fire service should be allowed immediate access to an MR
machine on fire due to the risk of explosion and the spread of fire to the rest of the hospital
c. A ‘quench’ must be initiated as an emergency to switch off a resistive magnet in the event of a fire or cardiac arrest
d. Oxygen cylinders should never be taken near an MR machine e. It is possible for a patient to become trapped against the MR
machine by a ferrous metal object brought into the room
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1a. True Spin angular momentum is an intrinsic property of an atom; those with equal numbers of protons and neutrons have no net spin and so no magnetic moment. With only a single proton, hydrogen has a large magnetic moment.
