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acmolt
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Chemical shift artifact appears in the?
frequency encoding direction
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_____may be given to slow peristalsis of the bowel during imaging in pelvis in MRI?
Glucagon
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Post contrast images are always?
t1 weighted
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since there is not TR in cardiac MRI imaging, the _____ marks the beginning and end of the data acquisition.
RR
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t/f: increasing the repetition time (TR), will increase SNR
True
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T/F: the diffusion gradient is applied before and after the 180 in a diffusion pulse sequencce diagram
true
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____exhibits the longest T1 relaxation time?
CSF
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_____ is that it null fat to better visualize surrounding anatomy.
the benefit of fat saturation
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____ occurs when there is no transverse magnetization
null point
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spatial LOCALIZATION is controlled by?
gradients(slice select, phase, frequency)
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A long TR and short TE will produce____
PD weighted images
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short TR and short TE
T1 weighted
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long TR and long TE will produce
T2 weighted images
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T/F: free water protons and fat protons have a resonance frequency separation of 3.5 ppm.
true
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the _______ is the mechanism used to rephase spins during GRE imaging.
gradient magnetic field
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indications for a MR breast exam are?
dense breast, family hx, evaluation of breast implants, staging of breast cancer
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____ is the best term to describe chelate
binding agent
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specific absorption rate is express as?
watts/kg
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protons that come into contact with gadolinium conrast will experience a ______?
shorter T1 relaxation
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_______ is the name of the mathematical caclulation appled to kspace to construct an image.
fourier transform
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_____have high SNR and are the most reliable for imaging the injuries of the menisucs in the knee, labrum of the shoulder, and triangluar fibrocartilage in the wrist
PD images
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T/F: decreasing the slice thickness will increase spatial resolution
true
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3 principle MRI parameters?
t1 t2 and pd
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___appears darker on a T2 weighted image?
water
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___ is the name of the exam used toimage the biliary system in MRI.
MRCP
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when imaging hte CNS in MRI _____ pulse sequnce is required for the indication of MS.
Flair
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the most upt to date mri safety website.
www.mrisafety.com
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an ______ is a pulse sequence that starts with a 180 degree rf pulse followed by a 90 degree RF pulse followed by anohter 180 degree RF pulse
inversion recovery
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for a T1 weighted pulse sequence the operator should choose a_____
choose a TR 500, TE 20.
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The most commonly employed MR pulse sequence is a Spin
Echo.
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The ___pulse sequence is
when refocusing is provided by a 180 degree RF pulse.
spin echo
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Some ways a technologist can try to calm the
claustrophobic patient may include:
sleep deprive the patient and medicate the patient.
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The biggest concern with RF fields in MRI concerning patient safety would be tissue heating.In gated cardiac MRI, the primary parameter that is used for triggering the RF pulses is the
R-R interval.
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Choosing an appropriate imaging matrix in imaging the MSK system in MRI is usually related to finding a balance between the need for high spatial resolution and the cost in terms of the scan time and poor resolution.
:)
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________ is placed over subcutaneous fat in the pelvis which helps to eliminate respiratory motion artifact.
Anterior fat saturation band
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________is considered the MRI principal advantage over all imaging modalities.
Contrast Resolution
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Motion is always seen in the _______ on an MRI image.
Phase Direction
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______ pulse sequence is the most common pulse sequence used for ________
Spin Echo;Diffusion Imaging.
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Inhalation=
Ingestion=
Intravenous=
Rectal=
- Inhalation=Oxygen
- Ingestion=geritol
- Intravenous=gad-dpta
- Rectal=water
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Turbo=
A pulse sequence that closely follows gradientecho imaging. This pulse sequenceis acquired when a preparatory pulse is applied followed by several variable flip angles
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GRASE=
a hybrid pulse sequence that combines gradientecho and fast spin echo pulse sequences.
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Echo Planar=
A pulse sequence that produces a train ofgradient echoes by continuously switching the read gradient rapidly inside theenvelope of the FID or Spin Echo. Usually fills k-space with 1 RF pulse.
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Flow Comp=
use of bipolar gradient magnetic fields toreduce flow artifacts by re-establishing phase coherence; gradient moment nulling.
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Flow Related Enhancement=
increase in signal intensity offlowing blood compared with stationary tissue when fully magnetized spinsreplace saturated spins.
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Flow Void=
blood moves fast, the protons in the blood are saturated by the 90 degree RF pulse and leave the imaging section before the 180 degree RF pulse and no signal is emitted.
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Plug Flow=
blood flows at the same speed across the vessel.
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Laminar Flow
- =blood flow varies. Flow at the wall of the vessel is
- slower than flow in the center of the vessel.
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Turbulent Flow=
blood flow swirls and mixes rather than following the path of the lumen of the vessel.
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Pulsatile Flow=
blood flow changes from plug to laminar.
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=Large flip angle, short TR, short TE
=Small flip angle, long TR, long TE
=small flip angle, long TR, short TE
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The most common rendering utilized in MRA?
MIP
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can be obtained by using the HLA to prescribe an obliqu plane through the right and left ventricle by placcing the slices perpendicular to interventricular septum
short axis
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Be able to define image artifact.
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Describe the null point in inversion recovery and name a pulse sequence that is an inversion recovery pulse sequence. (i.e. FLAIR or STIR)
transverse value of T1 where mz equals zero; stir
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Describe how TOF MRA and Phase Contrast MRA is
performed in MRI. Which
Application is used more in MRA.
For example: TOF MRA produces vascular contrast by manipulating thelongitudinal magnetization of the stationary spins. PHASE CONTRAST MRA uses the velocitydifferences and hence the phase shifts in moving spins to provide imagecontrast in flowing vessels. (TOF is still considered to be the most commonused MRA technique
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State three ways that a technologist can optimize the MRI image. Please use specific
examples, e.g. Increase SNR by
doubling NEX.
increase TR; decrease scan time; optimize spatial resolution
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Why is STIR and FLAIR pulse sequences used to image the muscoskeletal system and centralnervous system resectively?
stir- fat uses a short T1 which allows for the elimination of high fat signal
flair- used for CSF and bc fluid uses long T1 so it is best to use a T1 of 2 sec which works to minimize fluid signal from structures
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List the disadvantages to exogenous contrast administration.
Disadv=adds time, expense,invasive.
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List the appearance, cause and remedy fro one artifact common to MRI.
For example, if there was zipper artifact throughout your image, that tells us that there is an RF leak somewhere and the engineer needs to be called and repaired
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Define SAR and state the limit for the whole body:
SAR is the measure of the energyabsorbed per unit of time per unit of mass and whole body limit is 4 Watts/kg.
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State 3 items you would not allow in the MRI suite.
regular w/c, credit card, ladder
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Screening sheets are vital to patient and staff safety
in the MRI suite. What are 3
questions that the screening sheet my have on them? (This is time for you to provide typical questions that you would ask a patient prior to their MRI scan).
- do you have any metal on you?
- do you have a pacemaker?
- Any surgery of the brain or anywhere containing metal?
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Do to a number of serious accidents the ACR recommends identifying four zones of increasing potential hazard. Please list and describe the 4 zones.
1. Zone 1=areas freely accessible to the general public.
2. Zone 2=Reception are where patients and visitors are controlled.
3. Zone 3=The control room and immediate space. Access to this zone must be strictly controlled by MR personnel.
4. Zone 4=This is the MRI room itself. Should be clearly marked with warning lights and signage and MR personnel must ensure that unauthorized individuals are forbidden from entering this area.
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List 3 indications for imaging the abdomen in MRI.
1. Liver 2. Biliary Tract 3. Pancreas 4. Adrenal Glands 5. Kidneys
parenchymal disease, lesions, adenoma
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What is the advantage of imaging the pelvis in MRI over ultrasound?
Because MRI offersbetter contrast resolution and bigger FOV.
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When imaging the MSK system where should the part of interest be centered within the bore of the MRI scanner and why?
Should be centered in the middle or isocenter of the magnetbecause this is the are where the magnet is homogenous.
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When scanning a knee in MRI, list ways you could
position the patient to make them more comfortable.
To add patient comfort, you could use positioning sponges to alleviate any patient discomfort, etc.
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Describe why positioning an elbow in MRI is tricky:
The elbow may be scanned with the patient in a supine position and the arm at the side or with the patient prone and arm overhead. The patient should be scanned in a comfortable position to avoid motion artifact. Utilizing a surface coil to image the elbow is often necessary and must be positioned accurately.
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List two indications why the spine would be images in MRI.
1. Degenerative changes 2. Primary or mets to spine and cord 3. Osteoporosis 4. Infection 5. Congenital abnormalities
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What could happen to a patient with an aneurysm clip if they were imaged in MRI:
The clip could be become energized within the magnetic field and move around within the brain and possibly shift position thereby causing a potential life threatening situation due to the aneurysm clip movement within the MRI scanne
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When designing an MRI facility, list 3 items that would be important to consider.
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State your responsibility as an MRI technologist in
maintaining safety in the MRI suite.
the tech is responsible for all patients that enter the MRI suite. So the tech must screen the patient to maintain safty
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