Which of the following medical imaging modalities is the best choice when the objective is to characterize calcification patterns and periosteal reactions that may be a result of a sports-related injury?
A. conventional radiography
Which of the following is NOT considered a major component of a MRI system?
B. multiple row x-ray detectors
The strength of the magnetic field in MRI is measured in a unit known as the ____.
D. (Tesla)
Twisting injuries re responsible for what percentage of knee injuries?
A 10%
B. 25%
C. 50%
D. 70%
D. 70%
Which of the following is the only medical imaging modality that can visualize an anterior cruciate ligament (ACL) or meniscal tear of the knee?
B. MRI
Which of the following is not on of the articulations which make up the shoulder joint?
C. humeroradial
which of the following is the most common defect associated with glenohumeral instability of the shoulder?
D. Bankart lesion
labral tears of the hip joint are most frequently encountered in which of the following locations?
C. anterior and anterosuperiorly
which of the following is not one of the types of femoroacetabular impingment syndromes?
D. radial
if there is any question weather a rotator cuff tear of the shoulder is full-thickness or partial-thickness on conventional MRI, what is recommended?
A. MR arthrography
Which of the following is true?
D. all the above
which of the following statements about small bowel anatomy is false?
B. the jejunum comprises approximately 60% of the small bowel
Oral contrast agents for enterography should provide adequate bowel distention and also have which characteristic?
D. all the above
which of the following statement/s about IV contrast enhancement is/are/ true?
a.when to begin scanning after contrast will vary for each facility
b. both CTE and MRE use low-osmolality iodine base IV contrast
c. breastfeeding should be continued after receiving IVF contrast
both a and c
an injection rate of 5mL/sec the peak enhancement of the normal small bowel occurred approximately __ seconds after IV contrast administration.
D. 50
in MRE, motion-free T2 images (without fat suppression) enable:
C. clear evaluation of the bowel wall and mesentery with little artifact
MRE can safely perform for repeat imaging
A. True
B. False
A. True
Which sequence is very helpful for determining the time frame of a stroke?
a. T2 FLAIR
b. GRE
c. IR
d. ADC mapping
Spinning protons in MRI act like what?
Tiny magnets
When protons are exposed to a strong external magnetic field, what 2 things happen?
1. They align parallel and anti parallel to that field
2. They begin to precess
What is the equation to determine precessional frequency?
Larmor Equation
Wo=YBo
How do we get the NMV in the transverse plane?
With an RF pulse
What happens to the protons' phase when hit with RF moved into transverse plane?
They become in phase.
T1 relaxation time is the time it take ___ % of ___ magnetization to recover in a tissue.
1. 63%
2. Longitudinal
T2 relaxation time is the time it takes until only ___% of ___ magnetization remains.
1. 37%
2. Transverse
True False
T1 recovery happens mich quicker than T2 decay.
False
The sign decay that occurs as a result of the dephasing of the transverse magnetization is called :___
FID
What are the differences between intrinsic and extrinsic contrast parameters?
Examples?
1. Intrinsic are inherent to the body's tissues and cannot be changed
T1 recover, T2 decay, Proton Density
2. Extrinsic are external factors we can manipulate.
TR, TE, FA, TI, ETL, Bvalue
Image contrast and signal intensity are dependent on what 3 intrinsic parameters?
T1 recover, T2 decay, Proton Density
T1 is controlled by what imaging parameters? (Spin echo)
TR: repetition time
T2 is controlled by what imaging parameters? (Spin echo)
TE: Echo time
What combination of imaging parameters creates T1, T2, PD spin echo images?
1. T1= short TR and TE
2. T2= Long TR and TE
3. PD= Long TR, Short TE
How does a gradient echo produce an echo?
Rapidly dephase and then rephase the FID into an echo using the gradients.
How does flip angle affect image contrast in gradient echos?
T1= large
T2= small
PD= small
What 3 encodings do we use to spatially locate the signal?
Slice
Phase
Frequency/ read
What theorem must be obeyed to avoid aliasing?
Nyquist
What does the Nyquist theorem state?
Sampling frequency must be twice as high as the highest frequency
Where are the signals stored prior to being transformed into an image?
K space
What part of k space are made up of contrast information
Central
What is the gyromagnetic ratio of hydrogen
42.57 @ 1Tesla
What are the main types of pulse sequence?
Spin Echo
Gradient Echo
What are the advantages of Spin Echo
Versitile
Contrast based on T1 and T2 relaxation time
True T2 weighting
What are the disadvantages of Spin Echo?
Long scan times
What type of pulse sequence fills several, but not all, lines of k space in 1 TR?
Turbo/ Fast Spin Echo
What type of Spin echo aquires both PD and T2 weighting images in the same TR?
Dual spin echo
What makes fat bright on FSE?
J coupling
What is the precessional frequency of Hydrogen at 3t?
127.71 MHz
in what direction are fringe fields?
3D. all 4 walls, ceiling and floor
describe passive shielding
heavy steel plates around magnet to guide flux lines
describe active shielding
uses opposing electromagnetic fields from additional electromagnetic coils in scanner
what is a shim coil
an active electromagnetic shim to adjust for any field inhomogeneities
what tempurature is ideal for the superconductor cryogen?
4 K or -270 c
what is another name for the RF coil?
internal body coil
what is a local coil?
coils on or near the patient that can at least receive but some can also transmit/receive.
have to be
where does the RF come from for an exam using a receive only coil?
the internal body coil
what is a volume coil
2 phased array coils working together
the smaller the coil the ___ the SNR.
better
the smaller the coil the ____ penetration and coverage.
worse
what is a phased array coil?
multiple smaller coils overlapping, on multiple channels to achieve good SNR and coverage.
explain a Faraday cage.
covers entire room in copper, all 6 sides. keeps other sources of RF out so it doesn't affect the MR images.
also keeps RF in to not affect equipment through the building
what artifact is from a problem with the Faraday Cage?
zipper/ RF artifact
What are the static magnetic feild limits set by the FDA?
4T <1 month old
8T< for older than 1 month old
at what gauss are the general public restricted to?
5g
the biological affect of the static magnetic field are ___.
temporary
what is the best way to avoid body coil burns?
1 cm air gap/ 1cm padding between patients and the bore
what part of the scan is audible enough to cause hearing damage?
time varying gradients.
what is PNS and when does it happen?
Peripheral Nerve Stimulation.
during the time varying gradients
where is zone 1?
everwhere
where is zone 2?
between zone 1 and zone 3
where is zone 3
has a wall or door into zone 4. should be able to view patients in zone 4 from zone 3. also needs restricted acess
what zones can medical intervention occur? (example:Code Blue)
zones 1-3.
What zone is the quench pipe in?
zone 4
what zones have possible contact with the fringe fields?
zones 3 and 4
is MR Compatable a term still used?
no
is MR Conditional still a used term
yes
what is GBCA?
gadolinium based contrast agents
what do GBCA's do?
shorten recovery times of all tissues it comes in contact with
what are the 3 types of T1 contrast agents
GBCA
Manganese (outside of US)
Hyperpolarized helium (lungs)
what are the types of T2 contrast agents
SPIO (superparamagnetic agents, iorn oxides)
what are some examples of T2 contrast agents
feraheme
gastromark
pineapple and blueberry juice
for enterography you use ___ contrast agents.
T1 (IV) and T2 (oral) together
what is the average dosing of gadolinium?
0.1 mmol/kg
what are the 3 main contraindications for GBCA's?
severe allergy
pregnant
poor renal function
what is NSF and why does it happen?
Nephrogenic Systemic Fibrosis.
caused by GBCA in patients with compromised renal function.
gadolinium breaks from its bods and deposits in the body tissues causing hardening of the organs or skin
at what eGFR do you NOT give GBCA?
eGFR<30
what weighting of images are mostly found in Single Shot-Fast Sin echo.
t2
how does Single shot imaging fill K space?
fills around 60% then mirror images the rest
how does and IR pulse begin?
180 pulse
what type of contrast is mostly found in IR pulse sequences
T1 weighting
why do IR pulse sequences have a 180 RF pulse in the begining?
to suppress certain tissues
what is TAU
time between excitation and the end of TR
what doe a Short Tau Inversion Recovery null?
fat
what does Fluid Attenuated Inversion Recovery null?
CSF
what is the purpose of chemical pre-saturation?
to null a tissue from the images
what sequence "add ons" do chemical pre-saturations have?
90 degree pre pulse with gradient spoilers
how does a gradient echo pulse sequence begin?
variable flip angle
what is Steady State?
a type of contrast weighting
TR is too short for T1 and T2 relaxation
(TR <50 ms, FA 35-40)
What type of images are acquired in Fast Gradient Echo?
3D isotropic volumes
what is EPI
Echo Planar Imaging
diffusion weighted imaging
what happens with you increase magnetic field strength?
^ SNR
^ Chemical Shift
^ SAR
What happens when you increase TR?
+ longitudinal relaxation
- T1 weighting
+SNR
+ max # of slices
+ scan time
What happens when you increase TE
+ transvers decay
+ T2 weighting
- SNR
- max # of slices
+ gradient echo susceptibility
What happens when you increase FA?
+ transverse magnetization (more signal)
possible contrast swap
+ T1 weighting
ernst angle considerations
What happens when you increase TI?
selectively null certain tissues
+ contrast
- max # of slices
- SNR
+ scan time
What happens when you increase NEX?
+ signal
+ scan time
- artifacts
What happens when you increase Matrix?
+ spatial resolution
- SNR
+ scan time (phase direction only)
What happens when you increase FOV?
+ anatomy displayed
+SNR
- spatial resolution
What happens when you increase Slice Thickness?
+ anatomical coverage
+SNR
- spatial resolution
+ partial volume artifact
What happens when you increase Slice Gap?
+anatomical coverage
- crosstalk artifact
+ risk of missing pathology
What happens when you increase Receive Bandwidth (rBw)?
- SNR
- Chem shift
- metal artifacts
- min TE
- available spatial resolution in frequency direction
What happens when you increase Echo Train Length (ETL)?
- SNR
-Scan time
+ blurring
- susceptibility artifacts
What happens when you increase Echo Spacing (ESP)?
+ scan time
+ blurring
+ artifacts
+ parameter options
What happens when you increase Parallel Imaging
- scan time
-SNR
- SAR*
+/- artifacts
what are the 4 main ways to fill Kspace?
linear
centric
spiral
radial
what is linear kspace filling?
basic filling used in standard imaging
what is centric k-space filling?
start from center of k-space and move outward (up and down)
what is Spiral Kspace filling
start from center and spiral out (elliptic or swirl)
what is radial kspace filling?
center oversampling in rotating pattern (propeller/blade
What happens when you decrease TR?
-longitudinal relaxation ( more T1 weighting)
- SNR
- max number of slices
- scan time
What happens when you decrease TE?
-transvers decay (- T2 weighting)
+ SNR
+ max number of slices
- gradient echo susceptibility
What happens when you decrease FA?
- signal
- T1 weighting
What happens when you decrease TI?
- contrasts
+ max number of slices
+ SNR
- scan time
What happens when you decrease NEX?
- signal
- scan time
+ artifacts
What happens when you decrease Matrix?
- spatial resolution
+ SNR
- scan time (phase encoding)
What happens when you decrease FOV?
-anatomy coverage
- SNR
+ spatial resolution
What happens when you decrease Slice Thickness?
- anatomical coverage
- SNR
+ spatial resolution
- partial volume effect
What happens when you decrease rBw?
+ SNR
+ chemical shift
+ metal artifact
+ min TE
+ spatial resolution ( frequency direction)
What happens when you decrease ETL
+ SNR
+ scan time
- blurring
+ artifacts
What happens when you decrease ESP?
- scan time
-blurring
-artifacts
- parameter options
what direction will motion artifacts be?
phase encoding direction
motion artifacts are also called ___
phase mis-mapping
what warps the magnetic field and can be seen as warping on images
metal
what is phase wrap?
anatomy outside FOV wrapped into image
what direction is phase wrap seen?
frequency direction
what direction is zipper artifact seen?
phase encoding
what is the chemical shift between water and fat at 1.5T?
224Hz
what does chemical shift look like?
black and white banding in pixels that contain fat and water in the same pixel
what type of artifact will be present in a patient too large for the coil being used?
zebra
how do you midigate truncation artifact?
increase phase encoding matrix
what is a nyquist ghost?
3 brain artifact
fast zig-sag pattern in kspace filling causing eddy currents, heat and phase shifts
how can you lower SAR on l-spine imaging?
put in head first
What type of matrix does MRI have?
Variable
What is an average FOV for a head
25 cm
What are TR and TE measured in?
Mili seconds
What is generally considered a long TR
TR> 1500 ms
What is generally considered a long TE
TE> 60 ms
What is generally considered a short TR?
TR< 500 ms
What is generally considered a short TE?
TE<20 ms
What basic parameters do you need for T1 weighting?
Short TR\TE
What basic parameters do you need to get dark fluid.
Short TR\TE
What basic parameters do you need to get T2 weighting
Long TR\TE
What basic parameters do you need to het bright fluid
Long TR\TE
Due to proton distribution which body part(s) is(are) better seen with CT?
Lung
What is the Wo in the Larmor Equation
Wobble frequency
Frequency of precession in MHz
What is the Y in the Larmor Equation?
Gyromagnetic ratio MHz/T
What is the Bo in the Larmor Equation?
Magnetic field strength
What is the gyromagnetic ratio for hydrogen?
42.5759 ish
Define relaxation time
The characteristic time (63%) it takes the spin system to recover after being disturbed from equilibrium
What is the formula for acquisition time
TR/60 x Matrix x NSA
What do headphones/ear plugs need to be rated for
99 dBA
When do you need an orbital screening?
Metallic piercing injury to the eye that the patient saught medical attention for
Who should have hearing protection
Any one in zone 4 during scanning
What level does PNS happen
60 T/second
Where is the highest area for induced voltage?
30-35 cm from isocenter
What is normal modes head SAR Limit?
+0.5 C from normal body temperature
3.2 W/kg
What is normal mode SAR limit for body
+0.5 C from normal body temperature
2 W/kg
What is the length for an antenna effect
1.5T 25cm (10 inches)
3T 13 cm (5 inches)
Define spatial resolution
The abilty to see small structures
What determines the contrast in gradient echo
flip angle and TE
What parameters would you use for T1 weighting in gradient echo
Smaller FA
What type of weighting would this gradient echo be
Small FA + long TE
T2
Which direction is flow artifact
Phase
What is a general TI to supress fat
150 ms (1.5 T)
What Bvalue do you use in a brain to assess acute infarction
1000
What does IV contrast look like on diffusion
Dark
What are the types of coils
Linear
Quadrature
Phased array
What is the down fall of linear coils
Poor penetration. Needs to be very close to anatomy
What is an example of a linear coil
Prostate
TMJ
What is the most common quadratic coil
Head coil
"Bird cage"
Linear coils trade coverage for ___
High SNR
1T = ___ gauss
10,000
The law of physics that describes how the MRI signal is collected
Faraday's Law of Induction
Which magnet type requires the most power feed
Resistive
Per Faraday's Law what constitutes the "closed loop of wire"
Receiver coil
The type of coil most commonly used in volume coil designs
Quadrature
The term that describes gradient strength at maximum capacity is
Amplitude
How do you find the slew rate
Amplitude /rise time
A steep slice select gradient slope creates
Thinner slices
What is the Larmor frequency at 3T
127.8 MHz
The phenomenon that describes nuclear spins assuming a higher energy state with RF exposure
Resonance
Transverse relaxation is also known as
T2
Spin spin
Which technique requires injection of contrast
Perfusion
Which gradient changes strength with each repetition
Phase
In what order are gradients applied in spatial encoding
Slice\phase\frequency
Which pathology is best described by a Proton density weighted image
C.
Transmit bandwidth is indirectly controlled by which parameters
Slice thickness
What parameters in inversion recovery determines what material is suppressed
TI
What IR technique suppresses CSF
FLAIR
Fluid Attenuated Inversion Recovery
Compute the pixel size
128 x 192 matrix
TR500
BW 20.8
FOV 25.6 cm
2.0 x 1.5
(FOV/ P matrix) x (FOV/ R matrix)
Decreasing slice thickness increases
Spatial resolution
Decreasing slice thickness ___ SNR
Decreases
Increasing rBW increases
Image noise
Increasing NSA from 1 to 2 results in a SNR change of
+40%
How many linea of kspace/TR are filled with the following:
TR 1000
Matrix 256 x 256
ETL 4
NSA 1
4
What are 4 ways to suppress flow artifacts
Flow compensation
Presaturation
Echo spacing
Gating
Why do we use PD fat sat for orthopedic imaging?
Helps reveal fluid such as bone marrow edema, fat pad edema, bursa, and cysts.
Why do we use T1 weighting in orthopedic imaging?
Incidental bone or soft tissue lesions
Why do we use PD weighting in orthopedic imaging?
Detailed anatomy, fat helps to outline structures, good CNS
What has low signal on PD images in orthopedic imaging?
Ligaments, tendons, menisci
What does the FABS position look atm
Elbow
Assessment of the distal biceps tendon
How do you position for ABER images?
Pt supine, hand behind head or neck
Name the wrist bones
Scaphoid
Lunate
Traquitrum
Pisaform
Trapezoid
Capitate
Hamate
In Phase signal drop in the liver usually means what?
Iron deposit
How long after gad is arterial phasem
20-30 seconds
How long after gad is venus phasem
60-70 seconds
How long after gad is the liver equilibrium phase?
3-5 min
When after gad is the hepatobiliary phase?
10-30 min
What is RARE
Rapid
Acquisition and
Relaxation
Enhancement
What is FRFSE
Fast
recovery
Fast
Spin
Echo
Respiratory triggered 3D
What is HASTE?
Half-frouier
Aquisition
Single shot
Turbo spin
Echo
2D breath hold axial. Fat suppressed
Which one of these conditions may present with biliary enhancement and a pruned tree appearance?
B. ) Primary sclerosing cholangitis
What is mainly looked at when doing Chest MRI?
Breast
Cardiac
Thymus
What is being looked at with an arthrogram of the elbow?
Partial ulnar collateral ligament (UCL)
What is being looked at with an arthrogram of the hip?
Femoroacetabular impingement (FAI)
Labrum
What is being looked at with an arthrogram of the knee?
Repaired meniscus tears
What is being looked at with an arthrogram of the shoulder?
Instability/ labral tears
SLAP (superior labral anterior posterior)
HAGL (humeral avulsion of the glenohumeral ligament)
What is being looked at with an arthrogram of the wrist?
Triangular fibrocartilage (TFC)
Scapholunate ligament
What is the general TR, TE, and flip angle for T1 weighting?