week 1 final Flashcards
Calculate the scan time for a fast spin echo sequence with the following parameters: TR 500, TE 24, FOV 20cm 224 x 256 matrix, 4 NEX, 5 ETL, 4 mm slice thickness.
1 min. 29 sec.
The hydrogen proton induces a strong magnetic field because it is:
Charged and spinning
The more ETL, the more _____________ is needed.
TR
Energy is most effectively transferred from one system to another when the systems are at:
Resonance
Which of the following is always on?
B0
Relaxation Time refers to:
Time required for the nuclear spin to return to equilibrium
T1 weighted images are characterized by:
Bright fat and dark water
What level of sedation requires physiological monitoring?
All of the above (Parenteral, Enteral, General Anesthesia, Any patient unconscious)
Who is responsible for monitoring a patient who is connected to physiological vital signs equipment?
Advanced level care personnel such as RN
The purpose of a chelating agent such as DTPA is:
Neutralize the toxicity of a metal ion
What happens to the hydrogen protons when they are placed in a magnetic field?
They align parallel or anti-parallel
Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 16, TR 25, TE 12, 208 x 256 matrix, 1 NEX, 4mm slice thickness, 36 slices.
3 min. 7 sec.
In MR imaging, the term “spin” refers specifically to the spinning:
Nuclei
The tiny magnetic field of the hydrogen proton that is induced by spin and charge and has a north and south pole is called:
Magnetic moment
Calculate the scan time for a fast spin echo sequence with the following parameters: TR 3000, TE 100, 512 x 512 matrix, 2 NEX, 5 mm slice thickness, 18 ETL.
2 min. 50 sec.
What is the FDA recommended amount of SAR for whole body averaged over 15 minutes?
4 W/kg
What is the most important safety consideration associated with a quench?
Displacement of oxygen
The Larmor precessional frequency of hydrogen in a 3T magnet is:
127.74 MHz
What extrinsic factor controls the amount of T2 decay?
TE
What is “DRIVE”?
A reverse 90-degree pulse
Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 16, TR 20, TE 9, 192 x 256 matrix, 2 NEX, 5mm slice thickness, 40 slices.
5 min. 7sec.
What weighted image would be created with the following parameters: TR 15, TE 2, FA 25?
T2*
GRE T2*-weighted sequences use:
Gradient or RF spoiling
Dynamic enhanced T1 weighted MRA sequences of the renal arteries are performed with the use of:
Incoherent gradient echoes
The nucleus of a hydrogen atom contains:
One proton
The symbol for the primary static field is:
Bₒ
What is the 5 Gauss line?
The magnetic field strength and distance that is safe for a person with any device
T1 and T2 relaxation depends on:
Molecular tumbling rate matching Larmor frequency of hydrogen
What physiological monitoring device should be employed when a patient is heavily sedated for an MR exam?
All of the above (Pulse oximetry, Blood pressure, ECG)
What is NSF?
Nephrogenic systemic fibrosis
What is the primary purpose of gradient coils in MRI?
Spatial localization of the MRI signal
What is the main function of the RF coil in MRI?
Transmitting and receiving RF pulses
What determines the Larmor frequency of hydrogen?
Strength of the external magnetic field
What is the most important safety concern associated with MRI?
Ferromagnetic attraction
Who can sign the MRI screening form?
A, B, and C (Patient of legal age, legal representative, legal guardian)
What weighted image would be created with the following parameters: TR 500, TE 10, FA 90?
T1
What tissue is bright on diffusion-weighted imaging?
Abnormal tissue and tissue with low ADC
The time constant of the precessional frequency of a specific MR-active nucleus at 1 Tesla in MHz/T is called:
Gyromagnetic ratio
What determines the amount of ferromagnetic reaction/attraction?
All of the above (Size, shape, and material composition)
Whose law states that ‘a moving electric current creates a magnetic field’?
Michael Faraday
What is the Tesla strength for the Larmor precessional frequency of 170.32 MHz?
4T
What is a pulse oximeter?
A device that measures blood oxygen levels
SE scan time formula is:
TR × Phase matrix × NSA
The point in a tissue’s longitudinal recovery where no magnetization remains and no signal is created on an IR pulse sequence is called:
Null point
T2-weighted, fluid-attenuated inversion recovery (FLAIR) sequences are typically used for the evaluation of:
Periventricular white matter disease such as multiple sclerosis
Which combination of TE and TR creates a PD-weighted image?
Short TE, long TR
Gradient echo sequences acquired for high signal from fluid are known as all of the following EXCEPT:
Incoherent gradient echoes
Calculate the scan time for a fast spin echo with the following parameters: FOV 20cm, TR 3000, TE 120, 224 × 256 matrix, 3 NEX, 5 mm slice thickness, 12 ETL.
2 min. 48 sec.
What can cause NSF?
Certain types of gadolinium contrast remaining in the human body too long
Phase is:
A position at a given time
What were the early NMR machines used to study, and what was the name of this technique?
Chemicals, spectroscopy
A person who is allergic to seafood will have an allergic reaction to IV gadolinium contrast.
False
What zone should screening be completed in?
Zone 3
The application of an RF pulse that causes resonance to occur is termed:
Excitation
One of the reasons that the hydrogen atom is used in clinical MR imaging is its abundance in the body and:
Its solitary proton creates a large magnetic moment
What is a typical TI time for T2 FLAIR?
1700-2200 ms
What is a ‘quench’?
Sudden loss of liquid helium and magnetic field
In a dual-echo sequence for proton density and T2 weighting, which echo is the proton density?
TE 20ms
What is the term used to describe the rapid loss of superconductivity in an MRI magnet, resulting in the release of helium gas?
Quench
A condition where the TR is less than T1 and T2 relaxation times of tissues, where energy in equals energy out, is known as:
Steady state
What is the Ernst angle?
Flip angle that provides optimum signal intensity
What weighted image would be created with FSE, TR 6000, TE 100, ETL 16?
T2
Who was the first person to demonstrate a radio signal from the nucleus of an atom?
Isidor Rabi
Which of the following best describes an EPI sequence?
A “train” of gradient echoes
Gradient echo T1-weighted sequences use:
Gradient or RF spoiling
What is the most important safety consideration for a patient who has had a cardiac pacemaker removed?
That the pacer wires are still in the patient’s body
What is the first thing that should be done for a patient who is having a medical emergency during an MRI?
Remove the patient from the scanner, place them in zone 3, secure the MRI scan room door, and then call for help
TR 9000, TE 125, TI 2200, FM 256, PM 224, 10 ETL, slice thickness 5mm, 2mm gap would yield images with what weighting?
T2 FLAIR
What is the temperature of liquid helium?
4 K / -270 degrees C / -452 degrees F
What is the FDA-recommended amount of SAR for the head averaged over 10 minutes?
3 W/kg
In STIR sequences, which tissue is being suppressed?
Fat
What is a cochlear implant?
An implant in the inner ear
What conditions are necessary for resonance?
Energy applied at the precise frequency and at a right angle
An advantage of using gradient echo sequences is:
Faster scan times
Calculate the scan time for a fast spin echo sequence with the following parameters: FOV 16cm, TR 2500, TE 90, 224 x 256 matrix, 6 NEX, 5mm slice thickness, 18 ETL.
3.11 minutes
Calculate the scan time for a fast spin echo with the following parameters: TR 3500, TE 100, 256 x 256 matrix, 4 NEX, 5mm slice thickness, 14 ETL.
4 min. 16 sec.
Which statement is NOT true about FSE T2 pulse sequences?
Fat is darker than on SE pulse sequences
GRE with a small flip angle, long TR, short TE would yield:
PD weighted
In IR sequences, the resultant contrast depends primarily on the:
TI
All patients with joint replacements can safely undergo an MRI.
False
A patient with a spinal cord stimulator can never be scanned with MRI.
False
Spin echo sequences are useful for:
A, B, and C only (T1, T2, and PD weighted images)
Precessional frequency in MRI is measured in:
MHz
FSE/TSE sequences are useful for:
A, B, and C only (T1, T2, and PD weighted images)
Where can you find the latest information regarding MRI registry?
ARRT.org
A TI time of 150ms on a 1.5T magnet will null the signal from what tissue?
Fat
Arthrographic means:
Visualize joint spaces
What does GRASE stand for?
Gradient echo and spin echo
Which of the following is NOT one of the intrinsic contrast parameters?
TR
What is a transdermal patch?
A medication delivery device
When would a tattoo be considered MR unsafe?
If it has iron oxide inks
Myelographic means:
Spinal cord and nerve visualization
Calculate the scan time for a spin echo sequence with the following parameters: TR 500, TE 25, 224 x 256 matrix, 2 NSA, 3mm slice thickness.
3 min 44 sec
What is required if the MRI table is not detachable?
There must be an MRI-safe gurney readily available
Gradient echo sequences acquired for the evaluation of hemorrhagic lesions rely on:
Susceptibility
What is the precessional frequency for hydrogen on a 5T external static magnetic field?
212.9 MHz
What type of echoes are generated in EPI?
Gradient echoes
What extrinsic factor controls the amount of T1 recovery?
TR
If a quench has occurred, the operator should evacuate the room to avoid:
Asphyxiation and frostbite
Calculate the scan time for a 3D GRE echo sequence with the following parameters: TR 40, TE 24; FOV 30; 192 x 256 matrix; 1 NSA, F/A 45; 3.5 mm slice thickness; 31 slices.
3 min. 58 sec.
Imaging parameters in GRE T1-weighted sequences should have:
Large flip angle, short TR, short TE
What is the extrinsic contrast parameter unique to TSE/FSE?
Turbo factor or echo train length
What signal/s are sampled in coherent or rewind GE sequences?
The FID and the stimulated echo
What is the scan time for a proton density-weighted image assuming the following parameters: TR 3000ms, TE 20; 256 x 256, NSA 1, ETL 4?
3 minutes 12 seconds
The pulse sequence consisting of a variable flip angle RF excitation pulse followed by a pulse of the magnetic field gradients is called:
Gradient echo
What weighted image would be created with a CSE, TR 600, and TE 15?
T1
Where is a common place for a vascular filter?
IVC
Imaging parameters in GRE T2*-weighted sequences should have:
Small flip angle, long TR, long TE
A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as:
Incoherent/spoiled
With regard to energy, protons in parallel alignment are in the _________ state, whereas protons in anti-parallel alignment are in the __________ state.
Low, high
STIR sequences can suppress the signal from all of the following EXCEPT:
Fluid (CSF)
The B1 magnetic field is produced by:
RF coil
The null point of a tissue in an IR pulse sequence is calculated by:
0.69 x the T1 relaxation time of a tissue
The following parameters are suitable in a T2 FLAIR sequence EXCEPT:
Short TE to enhance T2 weighting
What image would be created with the following parameters: TR 2000, TE 60, TI 150?
STIR
What zone should all persons be supervised?
Zones 3 and 4
Spins aligned in the anti-parallel direction are in __________.
A high energy state
What is the Larmor equation used to calculate?
Precessional frequency
A technique that uses the differences in magnetic susceptibility between oxyhemoglobin and deoxyhemoglobin to image areas of activated cerebral cortex is:
BOLD
A rapid acquisition technique that begins with a sequence of one or more RF pulses and is followed by a series of gradient echoes:
EPI
What is an ‘active’ implant?
An implanted device that has a power source other than the human body itself
Which of the following is not one of the extrinsic parameters?
Proton Density (PD)
Angiographic means:
Visualize blood vessels and flow
What is a Hahn echo?
Any two 90° RF pulses produce one
In what year did MRI receive its FDA approval?
1985
Short tau inversion recovery (STIR) images are:
T2-weighted, fat-nulled images
Who is responsible for verifying that all the custodial staff are educated and trained about MR safety?
All MR technologists on staff
Which combination of TR and TE create a T1-weighted image?
TE 30ms, TR 300ms
Why should a patient have their kidney function tested before an MRI is performed with IV gadolinium contrast injection?
To make sure the contrast will be filtered out from the body in a reasonable amount of time
What type of echoes are generated in EPI?
Gradient echoes
What extrinsic factor controls the amount of T1 recovery?
TR
If a quench has occurred, the operator should evacuate the room to avoid:
Asphyxiation and frostbite
Calculate the scan time for a 3D GRE echo sequence with the following parameters: TR 40, TE 24; FOV 30; 192 x 256 matrix; 1 NSA, FA 45; 3.5 mm slice thickness; 31 slices.
3 min. 58 sec.
Imaging parameters in GRE T1-weighted sequences should have:
Large flip angle, short TR, short TE
What is the extrinsic contrast parameter unique to TSE/FSE?
Turbo factor or echo train length
What signals are sampled in coherent or rewind GE sequences?
The FID and the stimulated echo
What is the scan time for a proton density weighted image assuming the following parameters: TR 3000ms, TE 20; 256 x 256, NSA 1, ETL 4?
3 minutes 12 seconds
The pulse sequence consisting of a variable flip angle RF excitation pulse followed by a pulse of the magnetic field gradients is called:
Gradient echo
What weighted image would be created with a CSE, TR 600, and TE 15?
T1
Where is a common place for a vascular filter?
IVC
Imaging parameters in GRE T2*-weighted sequences should have:
Small flip angle, long TR, long TE
A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as:
Incoherent/spoiled
With regard to energy, protons in parallel alignment are in the _________ state, whereas protons in anti-parallel alignment are in the __________ state.
Low, high
What is the purpose of the initial RF pulse in a coherent gradient echo sequence?
Spin excitation
All surgical staples, clips, and metallic sutures are MR unsafe.
False
T2 relaxation time is defined as when:
63% of the transverse magnetization has decayed
What is the FDA recommended amount of SAR for the head averaged over 10 minutes?
3 W/kg
In STIR sequences, which tissue is being suppressed?
Fat
What is a cochlear implant?
An implant in the inner ear
What conditions are necessary for resonance?
Energy applied at the precise frequency and at a right angle
