MCPHS IMAGINGU MRI EXAM QUESTIONS AND
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED BY
EXPERTS
Active Shimming
is done at the time of imaging and consists of running current through specific coils to increase the
strength/homogeneity of certain areas in the MRI scanner to increase image quality.
Faraday's Law states that:
when a loop of wire is exposed to a moving magnetic field, a voltage will be induced into that loop of
wire
Calculate the voxel volume for a sequence with a 240x240mm FOV, 3mm Slice thickness, and a scan
matrix of 256(f)x192(ph).
= .94mm (freq pixel size) = 1.25mm (phase pixel size) x 3mm slice thickness
Gradient Echoes have what main advantage over spin echo imaging?
Lower acquisition times
Gradient echo imaging
uses this is due to lower flip angles used for excitation and allow GRE images to use lower TRs and TEs
The _______ gradient is used to fill information within k-space in the vertical axis (top-bottom).
Phase encoding
What technique is used to help reduce the saturation effect in 3D TOF acquisitions and keep a
consistent signal intensity from the flowing blood throughout the volume of interest.
Multiple Thin Slice Overlapping Acquisition (MOTSA)
_______ refers to an imaging technique that utilizes additional information about moving organs to
minimize motion by adjusting acquisition timing accordingly:
,Physiological gating and triggering
Echo Planar Imaging (EPI)
pulse sequence uses quickly switching phase and frequency gradients in order to fill all the lines of K-
space within a single excitation pulse.
Diffusion, Perfusion and functional MRI techniques all utilize the EPI sequence.
The regaining of longitudinal magnetization due to excited protons giving up their energy to the
surrounding environment refers to:
T1 recovery
This sequence is based on the natural, random motion of water within the body
Diffusion
Gradient Echo starts with
an RF excitation pulse below 90 degrees, followed by the application of rephasing gradients in order to
produce an echo.
What type of pulse sequence and k-space filling method would be best to use when acquiring CE-
MRA?
T1; keyhole
CE MRA (Contrast-enhanced MR angiography)
using contrast which causes a shortening of T1 so the pulse sequence needs to be T1 weighted to detect
the contrast. In addition, we have a small window to capture the contrast bolus so we need to image fast
so we use a combination of a gradient echo based sequence with a keyhole k-space filling.
Protons aligned (parallel) with the main magnetic field (B0) are said to have:
Low energy levels
This is a 3D post-processing technique used to re-display three-dimensional images in any plane.
Multi-Planar reconstruction (MPR)
, Proton density is described as
the number of hydrogen protons in a given tissue that can contribute to the size of the net
magnetization vector.
Calculate scan time if: TR = 3000ms, NSA = 3, scan matrix = 320(f) x 224(ph), TE = 45 ms, FOV =
256x256, ETL = 12.
3000/1000= 3 seconds; 3 x 224(ph)= 672; 672 x 3(NSA)= 2016; 2016/12(ETL)= 168 seconds; 168/60=2
minutes and 48 seconds
The center of K-space is responsible for storing information pertaining to:
Contrast
Magnetic Susceptibility artifact occurs as a result of:
metal or any other substance within the body that disrupts the homogeneity of the magnetic field.
Phase coherence results in:
Maximal signal
The parameter that is described as the size of the area covered within an image is
Field of view (FOV)
A Transmit / Receive coil is described as:
a type of imaging coil that is responsible for the delivery of RF energy as well as the recording of the MRI
signal.
Key-Hole Filling
is a K-space filling method that is mainly used in contrast enhanced angiography, where the very center
of k-space is acquired first in order to quickly capture the recording of all contrast information first
This is the estimated value given to represent the ability of water to diffuse/move within a given voxel
of tissue.
Apparent diffusion coefficient (ADC)
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED BY
EXPERTS
Active Shimming
is done at the time of imaging and consists of running current through specific coils to increase the
strength/homogeneity of certain areas in the MRI scanner to increase image quality.
Faraday's Law states that:
when a loop of wire is exposed to a moving magnetic field, a voltage will be induced into that loop of
wire
Calculate the voxel volume for a sequence with a 240x240mm FOV, 3mm Slice thickness, and a scan
matrix of 256(f)x192(ph).
= .94mm (freq pixel size) = 1.25mm (phase pixel size) x 3mm slice thickness
Gradient Echoes have what main advantage over spin echo imaging?
Lower acquisition times
Gradient echo imaging
uses this is due to lower flip angles used for excitation and allow GRE images to use lower TRs and TEs
The _______ gradient is used to fill information within k-space in the vertical axis (top-bottom).
Phase encoding
What technique is used to help reduce the saturation effect in 3D TOF acquisitions and keep a
consistent signal intensity from the flowing blood throughout the volume of interest.
Multiple Thin Slice Overlapping Acquisition (MOTSA)
_______ refers to an imaging technique that utilizes additional information about moving organs to
minimize motion by adjusting acquisition timing accordingly:
,Physiological gating and triggering
Echo Planar Imaging (EPI)
pulse sequence uses quickly switching phase and frequency gradients in order to fill all the lines of K-
space within a single excitation pulse.
Diffusion, Perfusion and functional MRI techniques all utilize the EPI sequence.
The regaining of longitudinal magnetization due to excited protons giving up their energy to the
surrounding environment refers to:
T1 recovery
This sequence is based on the natural, random motion of water within the body
Diffusion
Gradient Echo starts with
an RF excitation pulse below 90 degrees, followed by the application of rephasing gradients in order to
produce an echo.
What type of pulse sequence and k-space filling method would be best to use when acquiring CE-
MRA?
T1; keyhole
CE MRA (Contrast-enhanced MR angiography)
using contrast which causes a shortening of T1 so the pulse sequence needs to be T1 weighted to detect
the contrast. In addition, we have a small window to capture the contrast bolus so we need to image fast
so we use a combination of a gradient echo based sequence with a keyhole k-space filling.
Protons aligned (parallel) with the main magnetic field (B0) are said to have:
Low energy levels
This is a 3D post-processing technique used to re-display three-dimensional images in any plane.
Multi-Planar reconstruction (MPR)
, Proton density is described as
the number of hydrogen protons in a given tissue that can contribute to the size of the net
magnetization vector.
Calculate scan time if: TR = 3000ms, NSA = 3, scan matrix = 320(f) x 224(ph), TE = 45 ms, FOV =
256x256, ETL = 12.
3000/1000= 3 seconds; 3 x 224(ph)= 672; 672 x 3(NSA)= 2016; 2016/12(ETL)= 168 seconds; 168/60=2
minutes and 48 seconds
The center of K-space is responsible for storing information pertaining to:
Contrast
Magnetic Susceptibility artifact occurs as a result of:
metal or any other substance within the body that disrupts the homogeneity of the magnetic field.
Phase coherence results in:
Maximal signal
The parameter that is described as the size of the area covered within an image is
Field of view (FOV)
A Transmit / Receive coil is described as:
a type of imaging coil that is responsible for the delivery of RF energy as well as the recording of the MRI
signal.
Key-Hole Filling
is a K-space filling method that is mainly used in contrast enhanced angiography, where the very center
of k-space is acquired first in order to quickly capture the recording of all contrast information first
This is the estimated value given to represent the ability of water to diffuse/move within a given voxel
of tissue.
Apparent diffusion coefficient (ADC)
