1|Page
ASMIRT- MRI ACCREDITATION TEST BANK EXAM LATEST 2025/2026 ACTUAL
EXAM WITH COMPLETE QUESTIONS AND CORRECT DETAILED ANSWERS
(100% VERIFIED ANSWERS) |ALREADY GRADED A+| ||PROFESSOR VERIFIED||
||BRANDNEW!!!||
What is a fourier transform? - ANSWER-Fourier analysis allows
any time varying signal (such as a spin-echo) to be represented
as a spectrum of the frequencies present. Fourier Transformation
converts RF intensity vs. time into Signal amplitude vs. frequency
thus allowing us to reconstruct images. The mathematical
procedure relating the functions of amplitude against time and
amplitude against frequency is known as Fourier Transformation -
if one is known, the other can be readily calculated. This process
is ideally suited to MR image reconstruction which uses frequency
shifts to spatially localise the signal.
What is k-space? - ANSWER-K-Space is simply an array of
numbers whose Fourier Transformation is the MR image. Simply
K-Space is best thought of as temporary image space, which is
used to digitize MR signals during acquisition.
In 2DFT imaging, the position of the values tells us what about
where they were collected in echo? - ANSWER-In 2DFT imaging,
each horizontal row of K-space corresponds to the echo data
,2|Page
obtained by digitising the signal from one phase encoding step.
The values at the left of each row are collected early in each echo
those at the right are obtained late. The centre of the row will
correspond to the centre of each echo and will therefore contain
the largest values.
Why do rows of k-space data at the periphery ie. very top and
bottom contribute most to spatial resolution? - ANSWER-Each
row of k-space data is obtained by varying the amplitude of the
phase encoding gradient. The rows at the top and bottom of the k-
space grid are obtained with steep gradient slopes. This will
cause smaller signal amplitudes due to gradient-induced
dephasing, however this will maximise the phase separation of
adjacent points. These lines therefore contribute most towards the
spatial resolution of the image.
Why do rows of k-space data at the centre contribute most to
contrast? - ANSWER-The central rows are obtained using shallow
gradient slopes so the echo amplitudes will be larger due to little
gradient induced dephasing. These lines will contribute most
towards the contrast of the image.
,3|Page
Does every cell in k-space correspond to an individual pixel? -
ANSWER-It should be remembered that individual cells in k-
space do not correspond to individual pixels in the image - each
pixel is represented in every k-space cell.
Explain how 2D k-space filling occurs - ANSWER-2D volumetric
acquisitions fill one line of K-space for slice 1 and then fill the
same line of K-space for slice 2 etc. When one line of K-space
has been filled for all slices the next line of K-space is filled and
so on until all the Kspace data has been acquired for all slices.
Once the sequence is finished all of the slices are reconstructed
and displayed at the same time. This is the most common method
of K-space filling.
Explain 3D volumetric k-space filling - ANSWER-3D volumetric
techniques acquire data from an entire volume of tissue. The
excitation pulse is not slice selective rather the whole prescribed
imaging volume is excited. As such K-space is three dimensional.
At the end of the acquisition the volume slab is divided into slices
using an extra gradient called the slice select gradient. A 3D FT is
then used to reconstruct the images. An example of this technique
is a 3D T2* C-spine.
, 4|Page
How can k-space be manipulated and why? - ANSWER-K-Space
can be manipulated to suit the needs of the MRI examination
under progress. Many of these techniques are made possible due
to the mirrored halves of K-Space. That being the top and bottom
halves as well as the right and left halves of K-Space mirror each
other. This can be advantageous to the operator and patient as
manipulation of k-space can decrease scan times.
What is Partial / Fractional Echo? - ANSWER-• Relies on echo
symmetry from left to right sides of K-space
• Only the right hand side of the echo is read by the frequency
encoding gradient - the remaining portion is calculated. (ie sample
the right half of k-space and calculate the left)
• Allows the peak of the echo to occur closer to the RF excitation
pulse so shorter TE's are possible for MRA, T1 spin-echo and fast
GRE.
What is partial fourier transform? - ANSWER-• Also relies on
symmetry - this time between the positive and negative phase
encodings or halves of K-Space
ASMIRT- MRI ACCREDITATION TEST BANK EXAM LATEST 2025/2026 ACTUAL
EXAM WITH COMPLETE QUESTIONS AND CORRECT DETAILED ANSWERS
(100% VERIFIED ANSWERS) |ALREADY GRADED A+| ||PROFESSOR VERIFIED||
||BRANDNEW!!!||
What is a fourier transform? - ANSWER-Fourier analysis allows
any time varying signal (such as a spin-echo) to be represented
as a spectrum of the frequencies present. Fourier Transformation
converts RF intensity vs. time into Signal amplitude vs. frequency
thus allowing us to reconstruct images. The mathematical
procedure relating the functions of amplitude against time and
amplitude against frequency is known as Fourier Transformation -
if one is known, the other can be readily calculated. This process
is ideally suited to MR image reconstruction which uses frequency
shifts to spatially localise the signal.
What is k-space? - ANSWER-K-Space is simply an array of
numbers whose Fourier Transformation is the MR image. Simply
K-Space is best thought of as temporary image space, which is
used to digitize MR signals during acquisition.
In 2DFT imaging, the position of the values tells us what about
where they were collected in echo? - ANSWER-In 2DFT imaging,
each horizontal row of K-space corresponds to the echo data
,2|Page
obtained by digitising the signal from one phase encoding step.
The values at the left of each row are collected early in each echo
those at the right are obtained late. The centre of the row will
correspond to the centre of each echo and will therefore contain
the largest values.
Why do rows of k-space data at the periphery ie. very top and
bottom contribute most to spatial resolution? - ANSWER-Each
row of k-space data is obtained by varying the amplitude of the
phase encoding gradient. The rows at the top and bottom of the k-
space grid are obtained with steep gradient slopes. This will
cause smaller signal amplitudes due to gradient-induced
dephasing, however this will maximise the phase separation of
adjacent points. These lines therefore contribute most towards the
spatial resolution of the image.
Why do rows of k-space data at the centre contribute most to
contrast? - ANSWER-The central rows are obtained using shallow
gradient slopes so the echo amplitudes will be larger due to little
gradient induced dephasing. These lines will contribute most
towards the contrast of the image.
,3|Page
Does every cell in k-space correspond to an individual pixel? -
ANSWER-It should be remembered that individual cells in k-
space do not correspond to individual pixels in the image - each
pixel is represented in every k-space cell.
Explain how 2D k-space filling occurs - ANSWER-2D volumetric
acquisitions fill one line of K-space for slice 1 and then fill the
same line of K-space for slice 2 etc. When one line of K-space
has been filled for all slices the next line of K-space is filled and
so on until all the Kspace data has been acquired for all slices.
Once the sequence is finished all of the slices are reconstructed
and displayed at the same time. This is the most common method
of K-space filling.
Explain 3D volumetric k-space filling - ANSWER-3D volumetric
techniques acquire data from an entire volume of tissue. The
excitation pulse is not slice selective rather the whole prescribed
imaging volume is excited. As such K-space is three dimensional.
At the end of the acquisition the volume slab is divided into slices
using an extra gradient called the slice select gradient. A 3D FT is
then used to reconstruct the images. An example of this technique
is a 3D T2* C-spine.
, 4|Page
How can k-space be manipulated and why? - ANSWER-K-Space
can be manipulated to suit the needs of the MRI examination
under progress. Many of these techniques are made possible due
to the mirrored halves of K-Space. That being the top and bottom
halves as well as the right and left halves of K-Space mirror each
other. This can be advantageous to the operator and patient as
manipulation of k-space can decrease scan times.
What is Partial / Fractional Echo? - ANSWER-• Relies on echo
symmetry from left to right sides of K-space
• Only the right hand side of the echo is read by the frequency
encoding gradient - the remaining portion is calculated. (ie sample
the right half of k-space and calculate the left)
• Allows the peak of the echo to occur closer to the RF excitation
pulse so shorter TE's are possible for MRA, T1 spin-echo and fast
GRE.
What is partial fourier transform? - ANSWER-• Also relies on
symmetry - this time between the positive and negative phase
encodings or halves of K-Space
