age 1 of 44
PET/CT EXAM STUDY GUIDE 2025/2026 ACCURATE
QUESTIONS WITH CORRECT DETAILED ANSWERS ||
100% GUARANTEED PASS <RECENT VERSION>
Explain the difference between a pixel and a voxel
.......Answer.........A pixel is a 2D unit of measurement while voxel
is 3D
What is a CT number/ HU .......Answer.........CT number/HU: a
relative quantitative measurement of radio density, interpreted
by a greyscale image
What filter is used in CT and why? .......Answer.........Bow tie filter,
higher fluency and energy density of x-rays at edges of FOV,
the filter causes more attenuation in the periphery so that a
uniform signal results. Reduces patient dose w no loss of image
quality.
,age 2 of 44
What do Pre patient collimators do? .......Answer.........controls
patient dose, shapes beam
what is post patient collimation? .......Answer.........removes
scattered radiation, improve image quality
Over beaming .......Answer.........beam produced is wider than the
detector
over ranging .......Answer.........patient exposed beyond length of
scan, increases patient dose
What do CT detectors do? .......Answer.........captures x-rays and
converts x-ray photons to digital data
What is SFOV (scan field of view) .......Answer.........Determines
area from which raw data is acquired around isocentre middle
of gantry. anything outside SFOV not imaged
,age 3 of 44
What is DFOV? .......Answer.........How much raw data is used to
create image, can choose target body part can be = or less
SFOV
Relationship between DFOV, metric and pixel size
.......Answer.........· Pixel size (mm) = DFOV/
matrix
what are reconstruction kernels and how to they affect the
image? .......Answer.........soft tissue - smoothing kernel
Bone kernel - sharpening kernel
corrects image by reducing blurring/ sharpens
Window Width WW .......Answer.........The range of HU values
that an image contains
, age 4 of 44
Window Level WL .......Answer.........centre of range of greyscale
midpoint
Helical scanning interpolation .......Answer.........Approximating
data values to make axial slices, helical data is interpolated to
make a full dataset. use of projection data from outside the
reconstructed volume leads to reduction in axial resolution.
What is Pitch .......Answer.........Table distance travelled in one
360 degree gantry rotation
Pitch in Helical MSCT .......Answer.........Wider beams of MSCT
accentuate cone beam shape and lead to rays that do not even
lie within same plane.
Pitch = T/D
PET/CT EXAM STUDY GUIDE 2025/2026 ACCURATE
QUESTIONS WITH CORRECT DETAILED ANSWERS ||
100% GUARANTEED PASS <RECENT VERSION>
Explain the difference between a pixel and a voxel
.......Answer.........A pixel is a 2D unit of measurement while voxel
is 3D
What is a CT number/ HU .......Answer.........CT number/HU: a
relative quantitative measurement of radio density, interpreted
by a greyscale image
What filter is used in CT and why? .......Answer.........Bow tie filter,
higher fluency and energy density of x-rays at edges of FOV,
the filter causes more attenuation in the periphery so that a
uniform signal results. Reduces patient dose w no loss of image
quality.
,age 2 of 44
What do Pre patient collimators do? .......Answer.........controls
patient dose, shapes beam
what is post patient collimation? .......Answer.........removes
scattered radiation, improve image quality
Over beaming .......Answer.........beam produced is wider than the
detector
over ranging .......Answer.........patient exposed beyond length of
scan, increases patient dose
What do CT detectors do? .......Answer.........captures x-rays and
converts x-ray photons to digital data
What is SFOV (scan field of view) .......Answer.........Determines
area from which raw data is acquired around isocentre middle
of gantry. anything outside SFOV not imaged
,age 3 of 44
What is DFOV? .......Answer.........How much raw data is used to
create image, can choose target body part can be = or less
SFOV
Relationship between DFOV, metric and pixel size
.......Answer.........· Pixel size (mm) = DFOV/
matrix
what are reconstruction kernels and how to they affect the
image? .......Answer.........soft tissue - smoothing kernel
Bone kernel - sharpening kernel
corrects image by reducing blurring/ sharpens
Window Width WW .......Answer.........The range of HU values
that an image contains
, age 4 of 44
Window Level WL .......Answer.........centre of range of greyscale
midpoint
Helical scanning interpolation .......Answer.........Approximating
data values to make axial slices, helical data is interpolated to
make a full dataset. use of projection data from outside the
reconstructed volume leads to reduction in axial resolution.
What is Pitch .......Answer.........Table distance travelled in one
360 degree gantry rotation
Pitch in Helical MSCT .......Answer.........Wider beams of MSCT
accentuate cone beam shape and lead to rays that do not even
lie within same plane.
Pitch = T/D
