CT REGISTRY LATEST EXAM ACTUAL ALL QUESTIONS AND
ANSWERS SURE A+
✔✔As pitch increases so does the - ✔✔slice angle
✔✔Calculate the beam width used when the scanner is a 64 channel system and 0.5
mm slice thickness is programmed. - ✔✔(number of detectors x slice thickness)
32 mm
✔✔Given the following.. calculate the pitch: 32 channel MDCT system, 1.25 mm slice
thickness, table movement is 16 mm per rotation. - ✔✔MDCT pitch calculation = table
travel during tube rotation / beam width
beam width = slice thickness x number of detectors
(1st calculate beam width)
1.25x 32=40
(then calculate pitch)
16/40=0.4
✔✔as pitch decreases, slice angle ___________; & interpolation will ______________ -
✔✔decrease; decrease
✔✔Determine how much the table must travel for a pitch value of 1 to occur given a
slice thickness of 5 mm when gantry rotation is 1 second per slice. - ✔✔CT scan
coverage calculation - pitch x total acquisition x 1/ rotation time
1 x 5 x 1 = 5 mm
✔✔what is the data reconstruction process? - ✔✔The DAS "reads" each arriving ray
and measures how much of the beam is attenuated
This is a ray sum
Many ray sums make up a view
Many views are needed to create an image
An attenuation profile is created for each view
Information from all the profiles is projected onto a matrix
The process of converting the data from the attenuation profile to a matrix is known as
back projection
✔✔an important post processing tool that decomposes an image into components -
✔✔Fourier Transformation
✔✔A mathematical method of estimation the value of an unknown function using the
known value on either side of the function - ✔✔Interpolation
,✔✔Convolution - ✔✔The application of a filter function to an attenuation profile
✔✔During which phase is contrast media found in the arteries and veins enough to be
visible in each? - ✔✔non equilibrium
✔✔Back projection - ✔✔The process of converting the data from the attenuation profile
✔✔iterative reconstruction - ✔✔A complex reconstruction method that computes
projections from the image, compares it with the original projection data and updates
the image based on the difference.
✔✔Which algorithm types would provide the best soft tissue detail during a CT study of
a pelvis? - ✔✔low spacial frequency
✔✔An injury to the brain opposite to the site of traumatic impart is referred to as -
✔✔contrecoup
✔✔What symptoms indicate a vagal reaction to iodinated contrast - ✔✔
✔✔Which technical factors exhibits an effect upon longitudinal spacial resolution -
✔✔detector pitch; interpolation algorithm
✔✔The presence of outpocketings in the wall of the colon are termed - ✔✔diverticulosis
✔✔An MDCT image is reconstructed using a 512(2) matrix and a display field of view of
44 cm. If the detector collimation is to a section width of 2.5 mm, what is the volume of
each voxel. - ✔✔
✔✔The ability of a CT system to maintain consistant Housfield value across the entire
image of homogenous object is termed - ✔✔uniformity
✔✔_________________ is commonly caused by faulty detectors. - ✔✔Ring artifacts
✔✔The tube housing, cooling oil, and so on, constituate inherant filtration, which
amounts to approximately ___ mm of aluminum equivalent filtration - ✔✔3 mm
✔✔The detectors of a PET system absorb and measure what kind of radiation ? -
✔✔annihilation photons
✔✔best phase of renal contrast enhancement to display parenchymal lesions -
✔✔nephrographic phase (70 to 90 seconds)
, ✔✔Hallmark CT finding for focal nodular hyperplasia of the liver is - ✔✔central scar that
remains hypodense after initial contrast agent administration
✔✔The ability of a CT system to maintain consistent HU values across the entire image
of a homogeneous object is termed - ✔✔
✔✔An MDCT image is reconstructed using a 512² matrix and a DFOV of 38cm. If the
detector collimation is set to a section width of 1.25mm, what is the volume of each
voxel? - ✔✔The linear dimension of the pixel must first be calculated by dividing the
DFOV, in mm, by the matrix (380 mm/512= 0.74 mm). This linear pixel dimension is
squared to yield the pixel area in mm² (0.74 x 0.74= 0.55 mm²). The volume of the voxel
may be calculated by multiplying the pixel area by the section width (0.55 mm² x 1.25
mm= 0.69mm³).
✔✔Power output for a modern MDCT x-ray tube has an approximate range of: - ✔✔60-
100 kilowatts
✔✔During CT x-ray exposure, the product of the selected mA setting and the scan time
is called the - ✔✔constant mAs
✔✔What matrix size was used to reconstruct an image with the display characteristics
DFOV 25cm and pixel area 0.25mm²? - ✔✔512 x 512
The matrix size used to reconstruct an image can be calculated by dividing the display
field of view (DFOV) by the pixel dimension. A pixel whose area is 0.25 mm2 has a
linear dimension of 0.5 mm. Dividing the DFOV of 250 mm by the pixel dimension 0.5
mm gives a matrix size of approximately 512 x 512 pixels. square root of 0.25=0.5.
Convert units of DFOV.
✔✔Describe the retroperitoneum and what it contains - ✔✔The retroperitoneum is the
space located between the peritoneum and the posterior abdominal wall. It contains the
duodenum, pancreas, adrenal glands, kidneys, ureters, and bladder.
✔✔define hydrocephalus - ✔✔"water on the brain"
occurs when there is an increase in the volume of CSF
due to closed skull there is no place for CSF to expand, if pressure becomes too hight
the brainstem is forced to escape (herniate) through the foramen magnum
✔✔what 2 openings allow CSF to flow into the subarachnoid space? - ✔✔1) the
foramina of Luschka-- laterally
2) the foramen of Magendie---medially
ANSWERS SURE A+
✔✔As pitch increases so does the - ✔✔slice angle
✔✔Calculate the beam width used when the scanner is a 64 channel system and 0.5
mm slice thickness is programmed. - ✔✔(number of detectors x slice thickness)
32 mm
✔✔Given the following.. calculate the pitch: 32 channel MDCT system, 1.25 mm slice
thickness, table movement is 16 mm per rotation. - ✔✔MDCT pitch calculation = table
travel during tube rotation / beam width
beam width = slice thickness x number of detectors
(1st calculate beam width)
1.25x 32=40
(then calculate pitch)
16/40=0.4
✔✔as pitch decreases, slice angle ___________; & interpolation will ______________ -
✔✔decrease; decrease
✔✔Determine how much the table must travel for a pitch value of 1 to occur given a
slice thickness of 5 mm when gantry rotation is 1 second per slice. - ✔✔CT scan
coverage calculation - pitch x total acquisition x 1/ rotation time
1 x 5 x 1 = 5 mm
✔✔what is the data reconstruction process? - ✔✔The DAS "reads" each arriving ray
and measures how much of the beam is attenuated
This is a ray sum
Many ray sums make up a view
Many views are needed to create an image
An attenuation profile is created for each view
Information from all the profiles is projected onto a matrix
The process of converting the data from the attenuation profile to a matrix is known as
back projection
✔✔an important post processing tool that decomposes an image into components -
✔✔Fourier Transformation
✔✔A mathematical method of estimation the value of an unknown function using the
known value on either side of the function - ✔✔Interpolation
,✔✔Convolution - ✔✔The application of a filter function to an attenuation profile
✔✔During which phase is contrast media found in the arteries and veins enough to be
visible in each? - ✔✔non equilibrium
✔✔Back projection - ✔✔The process of converting the data from the attenuation profile
✔✔iterative reconstruction - ✔✔A complex reconstruction method that computes
projections from the image, compares it with the original projection data and updates
the image based on the difference.
✔✔Which algorithm types would provide the best soft tissue detail during a CT study of
a pelvis? - ✔✔low spacial frequency
✔✔An injury to the brain opposite to the site of traumatic impart is referred to as -
✔✔contrecoup
✔✔What symptoms indicate a vagal reaction to iodinated contrast - ✔✔
✔✔Which technical factors exhibits an effect upon longitudinal spacial resolution -
✔✔detector pitch; interpolation algorithm
✔✔The presence of outpocketings in the wall of the colon are termed - ✔✔diverticulosis
✔✔An MDCT image is reconstructed using a 512(2) matrix and a display field of view of
44 cm. If the detector collimation is to a section width of 2.5 mm, what is the volume of
each voxel. - ✔✔
✔✔The ability of a CT system to maintain consistant Housfield value across the entire
image of homogenous object is termed - ✔✔uniformity
✔✔_________________ is commonly caused by faulty detectors. - ✔✔Ring artifacts
✔✔The tube housing, cooling oil, and so on, constituate inherant filtration, which
amounts to approximately ___ mm of aluminum equivalent filtration - ✔✔3 mm
✔✔The detectors of a PET system absorb and measure what kind of radiation ? -
✔✔annihilation photons
✔✔best phase of renal contrast enhancement to display parenchymal lesions -
✔✔nephrographic phase (70 to 90 seconds)
, ✔✔Hallmark CT finding for focal nodular hyperplasia of the liver is - ✔✔central scar that
remains hypodense after initial contrast agent administration
✔✔The ability of a CT system to maintain consistent HU values across the entire image
of a homogeneous object is termed - ✔✔
✔✔An MDCT image is reconstructed using a 512² matrix and a DFOV of 38cm. If the
detector collimation is set to a section width of 1.25mm, what is the volume of each
voxel? - ✔✔The linear dimension of the pixel must first be calculated by dividing the
DFOV, in mm, by the matrix (380 mm/512= 0.74 mm). This linear pixel dimension is
squared to yield the pixel area in mm² (0.74 x 0.74= 0.55 mm²). The volume of the voxel
may be calculated by multiplying the pixel area by the section width (0.55 mm² x 1.25
mm= 0.69mm³).
✔✔Power output for a modern MDCT x-ray tube has an approximate range of: - ✔✔60-
100 kilowatts
✔✔During CT x-ray exposure, the product of the selected mA setting and the scan time
is called the - ✔✔constant mAs
✔✔What matrix size was used to reconstruct an image with the display characteristics
DFOV 25cm and pixel area 0.25mm²? - ✔✔512 x 512
The matrix size used to reconstruct an image can be calculated by dividing the display
field of view (DFOV) by the pixel dimension. A pixel whose area is 0.25 mm2 has a
linear dimension of 0.5 mm. Dividing the DFOV of 250 mm by the pixel dimension 0.5
mm gives a matrix size of approximately 512 x 512 pixels. square root of 0.25=0.5.
Convert units of DFOV.
✔✔Describe the retroperitoneum and what it contains - ✔✔The retroperitoneum is the
space located between the peritoneum and the posterior abdominal wall. It contains the
duodenum, pancreas, adrenal glands, kidneys, ureters, and bladder.
✔✔define hydrocephalus - ✔✔"water on the brain"
occurs when there is an increase in the volume of CSF
due to closed skull there is no place for CSF to expand, if pressure becomes too hight
the brainstem is forced to escape (herniate) through the foramen magnum
✔✔what 2 openings allow CSF to flow into the subarachnoid space? - ✔✔1) the
foramina of Luschka-- laterally
2) the foramen of Magendie---medially
