Scan Acquisition

Question 1

(i.e. the scanned
projection radiograph, often acquired by the
CT system to allow the user to prescribe the
start and end locations of the scan range)

Answer 1

CT localizer radiograph

Question 2

: Data acquisition while the
patient table remains stationary; the table
position may be incremented between x-ray
exposures to collect data over a longer z
axis range.

Answer 2

Axial scan mode

Question 3

Data
acquisition while the patient table is
continuously moving along the z axis

Answer 3

Helical or Spiral scan mode:

Question 4

: Data acquisition at multiple time
points over the same anatomic location(s)
while the patient table remains stationary; xray exposure can be continuous or
intermittent

Answer 4

Dynamic scan mode - single detector width

Question 5

: Data acquisition at multiple time
points over the same anatomic location(s)
while the patient table cycles back and forth
between designated start and end locations
in order image a region wider than the
detector

Answer 5

Dynamic scan mode - multiple detector
widths

Question 6

(mm) per 360 degree
rotation of the x-ray tube (axial scan
mode)

Answer 6

Table increment

Question 7

per 360 degree rotation of the xray tube (helical scan mode)

Answer 7

Table feed

Question 8

Diameter of the
circular region within the scan plane over
which projection data are collected.
Nominally equal to the diameter of the
primary beam at isocenter in the axial
plane

Answer 8

Field of measurment:

Question 9

Number of electrons
accelerated across an x-ray tube per unit
time, expressed in units of milliampere (mA)

Answer 9

Tube current:

Question 10

: The product of
tube current and exposure time per rotation,
expressed in units of milliampere • seconds
(mAs). In axial scan mode, this is equal to
tube current × (scan angle ÷ 360) × rotation
time. In helical scan mode, this is equal to
tube current × rotation time.

Answer 10

Tube current-time product

Question 11

: In
helical scan mode, this is the product of tube
current and rotation time (expressed in units
of milliampere • seconds (mAs) ÷ pitch)

Answer 11

Effective tube current-time product

Question 12

: The electric potential
applied across an x-ray tube to accelerate
electrons towards a target material,
expressed in units of kilovolts (kV)

Answer 12

Tube potential

Question 13

: Unitless parameter used to describe
the table travel during helical CT; equal to
table travel (mm) per gantry rotation ÷ total
nominal beam width (mm)

Answer 13

Pitch