CT Principles part 2

Question 1

What shape of beam geometry do we associate with MDCT?

Answer 1

Cone beam geometry

Question 2

What characteristic defines isotropic voxels?

Answer 2

that they are equal in each dimension

Question 3

What is the size and arrangement of parts like in a symmetric multi-slice detector array?

Answer 3

the are all the same

Question 4

What is the size and arrangement of parts like in an asymmetric/adaptive multi-slice detector array?

Answer 4

The detectors can vary in size and arrangement.

Question 5

Is it possible to change the slice thickness by combining detectors in an array in different configurations?

Answer 5

Yes!

Question 6

What is meant by ‘binning’ detectors?

Answer 6

combining them together to achieve a different slice thickness

Question 7

Which of the following utilizes a cone beam geometry? (a. single slice axial mode b. single slice helical mode c. single slice and multislice ct d. multislice ct)

Answer 7

d. multislice ct

Question 8

In the cone beam geometry, projections from the x-ray source ____ the scanner isocenter (a. pass through b. pass over c. do not pass through d. there is no relationship between cone beam geometry and isocenter)

Answer 8

c. do not pass through (in cone beam geometry, the projections are on the outside of the cone)

Question 9

In MDCT, an adaptive array detection system has _____. (a. detector elements of mixed size b. detector elements of the same size c. larger detector elements toward the scanner isocenter d. large and small detector elements throughout the longitudinal length)

Answer 9

a. detector elements of mixed size

Question 10

Multislice CT was introduced in 1992 with the Elscint CT Twin scanner but became a reality in 1998 when _____. (a. when dual scanners became available b. when quad scanners were designed c. after 8 slice scanners were available d. only with the introduction of 16 slice scanners)

Answer 10

b. when quad scanners were designed (introduced)

Question 11

MDCT detectors are aligned in the ____ and _____ directions. (a. vertical and longitudonal b. transaxial and vertical directions c. longitudinal and z-axis directions d. transaxial and z-axis directions)

Answer 11

d. transaxial and z-axis directions

Question 12

A voxel is isotropic when ___ of its sides are ____.

Answer 12

All of its sides are equal

Question 13

What kind of voxels will result in increased integrity of multiplanar reformations?

Answer 13

isotropic

Question 14

Star pattern noise is associated with what type of reconstruction method?

Answer 14

Simple back projection

Question 15

Algebraic reconstruction technique is a form of _____ method.

Answer 15

iterative

Question 16

The problem with the algebraic reconstruction technique is _____.

Answer 16

it results in an overwhelming number of calculations needed

Question 17

The basic idea behind simple back projection is to _______.

Answer 17

send projection data back through the image

Question 18

Filtered back projection uses a ____ to reduce star pattern blur

Answer 18

kernal (sometimes called a convolusion filter)

Question 19

Filtered back projection is also called _____ method

Answer 19

convolution method