Collimation

Question 1

Collimation for MDCT can be divided into 2 distinct components

Answer 1

Beam collimation
Detector (section) collimation

Question 2

Beam Collimation: general purpose

Answer 2

restrict exposure to area of interest, reducing dose and improving image quality

Question 3

3rd-generation scanner geometry

Answer 3

Tube and detector bank linked and rotating together

Question 4

Fan-beam of SSCT

Answer 4

Transverse (x-y) dimension corresponds to size of detector array and to max SFOV

Question 5

SSCT wider fan angle

Answer 5

extends coverage of detector array along the x- and y-axes

Question 6

SSCT fan angle of emitted beam determines

Answer 6

length of detector coverage in transverse direction

Question 7

SSCT pre-patient collimator

Answer 7

mechanical aperture (located just outside tube housing) responsible for beam restriction

Question 8

SSCT beam collimation along longitudinal/z-axis

Answer 8

collimated to anticipated slice thickness

Question 9

Pre-patient beam collimation in SSCT directly controls

Answer 9

Amount of tissue exposed to x-ray as tube rotates

Question 10

Retrospective slice thickness adjustment is not possible with

Answer 10

SSCT

Question 11

Postpatient (predetector) collimation

Answer 11

limit scatter radiation before it reaches detectors thus improving image quality

Question 12

2 components of prepatient collimation

Answer 12

tube housing
(primary) prepatient collimator

Question 13

Prepatient collimation: tube housing

Answer 13

tube aperture roughly shapes beam (into fan for SSCT or cone for MDCT) such that it emerges at specific fan angle corresponding to (in-plane) length of detector array

Question 14

Prepatient Collimation: Primary

Answer 14

Collimator positioned just beyond tube housing restricting beam along z-axis (controls slice thickness in SSCT)