11. CBCT Flashcards
4
What is the shape of the x-ray beam for CBCT?
4
A CBCT is the only _____ scan enough to acquire a full volume of images
4
What is the scan time for CBCTs?
5
Raw CBCT images are slightly offset ____ images.
5
Reconstruction algorithms:
Filtered back projection with _____ reconstruction used to produce _____.
6
What is the difference between CBCT and MDCT?
7
What are the three components of CBCT?
8
What are the two types of x-ray generation for CBCT?
8
Is continuous or pulse x-ray generation preferred? Why?
8
What factor is used to determine mA and kVp for CBCT?
8
Faster CBCt scans = _____ radiation exposure but ____ noise.
8
Slower CBCT scans = ____ basis images = ____ radiation exposure = better images
8
When generating a CBCT, limit the field size to the ______.
8
What is the rotation angle range for CBCTs?
8
What is the relationship etween rotation angle, radiation exposure, and noise?
9
What are two ways to detect x-rays?
9
What is the most common x-ray detector for CBCT?
10
What is the smallest element of a digital picture?
10
A pixel is synonymous to a ____ in a detector.
10
Pixels are arranged in rows and columns to form the ____.
11
What is the term for a 3D representation of a pixel?
11
What shape is a voxel in CBCT?
11
What term relates to the ability of an image to reveal fine detail?
11
What is the principal determinant of voxel size in a CBCT?
11
What is the relationship between pixel size and resolution?
11
What is a disadvantage of having a small pixel/voxel?
12
What is the term for the number of gray shades that can be displayed?
12
What is the number for the currently available gray shades for CBCT?
12
What effect does higher bit depth have on computational time and file sizes?
14
Describe the ideal size of the scan volume or field of view.
18
How many reformatting steps are done once the CBCT machine is run?
19
Were is the primary reconstruction of a CBCT done?
19
Where is the secondary reconstruction done?
24
What is a ray sum? What are two types of projections it can generate?
25
What does volume rendering visualization of?
26
What are inherent artifacts a result of?
26
What are procedure-related artifacts and what do they lead to?
26
What produces introduced artifacts?
26
What kind of artifacts do these three things produce:
-Scatter
-Partial volume averaging
-Cone-beam effect
26
What artifact do these things produce:
-Aliasing artifact
-Scanner related artifact
-Double contour artifact
26
What artifact do these result in:
-beam hardening: cupping artifact; extinction or missing artifact
-patient motion
28
What is a partial volume average inherent artifact?
30
What is an Aliasing Artifact?
31
What is a scanner related artifact?
32
What causes a double contour artifact?
33
What are beam hardening artifacts?
33
What are the 2 types of beam hardening artifacts?
33
What is the beam hardening artifact type where there is distortion of metallic structures as a result of differential absorption?
33
What is the beam hardening artifact type when dark bands are present between two dense objects?
36
What are three general applications for CBCT?
40
Are images distorted in panoramics or CBCTs?
40
What views are seen in panormaics?
40
What views are seen in CBCT?
40
Are structures superimposed in CBCTs and panoramics?
40
Does CBCT or panoramic have a higher radiation dose?
41
4 Strengths of CBCTs:
- _____ size compared with conventional CT equipment
- _____ acquisition
- ______ resolution
- relatively ____ patient radiation dose
41
2 Cons of CBCTs:
- ______
- ______
