7: Exposure Techniques Flashcards

1
Q

Position of what is most critical?

A

Source compared to specimen and film

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Using screens in energy levels between ____ and ____ can reduce exposure from 1/3 to 1/2 then they would without.

A

150 keV and 2 MeV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of materials are particularly susceptible to scatter?

A

Denser metals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe Category 1 materials:

A

Parts of uniform thickness that have good contact with film, such as flat butt welds or flat plates

(Scatter mainly absorbed - measures don’t need to be taken)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe Category 2 materials:

A

May produce scatter at the edges but this subtle loss of sensitivity would be acceptable

Ex. Parts with large radius, tapered parts, chamfered parts and flat but slightly irregular castings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe Category 3 materials:

A

Can exhibit undercut scatter from one section of image to other, reducing image quality/clarity

Ex. Parts with complex geometry and heavy section thickness

often require masking/blocking/filters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the 3 main factors that govern exposure?

A
  1. mA for X-rays OR source for gamma
  2. Time
  3. Source-to-film distance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

As a general rule, the mA required for a given exposure is directly proportional to the ___________

A

Square of focal film distance

M1/M2 = D^2,1/D^2,2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

If the mA can’t be changed, what should you do?

A

Adjust exposure or time

T1/T2 = D^2,1/D^2,2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

mA required for a given exposure is inversely proportional to what?

A

Time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is referred to as the reciprocity law?

A

M1T1 = M2T2 = M3T3 = constant

Relationship between mA and time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When does the reciprocity law not apply?

A

When fluorescent screens are used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Ideally, direction of beam should be where compared to part?

A

Perpendicular to main axis of part

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Medium tubular sections (20-40 mm) may require how many exposures?

A

Min. of 2 at 90 degrees to each other, but up to 4 may be necessary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Large tubular sections may require how many exposures?

A

3 exposures at 120 degrees or 4 exposures at 90 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Double wall exposures are common for pipe diameters less than what?

A

90 mm

17
Q

For pipe welds, a source placed perpendicular to weld plane is called what?

A

Double wall, double viewing

18
Q

How many exposures are generally required for the superimposed method?

A

Typically 3, 60 degrees or 120 degrees to previous

19
Q

When may it be acceptable for a source to be in contact with outside of pipe?

A

Diameters greater than 90 mm

This would be a double wall, contact exposure

20
Q

What degrees are elliptical exposures offset by? And how many exposures?

A

Typically offset by 15-30 degrees, requiring 2 exposures set at 90 degrees

21
Q

The location along a welded seam is usually indicated on a radiograph by means of what?

A

Lead numbers

22
Q

In order to ensure good contact with the weld or casting being radiographed, what are preferred?

A

Flexible cassettes

23
Q

Cassettes contains film are held in position for exposure by means of what 3 things?

A
  1. Wooden supports
  2. Magnetic strips or springs
  3. Tape
    (Whatever works)
24
Q

By using small diameter sources (0.3 mm), very small diameter pipes can be shot using the panoramic technique with the acceptable unsharpness. Although the source strength is low, exposure time is not too long because of what?

A

The source to film distance is small