Fluoro Lecture 1

Question 1

Most of the newer II (image intensifiers) are of the _____-______ type. (dual, tri and quad focus)

Answer 1

Multi- Field

Question 2

What crosses at the focal point?

Answer 2

Electrons coming from the photocathode heading toward the output phosphor

Question 3

Multi- field image intensifiers provide for greater ________ for all fluoroscopic exams.

Answer 3

Flexibility

Question 4

What is the largest number you look at on the image intensifier

Answer 4

The normal size, which is the actual size of the input phosphor

Question 5

What are the other numbers you see (smaller numbers) on the image intensifier other than the largest number for?

Answer 5

The size of the input phosphor you will be using to get the magnified image

Question 6

What are some routine sizes of the image intensifier?

Answer 6

12”, 9”, 6”, 4.5”

16” & 20”

Question 7

In the normal size (largest number), the ________ ________ of the IP is used to produce the image on the OP.

Answer 7

Entire Surface

Question 8

In the normal size, how much of the electrons being produced on the photo cathode will be striking the output phosphor to produce an image?

Answer 8

All of them

Question 9

What happens when you shift to a smaller size (number or FOV)?

Answer 9

The voltage of the electrostatic lens inside the image intensifier is increased

Increase the negative value of the voltage

Question 10

When you increase the negative value of voltage inside the image intensifier, what are you doing?

Answer 10

Forcing the electron beam closer and closer together, forcing the focal point to occur sooner than it did earlier

Question 11

Because the electrons focus closer to the input phosphor, what does this result in?

Answer 11

Less of the e- beam will strike the OP, which will cause the image to appear larger

Question 12

When the electrons focus closer to the IP what does the OP (output phosphor) think it’s seeing?

Answer 12

The OP in the normal mode thinks it’s seeing the electrons coming from the entire surface, so it will show a normal sized image

Question 13

When the electrons focus closer to the input phosphor, the electron beam diverges sooner. What happens to the electron beam

Answer 13

Some of the beam goes through the hole in the anode and some of it strikes the anode becoming part of the current

Question 14

What happens when you shift the number on the electrostatic focusing cup to a higher value?

Answer 14

• The electrons focus sooner
• Focal point is now closer to the IP
• Electrons diverge out
• Less electrons hit the OP (divergence of beam)
• Thinks it’s getting electrons from entire surface
• Image looks larger/ magnified

Question 15

If we magnify the image, what is the relationship between the number of electrons hitting the output phosphor in normal and the number of electrons hitting the output phosphor in a magnified view?

Answer 15

The normal view will have higher number of electrons

Magnified view will not be getting all the electrons

Question 16

Will you have more or less electrons hitting the output phosphor in a magnified mode?

Answer 16

Less

Question 17

What happens to the brightness level if you have less electrons hitting the output phosphor?

Answer 17

• It’s less bright and the image on the monitor dims.

- ABC will adjust technique (increasing mA)

Question 18

How does the magnified view affect patient dose?

Answer 18

It increases it (because of ABC)

Question 19

What are the 12, 9, 6 & 4.5 numbers on the control panel?

Answer 19

The different sized magnification.

Where 12 is the normal size, you use the entire surface of the input phosphor

Question 20

What are the sequence of events when you shift to a magnified mode?

Answer 20

• Less e- striking the OP
• Dimmer image from the OP
• Sensed by the ABC circuit
• Sends feedback signal to the x-ray tube
• Increases current to the x-ray tube filament
• Increases mA
• Increases # of x-rays produced
• Increases # of light photons produced at the IP
• Increases # of e- produced at the PC
• Increases the brightness of the image at the OP
• All result in an increase in Pt dose

Question 21

What is the Mirror Optical System?

Answer 21

A system of Mirrors and Lenses in Image Monitoring

Question 22

The Mirror Optical System magnifies the image from the OP onto a ________ glass.

Answer 22

Viewing (was really another mirror)

Question 23

What were some disadvantages of the Mirror Optical System?

Answer 23

• Screen too small
• Only allowed one viewer at a time
• Increased pt. dose
• Significant amount of light loss from OP
• Can increase light from OP, but it requires increasing technique (resulting in increased Pt dose)

Question 24

In the T.V Monitoring System, a T.V camera tube converts _____ ______ from the OP to an ________ signal and conveys it to the monitor

Answer 24

Light Image

Electrical

Question 25

What are the (2) most commonly used T.V cameras?

Answer 25

Vidicon

Plumbicon

Question 26

What were Advantages to the T.V Monitoring System?

Answer 26

• Brightness and Contrast adjust electronically (ABC)
• Several observers at one time
• Monitors can be placed outside the area for others to view

Question 27

T.V monitoring allows for what?

Answer 27

Storage of the image on Discs or tapes for future playback

Question 28

What is Vignetting?

Answer 28

• Decrease in the light intensity or brightness at the periphery (edge) of an image
• Unfocused

Question 29

Magnification mode results in?

Answer 29

• Better spatial resolution
• Better contrast resolution
• Higher patient dose

Question 30

What is a significant advantage of television monitoring?

Answer 30

Brightness levels and contrast can be controlled electronically

Question 31

What does the television camera tube do?

Answer 31

Converts light signal from the OP to an electric signal