Fluoro

Question 1

How does Fluoro compare to general radiographs?

Answer 1

1. Smaller Focal Spot(0.3-0.6mm)
2. Smaller mA (0-5)
3. Longer Exposure time

Question 2

How does a spot image compare to a last image hold?

Answer 2

1. Larger Focal Spot
2. More Dose
3. Better Spatial Resolution (3 lp mm)

Question 3

When is the source above the table and what are the side effects?

Answer 3

• Above Table in GU radiology

- Increase dose to the lens

Question 4

How does the image intensifier work?

Answer 4

1. Hits the Input phosphor (CSI) which converts X rays to Light
2. Photocathode Converts the Light to Electrons
3. Electrons move towards output phosphor with beams being focus by focusing electrodes
4. Output Phosphor converts electrons to light (minification)

Question 5

Why is the image inverted and Reversed on the output phosphor?

Answer 5

Due to point inversion (all pass through the same focusing point)

Question 6

What is Brightness Gain?

Answer 6

-Ability of the II to convert xray signal to light and increase brightness
=Flux Gain X Minification Gain

Question 7

What is Flux Gain?

Answer 7

• Increase in Magnitude of the input to the output phosphor due to voltage applied which increases the energy of the electrons
• Accelerating Electron= More Brightness

Question 8

What is Minification gain?

Answer 8

• Small size of output phosphor in comparison to input phosphor, means that more electrons for unit area–> More energy per unit area.
• Reducing image size= Increased Brightness

Question 9

What is Conversion gain?

Answer 9

Efficiency of the II at making x rays into light at output surface

Question 10

What happens to brightness and conversion gain with older II?

Answer 10

They are less efficient and require a higher dose to create the same level of brightness

Question 11

When do you change image intensifier?

Answer 11

When the conversion gain falls below 50%

Question 12

What is electronic magnification?

Answer 12

Making the input field of view smaller (increases dose) by magnifying the II

Question 13

How does Electronic Magnification affect spatial resolution?

Answer 13

Increased Electronic Magnification increases spatial resolution

Question 14

How do you determine if geometric magnification will increase or decrease spatial resolution?

Answer 14

R/F Ratio: Intrinsic Receptor Resolution/Focal Spot
If < 0.5, then it decreases resolution
If >0.5, then it increases resolution

Question 15

What does double the distance from the patient to source do to dose?

Answer 15

Decreases its by 4 times due to inverse square law

Question 16

What does collimation do to dose and scatter?

Answer 16

Decreases dose and scatter

Question 17

What is the Automatic Exposure Rate control limit?

Answer 17

10 R/Min or 87 mGy/min

Question 18

What is KERMA?

Answer 18

Kinetic energy released per unit mass

=Total Energy Deposited (Heat/Ionization)/Mass

Question 19

What is Air KERMA?

Answer 19

• Estimates the peak skin dose

- Total number of photons in the air right before you hit the skin

Question 20

What is Kerma Area Product?

Answer 20

-Dose X Cross sectional area of X ray beam

Question 21

How does electronic magnification affect KAP and Air Kerma?

Answer 21

• Increases Air Kerma bc the dose is increase

- Keeps KAP the same, smaller CSA to balance increased dose

Question 22

What is the Air Kerma Limit?

Answer 22

10 Roetngens/min or 87 mGy/min

Question 23

What is high level control for air kerma limit?

Answer 23

20 Roetngens/Min or 176 mGy/min

Question 24

What is pincushion artifact?

Answer 24

Bent lines in the periphery due to Large FOV

Question 25

What is S Distortion?

Answer 25

Distorted field due to earths magnetic field Worse with larger FOV Fix with Mu metal

Question 26

What is Lag Artfact?

Answer 26

Move the II and a Ghosted image is superimposed

Question 27

What is vignetting Artifact?

Answer 27

Edges are Darker than the center

Question 28

How does the FPD work in Fluoro?

Answer 28

1. X Rays pass through Carbon Fiber Surface (protective layer) 2. Hit CSI which converts x rays to light 3. Photodiode converts light to Electrons 4. Electrons get read out with read out elements

Question 29

What is pitch?

Answer 29

Linear dimension of the detector element

Question 30

What is Fill Factor?

Answer 30

``` Sensitive Area (to light)/Pitch^2 -% of the Photodiode in the Detector element ```

Question 31

What determines Pixel Size?

Answer 31

FOV/Matrix

Question 32

What is Binning?

Answer 32

Combine several detector elements to make one large Detector element (only with Flat Panel detectors) - Decreases spatial resolution - Less mottle (Decrease radiation with same noise) - Improves SNR Ratio

Question 33

What artifacts are seen with FPD?

Answer 33

- Lag (ghosting) and Bad Pixel | - No Vignetting, Pincushion, Glare, saturation or S distortion

Question 34

What limits resolution in II and FPD Fluoro system?

Answer 34

II: TV Display FPD: Detector element Size

Question 35

Does II or FPD have better spatial resolution?

Answer 35

II

Question 36

How does Pulsed Fluoro Reduce Dose?

Answer 36

- Reduces dose if pulse frame rate is less than 30 pulses/Second - 50% decrease in Pulse frame rate= 30% decrease in dose

Question 37

How does pixel binning affect spatial resolution?

Answer 37

Decreases spatial resolution

Question 38

What KVP do you choose to maximize iodine and barium?

Answer 38

Iodine: 70 kVp Barium: 100 kVp

Question 39

How is DSA Made?

Answer 39

- Removes anything that is not moving | - Performed at 70 kVp

Question 40

Where is the best place for the IR doc to stand?

Answer 40

Next to the image receptor (more compton scatter where the x rays enter the patient)