Fluoroscopy

Question 1

Input phosphor

Answer 1

• Converts incoming xray into light photons

- made cesium iodide

Question 2

Photocathode

Answer 2

Converts light photons from the input phosphor into free electrons

Question 3

Electrostatic lens

Answer 3

• located along the full length of the image intensification tube
• directs or focuses the path of electrons from the photo cathode to the surface of the output phosphorus screen

Question 4

Output phosphor

Answer 4

• convert electrons sent from the photocathode into light photons
• made of zinc cadmium sulfide

Question 5

Flat panel detectors

Answer 5

• indirect sold state system, xrays converted into light and then into an electronic signal
• better stability, lower pt dose, wider dynamic range

Question 6

Brightness gain

Answer 6

BG= minification gain x flux gain

Question 7

Minification gain=

Answer 7

Input phosphor (squared) / output phosphor (squared)

Question 8

Flux gain

Answer 8

-fixed factor in II tube that deals with the increase in the # of light photons exiting the tube for every light photon produced at the input end of the tube

Question 9

bright light vision (photopic)

Answer 9

• cone cells
• concentrated at fovea of the eye
• provides high visual acuity

Question 10

Low light or night vision (scotopic)

Answer 10

• rod cells
• distributed along periphery of eye
• provides poor visual acuity- gross detail

Question 11

Vignetting

Answer 11

Loss of detail along the edge of the fluoroscopic image

Question 12

Cine fluoroscopic device

Answer 12

• will give highest pt dose (10x)

- exposed by light from the output end of the image intensification tube

Question 13

Automatic brightness control (ABC)

Answer 13

• fluoroscopic mA is directly related to the brightness of the fluoroscopic image
• light intensity is measured by a photocell at the output phosphor end of the image intensification tube

Question 14

Magnification mode

Answer 14

• magnification of fluoroscopic image is a function of the input phosphor size
• by reducing the size of the area of the input phosphor focused to the output phosphor screen results in an electronic mag. of the image

Question 15

When switching from a larger to a smaller input phosphor size, the electron focal spot moves _____ from the output phosphor, which reduces the FOV and magnifies image

Answer 15

Further

Question 16

Magnification factor

Answer 16

MF= input phosphor 1/ input phosphor 2

Question 17

Magnifying the fluoro image causes what

Answer 17

• increased pt dose
• better SR
• better CR

Question 18

Patient dose increase formula

Answer 18

Pt dose increase = input phosphor 1 (squared) / input phosphor 2 (squared)

Question 19

When in mag mode of fluoro, your focal point moves _____ to the input phosphor

Answer 19

Closer

Question 20

When not in mag mode, focal point moves _____ to output phosphor

Answer 20

Closer

Question 21

As the distance between the image intensifier and the fixed source of radiation decreases what happens to patient dose

Answer 21

Decreases

Question 22

Fluoroscopy is the single greatest source of acute radiation exposure to the patient in the diagnostic radiology environment