fluoroscopic system: flat panel (modern)

Question 1

what is the difference between the production of xrays in flat panel and image intensifier fluroscopu

Answer 1

flat panel = receives xrays from high spec medium frequency generator

image intensifier = receives xrays from regular xray tube

Question 2

what is the power range of the frequency generator in flat panel fluroscopy

Answer 2

65-126kw

Question 3

what is the exposure range of the xrays the frequency generator makes for static images and fluroscopy

Answer 3

static imaging = 40-150kV, 32-63mA

Fluroscopy = 40-125kV, 0.5-4mA

both have 5ms-5 second times

Question 4

what is the range of pulsed images per second the can be produced by the frequency generator

Answer 4

1 - 8 per second

(cardiac systems up to 30/sec)

Question 5

describe the process of how a flat panel fluoroscopic system works

Answer 5

1. xrays converted to light using caesium iodide in a scintillator

(no electron acceleration or minification to reduce noise)

2. light then reaches a low-noise amorphous silicon (a-Si) photodiode array where it is converted into an electrical charge
3. Each photodiode represents a single pixel, and each produces an electrical charge that is read out digitally by the TFT array layer underneath
4. then finally being sent to the image processor

Question 6

why is the caesium iodide layer thicker in flat panel than image intensifier system

Answer 6

for greater xray absorption/sensitivity

Question 7

flat panel does not have electron acceleration to minimise noise production, so what does it do instead to reduce noise

Answer 7

pixel binning

• adding together groups of pixels to make a smoother image

Question 8

what is a negative of pixel binning

Answer 8

reduced resolution

Question 9

how can pixel binning affect frame rate

Answer 9

increase/faster frame rates as it reduces the amount of data to be handled

Question 10

what are the 2 ways to magnify an image using the flat panel system

Answer 10

1. electronic zoom of binned pixels (no increase in resolution, just part of panel is displayed magnified
2. pixels unbanned in centre of detector, increases resolution

Question 11

both fluroscopy and recorded images are dynamic methods

achieved nu pulsing xrays at several frames per second

Question 12

what controls the xray pulses in fluroscopy

Answer 12

gridded tube, it suspends electrons ready to expose

Question 13

compare the dosage of pulsed and continuous fluroscopy

Answer 13

pulsed fluroscopy significantly reduces dose to patient

Question 14

pulsed fluroscopy does reduce dosage to patient however there are disadvantages associated, what are they

Answer 14

• blurred when patient moves

Question 15

for very slow pulse rates as in pulsed fluroscopy, when several frames have been averaged to smooth out the noise what can happen to the contrast of the imageq

Answer 15

• have higher contrast resolution due to reduced noise

Question 16

what is the typical fluroscopy pulse rate

Answer 16

1-15 frames per second

Question 17

what are the 5 things you can adjust to control flat detector image quality

Answer 17

1. ABC, AGC, AEC
2. collimation
3. edge-enhancement
4. noise reduction filter
5. pulsed imaging to reduce dose

Question 18

what are the 4 types of noise reduction filters/systems

Answer 18

• temporal/recursive filtering / frame averaging
• motion tracking
• background supression
• pixel binning

Question 19

what type of artefact/effect will you find in image intensifier but not flat panel system

Answer 19

no pin-cushion effect due to curvature of front of image intensifier causing blur at the edges

Question 20

why is there no s-distortion found in flat panel but is in image intensifior

Answer 20

• no magnets accelerating electrons in flat panel
• so no s-distortion caused by earths magnetic field acting on focussing electrodes

Question 21

what is done to correct s-distortion in image intensifier system

Answer 21

s-distortion corrections are made to the system by the service engineer

Question 22

what is another advantage that flat panel has over image intensifier system

Answer 22

no vignetting, where the periphery of the image is less bright than the center and has lower resolution

Question 23

know that overall the flat panel has 3 major benefits over image intensifier in terms of artefacts/errors that can occur in image production

Answer 23

1. pin cushion effect
2. s-distortion
3. vignetting

Question 24

what are edge detection filters used for

Answer 24

edge enhancement

Question 25

how does the fluoroscopic machine differ from the catheter lab/ high-performance systems to regular

Answer 25

- gantry c-arm suspended from floor or ceiling mount

Question 26

describe how the additional advantages/features found in high performance systems

Answer 26

anti-collision software, gantry and table (predictive and actual) fast moving (moves 180 degrees in 30 seconds)

Question 27

all high performing systems use flat panel not image intensifier

Question 28

high performance systems have virtual collimation, what is this

Answer 28

allows you to quickly collimate or perform adjustments at the workstation right before X-ray exposure

Question 29

high performance systems have roadmapping, what is this

Answer 29

can overlay the vessel to reduce fluroscopy to check location of guide wire

Question 30

what is LIH

Answer 30

last image hold

Question 31

high performance systems have live stent enhancement, what is this

Answer 31

real-time verification of the stent positioning while moving the device.

Question 32

high performance systems can image fuse with CT, US etc

Question 33

what are the highest risk dose procedures in R&F and other fluoroscopic systems

Answer 33

R&F (continuous xray image) = multiple lateral images of the pelvis/lower spine other systems = cardiac and neurological intervention

Question 34

what is the optimal distance of the patient to the tube and patient from detector

Answer 34

patient to tube distance = 80cm patient to detector (flat panel or image intensifier) = 30cm

Question 35

why is there an optimal distance of the detector and tube from patient?

Answer 35

- reduces the scatter pattern of the radiation to minimise risk to operator and surrounding ppl

Question 36

what is dose awareness

Answer 36

back scatter to operator when they normally work from the right

Question 37

when the c arm is lateral, where is the back scatter the highest

Answer 37

on the tube side of the patient (right beside where the x-rays are coming out of tube)

Question 38

left lateral, a common projection gives highest operator dose when operators put catheters into femoral and radial arteries

Question 39

what are the ranging radiation protection equipment when using fluroscopy

Answer 39

- lead curtains/suspended drapes (mobile or suspended from table) - lead apron - lead gloves - lead goggles - lead thyroid collar - mask - lead shoes - lead panties

Question 40

what are some dose control activities you can do

Answer 40

- dosimeter under lead apron, fingers or next to eyes - never stand within 2m of patient - keep fluroscopy to minimum (use it pulsed) - last image hold to avoid need for further xrays - use 2nd monitor for reference images to avoid live fluroscopy - store fluoroscopic images when image quality is enough - keep operator aware of flare time and patient dose displayed - keep image receptor close to patient as possible - dont magnify imaging unless needed - collimate

Question 41

greatest patient dose risk in order of different imaging: 1. angiography system with 3D 2. catheter lab 3. R&F system 4. Surgical mobiles 5.finger xray