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Physics - Applied imaging Technology > Fluoroscopy > Flashcards

Fluoroscopy Flashcards

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1
Q

What is Fluoroscopy?

A

Real time imaging viewed on a display monitor in the clinical room

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2
Q

What is the matrix size and grey scale for Fluoroscopy?

A

512 x 512 pixels and 8 bits of grey scale

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3
Q

What types of images can Fluoroscopy acquire?

A

Continuous (cine) or pulsed fluorographic images

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4
Q

What is Fluorography?

A

Images usually formed and viewed after the x-ray exposure is complete

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5
Q

What are the advantages of Fluorography over Fluoroscopy?

A

Better quality images but at higher doses

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6
Q

What is the matrix size and grey scale for Fluorography?

A

1024 x 1024 pixels with each pixel representing 10 bits of grey scale information

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7
Q

What are ‘Greyscale’ digital x-ray imaging modes?

A

Fluoroscopy, digital cardiac, and digital spot imaging

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8
Q

What is Subtractive digital imaging?

A

Base image taken which is then subtracted from the image with contrast to result in an image showing the contrast only

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9
Q

What is an Image intensifier (II)?

A

A system that converts the input light into a much higher output (gain or intensification)

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10
Q

What is the formula for brightness gain (Gbrightness)?

A

Gbrightness = Gminification x Gflux

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11
Q

What does Gminification describe?

A

The increase in brightness due to the demagnification of the image in the II tube

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12
Q

What is the formula for Gminification?

A

Gminification = (Dinput / Doutput)^2

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13
Q

What is the Image intensifier conversion factor (Gx)?

A

Gx = L / X’ where L = luminance of the II output and X’ = II entrance dose rate

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14
Q

What factors affect the brightness gain of an II tube?

A

Magnification and Flux

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15
Q

What are the standard configurations of radiography/fluoroscopy equipment?

A

Under table x-ray tube with an over-couch II system, Table can be tilted and rotated, Radiologist stands beside patient

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16
Q

What are the configurations of Remote control R/F equipment?

A

X-ray tube mounted over the bed and II system underneath, Higher scattered dose so radiologist stands behind screen

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17
Q

What is a Fixed C-arm?

A

II x-ray tube and II system attached to a C-structure that allows rotation and movement

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18
Q

What is a Mobile C-arm?

A

System that can be transported on wheels to different locations

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19
Q

What is the II input window?

A

Convex metal shield, usually aluminium or titanium foil, that covers the input face of the II

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20
Q

What is the Input phosphor made of?

A

Layer of sodium activated caesium iodide (CsI:Na)

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21
Q

What is the thickness of CsI:Na in the Input phosphor?

A

400-500μm

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22
Q

What does the Photocathode do?

A

Absorbs fluorescent light photons and releases a pattern of electrons

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23
Q

How many electrons are released per absorbed x-ray photon in the Photocathode?

A

Approximately 200 electrons

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24
Q

What does the Electron focusing system do?

A

Focusing electrodes direct electrons to the output screen to create an exact but minified image

25
Q

What is the material used for the Output screen in an II tube?

A

Thin layer of silver-activated zinc cadmium sulphide (ZnCdS:Ag) crystals

26
Q

What is the purpose of the Output Window?

A

Optically transparent glass block port through which the intensified light image exits the II tube

27
Q

What are the methods to minimize halation in the Output Window?

A

Smoked glass, Special optical coatings, Very thick glass, Fibre-optic bundle

28
Q

What is Magnification in fluoroscopy?

A

Achieved electronically with electronic focusing of the electron beam

29
Q

What is the effect of Magnification on image brightness and dose?

A

Less bright image and increased dose required

30
Q

What is the benefit of using a Charged Coupled Device (CCD) sensor over a TV camera tube?

A

Small, inexpensive, compact, low-power consumption, self-scanning image readout, negligible lag, excellent stability, long life-time, compatibility with digital x-ray imaging modalities

31
Q

What does Automatic brightness control (ABC) do?

A

Maintains constant viewing condition by regulating mA and kV

32
Q

What are the modes of Automatic brightness control (ABC)?

A

Minimum patient dose rate mode, Standard patient dose rate mode, High patient dose rate mode

33
Q

What is the purpose of Digital image processing in fluoroscopy?

A

To improve the appearance of the image on the screen

34
Q

What are the types of Digital image processing?

A

Greyscale processing, Spatial filtering, Temporal filtering

35
Q

What is a Flat Panel Detector (FP detector)?

A

Flat panel of detectors that provide a direct electronic readout instead of requiring the conversion of analogue to digital

36
Q

What are the benefits of Flat Panel Detectors?

A

Smaller equipment, digital video signal, better temporal resolution, better image quality, fewer artefacts, higher detective quantum efficiency, zoom option

37
Q

What is Digital Subtraction Angiography (DSA)?

A

Procedure that highlights contrast-outlined structures by removing background anatomical structures

38
Q

What is the dose limit for Maximum entrance skin dose rate?

A

100 mGy per minute

39
Q

What is the dose range for Digital fluoroscopy?

A

10 to 30 mGy per minute for larger patients

40
Q

What is the main contribution to staff dose?

A

Scatter of x-rays from the patient

41
Q

What are the methods to minimize staff dose?

A

Use of lead aprons and other radiation shields, Maintain maximum possible distance from patient, Monitor individual staff doses

42
Q

What are the methods to minimize patient dose?

A

Tight collimation of x-ray beam, Appropriate x-ray beam spectral filter, Increase distance between patient and x-ray source, Minimize gap between patient and II entrance, Remove anti-scatter grid if possible

43
Q

What is Fluoroscopy in simple terms?

A

Real-time imaging viewed on a display monitor

44
Q

What is Fluorography in simple terms?

A

Image displayed after x-ray exposure

45
Q

How is image intensification measured in IITV?

A

Brightness gain = minification gain x flux gain

46
Q

What factors affect brightness gain in IITV?

A

More minimisation, reduction in input field area, higher voltage across II tube

47
Q

What materials are used in the II input window?

A

Aluminium or titanium foil

48
Q

What is the purpose of the input phosphor in IITV?

A

Good x-ray absorption efficiency

49
Q

What is the main function of the photocathode in IITV?

A

Releases electrons into the II tube

50
Q

What happens during electron focusing in IITV?

A

Electrons are directed to create an exact but minified image

51
Q

What is the output screen made of in IITV?

A

ZnCdS:Ag that converts electrons into light photons

52
Q

What does the II TV camera do?

A

Scans photoconductive target to create a flow of electrons corresponding to light intensity

53
Q

What is the function of CCD sensors in IITV?

A

Each pixel has an associated electrode, charge accumulation proportional to light intensity

54
Q

What technology do Flat Panel Detectors use?

A

Same as digital radiography

55
Q

What is Automatic brightness control (ABC)?

A

Maintains constant viewing condition by regulating mA and kV

56
Q

What are the types of digital processing in IITV?

A

Greyscale processing, Spatial filtering, Temporal filtering

57
Q

What is the main source of staff dose in fluoroscopy?

A

Scatter of x-rays from the patient

58
Q

What are the strategies to minimize staff dose in fluoroscopy?

A

Use lead aprons, maximize distance from patient, monitor doses

Physics - Applied imaging Technology (16 decks)

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