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Spot Filming. Cinefluorography. Fluoro Room Shielding. Radiation Areas. Spot Filming. Spot Film Cassettes Uses conventional radiographic cassettes. Bypasses image intensifier for direct exposure. Uses mA > 100 X that of photofluoro camera. Spot Filming. Spot Film Cameras

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Spot Filming


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slide1

Spot Filming

Cinefluorography

Fluoro Room Shielding

Radiation Areas

spot filming

Spot Filming

Spot Film Cassettes

Uses conventional radiographic cassettes.

Bypasses image intensifier for direct exposure.

Uses mA > 100 X that of photofluoro camera.

slide3

Spot Filming

  • Spot Film Cameras
    • Image the output phosphor of II.
    • Same mA as fluoroscopy (1-3 mA typically).
    • Exposes one frame/exposure.
    • Uses 70, 90, or 100/105 mm film size.
    • As you increase film size, increase image quality and patient dose.
    • Method of choice for spot filming compared to spot film cassettes.
slide4

Spot Filming

  • Framing (matching II output size to film area)

Total Overframing

Overframing

Exact Framing

Underframing

slide5

Framing and Patient Dose Reduction

Underframing

Exact Framing

  • Int. image = small dimension of frame
  • No part of image lost
  • Only 58% of frame used
  • Fluoro image < frame
  • Should be avoided

P. 31

slide6

Framing and Patient Dose Reduction

Total Overframing

Overframing

  • Image circle > short film dimension
  • Part of image lost
  • Circular image = diameter of frame
  • All of film used
  • 39 % of image wasted
slide7

Cinefluorography

  • The process of recording fluoro images on movie (cine) film.
  • Film sizes
    • 16 and 35 mm
    • The larger the film size, the greater the resolution and greater the patient dose.
slide8

Film Size

12.6 mm

30 mm

slide9

Cinefluorography

  • Synchronization
    • Camera shutter timed to the same frequencyas the x-ray pulses.
    • Shutter open only during x-ray pulses.
  • Framing Frequency
    • Number of exposed frames/second.
    • Divisions or multiples of 60 Hz line rate.
      • Examples: 7.5, 15, 30, 90, 120 frames/second.
slide12

Cinefluorography, cont’d

  • Framing Frequency
    • Patient Exposure
      • Directly proportional to framing frequency.

P. 30

slide13

Cinefluorography, cont’d

  • Framing Frequency
    • Patient Exposure Conversions
      • 2000 mR/frame X 1 mR/1000 mR = 2 mR/frame
      • 2 mR/frame X 30 frames/second X 60 seconds/minute = 3,600 mR/minute
      • 3,600 mR/minute X 1 R/1000 mR = 3.6 R/minute

P. 30

cinefluorography cont d
Cinefluorography, cont’d
  • F-number
    • Number indicating the ratio of the focal length of the camera lens to the diameter of the lens.
    • F-number = Focal Length of Lens/Diameter of Lens
    • The smaller the f-number = more light into the camera and less patient exposure.

P. 30

slide15

Focal length of lens

Lens Diameter

F-num =50 mm / 20 mm = F 2.5

slide16

F-numbers

Iris diaphragm

The smaller the f-number - the larger the aperture opening.

The larger the f-number - the smaller the aperture opening.

slide18

QA Concerns

Spot Film and Cine Cameras

  • Beam and image size match within 3 % of SID
  • A small aperture (large f-number) will require greater patient exposure but result in low noise image.
  • Patient entrance exposures of 50 - 150 rads or more.

P. 110

structural fluoro room shielding provisions
Structural Fluoro Room Shielding Provisions
  • Barriers
    • Primary
      • A barrier to attenuate the useful beam to the required degree.
    • Secondary
      • Used to attenuate stray (scattered and leakage) radiation to the required degree.
  • Useful Beam
    • Radiation that passes through window, aperture, or cone.
  • Stray Radiation
    • Leakage and secondary radiation. No useful purpose.

p. 121

primary secondary barriers
Primary/Secondary Barriers

Exception would be in R/F room where all walls would be a primary barrier.

(Source: Principles of Imaging Science and Protection. Thompson, Hattaway, Hall, Dowd, 1994)

structural fluoro room shielding provisions1
Structural Fluoro Room Shielding Provisions
  • Tube Leakage
    • Maximum exposure @ 1 meter is 0.1 R/hour.
  • Half-Value Layer (HVL)
    • Thickness of material that reduces beam exposure rate by half of original value.
  • Tenth-Value Layer (TVL)
    • Thickness of material that reduces beam exposure rate to 1/10 of original value.
slide23

Tube Leakage

1 meter

Maximum permissible =

0.1 R/hr. @ 5 mA

radiation areas
Radiation Areas
  • Radiation Area
    • Any area where whole body dose could be = or > 0.005 rem/1 hr. at 30 cm from source.
  • High Radiation Area
    • Any area where whole body dose could be = or > 0.1 rem/1 hr. at 30 cm from source.
  • Controlled Area
    • Any area where radiation safety rules enforced.
  • Unrestricted Area
    • An area in which access is neither limited nor controlled.
slide25

Radiation Areas, cont’d.

  • Restricted Area
  • Any area where access is limited by thelicensee to protect individuals against undue risks from radiation exposure.
slide27

Controlled

Area

Unrestricted

Area

slide28

Spot film

Cine Processor

Film

Cameras

Flare

Exposure Timer

Image Lag

Film-Screen Contac t

QC-Semi-annual checks

mAs Linearity

Image Quality

Exposure Reproducibility

Grid

Alignment

Phototimers

Linearity

Spot Film-Cine Image

Cine Film Processor

Camera Exposures

Cine Film Exposure

Spot Film

Beam Limitation

Resolution –Distortion

Film

slide29

Video Recording of Fluoroscopic Image

  • Video Tape
  • Video Disc

Laser Disc

CD

  • Electronic Radiography

DVD

slide30

Video Tape

  • AdvantagesInstant Replay No increase in patient exposure
  • DisadvantagesPoor image quality Fixed framing rate- 30 frames/sec.
slide31

Video Disc (Electronic Radiography)

  • AdvantagesLast image freeze “sticky fluoroscopy” Instantaneous imaging Short exposure times 95% dose reduction during fluoro Variable framing rates – 1-30 frames/sec. Multiple image storage Random access of images
  • DisadvantagesNone significant