1 / 33

Spot Filming

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

maris
Download Presentation

Spot Filming

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Spot Filming Cinefluorography Fluoro Room Shielding Radiation Areas

  2. Spot Filming Spot Film Cassettes Uses conventional radiographic cassettes. Bypasses image intensifier for direct exposure. Uses mA > 100 X that of photofluoro camera.

  3. 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.

  4. Spot Filming • Framing (matching II output size to film area) Total Overframing Overframing Exact Framing Underframing

  5. 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

  6. 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

  7. 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.

  8. Film Size 12.6 mm 30 mm

  9. 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.

  10. 35 mm Cine Camera

  11. Shutter Synchronization

  12. Cinefluorography, cont’d • Framing Frequency • Patient Exposure • Directly proportional to framing frequency. P. 30

  13. 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

  14. 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

  15. Focal length of lens Lens Diameter F-num =50 mm / 20 mm = F 2.5

  16. F-numbers Iris diaphragm The smaller the f-number - the larger the aperture opening. The larger the f-number - the smaller the aperture opening.

  17. Depth of field

  18. 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

  19. 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

  20. 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)

  21. 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.

  22. Tube Leakage 1 meter Maximum permissible = 0.1 R/hr. @ 5 mA

  23. 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.

  24. Radiation Areas, cont’d. • Restricted Area • Any area where access is limited by thelicensee to protect individuals against undue risks from radiation exposure.

  25. Unrestricted/Controlled Areas

  26. Controlled Area Unrestricted Area

  27. 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

  28. Video Recording of Fluoroscopic Image • Video Tape • Video Disc Laser Disc CD • Electronic Radiography DVD

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

  30. 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

More Related