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 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.

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

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

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

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.

Film Size 12.6 mm 30 mm

Cinefluorography Synchronization Framing Frequency Camera shutter timed to the same frequency as 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.

35 mm Cine Camera

Shutter Synchronization

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

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 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

Focal length of lens

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

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

Depth of field

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 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 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 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.

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

Radiation Areas Radiation Area High Radiation Area Controlled 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.

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

Unrestricted/Controlled Areas

Unrestricted Area Controlled Area

QC-Semi-annual checks Spot film Film Cine Processor Cameras Flare Exposure Timer Image Lag Film-Screen Contac t QC-Semi-annual checks mAs Linearity Image Quality Grid Exposure Reproducibility Alignment Phototimers Linearity Cine Film Processor Spot Film- Cine Image Camera Exposures Cine Film Exposure Spot Film Beam Limitation Resolution – Distortion Film

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

Video Tape Advantages Instant Replay No increase in patient exposure Disadvantages Poor image quality Fixed framing rate- 30 frames/sec.

Video Disc (Electronic Radiography) Advantages Last 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 Disadvantages None significant

The End