Spot FilmingSpot Film Cassettes Uses conventional radiographic cassettes. Bypasses image intensifier for direct exposure. Uses mA > 100 X that of photofluoro camera.
Spot FilmingSpot Film CamerasImage 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 FilmingFraming (matching II output size to film area)
UnderframingExact FramingP. 31 Fluoro image < frame Should be avoided
Int. image = small dimension of frame No part of image lost Only 58% of frame used
OverframingTotal Overframing Image circle > short film dimension Part of image lost Circular image = diameter of frame All of film used 39 % of image wasted
CinefluorographyThe process of recording fluoro images on movie (cine) film.Film sizes16 and 35 mmThe larger the film size, the greater the resolution and greater the patient dose.
12.6 mm30 mm
CinefluorographySynchronizationCamera shutter timed to the same frequency as the x-ray pulses.Shutter open only during x-ray pulses.Framing FrequencyNumber of exposed frames/second.Divisions or multiples of 60 Hz line rate.Examples: 7.5, 15, 30, 90, 120 frames/second.
Cinefluorography, contdFraming FrequencyPatient ExposureDirectly proportional to framing frequency.P. 30
Cinefluorography, contdFraming FrequencyPatient Exposure Conversions2000 mR/frame X 1 mR/1000 mR = 2 mR/frame2 mR/frame X 30 frames/second X 60 seconds/minute = 3,600 mR/minute3,600 mR/minute X 1 R/1000 mR = 3.6 R/minuteP. 30
Cinefluorography, contdF-numberNumber 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 LensThe smaller the f-number = more light into the camera and less patient exposure.P. 30
Focal length of lens
F-num = 50 mm / 20 mm = F 2.5 Focal length of lensLens Diameter
The smaller the f-number - the larger the aperture opening.The larger the f-number - the smaller the aperture opening.Iris diaphragm
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 ProvisionsBarriersPrimaryA barrier to attenuate the useful beam to the required degree.SecondaryUsed 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.
Primary/Secondary Barriers(Source: Principles of Imaging Science and Protection. Thompson, Hattaway, Hall, Dowd, 1994)Exception would be in R/F room where all walls would be a primary barrier.
Structural Fluoro Room Shielding ProvisionsTube LeakageMaximum 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.
HVL Lead (mm)
HVL Lead (mm)
Lead (mm)Concrete (in.)
1 meter0.1 R/hr. @ 5 mAMaximum permissible =
Radiation AreasRadiation AreaAny area where whole body dose could be = or > 0.005 rem/1 hr. at 30 cm from source.High Radiation AreaAny area where whole body dose could be = or > 0.1 rem/1 hr. at 30 cm from source.Controlled AreaAny area where radiation safety rules enforced.Unrestricted AreaAn area in which access is neither limited nor controlled.
Radiation Areas, contd. Restricted Area Any area where access is limited by the licensee to protect individuals against undue risks from radiation exposure.
QC-Semi-annual checksFlareImage LagmAs LinearityExposure ReproducibilityPhototimersCamera ExposuresSpot FilmFilmCine Film ExposureSpot Film- Cine ImageBeam LimitationResolution DistortionCine Film ProcessorGridAlignmentLinearityImage QualityFilm-Screen Contac tExposure TimerCamerasSpot filmFilmCine Processor
Video TapeVideo DiscElectronic Radiography
Advantages Instant Replay No increase in patient exposure Disadvantages Poor image quality Fixed framing rate- 30 frames/sec.
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