Week 3c Chapter 13 Radiographic Film

Week 3c Chapter 13 Radiographic Film - Chapter 13...

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Chapter 13 Radiographic Film Remnant Radiation: the x-rays that interact with the x-ray film. Few of the original x-rays actually make the image. The remnant radiation is the image forming radiation that passes completely through the patient.
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Types of X-ray A- X-rays scatter by Compton interactions B- x-rays absorbed by photoelectric absorption C- X-rays that exit the patient without interaction.
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Remnant Radiation The beam started as a relatively uniform intensity as it exited the tube. Upon striking the patient, the beam is attenuated by the patient; some were absorbed, others are scattered. Those that actually hit the film are referred to as the useful or remnant radiation .
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Remnant Radiation The remnant radiation consists of x-rays scattered away from the receptor and the useful beam. The film is sandwiched between radiographic intensifying screens in a protective cassette.
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The intensifying screens change the x- rays into visible light. The visible light exposes the radiographic film. Radiographic film is similar in construction and characteristics to photographic film. Its spectral response is different from photographic film but is mechanism of operation is the same.
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Film Construction Radiographic Film has two basic parts. Base Emulsion Most film has two layers of emulsion so it is referred to as Double Emulsion Film
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Film Construction An adhesive layer attaches the emulsion to the base. The emulsion is enclosed in a protective layer or overcoat.
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Radiographic Film Base Initially x-ray were taken on glass plates. In 1918 cellulose nitrate bases film replaced glass due to WWI and a shortage of glass. Cellulose Nitrate was flammable so x-ray film was a fire hazard. Several severe hospital fire were caused by the x- ray film.
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Radiographic Film Base 1920 Cellulose triacetate or safety base was introduced. Not as flammable. Polyester base replaced Cellulose Triacetate in the 1960’s. Still used today. It is semi-rigid and about 150 to 300 µm thick.
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Emulsion The emulsion is the heart of the film. The x-rays or light from the intensifying screens interact with the emulsion and transfer information to the film The emulsion consists or a very homogeneous mixture of gelatin and silver halide crystals about 3 to 5 µm thick.
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Gelatin The gelatin is clear so it transmits the light to the silver halide crystals. It is porous so the processing chemicals
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This note was uploaded on 01/03/2012 for the course LC 232 taught by Professor Wilson during the Fall '08 term at Palmer Chiropractic.

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Week 3c Chapter 13 Radiographic Film - Chapter 13...

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