vet-120 diagnostic imaging

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VET-120 Diagnostic Imaging. Course Set-up. 5 Lessons (Webinars) 5 Lesson Exams Final Proctored Exam Required Reading Diagnostic Imaging Study Guide Radiography in Veterinary Technology (Lavin 4 th edition). Studying for Exams. Make copy of Lesson PowerPoints - PowerPoint PPT Presentation


  • VET-120Diagnostic Imaging

  • Course Set-up5 Lessons (Webinars)5 Lesson ExamsFinal Proctored ExamRequired ReadingDiagnostic Imaging Study GuideRadiography in Veterinary Technology (Lavin 4th edition)

  • Studying for ExamsMake copy of Lesson PowerPointsTake excellent notes during WebinarsRead & highlight Assigned Readings in Study Guide & Lavin bookPerform Self Checks in Study GuideLearn the Glossary at the beginning of each Chapter in Lavin bookStudy Key Points & Review Questions at end of each Chapter in Lavin book

  • Lesson 2 Producing a Radiographic Image

  • Glossary Terms Page 36

  • The 4 Exposure FactorsMilliamperage (mA)Time (S)Kilovoltage (kVp)Distance (SID)

  • The 4 Exposure FactorsExposure factors are THE KEY to taking good quality diagnostic x-raysDefinition Machine settings that a technician can adjust on the machine to take diagnostic x-raysSIBKIS when it comes to changing exposure factors!

  • Milliamperage (mA)Figure 4-1, Page 36Amount of electrons to produce x-raysFundamental Use the highest mA your machine can doAllows you to use much lower time settingsLess exposure time to x-raysThe higher the mA, the more exposed your film will be (the DARKER it will be) if all other exposure factors are kept the same

  • Exposure Time (S)The longer the exposure time, the greater the number of x-rays producedThe longer the exposure time, the greater the exposure to scatter radiationInverse relationship to mABenefits of shorter exposure timesLess movement on x-ray (thoracic films)Technician safety

  • Kilovoltage Peak (kVp)Figure 4-4, Page 38Speed of electrons used to create x-raysQuality of x-rayNot faster x-rays, but more penetratingAffects both exposure (darkness) of film, and contrast of filmSantes Rule (2 X thickness of body part) + 40 = kVp

  • CalipersFigure 4-5, Page 38 DefinitionA tool used to measure the thickness of a body part to be x-rayedUse centimeters (cm), not inchesIf in between numbers latitude

  • Latitude

    kVp rangeExposure latitude (kVp)40-50+270-80+490-100+6

  • Kilovoltage SummaryIt affects both contrast and exposureIncreased kVp more penetrating x-raysIncreased kVp increased scatter radiationIncreased kVp decreased contrast (leading to more latitude)

  • Milliamperage and TimeMilliamperesExposure timeFormula mAs = mA X sExamples same mAs, different mASame darkness (exposure)

  • Distance (SID)Source-image distance (SID)Aka Focal-film distance (FFD)Should be 40 inches for both table top technique and grid techniqueInverse Square Law Figure 4-6, Page 39Definition KISS Fundamental distance should always stay constant if possible

  • Greater Distance = Less Shadows

  • Greater Distance = Less Intensity (Exposure)Figure 4-6, Page 39

  • Review of X-ray ProductionFigure 4-7 on page 40X-ray tube partsPrimary vs. secondary radiationExposure factors

  • Radiographic Quality

  • Glossary Terms Page 44

  • Radiographic QualityDefinitionHow easily details can be seen on an x-rayHow sharp the details are

  • Radiographic Quality FactorsRadiographic DensityRadiographic ContrastExposure FactorsScatter RadiationGrids

  • Radiographic DensityDefinition amount of darkness (exposure) in x-ray filmWhen looking at a film for exposure, look at the body part you are interested inWhat causes density, you ask? ---

  • Densities of Various StructuresSubject densities: 1, Air. 2, Fat. 3, Water. 4, Bone. 5, Metal. Air is least dense, allowing x-rays to penetrate and expose the film. Metal is the most dense, absorbing most of the x-rays and allowing only a few to penetrate, exposing the film.

  • Factors Affecting Radiographic DensityAll 4 exposure factorsFigure 5-2 on page 46Same mAs (exposure), different thickness of body partWhite structures on x-raysRadio-opaque.. Why?Black structures on x-raysRadio-translucent.. Why?

  • Density on X-raysFigure 5-3, Page 47

  • Subject Density/Exposure

  • How is the Exposure on This X-ray?Overexposed (Figure 5-7 on page 49)Body parts too darkWhy? Under-exposed (Figure 5-6 on page 48)Body parts too lightMore common than overexposedCorrect exposure (just right!)

  • Overexposed Film (Too Dark)

  • Underexposed Film(Too Light)

  • Just Right, Goldilocks!

  • Underexposed or Overexposed?

  • Underexposed or Overexposed?

  • Underexposed or Overexposed?

  • Radiographic Contrast DefinitionThe density differences between 2 adjacent areas of an x-rayHigh contrast (short scale)Low contrast (long scale)Just like exposure, look at body parts (not background) on film

  • High Contrast vs. Low ContrastTable 5-1, Page 46

  • High Contrast X-raysLots of black and white on the film with very little shades of grayBone x-rays should be high contrast

  • Low Contrast X-raysThe film has black, white, and lots of shades of gray in betweenUsually soft tissue x-raysLatitude

  • Factors Affecting Radiographic ContrastkVp Relationship of contrast and kVp (Table 5-1 on page 46)***LatitudeSubject contrastDifference in density between 2 body partsDepends on thickness & density of part (Table 5-2 on page 46)

  • Exposure Factors and X-ray QualitymAskVpSID

  • Digital Control Panel with Exposure Factors

  • Milliamperage-Seconds (mAs)Affects density (darkness, exposure) onlyDoes not affect contrast

  • Kilovoltage (kVp)Affects both contrast and densityIncreased kVp causes increased scatter radiationIncreased kVp causes decreased contrast, which leads to more latitudeSoft tissue x-rays

  • Distance (SID)Affects density (exposure, darkness) onlyDoes not affect contrast

  • Scatter RadiationDefinitionSecondary radiation formed as a result of objects in the path of the primary beamMainly originates from the patient, but could come from increased kVpFogs the filmPotentially damages RVT!!!

  • Backscatter Definition When primary beam strikes patient, table, tray, or floor. scatter radiation bounces back to patient, film, and you!Therefore GLOVE UP, OR ELSE!

  • Grids Definition Device placed between patient & x-ray filmDesigned to absorb scatter radiationComposed of lead stripsAligned so that most of primary beam can get through them, but all secondary radiation is absorbedFound under table, usually permanently mounted

  • Grid Under Table

  • Figure 5-11, Page 50

  • Grid Ratio

    Definition Relation of height of the lead strips to distance between themFigure 5-13 on page 51Example 10:1So what does it mean?

  • Grid FactorDefinitionAmount that mAs must be increased if a grid is usedExample grid factor of 2

  • Grid PatternsFigures 5-14 & 5-15 on Pages 51 & 52Linear gridsCrossed gridsFocused gridsGrid linesMovable gridsPotter-Bucky Diaphragm (Figure 5-18 on page 53)

  • Potter-Bucky Diaphragm

  • Care of GridsLeave them aloneExpensive and delicate

  • To Use a Grid or Not?Grid TechniqueTable Top Technique

  • Grid TechniqueCapture of scatter radiationCaptures some of primary beam alsoLess foggingHigher exposure factors neededGenerally used for larger dogs & cats

  • Table Top TechniqueAnimal closer to the filmLower exposure factors needed Less shadowingFigures on page 55Object-Film Distance (OFD) lowerGenerally used for smaller animals/extremities

  • Table Top Less Shadowing

  • Image Receptors

  • Glossary Terms Page 60

  • What Are Image Receptors?Definition Tools used to capture invisible x-rays in such a way that they can be seen with the naked eye

  • Types of Image ReceptorsRadiographyXeroradiographyComputed TomographyNuclear Scintigraphy

  • RadiographyLight-sensitive film in a light-proof cassetteFilm is sandwiched between 2 intensifying screens in this cassette95% of exposure on film due to light emitted on these screens!Only 5% from x-rays themselves

  • The Cassette Definition Lightproof encasement designed to hold x-ray film, with intensifying screens in close contact with film

  • Types of Cassettes

  • Cassette CareHandle with care! Or ELSE!

    Some physical abuse in large animal practiceFilm-screen contact a MUSTCleaning cassettes regularly with mild soap & water

  • Intensifying ScreensDefinition Sheets of luminescent phosphor crystalsWhen these phosphor crystals are struck by x-rays they fluoresce2 screens per cassetteRequires less radiation exposure (mAs)~95% of exposure on film due to light from intensifying screens!

  • Cassette with Screens

  • Desired Properties of ScreensHigh level of x-ray absorptionHigh x-ray to light conversionLittle or no afterglow

    AfterglowDefinition tendency of a phosphor to give off light after x-ray production has stopped

  • Intensifying Screen AnatomyFigure 6-5 on page 632 screens per cassette4 layersPlastic base support layer, tight to cassetteReflective layer thin Phosphor crystal layerLayer that fluorescesProtective coat thin, tight to film

  • Cassette/Screen/Film Anatomy

  • Phosphor TypesThomas Edison 1896Calcium tungstateHigh x-ray absorptionStill used todayRare earth phosphors 1972ExpensiveGreat x-ray to light conversionNeeds a special type of film

  • Rare Earth Screens

  • Scre