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Quality Control

Quality Control

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Quality Control

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  1. Quality Control

  2. HIGH QUALITY FILMS • REPRODUCES ANATOMICAL IMAGE EXACTLY • FILM HAS: • CORRECT TECHNICAL FACTORS • NO MOTION • NO ARTIFACTS • PROCESSED CORRECTLY

  3. RESOLUTION • ABLE TO VISUALLY SEPARATE OBJECTS • BONE VS. TISSUE-- IE: SPATIAL RESOLUTION • CR VS CONVENTIONAL FILM • DIFFERENCES BETWEEN DIFFERENT TISSUES-- IE: CONTRAST RESOLUTION • CR VS. CONVENTIONAL FILM

  4. NOISE • FILM GRAININESS (INHERENT) SIZE OF FILM CRYSTALS • STRUCTURE MOTTLE (INHERENT), PHOSPHOR IN SCREEN • QUANTUM MOTTLE

  5. QUANTUM MOTTLE • LOW NUMBER OF X-RAY PHOTONS INTERACTING WITH SCREEN. INSUFFICIENT AMOUNT OF PHOTONS STRIKING INTENSIFYING SCREEN CAUSING AN INSUFFICIENT LIGHT TO EMIT FROM PHOSPHOR CRYSTALS. • How do we adjust technique for this? • CR and Quantum Mottle

  6. SPEED • FILM’S ABILITY TO RESPOND TO X-RAY EXPOSURE • IF FILM “A” RECORDS MORE DENSITY SOONER THAN FILM “B”, WHICH FILM HAS A HIGHER SPEED? • A

  7. SENSITOMETRY • MEASUREMENT OF SENSITIVITY TO LIGHT AND THE FILM’S RESPONSE TO CHANGES IN TECHNIQUE AND PROCESSING.

  8. DENSITOMETRY • MEASUREMENT OF THE DENSITY OF THE FILM BASED ON THE PERCENTAGE OF LIGHT TRANSMITTED THROUGH THE FILM.

  9. ANATOMY OF A CHARACTERISTIC(H & D CURVE)

  10. OVERHEADS!!!!!!!

  11. RECIPROCITY LAW • OD REMAINS THE SAME NO MATTER THE LENGTH OF EXPOSURE • 100 mA X 1 sec = 100 mAs ↓↓ 200 mA X .5 sec= 100mAs ↓↓ 400 mA X .25 sec =100mAs →→same OD 500 mA X .2 sec = 100mAs ↑↑ • Applicable to direct screen exposures

  12. RECIPROCITY LAW FAILURE • FILM/SCREEN RADIOGRAPHY • EXPOSURE TIMES LESS THAT 10 MILLISECONDS • EXPOSURE TIMES GREATER THAN 5 SECONDS • INTERVENTIONAL STUDIES • MAMMOGRAPHY

  13. RADIOGRAPHIC CONTRAST IMAGE RECEPTOR CONTRAST PLUS SUBJECT CONTRAST

  14. IMAGE RECEPTOR CONTRAST • Formerly known as film contrast. Why the change in name? • Inherent to film • Affected by processing

  15. SUBJECT CONTRAST • SIZE • SHAPE • X-RAY ATTENUATION OF THE ANATOMY AND ENERGY OF BEAM

  16. REVIEW • L ATITUDE (REMEMBER THIS IN REFERENCE TO THE FILM) • W I D E LATITUDE = LOOOOONNNNG GRAY AKA LOW OR LONG SCALE CONTRAST • NARROW LATITUDE = SHORT SCALE =HIGH CONTRAST

  17. WIDE LATITUDE FILM, BECAUSE OF LONG GRAY SCALE ALLOWS AS MUCH AT 15% ERROR BY RADIOLGRAPHER

  18. MAGNIFICATION FACTORS • MOST IMAGES ARE LARGER ON RADIOGRAPH THEN IN ACTUALITY DUE TO SID AND SOD! • FOR EVERY 1” INCREASE IN OID, SID MUST BE INCREASED BY 7” TO COMPENSATE FOR MAGNIFICATION

  19. SID AND SOD? • SID: SOURCE TO IMAGE DISTANCE • SOD: SOURCE TO OBJECT DISTANCE • MAG. FACTOR IMAGE SIZE OR SID OBJECT SIZE SOD TO FIND SOD SUBTRACT THE OID FROM THE SID

  20. IF YOU COULD MEASURE A HEART AND IT MEASURED 12.5 CM BUT ON THE RADIOGRAPH IT MEASURED 14.7 CM, THE MAGNIFICATION FACTOR WOULD BE CALCULATED AS 14.7 DIVIDED BY 12.5 WHICH EQUALS A MAGNIFICATION FACTOR OF 1.17.

  21. WAYS TO DECREASE MAGNIFICATION • IF OID IS INCREASED? • INCREASE SID! • CHEST • LATERAL AND OBLIQUE C-SPINE

  22. DISTORTION • Foreshortening • Object at an angle and CR is perpendicular to the part that is angled-trauma elbow • Spatial • Tube is angled to separate body parts • Clavicle • Elongation • object is parallel but tube is angled • sigmoid

  23. FOG LEVEL/CONTRAST AND THE PROCESSOR • As time extends in the developing process the fog level____(toe of the characteristic curve) and the contrast____ • increases • decreases

  24. 90 seconds is the optimal developer time • A variation of 5 seconds either way can affect quality of film.

  25. Developer temperature • As the temperature increases the fog level______ • increases • optimum temperature is usually 90 degrees F.

  26. SUBJECT CONTRAST • Review: • Rad. Contrast=film contrast plus subject contrast • film contrast is controlled latitude of film, and processing factors

  27. Subject contrast • Patient (Size) • Tissue (KUB) • Atomic # ( higher produces high contrast) • object shape

  28. MOTION • PATIENT • TUBE MOVEMENT • TOMOGRAPHY

  29. MOTION • LARGE SID = LESS FOCAL SPOT BLUR • SMALL SID = MORE FOCAL SPOT BLUR

  30. FOCAL SPOT BLUR

  31. KVP • GIVES ELECTRONS ENERGY TO HIT THE ANODE • HIGH AMOUNT OF KINECTIC ENERGY IN AN ELECTRON PRODUCES A HIGHLY ENERGIZED X-RAY PHOTON • BETTER PENETRATION=LOTS OF GRAYS

  32. KVP • LOW KVP PRODUCES A BLACK AND WHITE IMAGE. • TO PRODUCE AN ADEQUATE OD MUST USE HIGHER MAS • HIGHER MAS MEANS MORE EXPOSURE TO THE PATIENT

  33. +Greater margin of error +Reduction in patient dose +Wider latitude -increase scatter -increase fog +Higher OD +Lower Rad noise -increased pt. Exposure -less margin of error HIGH KVP HIGH MAS

  34. The Radiographer controls • kVp • mAs • focal spot size • distance • added filtration • screen speed

  35. REMEMBER • 200 mA increased to 300mA is a 50% increase in electrons being produced • As mA increases, time must decrease to maintain same density • Distance Maintenance formula--New Sid over Old Sid Squared

  36. REMEMBER • Small mA station uses smaller focal spot • smaller focal spot = more detail • Inherent = .5 mm • additional 2 mm of aluminum between housing and collimator • collimator adds 1 mm