Plain Film
Tomography
George David
Associate Professor
Department of Radiology
Medical College of Georgia
Resident Physics...
Body Section
Tomography
Body Section
Tomography
• Not CT
• Body Section Imaging
• Goal
 keep plane of interest in focus
...
George
David
Tomography HistoryTomography History
• Predates CT by decades
• Used to be popular for inner ear
studies
• St...
Tomography BlurringTomography Blurring
• Blurring accomplished
by synchronous
movement of tube &
film
 tube & bucky physi...
George
David
Conventional Tomography BlurringConventional Tomography Blurring
• Image produced on
film
• Objects above or
...
Tomography BlurringTomography Blurring
• the further from the
fulcrum an object is,
the more it blurs!
Tomography BlurringTomography Blurring
• objects shaped &
oriented in direction of
motion
 elongate
 do not blur
Tomographic BlurringTomographic Blurring
• Blurring improved by use of
complex motions
circular
tri-spiral
elliptical
Hypo...
George
David
Complex BlurringComplex Blurring
• The more complex the blurring
motion
 the sharper the tomographic image
»...
George
David
Tomo Patient DosesTomo Patient Doses
• Tomo can be high dose procedure
 several rads not unusual
• one image...
Thickness of CutThickness of Cut
• Same as thickness of
region in focus
• Determined by angle
tube moves
• Larger angles y...
Thickness of CutThickness of Cut
Smaller Angle;
Thicker Cut
Larger Angle;
Thinner Cut
George
David
Cut ThicknessCut Thickness
• Approximate cut thickness for
linear tomo
Tomo Angle Thickness of Cut (mm)
(degr...
George
David
Grids & TomoGrids & Tomo
• Linear grid used
• Grid lines parallel with table for
linear tomo
• Grid must chan...
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Conventional (Body Section) Tomography

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Conventional (Body Section) Tomography

  1. 1. Plain Film Tomography George David Associate Professor Department of Radiology Medical College of Georgia Resident Physics LecturesResident Physics Lectures
  2. 2. Body Section Tomography Body Section Tomography • Not CT • Body Section Imaging • Goal  keep plane of interest in focus  blur all other plans » enhances contrast • Popularity decreasing because of  CT  MRI
  3. 3. George David Tomography HistoryTomography History • Predates CT by decades • Used to be popular for inner ear studies • Still used at MCG for IVP’s
  4. 4. Tomography BlurringTomography Blurring • Blurring accomplished by synchronous movement of tube & film  tube & bucky physically connected by rod  rod pivots around fulcrum  tube moves one direction  film moves in other direction
  5. 5. George David Conventional Tomography BlurringConventional Tomography Blurring • Image produced on film • Objects above or below fulcrum plane change position on film & thus blur
  6. 6. Tomography BlurringTomography Blurring • the further from the fulcrum an object is, the more it blurs!
  7. 7. Tomography BlurringTomography Blurring • objects shaped & oriented in direction of motion  elongate  do not blur
  8. 8. Tomographic BlurringTomographic Blurring • Blurring improved by use of complex motions circular tri-spiral elliptical Hypocycloidal
  9. 9. George David Complex BlurringComplex Blurring • The more complex the blurring motion  the sharper the tomographic image » better blurring  the more expensive the machine $
  10. 10. George David Tomo Patient DosesTomo Patient Doses • Tomo can be high dose procedure  several rads not unusual • one image per cut with film  cuts at many levels routinely employed to find cut of interest  each cut exposes entire field • Can do multiple images per cut with digital receptor
  11. 11. Thickness of CutThickness of Cut • Same as thickness of region in focus • Determined by angle tube moves • Larger angles yield thinner cuts  more motion = more blurring • Smaller angles yield thicker cuts  0o (stationary) yields conventional film
  12. 12. Thickness of CutThickness of Cut Smaller Angle; Thicker Cut Larger Angle; Thinner Cut
  13. 13. George David Cut ThicknessCut Thickness • Approximate cut thickness for linear tomo Tomo Angle Thickness of Cut (mm) (degrees) ------------------------------------------------------- 0 Infinite (non-tomo) 2 31 4 16 6 11 10 6 20 3 35 2 50 1
  14. 14. George David Grids & TomoGrids & Tomo • Linear grid used • Grid lines parallel with table for linear tomo • Grid must change orientation (rotate) in complex motion tomo  eliminates grid cutoff

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