COMPUTED TOMOGRAPHY HISTORICAL PERSPECTIVE

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COMPUTED TOMOGRAPHY HISTORICAL PERSPECTIVE
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OUTLINE

• TOMOGRAPHY DEFINITION
• WHY CT LIMITATIONS OF RADIOGRAPHY AND
  TOMOGRAPHY
• CT- BASIC PHYSICAL PRINCIPLE
• HISTORICAL TRAIL
• CT GENERATIONS

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Tomography From the Greek word tomos section.
The process for generating a tomogram, a
two-dimensional image of a section through a
three-dimensional object. Tomography achieves
this result by simply moving an x-ray source in
one direction as the x-ray film is moved in the
opposite direction during the exposure to sharpen
structures in the focal plane, while structures
away from the focal plane appear blurred.
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CONVENTIONAL RADIOGRAPHY HAS LIMITATIONS

• TWO DIMENSIONAL IMAGE WITH INFINITE DEPTH -
  SUPERIMPOSITION OF UNDERLYING STRUCTURES (LATERAL
  AND OBLIQUE VIEWS DONT SOLVE IT COMPLETELY).
• INABILITY TO DEMONSTRATE SLIGHT DIFFERENCES IN
  SUBJECT CONTRAST CHARACTERISTIC OF SOFT TISSUE.

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TOMOGRAPHY SOLUTION?

• CONVENTIONAL TOMOGRAPHY ATTEMPTED TO ELIMINATE
  THE SUPERIMPOSITION PROBLEM BY BLURRING THE
  STRUCTURES ABOVE AND BELOW THE TOMOGRAPHIC FOCAL
  PLANE.
• CONTRAST OF AN IMAGE CAN ALSO BE CHANGED BY
  VARYING TOMOGRAPHIC ANGLE (DISTANCE OF A TUBE
  TRAVEL)
• MULTIDIRECTIONAL TUBE MOVEMENT MAKES THE BLURRING
  OF UNWANTED STRUCTURES EVEN MORE EFFECTIVE.

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TOMOGRAPHY STILL LIMITED

• IMAGE BLURR PRESENT
• EXCESSIVE SCATTER RADIATION FILM FOG

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RADIOGRAPHY AND TOMOGRAPHY

• TISSUE DIFFERENCE SENSITIVITY
• 5-10

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CT GOALS
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CT EVOLUTION OF TERMS
COMPUTERIZED TRANSVERSE AXIAL TOMOGRAPHY
COMPUTER ASISSTED TOMOGRAPHY
COMPUTERIZED AXIAL TOMOGRAPHY
COMPUTED TOMOGRAPHY
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FORMATION OF CT IMAGE
DATA AQUSITION
IMAGE RECONSTRUCTION
IMAGE DISPLAY, MANIPULATION, STORAGE COMMUNICATIO
NS RECORDING
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DATA ACQUISITION

• COLLECTION OF X-RAY PHOTONS TRANSMITTED THROUGH
  THE PATIENT BY THE CT DETECTORS.

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DETECTORS
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IMAGE RECONSTRUCTION

• TRANSMISSION MEASUREMENTS COLLECTED BY THE CT
  DETECTORS ARE SENT TO THE COMPUTER FOR THE
  PROCESSING. COMPUTERS USES MATHEMATICAL ALGORITHM
  TO RECONSTRUCT THE IMAGE.

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IMAGE DISPLAY, MANIPULATION, STORAGE,
COMMUNICATION.

• AFTER RECONSTRUCTION IMAGE CAN BE DISPLAYED ON
  THE MONITOR
• IMAGE CAN BE MANIPULATEDIMAGE CAN BE STORED ON
  MOD OR CD.
• DURING COMMUNICATION PHASE IMAGE MAY BE
  TRANSMITTED TO A REMOTE LOCATION

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Sir Godfrey Newbold Hounsfield CBE, FRS, (28
August 1919 12 August 2004) was an English
electrical engineer who shared the 1979 Nobel
Prize for Physiology or Medicine with Allan
McLeod Cormack for his part in developing the
diagnostic technique of X-ray computed tomography
(CT).
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CONSTRUCTION OF FIRST CT

• RADIATION SOURCE AMERICUM GAMMA SOURCE
• SCAN9 DAYS
• COMPUTER PROCESSING2.5 HOURS
• PICTURE PRODUCTION 1 DAY

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HOUNSFIELDS LATHE BED SCANNER
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DR.HOUNSFIELD DR. AMBROSE

• READINGS FROM SPECIMEN OF HUMAN BRAIN. TUMOR
  FINDINGS APPARENT.

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1972

• FIRST CLINICAL PROTOTYPE CT BRAIN SCANNER
• FIRST SCANS20 MIN.
• LATER REDUCED TO 4.5 MIN.

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CLINICALLY USEFUL CT SCANNER
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DR. HOUNSFIELD

• 1972 McROBERT AWARD
• 1979 NOBEL PRIZE

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ALLAN M. CORMACK

• 1979 NOBEL PRIZE SHARED WITH DR. HOUNSFIELD.
  DEVELOPED SOLUTIONS TO MATHEMATICAL PROBLEMS IN
  CT.

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1974

• DR. ROBERT LEDLEY DEVELOPED THE FIRST WHOLE BODY
  CT SCANNER .

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SCANNING DEVELOPMENT

• 5 MIN. 1972
• 1 SEC 1993

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CT SCANNING GENERATIONS
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HIGH SPPED CT V GENERATION ( CARDIVASCULAR CT)
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EBCT ( SIEMENS)
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1990SPIRAL CT ( HELICAL) SLIP RING TECHNOLOGY
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CT SCANNING IN SPIRAL-HELICAL GEOMETRY BASED ON
SLIP RING TECHNOLOGY
Slip rings
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SCANNER POWER SUPPLY-SLIP RINGS DISK
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1992

• DUAL SLICE CT HELICAL SCANNER

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1998

• MULTISLICE CT SCANNERS

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