16. OUTLINE
CT SYSTEM COMPONENTS – DEFINITION OF A
SCANNER
SCANNER COORDINATE SYSTEM – XYZ,
ISOCENTER
IMAGING SYSTEM
COMPUTER SYSTEM
DISPLAY, RECORDING, AND STORAGE
SYSTEMS
16
17. CT MAIN SYSTEMS
IMAGING SYSTEM
COMPUTER SYSTEM
DISPLAY, RECORDING, STORAGE SYSTEM
DATA ACQUISITION SYSTEM
17
18. CT SYSTEM
GANTRY
DETECTORS
SAMPLE HOLD UNIT
ADC
ARRAY PROCESSOR
HOST
COMPUTER
STORAGE
CONSOLE
SCAN CONTROLLER
DAC
GANTRY CONTROL
HIGH VOLTAGE
GENERATOR
X-RAY TUBE
18
47. S –time of exposure
mAs tube current for certain
length of time
47
48. X-RAY PRODUCTION
RESULTS IN A LOT OF HEAT
AND VERY LITTLE
X-RAYS BEING GENERATED
HEAT UNITS CALCULATION
HU= kVp X mA x time
MOST CT TUBES HEAT CAPACITY
3-5 MILLION HU
48
49. REDUCTION OF HEAT UNITS –
TECHNIQUE
COMPENSATION kVp
mA
Time
INCREASED NOISE
49
67. SCINTILLATION CRYSTALS
USED WITH PM TUBES:
SODIUM IODIDE –AFTERGLOW + LOW DYNAMICAFTERGLOW + LOW DYNAMIC
RANGERANGE ( USED IN THE PAST)( USED IN THE PAST)
CALCIUM FLUORIDE
BISMUTH GERMANATE
67
68. S. CRYSTAL USED WITH
PHOTODIODE
CALCIUM TUNGSTATE
RARE EARTH OXIDES - CERAMIC
68
70. EFFICIENCY OF
DETECTORS- QDE
SCINTILLATION – 95% - 100%- COMMONLY USED INCOMMONLY USED IN
III & IV GENERATION SCANNERSIII & IV GENERATION SCANNERS
GAS – 50% - 60%
70
71. COMPUTER SYSTEM
RECONSTRUCTION AND POSTPROCESSING
CONTROL OF ALL SCANNER COMPONENTS
CONTROL OF DATA ACQUSITION, PROCESSING,
DISPLAY.
DATA FLOW DIRECTION
71
78. HOST COMPUTER
CONTROL OF ALL COMPONENTS
CONTROL OF DATA ACQUSITION, PROCESSING,
DISPLAY.
DATA FLOW DIRECTION
78
79. ARRAY PROCESSOR
TAKES DETECTOR MEASUREMENTS FROM HUNDREDS OF
PROJECTIONS. RESPONSIBLE FOR RETROSPECTIVE
RECONSTRUCTION AND POSTPROCESSING OF DATA.
THE MORE PROCESSORS IN THE COMPUTER
THE SHORTER THE RECONSTRUCTION TIME
79
80. DATA ACQUISITION
SYSTEM (DAS)
SET OF ELECTRONICS BETWEEN DETECTORS AND
HOST COMPUTER.
IT CONTAINS: AMPLIFIER, ADC, DAC, GENERATOR,
S/H.
80
81. AMPLIFIER
SIGNAL FROM DETECTORS GOES TO AMPLIFIERS
FOR SIGNAL MAGNIFICATION AND THEN IS SENT
TO SAMPLE/HOLD UNIT
81
82. ADC
CONVERTS ANALOG SIGNAL OUTPUT FROM THE
SCANNING EQUIPMENT TO A DIGITAL SIGNAL SO IT
CAN BE PROCESSED BY A COMPUTER.
82
83. SAMPLE/HOLD UNIT (S/H)
LOCATED BETWEEN AMPLIFIERAMPLIFIER AND ADCADC PERFORMS SAMPLING
AND ASSIGNS SHADES OF GRAY TO THE PIXELS IN THE DIGITAL
MATRIX CORRESPONDING TO THE STRUCTURES
83
85. IMAGE DISPLAY,
RECORDING, STORAGE
DISPLAYS IMAGE ( OUTPUT FROM COMPUTER)
PROVIDES HARD COPY OF THE IMAGE
FACILITATES THE STORAGE AND RETRIEVAL OF
DIGITAL DATA
COMMUNICATES IMAGES IN THE NETWORK
85
91. NETWORK
WHILE MOST TELERADIOLOGY SYSTEMS
PURCHASED OVER THE LAST DECADE WERE
INTENDED FOR ON-CALL PURPOSES, THE PAST
TWO YEARS HAVE SEEN A RAPID INCREASE IN
THE USE OF TELERADIOLOGY TO LINK
HOSPITALS AND AFFILIATED SATELLITE
FACILITIES, OTHER PRIMARY HOSPITALS, AND
IMAGING CENTERS. A NUMBER OF THE
ENABLING TECHNOLOGIES NEEDED FOR
EFFECTIVE OVERREAD NETWORKS, SUCH AS
MORE AFFORDABLE HIGH-SPEED
TELECOMMUNICATIONS NETWORKS AND
IMPROVED DATA COMPRESSION TECHNIQUES,
HAVE MATURED IN RECENT YEARS.
91
92. NightHawk Radiology Services has developed
an innovative approach to the delivery of
radiology services by operating centralized,
state-of-the-art reading centers in Sydney,
Australia and Zurich, Switzerland. Staffing
U.S.-trained, board-certified radiologists
specializing in emergency radiology, these
locations are ideally situated for U.S. care
because when it’s the middle of the night in
Boston, it’s daytime “Down Under.” When it’s
early morning in Los Angeles, it’s daytime in
the Alps. From the centralized reading centers,
NightHawk radiologists interpret exams and
report the results to attending physicians in
real-time, usually less than 20 minutes.
92