9 CT Instrumentation
9 CT Instrumentation
9 CT Instrumentation
INSTRUMENTATION AND
OPERATION
OUTLINE
CT MAIN SYSTEMS
IMAGING SYSTEM
COMPUTER SYSTEM
DISPLAY, RECORDING, STORAGE
SYSTEM
DATA ACQUISITION SYSTEM
CT SYSTEM
GANTRY
X-RAY TUBE
GANTRY CONTROL
DETECTORS
S/H
ADC
DAC
HIGH VOLTAGE
GENERATOR
SCAN CONTROLLER
ARRAY PROCESSOR
HOST
COMPUTER
STORAGE
CONSOLE
SCANNER
SCANNER
GANTRY
PATIENT COUCH
GANTRY HOUSES:
X-RAY TUBE
GENERATOR (LOW VOLTAGE DESIGN)
COLLIMATORS
DETECTORS
GANTRY CHARACTERISTICS
APERTURE
TILTING RANGE
70 CM
COORDINATE SYSTEM
COORDINATE SYSTEM
COORDINATE SYSTEM
ISOCENTER
PATIENT COUCH :
450 LBS (204 KG)
DISTRIBUTED WEIGHT LIMIT
SCANNABLE RANGE:
COVERAGE FROM HEAD TO
THIGH (162CM)
IMAGING SYSTEM
PRODUCTION OF X-RAYS
SHAPING OF X-RAY BEAM ENERGY
FILTERING X-RAY BEAM
IMAGING SYSTEM
COMPONENTS
X-RAY TUBE
GENERATOR HIGH VOLTAGE
COLLIMATORS
FILTER
DETECTORS
DETECTOR ELECTRONICS
THERMIONIC EMISSION
mA tube current
kVp
S time of exposure
mAs tube current for certain
length of time
kVp
mA
Time
INCREASED NOISE
NOISE !!!!
X-RAY EMISSION
INTENSITY
ENERGY NO CHANGE
2 * mA = 2 * number of photons
4 * mA = 4 * number of photons
Why changing
mA or time
Avoiding motion mA
time
Pediatric technique modification
Reducing noise - mAs
NOISE
MOTION
INTENSITY kVp
ENERGY
kVp IN CT
80-140
TOO LOW NOISE
(NOT ENOUGH PENETRATION OF THE PATIENT )
PHOTON STARVATION - NOISE!!!!!
CT GENERATOR
5-50 kHz
30-60 kW
KVP SELECTION:
80, 100, 120, 130,140
mA selection:
30, 50, 65, 100, 125, 150, 175, 200, 400
COLLIMATION IN CT
PRE-PATIENT COLLIMATION
POST-PATIENT COLLIMATION
ADC
ADC
FILTRATION CHANGE
INTENSITY
FILTRATION
ENERGY
FILTRATION MATERIAL
BOWTIE
TO MAKE THE BEAM HARDER AND
MORE MONOENERGETIC
Filter
DEFINES SLICE
THICKNESS
Patient
REDUCES SCATTER
RECHING THE PATIENT
Detector
CT DETECTORS
DETECTOR TYPES:
SCINTILLATION
S. CRYSTAL
S. CRYSTAL
PHOTODIODE
PM TUBE
SCINTILLATION CRYSTALS
USED WITH PM TUBES:
CALCIUM FLUORIDE
BISMUTH GERMANATE
CALCIUM TUNGSTATE
RARE EARTH OXIDES - CERAMIC
XENON GAS
30 ATM
EFFICIENCY OF DETECTORSQDE
COMPUTER SYSTEM
RECONSTRUCTION AND
POSTPROCESSING
CONTROL OF ALL SCANNER
COMPONENTS
CONTROL OF DATA ACQUSITION,
PROCESSING, DISPLAY.
DATA FLOW DIRECTION
COMPUTER SYSTEM IN CT
MINICOMPUTERS
COMPUTER SYSTEM
COMPOSED OF:
HARDWARE
SOFTWARE
COMPUTER PROCESSING IN
CT
SEQUENTIAL PROCESSING
MULTITASKING
MULTIPROCESSING
CT OPERATING SYSTEM
UNIX
WINDOWS
HOST COMPUTER
ARRAY PROCESSOR
AMPLIFIER
ADC
DAS
GANTRY
X-RAY TUBE
GANTRY CONTROL
DETECTORS
S/H
ADC
DAC
HIGH VOLTAGE
GENERATOR
SCAN CONTROLLER
ARRAY PROCESSOR
HOST
COMPUTER
STORAGE
CONSOLE
IMAGE
DISPLAY
SOLID STATE
LASER PRINTERS
GAS LASER
PRINTERS
HARD COPY
MAGNETIC TAPES
MAGNETO-OPTICAL DISK (MOD)
CD
COMMUNICATION
PACS
OVERREAD 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 highspeed telecommunications networks and
improved data compression techniques, have
matured in recent years.
CT ROOM LAYOUT