1
History of X-ray CT Systems
"What is CT?"
1.
Dawn of X-ray CT
2.
Advances in CT scanning methods
2
Dawn of X-ray CT
Around 1964:
The English
company EMI (Hounsfield)
developed a CT scanner.
1973: EMI released a commercial model,
the "MARK1".
In Japan, Toshiba obtained the rights to sell and
maintain this model.
1975: The first CT system in Japan was
installed at Tokyo Women's Medical
University Hospital.
3
Dawn of X-ray CT
First-generation CT systems
ハンスフィールド
Data acquisition
→ 9 days
Image reconstruction
→ 2.5 days
External appearance of
the experimental system
4
EMI MARK１
→ Radiological Society of
North America (1972)
External appearance of
the CT system
5
Image acquired using the EMI MARK1
→ 5th International
Congress of
Neurological Surgery
(1973)
→ Scan time
270 s
6
First clinical case in Japan
→ Tokyo Women's
Medical University
Hospital
EMI 1000
1975
7
First head CT system developed
in Japan
1975
→ Fujita Health University
(Hitachi)
External appearance
of the CT system
8
Other manufacturers following EMI
(At the Radiological Society of North America in 1975)
GE → Presented a third-generation CT
system
Scan time: 5 s
EMI → Second-generation CT system
Scan time: 20 s
9
Distribution of a budget totaling 10 billion yen
Major order from The General Insurance Association of Japan (1976)
CT scanners
→ Total 32 systems
EMI scanners: 27 systems
ACTA scanners: 5 systems
10
Multislice scanning (1976)
EMI 1010
11
First whole-body CT system developed in Japan
1978
→ National Cancer Center
(Toshiba TCT-60A)
External appearance of the
CT system
12
Dawn of CT systems → Third-generation CT
EMIgoesintoadecline
(Exhibition of CT systems at the Radiological Society of North America in 1975)
SYNTEX
EMI
G.E
VARIAAN
PFIZER(ACTA)
AS&E
PHILIPS
HITACHI
PICKER
C.G.R
ELSCINT
OHIO NUCLEAR
ARTRONIX
NEUROSCAN
SEARLE
LITTON
13
Third-generation C T → HelicalC T
SIEMENS
G.E
PICKER
Toshiba
HITACHI
SHIMAZU
14
Birth of continuous rotation-type CT
EMI
EMI Medical
GE (otherthan theUSA)
B.I.R
THORN EMI
EMI Medical America
Toshiba
Started development of a continuous rotation-type CT scanner (1979)
Release of the TCT-900S (1985)
Fujita Health University
Fukushima Medical
University
National Cancer Center
Announcement of helical scanning (1989)
15
Principles of X-Ray CT
The absorption of X-rays varies due to differences in the
composition or thickness of anatomical structures as they pass
through the human body.
These variations in X-ray absorption are
used to reconstruct images.
16
Principles of X-ray CT - configuration
X-ray tube
ref.det.
Reconstruction
processing
Magnetic
disk
Detector
Image
DA converter
DAS
17
X-ray CT - First generation (T/R method)
First-generation CT-scanner (1/2)
(translate / rotate)
X-ray tube
Translation movement
Single
Detector cell
Data collection
(X-ray)
Rotation movement
No
Data collection
18
History ofC T systems
First generation CT-scanner (2/2)
• For the reconstruction we
need a set of data obtained
with parallel projection
(also called : views)
originating from all
directions within 180o.
• First the detector and tube
move linear (translation),
then a rotation (eg. 1o)
followed by translation, etc
19
History ofC T systems
Second generation CT-scanner (1/2)
(translate / rotate)
X-ray tube
Translation movement
Small
Detector array
(about 20 cells)
Data collection
(X-ray)
Rotation movement
No
Data collection
20
Historyof C T Systems
Second generation CT-scanner (2/2)
• Very similar to first
generation scanners,
instead of a single cell an
array of cells is used (~ 20
cells).
• The scan time could be
decreased to 1/10 th.
• Still translation and rotation
movements are used.
21
HistoryofC T systems
Third generation CT-scanner (1/2)
(rotate / rotate)
X-ray tube
Detector array
Non-continuous rotation : CW and CCW rotation
Continuous rotation : only CW rotation
22
History of C T systems
Third generation CT-scanner (2/2)
• The detectors (eg. 512) are
mounted in an arc.
• No translation movement
necessary because the
length of the linear path is
covered by the detectors.
• The scantime is again
reduced.
23
X-ray CT - Third generation (R/R method) -
X. ray tube
Cables
Disadvantages
• Scanning takes a long time
Rotation
orbit
Rotation
orbit
Detector
because reverse rotation is
required after every rotation.
• Breath-holding is required
for every rotation.
Results in patient
discomfort
24
X-ray CT - Third generation (R/R method) -
Advantages
• The X-ray tube and the detector can be
Brush
rotated continuously in a paired manner to
acquire data.
• Since reverse rotation is not required, the
scan time can be reduced to 1/10 that of a
conventional scanner and high-quality
images can be obtained.
Helical scan
Slipring
25
Slipring method
Power supply slipring
HVSR: External generator
LVSR: Generator mounted in the gantry
Signal transmission/reception
slipring
Contact type or non-contact type
(optical slipring)
Power supply
Control/processing system
26
HistoryofC T systems
Fourth generation CT-scanner (1/3)
Stationary / Rotate
Detector ring
Tube orbit
Conventional system
Nutate system
Tube rotates, Detector is stationary (full ring of detectors)
27
History of C T Systems
Conventional system
Fourth generation CT-scanner (2/3)
The tube rotates inside the detector ring.
28
History of C T systems
Nutate system
Fourth generation CT-scanner (3/3)
Nutate mechanism
(moves detector in x-ray beam)
29
X-ray CT - Fourth generation (S/R method)
Sampling point of projection data during rotation
X. ray tube
<Disadvantages>
• The positional relationships with the
X-ray tube focus are not optimal,
resulting in a reduction in X-ray
utilization efficiency.
• There are difficulties in X-ray
Detector (600 to 2500 channels)
collimation, and the system tends to
be strongly affected by scattered Xrays.
30
X-ray CT - Fourth generation (N/R method)
For the TCT-900S
Advantage
Fan beam
Tube orbit
• The diameter of the detector
ring (detector element array)
can be made smaller than that
for the S/R method.
X-ray source
rotation orbit
High spatial resolution
Detector ring
31
Generations (scan methods)
Translate/Rotate
Pencil-type X-ray beam
3 to 4 minutes
Rotate/Rotate
Wide X-ray fan beam
2 to 10 s
(1 s)
Translate/Rotate
Narrow X-ray fan beam
10 to 20 s
Stationary/Rotate
Wide X-ray fan beam
1s
32
Outline of CT systems
1. Standard configuration, reconstruction
principles
2. Basic performance and component
technologies
• Advances in scan time
• Advances in reconstruction time
• Advances in resolution
• Advances in tube capacity
3. Cutting-edge technologies
33
Advances in scan time
３００
１０
０７
０５
０
Helical
３０
２０
Multi
１
０
７
５
３
２
: Non-slipring CT
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Scan time (s)
２００
: Slipring CT
34
Basic configuration (units) of an X-ray
CT system
Gantry
Console
Patient couch
35
High-voltage generator
X-ray tube
Scanning (data acquisition)
Image
display/processing
/storage/filming
Detector
CPU/Disk
Image reconstruction
unit
Data acquisition
unit
Data acquisition unit
Raw data storage
Image reconstruction
36
Basics of CT image
reconstruction
37
General CT system
Gantry
Monitor
RAW DATA
Reconstructor
IMAGE DATA
Storage
Medium
38
CT image reconstruction (data flow)
TUBE
Gantry
DETECTOR
DAS
CALIBRATION
DATA
Pre-Proc
RAW DATA
Reconstructor
Console
IMAGE DATA
39
TUBE
DETECTOR
DAS
CALIBRATION
DATA
Pre-Proc
RAW DATA
Reconstructor
IMAGE DATA
40
TUBE
REFERENCE DETECTOR
FAN ANGLE
ROTATION（９００VIEW）
FOV
DETECTOR
８９６CH
PROJECTION DATA（投影データ）
41
X-ray path
T
TUBE
Collimator
Wedge
Slit
x-ray
beam
Beamtrimmer
Detector
Detector
42
TUBE
DETECTOR
DAS
CALIBRATION
DATA
Pre-Proc
RAW DATA
Reconstructor
IMAGE DATA
43
Pre-Processing
CALIBRATION
DATA
TUBE
Input = Pure Raw Data
DETECTOR
DAS
Pre-Proc
RAW DATA
Reconstructor
IMAGE DATA
Pre Processing functions :
• Offset correction
• Reference correction
• Water Calibration
• Air Calibration
• FSMC
Output = Raw Data
44
Reconstruction Flow (S&V)
From DAS
(Pure Raw Data)
Pre
Processing
Reconstructor
To HDD
(Raw Data)
Filtering
Back
Projection
To Monitor and HDD.
(Image Data)
45
Linear superposition method
T
T
46
Result of Lineair superposition method
Original object
Result of Lineair
Superposition method
Unsharp result
IMPROVEMENT:
Filtered Backprojection
47
Filtered Backprojection
Measurement
data
Filter data
Result after
filtering
Convolution
48
Filtered backprojection
T
T
49
Linear superposition vs. Filtered backprojection
Original object
Result of Linear
Superposition method
Result of Filtered
backprojection
50
Viewing
• The values in the backprojector memory are
Hounsfield units (after Sir G.N. Hounsfield).
• The definition of the Hounsfield unit is :
x - H2O
CT number = 1000 x −−−−−−−−−
H2O
51
Advances in reconstruction time
From still image to dynamic image
8
Time 7
6
(s)
Still image
5
4
3
Real-time
2
1
Dynamic image
99
97
95
93
91
89
87
0
Year
52
Reduce contrast medium?
Since the liver can be scanned in 2 s, if the timing of
contrast enhancement is incorrect, it is possible that no slices
are enhanced.
→ SureStart is essential.
HU
2sec
SEC
53
Realtime Reconstruction
Realtime
Realtime Helical
Helical
Real
Real Prep
Prep
Stop
54
Real-time CT
Continuous scan
(0.75 s/rot.)
Image reconstruction
Immediate
(0.5 s)
Continuous image display
(8 fps)
55
SureStart
Pilot scan
Real-time
CT number
CT number in the abdominal
aorta
Conventional
CT number
Time
Scan start
Scan
Time
56
SureStart
CT number
Contrast medium curve
DELAY
Threshold
Time
Monitoring
Scan start
57
Real-time fluoroscopy
(CT fluoroscopy mode)
• Biopsy procedures can be performed easily and safely under CT
fluoroscopic guidance (image reconstruction and display: 3 fps, 30 mA to 50 mA) while observing
images in real-time.
• The local console permits the operator to
perform various system operations during
scanning, such as gantry tilting, couch-top
sliding, couch vertical movement, and Xray ON/OFF.
• X-ray exposure to the operator and patient
is reduced.
58
Multislice CT fluoroscopy
* 3-slice (plane) real-time reconstruction/display
* Display at 8 fps for 3 slices
* Reconstruction at 0.125 s x 3 slices
* Improved accuracy in biopsy procedures
* Reduced biopsy time
* Enhanced safety
59
X-ray generation
60
Functions of X-ray generator
MAINS IN
TO XRAY TUBE
Low Voltage
Increase
High Voltage: kV
High Current
Decrease
Low Current: mA
AC
Rectify
DC
kV
mA time
Operator Controls
61
Basic circuit of X-ray generator
AUTO
TRANSFORMER
TIMER
HIGH VOLTAGE
TRANSFORMER
X-RAY
TUBE
RECTIFIER
High Voltage
Low Voltage
Low Current
High Current
DC
AC
kV
S
mA
CATHODE
HEATER
POWER
LINE
62
Metal Section X-ray Tube
Primary
Electrons
Metal
Center Section
ANODE 90 mA
CATHODE
100 mA
Secondary
Electrons
Center Section Lead
10 mA
90 mA
100 mA
63
Metal Section X-ray Tube (2 focus)
Filament for Small Focus
ANODE
CATHODE
Common
Filament for Large Focus
ANODE
ANODE
ANODE
Filament for Small Focus
Common
Large
Focus
Small
Focus
Focal
Spot
Filament for Large Focus
64
Metal Section X-ray Tube (2 focus)
Small Focus
Large Focus
– Lower power input
(eg: 120kV 200mA)
+ High power input
(eg: 120kV 300mA)
+ For small objects
(thin slices)
– Not for thin slices.
65
Heat produced in X-ray tube (1/3)
kV
mA
Time
Heat
Produced
Cooling Unit
OIL
Housing
Anode
Focal Spot
66
Heat produced in X-ray tube (3/3)
HEAT
HEAT
Temperature
4000o
3000o
2000o
1000o
0o
Small heat capacity
Large heat capacity
67
OverLoad Protection (OLP)
• OLP will protect the tube. It will prevent
exposure if the tube is too hot.
• OLP is calculated by the input kV, mA and
time. This is expressed in Heat Units (HU).
kHU = kV  mA  sec  1.4
• The X-ray tube specification will state the
maximum amount of HU the tube can
handle. Also a cooling curve is specified.
68
Anode heating and cooling curves
CXB-200 (example)
120%
100%
%OLP
80%
60%
Cooling-rate
Continuous Scan 120kv/100mA
Continuous Scan 120kv/50mA
40%
Scan 120kv/70mA/4s + 4s wait
20%
0%
0
4
8
12
16
20
24
28
32
time (minutes)
36
40
44
48
52
56
60
69
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‘９８
‘９９
Advances in CT X-ray tube capacity
‘８４
MHU
‘８２
８
‘８０
６
‘７８
４
‘７６
２
０
‘７４
70
Liquid metal bearing (LM tube)
• Large-capacityX-raytubewithahighcoolingrate
Large-capacity X-ray tube with a high cooling rate
In order to provide the X-ray output required for high-speed scanning as well as to
minimize the cooling time, the "HeliCool" tube, which offers high cooling efficiency and a
short cooling time, is installed.
With the use of a liquid metal bearing, the HeliCool tube avoids the disadvantages of ball
bearings (vibration, noise, instability, short service life, etc.) and achieves a maximum
cooling rate of 864 kHU/min.
• Rotating-anode design•
- X-ray target consisting of molybdenum and tungsten
- Rotor section
- Bearing section
• Bearingstructure
Three-layer heat
insulation mechanism
- Herringbone-patterngroovesonthesurface
- Shaftsectionandrotationsection
Liquid galliumalloy
• Rotation characteristics
- Vibration: 0.002 G or less
- Noise: 40 dB or less
71
Performance and resolution of
CT systems
72
CT performance evaluation
1. Spatial resolution
This is the ability to identify an object with a significantly different CT number
(i.e., with a large difference in X-ray absorption) compared with surrounding
tissues. This is also referred to as "high contrast resolution".
2. Density resolution
This is the ability to identify an object with a slightly different CT number (i.e.,
with a small difference in X-ray absorption) compared with surrounding tissues.
This is also referred to as "low contrast resolution".
3. Resolution in the axial direction
This is the ability to discriminate objects in the axial direction in MPR images
and 3D images.
4. Temporal resolution
This is the ability of the CT system to complete scanning within a short time
(shorter is better).
This is evaluated from two viewpoints: scan time and scan cycle.
73
1. Spatial resolution
<Evaluation method>
•An acrylic phantom with holes measuring 0.3 mm to 0.5 mm in diameter is scanned to
evaluate the system. The spatial resolution is calculated based on the diameters of the
holes that can be identified in the image.
• A high-resolution function (FC30, FC890, etc.) is used as the reconstruction function.
0.35mm
●
0.4mm
Scanning
0.5mm
0.45mm
High-contrast resolution phantom
74
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Diameter of the hole that can be identified (mm  )
Advances in spatial resolution
２．００
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５１．５
０１．２
５１．０
００．７
５
０．５
００．
75
Factors related to spatial resolution
X-ray tube
1. Focus size
2. Detector channel width, number of channels
Detector
3. High-resolution reconstruction method
Q/Q reconstruction (offset reconstruction)
4. Number of views (angle sampling pitch) ）
76
MTF：Modulation TransferFunction
Method for evaluating spatial resolution
Evaluated in terms of frequency. Unit: Lp/cm
Line pair
77
Reconstruction function
ＭＴＦ
2.00
1.80
1.60
1.40
1.20
1.00
0.80
FC01
FC10
FC20
FC30
F C 50-x
FC70
FC80
0.60
0.40
0.20
0.00
78
2. Density resolution
<Evaluation method>
•A low-contrast phantom is scanned using standard scan conditions (120 kV, 200 mAs, 10 mm) to
evaluate the system based on the differences in the contrast and diameter of the objects that can be
identified.
• Evaluation unit: %mm → An object with a diameter of 2 mm at 3% can be identified = 0.6%mm
• The reconstruction functions used are those for the head and abdomen (FC20, FC43, etc.).
0.3%
0.5%
Scanning
0.1%
1.0%
Low-contrast resolution phantom
79
Factors related to density resolution
1. X-ray detectability
Xe detector → Solid-state detector
2. X-ray beam quality (effective energy)
Tube target, X-ray filter
3. Detector energy characteristics
Xe detector → Solid-state detector
4. Electrical noise in the X-ray detection system
5. Image noise
(Noise)  1/√¯(number of X-ray quanta)
80
Xenon detector (mech. 1/2)
Incident radiation
Entrance window
Heater (34 °C / 40 °C)
Xenon gas (10 .. 20 bar)
High-Voltage electrode
Collector electrode
81
Xenon detector (mech. 2/2)
100 .. 200V
Signal
1 .. 2 A
82
Solid State Detector (SSD) (1/2)
External
Collimator
Plate
x-ray
ch x
ch x+1
ch x+2
ch x+3
ch x+4
ch x+5
ch x+6
ch x+7
to DDC
Scintillator
Internal
Collimator
i
Light
Photo diode
83
Solid State Detector (SSD) (2/2)
•Collimator:
External
Collimator
Plate
– Molybdenum
• 0.1mm thickness
• 1.028 pitch
• eliminate
x-ray
•Scintillator:
to DDC
Scintillator
Internal
Collimator
Light
i
– material is secret
• converts x-ray to visible
light
• too much x-ray can change
the sensitivity
•Photo diode:
Photo diode
• converts visible light to an
electrical signal
84
Comparison of detector density resolution
Xe detector
Solid-state detector
85
Reconstruction function
Image SD
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
Function
86
Processing to reduce image noise
• Reconstruction function
• Image filter
87
Advances in scan time
３００
１０
０７
０５
０
Helical
３０
２０
Multi
１
０
７
５
３
２
：Non-slipring CT
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Scan time (s)
２００
：Slipring CT
88
What is helical scanning?
[Principle]
This is a scanning method in which the X-ray tube is rotated
continuously while the patient is moved in the longitudinal direction.
The tube therefore follows a helical path relative to the patient's
body, permitting the rapid acquisition of continuous projection data.
[Advances helping to make this scan method possible]
1. Slipring technology
2. High-voltage power transfer
technology
3. High-speed couch movement
control
4. Large-capacity, high-speed
memory system
5. Interpolated reconstruction
algorithm
Axial direction
89
HelicalInterpolation
90
Principles of the 360 interpolation method
Sub data area (180)
Main data area (360)
Sub data area (180)
X-Ray Line
B
C A
A C
B
Slice center position
91
Principles of the 180 opposed-beam
interpolation method
Main data area
(360)
Sub data area
(Fan angle/2)
Sub data area
(Fan angle/2)
X-Ray Line
B
ｂ
C A
B
AC
ｂ
Slice center position
92
Relationship between the interpolation
method and the effective slice thickness
For 10 mm - 10 mm/r
[%]
100
360 interpolation
180 interpolation
50
0
-15
-10
-5
0
5
[mm]
10
15
93
Differences in image quality due to
the interpolation method
180 opposed-beam interpolation method
360 interpolation method
94
Usefulness of helical scan
1. Shorter scan time
(a wide range can be scanned in a short time)
2. Improved scan accuracy
(volume data is acquired)
3. Applicable to three-dimensional image
diagnosis
95
Usefulness 1: Shorter scan time
Helical scan
Image
acquisition
Couch-top
movement
Couch-top sliding at 10 mm/s
Image
reconstruction
Conventional scan
2.7-s scan
Image
acquisition
Couch-top
movement
Couch-top
movement
Couch-top
movement
Couch-top
movement
Couch-top
movement
Couch-top
movement
Couch-top
movement
…
Couch-top
movement
Couch-top
movement
3-s Image reconstruction
96
Usefulness 2: Improved scan accuracy
Helical scan
Since volume data is acquired,
this method is particularly
useful for the visualization of
small tumors.
Conventional scan
Since breath-holding is required
in each scan, the organs tend to
shift longitudinally.
97
Usefulness 3: Applicable to three-dimensional
image diagnosis
Helical scan
Conventional scan
An aneurysm measuring approximately 1 mm (which is
difficult do depict in MRI studies) can be visualized.
In helical scanning, continuous volume data can be acquired
in a shorter time than in conventional scanning, thus making
it possible to reconstruct a large number of images at smaller
intervals. As a result, the courses of cerebral blood vessels
and pulmonary blood vessels can be examined with high
precision.
98
The source images are important when 3D
images are generated!
High-image-quality
helical scan
High-image-quality
3D processing
99
Helical Scan
Helical scan can be used in many different ways :
Single Helical Scan
Serial Helical Scan
Go & Return Helical
Combined Helical Scan
Tilted Helical Scan
100
CT scanning methods and exposure dose
evaluation
–Evaluation
methods –
1. CTDI
Single-sliceCT Conve Scan Single-sliceCT Helical Scan
2. HTDI
3. CTDI100
4. CTDIW
5. Other
Multi-sliceCT Conve Scan
Multi-sliceCT Helical Scan
101
CTDI：CT Dose Index
14scan
Skin dose
●
Dose at
the center
of the
object
●
102
CTDI：CT Dose Index
What is CTDI?
This is obtained by dividing the integrated value of the dose
profile (line integral dose) in the axial direction (Z-axis) in a
single scan by the slice thickness and the number of slices.
This value is obtained by converting the dose needed to
acquire a single image in a single scan to a value per unit slice
thickness.
103
HTDI：Helical Scanning CT Dose Index
Skin dose
●
Dose at
the center
of the
object
●
104
CTDI 100
Skin dose
●
100mm
Dose at
the center
of the
object
●
105
CTDI：CT Dose Index
Cylindrical
phantom
TLD probe
TDL
Dose profile
106
CTDI：CT Dose Index
1•2…13•14scan
●
●
●
• Measurement method
1. Several TLD probes are arranged along the
scan direction at the center and in
surrounding areas of acrylic phantoms with
diameters comparable to the human body
(160 mm in diameter, 320 mm in diameter).
2. Scanning is performed for a total of 14
slices (7 slices each before and after the
center of the phantom).
3. The value obtained by averaging the
measurements obtained using the multiple
TLD probes arranged in the scan range is
the CTDI value.
Dose profile
107
Conventional X-ray imaging and CT scanning:
Differences in the X-ray exposure methods
108
CT exposure dose
Single-sliceCT Conve Scan
Center
Head
18
Surrounding
areas
20
Abdomen
6
10
(mGy)
Single-sliceCT Helical Scan
Center
Head
15
Surrounding
areas
17
Abdomen
5
8
(mGy)
Converted to an equivalent value for 120 kV/100 mAs/10-mm slice.
109
Comparison with other examination methods skin dose
• CT:
Head · · · · · · · · · · · · · · · 60 mGy (conventional CTDI 300 mAs)
Chest · · · · · · · · · · · · · · ·12 mGy (helical 150 mAs)
Abdomen · · · · · · · · · · · 16 mGy (helical 200 mAs)
• Fluoroscopy of the esophagus
(per examination) · · · · · · · · · · 85 mGy
• Fluoroscopy of the entire chest
(per examination) · · · · · · · · · · 85 mGy
• Fluoroscopy for barium enema
(per examination) · · · · · · · · · · 200 mGy
• Cardiac catheterization
(per examination) · · · · · · · · · · 470 mGy
110
Leading-edge CT technologies
111
SINGLE-SLICE DETECTOR
MULTI-SLICE DETECTOR
112
Differences in collimation
Upper collimator
X-ray tube
Lower
collimator
The slice width is adjusted by
the collimators.
SINGLE-SLICE DETECTOR
The slice width is adjusted by bundling
detector elements.
Data for multiple slices is acquired by
bundling detector elements.
MULTISLICE DETECTOR
113
Axial
direction
Equivalent to 20 mm
Minimum slice
thickness
Minimum slice
thickness
0.5 mm  4 rows
1.25 mm  4 rows
Minimum slice
thickness
0.5 mm  2 rows
Toshiba
GE
SIEMENS
Detector elements
for 2.5-mm slice
Detector elements
for 5-mm slice
Detector elements
for 1.5-mm slice
Detector elements for 5-mm slice
Detector elements
for 2.5-mm slice
Detector elements
for 1.5-mm slice
Detector elements for 1-mm slice (2)
1.25mm x 16 seg.
Geometric efficiency of
95% or more in the
axial direction
0.5mm x 4seg.
1mm x 15seg.
1mm x 15seg.
Comparisonofmultislicedetectorsoffered by various
manufacturers
Equivalent to 32 mm
Equivalent to 20 mm
114
Multislice detector
Single-slice detector
Multislice detector
Axial direction
115
Isotropic volume data
Ba.Top An.0.5/3/0.5/160
Adeno Ca 0.5/3/0.5/256
気胸1/6/1/400
116
<Wide-range 3D diagnosis>
Aquilion Multi Slice
Slice thickness:
3-mm slice
Helical pitch:
6
Scan time:
0.5 s
Scan range:
1000 mm
Total 30sec
Xvigor Single Slice
Slice thickness:
5-mm slice
Helical pitch:
1
Scan time:
1s
Scan range:
150 mm
117
Important points in gantry
development
0.5-s high-speed
scanning
Centrifugal force = 13 G
Example:
X-ray tube 70 kg → 910 kgf
A large load is applied to the
rotation base due to
centrifugal force.
0.5s/rot.
The design must
withstand high G
(centrifugalforce).
118
Toensureabsolutesafety
Adoption of a cylindrical rotation base
Conventional rotation base
Cylindrical rotation base
The units in the rotation section are directly supported by the inner wall.
It is impossible for the units to fly out.
119
Minimizing vibration and noise
Adoption of the direct-drive method
Belt-drive method
Direct-drive method
Motor
Belt
Direct-drive motor
120
Important points in X-ray tube
development
• Improvement in the ability to withstand high G
forces
Adoption of a design in which the target is
supported at both ends
• Increasing the heat capacity
and cooling rate
Adoption of an anodegrounded design
(World's first anodegrounded X-ray tube for CT
systems)
121
New-model X-ray tube
• Compact design
Same size as a
conventional X-ray
tube
• Separation of the
cooler from the Xray tube main unit
Advantages in
cost and
maintenance
Cooler
X-ray tube main unit
122
Applications of the latest helical CT systems
• IVR-CT system
Xactive
• Radiotherapy system CTport
• For heavy particle radiotherapy Horizontal CT
• Intraoperative CT
Self-propelled helical CT
• Mobile helical CT
123
Applications of the latest helical CT systems
• IVR-CT system
Xactive
• Radiotherapy system
CTport
• For heavy particle radiotherapy Horizontal CT
• Intraoperative CT
Self-propelled helical CT
• Mobile helical CT
124
Applications of the latest helical CT systems
• IVR-CT system
Xactive
• Radiotherapy system CTport
• For heavy particle radiotherapy
Horizontal CT
• Intraoperative CT
Self-propelled helical CT
• Mobile helical CT
125
Applications of the latest helical CT systems
• IVR-CT system
Xactive
• Radiotherapy system CTport
• For heavy particle radiotherapy Horizontal CT
• Intraoperative CT
Self-propelled helical CT
• Mobile helical CT
126
Applications of the latest helical CT systems
• IVR-CT system
Xactive
• Radiotherapy system CTport
• For heavy particle radiotherapy Horizontal CT
• Intraoperative CT
Self-propelled helical CT
• Mobile helical CT
127
Mass screening
–The Tokyo Society for the Eradication of Lung Cancer –
• Scan conditions: 120 kV, 50 mA (standard: 100 to 200 mA)
• Slice thickness: 10 mm
• Scan speed: 1 s/rot.
• Couch-top movement speed: 20 mm/s
Same level as for indirect radiography of the stomach
128
Findings detected by standard chest CT
• Lesions of the mediastinum and large blood vessels
Aortic aneurysms, mediastinal tumors, hilar
lymphadenopathy, etc.
• Lesions in the lung fields
Lung cancers, shadows of pulmonary aneurysms,
cysts, pleural lesions
• Thoracic lesions
Calcification, invasion of the chest wall by tumors,
aneurysms, etc.
129
Improvements in CT performance and
expansion of clinical applications
Adoption of a two-dimensional
Shorter
scan time
detector
Example of clinical application
Advantages etc.
1s
• Widespread acceptance of helical scanning
• Lung cancer screening
• Routine use of real-time CT
0.75 s
• Wider helical scan range (increased by 30%)
• Improved real-time response in CT fluoroscopy
Faster scan speed
Larger number of
slices acquired
simultaneously
•Lung cancer screening of the entire lung fields
with a slice thickness of 10 mm
• ECG-gated scanning
• Reduced X-ray tube load
• Improved throughput
•Lung cancer screening in detailed examination
mode
•High-precision three-dimensional imaging over
a wide range
130
Lung cancer screening using helical CT
Background:
• Increase in lung cancer mortality
• Limited detectability of lung cancer by mass screening
with chest X-ray
• Widespread acceptance of helical CT and improved
performance
Purpose:Early detection of lung cancer
Challenges:
• Validation with regard to the relationship between
exposure dose and effectiveness → Reduction in
exposure dose
• Reduced efficiency in image interpretation → Diagnostic
support system
131
Concept of a CAD system for lung cancer CT screening
Film or CRT
Helical CT
TOSHIBA
CAD
(Ｗ/Ｓ)
Image data
Suspected
lung cancer
Image
interpretatio
n
Judgement
・This slice
・Biopsy
・Follow-up
observation
・Other
132
Development of automatic lung cancer screening/diagnosis system
肺野領域の抽出
Visualization of the blood vessels
133
Detection of an abnormal shadow in contact
with the chest wall
Lesion
Size?
Roundness?
Bone present in adjacent areas?
Artifacts
134
Example of diagnostic results
135
Helical CT screening vehicle
Mass screening vehicle
in which a helical CT
system is installed
136