3. CT Training for Radiographers.
• Computerized Axial Tomography (CAT)
• Computer Aided Tomography (CAT)
• Computer Assisted Tomography (CAT)
• Computerized Transverse Axial
Tomography (CTAT)
• Computerized Transaxial Transmission
Reconstructive Tomography (CTT)
• Reconstructive Tomography (RT)
• Computerized Tomography (CT)
POPULAR NAME OF CT
3
4. CT Training for Radiographers.
8 NOVEMBER 1895 SINAR X DITEMUKAN
FISIKAWAN BERKEBANGSAAN JERMAN
WILHELM CONRAD
RONTGEN
March 27, 1845
MERUPAKAN GEM DENGAN PANJANG
GELOMBANG BERKISAR 0,01 nm – 10 nm
(3 x 1016 Hz – 3 x 1019 Hz)
KARAKTERISTIK SINAR X
4
5. CT Training for Radiographers.
Memiliki daya tembus yang besar.
ƒDapat diserap oleh materi
(tergantung dari nomor atomnya)
ƒƒDapat dibelokan / dihamburkan
(difraksi sinar-x)
ƒMenimbulkan ionisasi.
Memiliki efek fotografi /
menimbulkan fluoresen.
KARAKTERISTIK SINAR X
5
6. CT Training for Radiographers.
RADIOGRAFI
KONVENSIONAL
.
PEMANFAATAN SINAR X
6
RADIOGRAFI
TOMOGRAPHY
7. CT Training for Radiographers.
X-ray based
Multiple Projections (each from different Angle)
X-ray tube motions around the patient
Detector motions around the patient opposite the tube
In special technique :The patient's body is move
continuously as the x-ray beam is scanned around the
body
Detector output and angular position fed into a
computer
Computer perform calculation to estimate density of
tissues in each square of a slice
Mathematically reconstruct image
Create Voxel to Hounsfield Unit Value (CTNs)
CTNs represent linear attenuation coefficient
CT SCAN
7
8. CT Training for Radiographers.
TAHUN 1971 GENERASI PERTAMA CT SCAN
DIPUBLIKASIKAN
Godfrey Newbold Hounsfield
28 August 1919 – 12 August 2004
Allan M. Cormack
23 Februari 1924 – 7 Mei 1998
CT SCAN
8
9. CT Training for Radiographers.
CT DEVELOPMENET
9
1970 1972
1976
1978
1990
10. CT Training for Radiographers.
ELECTRON BEAM OF CT
10
Electron beam scanner
Primarily for cardiologist, 50 msec scan times
Tungsten target and high energy electron beam
https://www.youtube.com/watch?v=E9vLclEQRtc
11. CT Training for Radiographers.
CT DEVELOPMENT
11
HELICAL, 1990
Slip ring technology
Acquired data while table
is moving
Typical pitch ratio 0.5 - 2
on)(collimatithicknessslice
rotationpermovementtable
pitch
MULTI DETECTOR, Late1990’s-
2000
Multiple detector array
Cone beam
MSCT
12. CT Training for Radiographers.
CT DEVELOPMENT
12
DUAL SOURCE, 2005
A Scanner using two x-ray source
and two detectors at the same
time
Enables scanning a heart at any
heart rate and at the lowest
radiation dose possible
Dynamic Focal Spot,
Flying focal spot
Double ray density
Double spatial resolution
13. CT Training for Radiographers.
CT DEVELOPMENT
13
MULTI ENERGY DETECTOR
Consist of upper and bottom
detector
Upper detector to detects lower
energy
Bottom detector to detects higher
energy
Signal from both can be combine
as well
19. CT Training for Radiographers. 19
DETECTORS
Scintillation + PMT
XENON GAS
Ceramic Scintillation
+ Photodiode
20. CT Training for Radiographers. 20
CT DETECTOR
• High efficiency
• Quick response time
• High dynamic range
• Stability
CT Detector Technology:
Desirable Characteristics
21. CT Training for Radiographers.
Efficiency
• Ability to absorb & convert x-ray
photons to electrical signals
22. CT Training for Radiographers.
Response Time
• Minimum time after detection of
1st event when detector can
detect 2nd event
• If time between events shorter
than response time, second event
may not be detected
• Shorter response time better
23. CT Training for Radiographers.
Stability
• “Steadiness” of detector
system
• Consistency of detector signal
over time
• The less stable, the more
frequently calibration
required
24. CT Training for Radiographers.
Dynamic Range
• Ability to faithfully detect large
range of intensities
• Ratio of largest to smallest
signal which can be faithfully
detected
• Typical dynamic range:
1,000,000:1
– much better than film
25. CT Training for Radiographers. 25
DETECTORS
• Scintillation Cristal+ PMT
Sodium Iodide (Na I + Tl)
Calcium Fluoride (Ca F2)
Bismuth Germinate (BGO)
• Gas
Xenon Gas
• Scintillation + photodioda + Ceramic
cadmium tungstate (CdWO)
Bismuth germinate oxide (BGO)
Lutetium Terbium Aluminum Garnet (LuTAG)
Yttrium Gadolinium Oxide (YGO)
27. CT Training for Radiographers.
It = Io exp (-μx)
Absorption and Attenuation
27
Io It
x
t
o
I
I
x
ln
1
μ1 μ2 μ3 μ4 μn
x x
Io
It
t
o
i
i
t
o
n
xxxx
I
I
x
I
I
x
eIIeIIeIIeII
ln
1
ln
1
...
,,,
1
4321
4
34
3
23
2
12
1
01
31. CT Training for Radiographers.
VOXEL, PIXEL, MATRIX SIZE
31
VOXEL PIXEL
MATRIX SIZE, 16 x 16
PIXEL = SFOV / MATRIX SIZE
µ
(x,y,z)
p
(x,z)
32. CT Training for Radiographers.
VOXEL, PIXEL, MATRIX SIZE
• Voxel (volume element) - for each image
slice, there is an x, y and z dimension.
These are coming close to isotropic (the
same in each dimension). A typical
voxel would be created from a 35 cm
FOV, 512 x 512 matrix and 0.6 -10.0
mm thick slice.
10 mm
.68 mm
.68 mm6 mm
.68 mm
.68 mm
33. CT Training for Radiographers.
VOXEL, PIXEL, MATRIX SIZE
Pixels
and
Voxels
34. CT Training for Radiographers.
CT NUMBER
34
• Hounsfield Units (HU), normalize to water.
HU1000x
-)(
),('
water
water
x,y
yxsCTN
HU1000x
-)(
),('
water
water
x,y
yxsCTN
• CTN Water = 0 HU (all energies)
• CTN range = -1024 to +3072
• 12 bit, 212
= 4096
35. CT Training for Radiographers.
CT NUMBER
Find the CTN of some tissues bellow :
• Bone = 0.528
• Blood = 0.208
• Gray Matter = 0.212
• White Matter = 0.213
• CSF = 0.207
• Water = 0.206
• Fat = 0.185
• Air = 0.0004
40. CT Training for Radiographers.
IMAGE FORMATION CT NUMBER
Some Preset Window and Levels
• Tissue Level Window
• Lung -550 HU 1600
• Soft Tissue 100 400
• Bone 800 1000
0
-1000 HU
Output gray levels
256
0 (black)
1000
0 HU
2000
1000 HU
41. CT Training for Radiographers.
CT RECONSTUCTIONS
41
Io It(y)
x
y
Io
It(d,Ө) x
y
d
dxyxyII
IdxyxyI
t
t
),())(/ln(
)),(exp()(
0
0
dlldldtII )cossin,sincos()),(/ln( 10
dlldldfdg )cossin,sincos(),(
F(x,y)
g(d,Ө)
Radon Transform
42. CT Training for Radiographers. 42
Fourier Transform
)()(
~
~
tetfF tj
The fourier transform changes SIGNAL from TIME
DOMAIN to FREQUENCY DOMAIN back again
F(ω) can be represented as :
Real + Imaginer
or
Magnitude + Phase
)()()()()(
~
~
~
~
dttjSintfdttCostfF
43. CT Training for Radiographers. 43
Reconstruction process
intensityattenuated:)(intensity,incident:)(
[Np/m]ted)reconstrucbe(totcoefficienabsorption:),(
0 xIxI
yxf
0
0
),(
0
),sincos(),(:projectionBack
),(ofFFT1Dis),(ewher
),(
2
1
),(:dataFiltered
)(
)(
ln),(),(:dataprojection
)()(:intensityattenuated
dyxpyxf
XpUP
dXeUUPXp
XI
XI
dYyxfXp
eXIXI
f
jUX
f
dYyxf
44. CT Training for Radiographers.
Back Projection
44
Backprojection at 4, 16, and 100 angles
-1
0
1
-1
0
1
-0.5
0
0.5
1
1.5
-1
0
1
-1
0
1
-0.5
0
0.5
1
1.5
-1
0
1
-1
0
1
-0.5
0
0.5
1
One, two, and four angles of backprojection
45. CT Training for Radiographers.
Attenuation Correction Factor
45
(a) Can be determined from attenuation coefficient measurements
determined from CT scan; (b) Array of attenuation correction
factors; (c) to provide final attenuation-corrected CT scan
46. CT Training for Radiographers.
Back Projection
46
Sample Back Projection Filtered Back Projection
FILTER
58. CT Training for Radiographers.
DETECTOR CONFIGURATIONS
X-ray Tube Focal Spot
X-ray Beam Collimator
4 x 2.5 mm Detector Configuration
16-row Mosaic Detector
Diode FET Switching Array
Flex Connector A Flex Connector B
59. CT Training for Radiographers.
X-ray Tube Focal Spot
X-ray Beam Collimator
4 x 3.75 mm Detector Configuration
DETECTOR CONFIGURATIONS
16-row Mosaic Detector
Diode FET Switching Array
Flex Connector A Flex Connector B
60. CT Training for Radiographers.
DETECTOR CONFIGURATIONS
X-ray Tube Focal Spot
X-ray Beam Collimator
4 x 5.0 mm Detector Configuration
16-row Mosaic Detector
Diode FET Switching Array
Flex Connector A Flex Connector B
62. CT Training for Radiographers.
Wide Area Coverage
62
Philips Brilliance 40Philips Brilliance 64
Over 525
40-mm
systems
installed
worldwide
as of
December
2005
Philips-Expertise in Detectors
Tomorrow- 256 Nano-panel
Working 256 Nano-panel detector
array
63. CT Training for Radiographers.
MSCT DETECTOR CONFIGURATIONS
63
65. CT Training for Radiographers.
DFSTM
X-Ray Tube Design
65
Dynamic Focal Spot
X-ray Tube Design
Doubles
Ray Density and thus
Doubles
Spatial Resolution
with the same number
of detectors
66. CT Training for Radiographers.
PHILIPS : DFSTM
X-Ray Tube Design
66
WithWithout
67. CT Training for Radiographers.
PITCH
67
• Pitch = table travel per gantry
rotation (mm) / total nominal beam
width
• Pitch = table travel per gantry
rotation (mm) / (slice width ×
number of slices).
• Pitch = 0,13 -1,5, disarankan > 1
• mAs eff = mAs / pitch.
68. CT Training for Radiographers.
PITCH
68
• 16 Slice MSCT dengan 0,625 mm
slice thickness dan pergerakan
meja 15 mm per rotasi x ray tube.
• Tentukan Beam Pitch ?
pitch1.5
)625.0)(16(
15
mm
mm
BP
69. CT Training for Radiographers.
MSCT FASTER SCANNING
69
Detector Beam Thick
(mm)
# Rotation Total scan
time (sec)
1 x 1.25 1.25 160 128
4 x 1.25 5 40 32
8 x 1.25 10 20 16
16 x 1.25 20 10 8
64 x 0.625 40 5 4
1.25 mm images and 20 cm scan length at 0.8 sec
rotation and 1.0 pitch
70. CT Training for Radiographers.
Metode ABC/2 didasarkan pada penghitungan
volume ellipse, dengan menggunakan
persamaan :
V = 4/3 π r3 atau V= 4/3 x π x r1 x r2 x r3
Dengan penyederhanakan diameter d, , maka
diperoleh
V = ½ (d1 x d2 x d3)
Shg dapat ditulis menjadi
VOLUME IN CT SCAN
70
V = ABC / 2
71. CT Training for Radiographers.
The Total volume (V) was calculated by equation
• HU min adalah range HU minimum pada cairan
yang terdeteksi ROI
• HU max adalah range HU maksimum pada
cairan yang terdeteksi ROI
• from CAVA (Computer Assited Volumetric
Analysis)
VOLUME SUBJEK PADA CT SCAN
71
72. CT Training for Radiographers.
BASIC IV
72
Multiple-scan average dose
CT DOSIMETRY
73. CT Training for Radiographers.
CT DOSIMETRY
• MSAD = Multy Sice Average Dose
• CTDIw
• CTDIvol
• DLP
CTDI100
MSAD
Effective
Dose
74. CT Training for Radiographers.
CT DOSIMETRY
• CTDI menggunakan CTDI phantom dan
Ionization chambar
• CTDIw adalah CTDI weighted average
ditentukan berdasarkan :
CTDIw = (2*CTDIperiphery+CTDIcenter)/3
CTDIvol = CTDIw/Pitch
DLP = CTDIvol * L
L is the Z-length of the scan
75. CT Training for Radiographers.
DLP DAN DOSE EFEKTIF
DLP = CTDIvol * L
L is the Z-length of the scan
DOSE EFEKTIF = DLP * WT
WT adalah faktor bobot jaringan diperoleh
dari ICRP
77. CT Training for Radiographers.
CTDIw: Dose for a “Procedure”
78. CT Training for Radiographers.
Present Calculation CT Dose
))((
2
LAT
2
AP
22
DiameterEffective
,
2
;
2
21
2
21
LATviewAPviewDEff
A
DEff
rrrALUASAN
ViewLAT
r
ViewAP
r
79. CT Training for Radiographers.
)(DefffCTDISSDE vol
SSDE (Size Specific Dose Estimate)
f (Deff) = Konversion factor pada diameter efektif
diperoleh dari AAPM Report 204
80. CT Training for Radiographers.
Doses From CT
BERT*Eff Dose (mSv)Exam
2.4 days0.02Chest x ray (PA film)
8.5 days0.07Skull x ray
158 days1.3Lumbar spine
304 days2.5I.V. urogram
1.0 year3Upper G.I. exam
2.3 years7Barium enema
243 days2CT head
3.3 years10CT abdomen
1.3 years3.9PET FDG Exam (10 mCi)
158 days1.3NM Bone Scan (20 mCi)
* Time to receive equivalent effective dose from
natural background radiation
81. CT Training for Radiographers.
Typical doses in mGy during CT in adults
(Shrimpton et al. 1991)
Exam Eyes Thyroid Breast Uterus Ovaries Testes
Head 50 1.9 0.03 * * *
Cervical
spine
0.62 44 0.09 * * *
Thoracic
spine
0.04 0.46 28 0.02 0.02 *
Chest 0.14 2.3 21 0.06 0.08 *
Abdomen * 0.05 0.72 8.0 8.0 0.7
L. spine * 0.01 0.13 2.4 2.7 0.06
Pelvis * * 0.03 26 23 1.7
The symbol * indicates that dose is < 0.005 mGy
85. CT Training for Radiographers. 85
REFFERENCES
Edward M. Hsiao, Frank J. Rybicki, and Michael Steigner.
(2010) CT Coronary Angiography: 256-Slice and 320-
Detector Row Scanners. Curr Cardiol Rep. 12(1): 68–75.
Hameed T, Teague S, Vembar M, et al. Low radiation dose
ECG-gated chest CT angiography on a 256-slice
multidetector CT scanner. Int J Cardiovasc Imaging.
2009;25:267–278.
Kalendar, W.A. (2005) Computed Tomography.2nd Ed.
Mahesh, 2002. Physics Tutorial for Residents. Radiographics
22: 249-962
Nagel, H.D. (2004). MSCT Technology. Philips Medical
system Germany. www.multislice-ct.com
Philips. MSCT 256 Slices. PT BERCA NIAGA MEDIKA
Seeram, E. (2009). COMPUTED TOMOGRAPHY. Physical
Principles, Clinical Applications, and Quality Control. 3rd
Ed. St Louis: Saunders.
Walker M, Olszewski M, Desai M, et al. New radiation dose
saving technologies for 256-slice cardiac computed
tomography angiography. Int J Cardiovasc Imaging.
2009;25:189–199.
86. CT Training for Radiographers.
TERIMA KASIH
• شكرا
• THANKS YOU
• ありがとう
• 감사합니다
• Спасибо
• Merci
• Danke
• igracias
• Matur nuwun
86