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endali Mutu CT Scan
:Oleh. . Wahyu Widhianto S SiT Quantum Inti Akurasi: ( ) ,Telp 6221 5324238 5326575: . .Email wahyu_widhi@dnet net id
horkshop Quality Control CT Scan dan- ,D IV Teknik Radiologi Poltekkes Semar
,Semarang 22 Agustus 2
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Proses Kendali Mutu
emilihan Peralatan
est Penerimaanan Instalasi
endali Mutu ,Prosedur Evaluasi yang periodik untukmemastikan performa peralatan reliable danberkelanjutan
Memastikan peralatan yang telah diinstallsesuai spesifikasi dan aman digunakan pada
pasien
Pemilihan peralatan sesuai dengantujuan penggunaan
( , )Shepard et al 2002
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Grafik analisa trend alat
B a ta s to le ra n si
B atasto le ra n si
Baseline
Waktu
pengukuran
Batas kerusakan
Batas kerusakan
,engan kendali mutu dapat dilakukan pencegahan sebelum alat mengalami kerusakan
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Pioneer CT Scan
A lla n M a cLe
o d
C orm ack
S irG odfreyH ou n s eld
Jo h an nR a d o n
W ilh e lm C on ra dR n tg e n
:C re d it to
: ( ,S u m b e r T h o rste d)2 0 0 8
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y
x
z
Prin sip C T S ca n
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y
x
z
Prin sip C T S ca n
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y
x
sourc
edetecto
r
Prinsip CT Scan
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y
x
x
y
Prin sip C T S ca n
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y
x
Prinsip CT Scan
Tra n sfo rm a siR a d o n
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Transformasi Radon
( / )matlab help radon
Nama Radon diambil dari penemunya seorang matematikawan asal austria
.J Radon tahun 1917
Transformasi radon dari 180
Back projection transformasi radon
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Prinsip CT Scan
F
orw
ard
pro
jection
Backward
projection
( / )matlab help radon
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Kendali Mutu CT Scan menurutAAPM Report no. 74
harian ulanan dan 2 x pertahunrtifacts
aterT NumberAccuracy
ImageUniformity
ImageNoiseow ContrastDetectability
Dosimetry
patial Resolutio
ose ProfileWidth
ImageliceThickness
lice positioaccuracy
T Number Scale
ard copyfilm
QC
( , )Shepard et al 2002
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Alat dan Bahan
Alat Ukur Radiasi dan Phantom Dosimetry
/Phantom Image Quality Performance Phantom
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Phantom CT PerformancePhantom CT
Performanceterdiri dari,beberapa bagian
salah satunyawater phantomuntuk pengukuran
, ,Noise artifactuniformity danCT number
accuracy ofwater
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Image Noise/derau citraJika mencitrakan sebuah objek dengan
( )material yang seragam uniform seperti, -water bath kemudian kita mengamati CT
,numbers pada suatu bagian pada citraternyata CT number tidak sama persis namun
- .bervariasi di sekitar nilai rata rata,Variasi tersebut adalah noise system
( , . . , ., )Judy P F Ph D dkk 1977
?
( , )Thorsted 2008
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Image Noise/derau citra10 10 10 12 10 10
11 10 11 12 10 11
10 11 10 10 11 10
10 9 10 10 10 10
9 10 11 10 10 10
10 10 10 10 10 10
= ,0 63
Standard deviasi
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Artifact
=R in g A rtifa ct d ika re n a ka n/keg ag a lan d efect salah satu
(d e te cto r m e n a n g ka p sin ya l terja d i)p ad a C T S can g en erasiketig a
,ketika scan n o g ra m p o sisid e tecto r ya n g,m en g alam id efect tetap n am p ak
se p e rti g a ris v e rtica l
,Pa d a citra a x ia l d e fe ct d e te cto r y a n gg ag alm en an gkap sin yalm en g akib atkan
d a e ra h te rseb u t tid a k d ap a t.d ire ko n stru ksi m e n ja d i citra A kib a tn y a .m u n cu l g a m b a ra n m irip cin cin rin g
( ,Thorsted)2 0 0 8
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Uniformity/keseragaman
Nilai CT number dari obyek yanguniform hendaknya sama pada
setiap daerah citra
=Cupping effect beam hardeningartifact menyebabkan citra tidak
uniform
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=Beam Hardening Karena detektor
-menangkap nilai integral sinar x yangmelewati ketebalan obyek tertentu,dari berbagai arah yang berbeda maka
pada suatu obyek tertentu didapatkan.data yang tidak sama Ketidak samaan
tersebut mengakibatkan projeksi balik
.yang tidak sesuai satu sama lain
Uniformity/keseragaman
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CT number of water
= - = (CT Number CT Value Hounsfield Unit H
-Attenuasi sinar x oleh bahan
Citra water phantom harusnya
=memiliki nilai HU 0
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Phantom CT PerformanceBagian lain dari
CT PerformancePhantom dapat.dibongkar pasang
Tergantungparameter yang
.hendak diukur
Parameter tersebut
:antara lainslice image
,thickness CT,Number Scale Low
contrastdetectability dan
Spatial resolution
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Thickness/Ketebalan Irisan
Citra
T a m p a katas
H a silscan n in g
S e m a kin te b a l irisa n
( ),z maka garis akansem a kin p a n ja n g
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=FW H M Fu llW id th a t H alf M ax im u m,M e n ya ta ka n kela n ju ta n sua tu fu n g si
d ije la ska n se b a g a i se lisih d u a n ila ie ktrim d a ri v a ria b le ya n g
,in d ep e n d e n d im a n a va ria b le-d e p e n d e n t n y a sa m a d e n g a nsete n g a h n ila im a ksim u m
( )Wikipedia
Thickness/Ketebalan Irisan
Citra
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2 2 2 2 2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2 2 2 2 2
2 8 10 14 16 19 20 16 14 10 8 2
2 2 2 2 2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2 2 2 2 2
2 8 10 14 16 19 20 16 14 10 8 2
=Maximum 20=Half Maximum 10
FWHM
Thickness/Ketebalan Irisan
Citra
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= ( ) = Slice thickness Z mm FWHM x tan
z
FWHM
Thickness/Ketebalan Irisan
Citra
CT Number Scale/skala CT
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CT Number Scale/skala CTNumber
CT Number Scale/skala CT
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KeV Teflon Udara LDPE Acrylic Air
405060626466
687072747678
8090100
0.5560.4470.3950.3860.3800.374
0.3700.3630.3590.3550.3510.346
0.3420.3280.315
000000
000000
000
0.2090.1910.1810.1790.1780.177
0.1750.1740.1720.1710.1700.168
0.1670.1630.158
0.2770.2440.2270.2240.2210.219
0.2170.2150.2150.2110.2100.208
0.2070.1990.194
0.2680.2270.2060.2030.2000.197
0.1950.1930.1910.1890.1870.185
0.1840.1770.171
K o e fisie natenuasiterhada
p e n ergifo to n
CT Number Scale/skala CTNumber
CT Number Scale/Skala CT
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CT Number Scale/Skala CTNumber
Teflon Udara LDPE Acrylic Air
0.363 0 0.174 0.215 0.193
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Low Contrast Detectability
Ph an to m b e risio b je ctd en g an kon tra st kura n g
% ( )d ari 1 1 0 H U
Ph a n to m b e ru p a silin d e rde ng an d iam eter yan gb e rv a ria si
Pengam atan secaraq u a lita tiv e b a n ya kn y a
,ob je ct ya n g n a m p a k je la s
d e n g a n m e n g g u n a k a npa ram eter yan g sam a
se ca ra p e rio d ik
Spatial Resolution / Image
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Spatial Resolution / ImageSharpness
Ph an to m b e risio b je ct.lin g ka ra n S e tia p
G ru p o b je ct te rd iri d a ri 5lin g ka ra n d e n g a n d ia m e te r.y a n g sa m a G ru pb e riku tn y a m e m iliki
d ia m e te r ya n g le b ih ke cil
Pengam atan secara
,q u a lita tiv e citra d ika ta ka nta ja m a p a b ila se m u alin g ka ra n d a p a t d ilih a t tid a km e n ya tu d e n g an lin g karan
y a n g la inR e so lu sisp a sia l b a ik R e solu sisp a sia l
buruk
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Accuracy/ketepatan posisi
irisan
.1 K e te p a ta n la serp e n u n ju k lo ka si
.2 K e te p a ta n p o sitio n in gslice b e rd a sa r
scannogram.3 Ketepatan
p e rg e rak a n m e ja
Dose Profile Width/lebar
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Dose Profile Width/lebarprofil dosis
S istem koo rd in a t p a d a C T:S c a n
(Leba r scann ing scan)w id th d iu ku r p ad a
s u m b u zz x
y
Dose Profile Width/lebar
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D istrib u si D o sis se p a n ja n g a xis( - )cen tral sum b u Z ata u p a rralelterh ad ap su m b u p u tar p ad a satu
ka li p u ta r an gantry
S c a n/w id th co llim a tio n
Le b a r m e d a n
ra d ia si
G e o m e tric=E fficie n cy
Dose Profile Width/lebarprofil dosis
Dose Profile Width/lebar
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D e n g a nPh an tom
TanpaPh an tom
Dose Profile Width/lebarprofil dosis
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Multi Row Detector CT Scan
/o llim a tio n d e te cto r co v e ra g e a d a la h h a sil ka li ju m la h slice d e n g a n ke te b a la nlice
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H e lica l S ca n
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:// . /http hps org hpspub
Dosimetry
D i R di i CT S
http://hps.org/hpspublications/articles/dosesfrommedicalradiation.htmlhttp://hps.org/hpspublications/articles/dosesfrommedicalradiation.htmlhttp://hps.org/hpspublications/articles/dosesfrommedicalradiation.html8/9/2019 Quality Control CT
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Dosis Radiasi CT Scan-Ta b u n g x
ra y
O byek
Distribusi Dosis padaRadiografi konvensional( ).posisi tabung tetap
Entrance skin dose lebihbesar dibanding dosis radiasi
pada bagian tubuh sisi
.sebaliknya Diilustrasikan,dengan garis warna merahsemakin tebal garis
menunjukkan dosis yangsemakin besar
( - , )McNitt Gray 2002
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Dosis Radiasi CT Scan
D istrib u si d o sis d a ritab un g yan g be rpu tar
(mengelilingi obyek).3 6 0
Lin g ka ra n te b a lm e n g ilu stra sika n d o sis
,ya n g b esar b eg ituju g a se b a likn ya
d en g an lin g kara n y an g.tip is D istrib u si d o sisp ad a p erm u kaa n leb ihb esar d ib an d in g p ad a
.b a g ian d a la m
D istrib u si d o sis p a d ap h a n to m a krilik
b e rd ia m e ter 32 cm
D istrib u si d o sis p a d ap h a n to m a krilik
b e rd ia m e ter 16 cm
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D o sim e try
CTDI100 = CTDI sepanjang 100mm
( - , )McNitt Gray 2002
D i
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Dosimetry
CTDI = -TDI rata rataerdistribusi alam
enampang elintangphantom
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P k CTDI
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Pengukuran CTDI
( )Nilai CTDIvol dan DLP Dose Length Product biasanya ditampilkan pada,console CT Scan
( )Nilai ini merupakan perhitungan secara matematis bukan hasil pengukuran
Faktor yang mempengaruhi
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Faktor yang mempengaruhiCTDI
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Daftar Pustaka
Cederquist, Bjorn, 2008, Evaluation of Two Thin CT Dose ProfileDetectors and a New Way to Perform QA in a CTDI Head Phantom,Goterborg University, Sweden
Dixon Robert L, 2010, Comprehensive Methodology for theEvaluation of Radiation Dose in X-Ray Computed Tomography(AAPM Report No. 111), American Association of Physicist inMedicine
Handee William R, and Ritenour E Russel, 2008, Medical ImagingPhysics, Willey-Diss, New York, USA.
Judy, P. F. Ph. D, dkk., 1977, Phantoms For Performance Evaluationand Quality Assurance of CT Scanners, AAPM Report no. 1,Chicago, USA.
Lin Pei-Jan Paul, Beck Thomas J., dkk., 1993, Specification and
Acceptance Testing of Computed Tomography Scanners , AAPMReport no. 39, Chicago, USA.
Shepard S. Jeff, dkk., 2002, Quality Control in Diagnostic Radiology,AAPM Report no. 74, Chicago, USA.
Thorsted M. Buszug, Prof. Dr., 2008, Computed Tomography : FromPhoton Statistic to modern Cone Beam CT, Springer-Verlag BerlinHeidenberg, Germany
McNitt-Gray, 2002, Michael F., AAPM/RSNA Phyisics Tutorial for
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End Of Session