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Quality Control CT

May 29, 2018

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Wahyu Widhianto
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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.html
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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