CT-SCAN

Dr.H.Sigit Widodo,Sp.RBagian RadiologiFakultas Kedokteran Universitas Trisakti

Computed Tomography (CT)Scan

Basis Principle

The Interval Structure Of Any 3 Dimensional Subject Can be Reconstructed from many different Projections / Views of that subject

Minimal diperlukan 180 Projections yang berbeda untuk memperoleh Radiograph yang bernilai Diagnostik (X-Ray Beam Were Directed Through The Tissue at 1° Interval Until 180 Readings were made)

Fungsi Scan Unit

Collecting Large Amount of Transmission Data for Processing By the Computer

CT-Scan Generasi -1

EMI Mark-I 80x80 Pixel Resolution (th 1972)

1 Slice 4.5 Min Scan time 1.5 Min Reconstruction time

Karena Long Acquisition Time & Cardiac & Respiration Motion

Semula CT-Scan hanya untuk Head Scan Rotate / translate, pencil Beam hanya 2

(dua) detector, Keuntungan : Scatter ↓ (Pencil Beam )

CT-Scan ,4 bagian Utama :

1.Scan Unit

a.Patient Table / Couch

b.Gantry Central Opening Gantry Aperture

*Ada X-Ray Tube Radiation Detector Array

2.Processing Unit :

Computer takes raw data and convert it into picture form

Computer yang membedakan CT dari Conventional Radiography

3.Display unit / Direct Display Console Gray-Scale Television Screen Enlargement Contrast Scale Manipulatorry Substraction Operator Console

4.Storage System Main Memory , Floppy Disc. Magnetic

Tape Radiograph / Polaroid Film

CT-SCAN GENERASI 2

Rotate / translate / Narrow Fan Beam Detector 30 X-Ray : 30x D.P.I Scan Time / 1 Slice : 18 Sec

(15 x > cepat D.P 1 )

CT-SCAN GENERASI 3

Rotate / translate / Wide Fan Beam Detector > 800

Joined X-Ray tube dan detector rotate together around the patient without translation Scan time 0.5 – 5 Sec

Problem : Ring artefacts

The Scope of Diagnostic Imaging

Scanner Principles Sejak CT generasi 1(th 1972), Data Gathering

has Progressed through 4 (four) generations. Generasi 1 perlu 4 ½ Minute per slice Generasi berikutnya mempersingkat Scan

Time CT generasi 4 : Scan Time per slice 2- 10

second Ada ≥ 600 Detector melingkari pasien dalam

Gantry 1 (Satu) X-Ray tube berotasi 360º Data

Collection

CT-SCAN GENERASI 4 (AKHIR 70)

Rotate/ Stationary Meniadakan Problem Ring Artefact

4800 Detector Removed From Rotating Gantry Placed in Stationary 360º Ring Around the patient

CT-SCAN GENERASI 5 Stationary Khusus untuk jantung Tidak digunakan Conventional X-Ray

Tube ART Of Tungsten Encircles The Patient,opposite to detector Ring

High Energy Electron Beam Strike Tungsten X-Ray Scan Time 50 MSec Dapat CT-Movies of Beating Heart

disebut juga Electron Beam Scanner

CT-SCAN GENERASI 6 (Helical Spiral)

The X-Ray Tube Rotates around the patient in a helical pattern, while the patient and the table are translated through the gantry

Entire scan time can be performed within a single breth hold (30 second for entire abdomen)

CT-SCAN GENERASI 7

Multiple Detector Array

DETECTOR

1.Xenon (Gas) High Pressere 25 ATM Position Fixed to X-Ray Source

Tidak bisa pada generasi 4 Ionization Detector Electronic

Signal Amplified & Digitized

2.Solid Detector Crystalline Dielectric CdWO4 /

Yurium / Gadolinium Ceramic X-Ray Scintillator Light

Photo Detector Electrical Signal Dipakai pada generasi 4

CT-Scan Cranium

Irisan Sejajr OML (Orbito Meatal Line)

Dari Foramen Magnum s/d Vertex Ketebalan Irisan 5-10 mm Polos – Kontras Window : 1.Otak 2.Tulang

OML = Reids

Deskripsi = Evaluasi

I.Differensiasi antara White Matter (Substansia Alba) dengan Grey Matter (Substansia Grisea)

II.1.Brain Stem (Med.Oblongata, Pons) dan Cerebellum2.Cerebral Hemisphere (Lobus Frontalis, Temporalis, Parietalis Occipitalis)3.Basal ganglia, Thalamus

Rongga Cairan Cerebrospinal Sistem ventrikel Cisterna, Fissura, SulciIII.Tulang - tulang

CT-Scan Abdomen

Potongan Axial = Transversal Whole Abdomen : Proc.Xyphoideus

s/d Symphisis Pubis Abdomen Atas : Proc.Xyphoideus s/d

Spina Iliaca Superior (Ginjal) Abdomen Bawah (Pelvis) : L-5 s/d

Buli-buli (Prostat)

Puasa : 8 jam Media Kontras :1. BaSO4 1 jam . ½ jam 5- 10 menit sebelumnya @300-400

cc (Gaster-Usus Halus) 2- 3 jam

sebelumnya 400-600 cc(Colon Proximal)

Enema 200 – 300 cc (Colon Distal)2.Intra Venous

Bone +1000

+400

Hematoma +100Grey MatterWhite MatterOedemaCSFWater 0Fat Tissue

- 100

AIR - 1000

CT-Scan Thorax

Potongan Axial dari Apex PAru s/d Diapgragma langsung dengan kontras I.V

Tebal 5-10 mm Dicetak dalam 2 window level

paru dan mediastinum

Evaluasi :1.Pulmo Parenchyme : Nodule / Mass Bronchus : Terbuka A.V Pulmonalis : Tapering Hilus :KGB Pleura

2.Mediastinum :KGB Pengelompokkan/ Pembesaran

3.Cor, Aorta Thoracalis, V.Cava Superior

4.Tulang dinding thorax (Vert.Thoracalis, Costae, Sternum)

Kelebihan CT-Scan

1. Cross-Section Imaging,Over Laping(-)2. Contrast Resulotiun baik.Dapat bedakan

Soft Tissue(Grey Matter dari White Matter,Brain)

3. Geometric Accuracy,Distortion Free dapat mengukur tepat : Jarak,diameter, tebal, displacement.Digunakan untuk rencana operasi / Radioterapi

4. Tissue characterization Menggunakan CT Number Soft Tissue Mengukur Bone Mineral Content

Kekurangan CT-Scan

1.Geometric Miss GM Contrast Miss CM Nodule yang luput antara 2 (dua) slice :

GM

Window widh yang lebar (contrast Kurang) Window Widh yang sempit pada window

level yang salah : CM

2.Artefact Partial volume avera ging Geometric oversight High Density oversight High Density Artefact Motion Artefact