Basics Principles of Radiology

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BASIC PRINCIPLES OF

RADIOLOGY

Bachtiar Murtala


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BASIC PRINCIPLES OF

RADIOLOGY

Bachtiar Murtala


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General objective

To provide a basic understanding of

ionizing radiation and other radiation

sources as a tool of diagnosis


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Specific objectives :

- Types of radiation- Equipments

- Basics of interpretation

- Biologic effects- Radiation protection


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History in brief

Radiology started when Prof.Wilhelm Conrad Roentgendiscovered ofa new kind of rays (x-rays) in November8,1895 in Germany

He made a first photograph of his wifes (Bertha) hand inDec 22, 1895 using the rays, signed the true birthday ofradiology as a medical specialty.

He was awarded Nobel Prize in Physics in 1901

Later, CT (Computed Tomography) and US(Ultrasonography) introduced in the seventies dan MRI

( Magnetic Resonance Imaging ) in the eighties. CT was discovered by Sir Godfrey Hounsfield, andtogether with Allen Cormack , awarded Nobel Prize in1979.


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Radiology can be categorized as :

Diagnostic radiologyRadiations

(ionizing and nonionizing ), used as a tool

to make diagnosis of diseases.

Radiotherapy or radiation oncology --

radiation used as an agent to eradicate/to

kill tumor/cancer


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Types of radiation source

Radiations can be categorized into two

main forms :

(1) Electromagnetic

X-rays,gamma-rays, uv, infra red, visible

light, radio waves.

(2) Particles Electron, positron,etc


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X-ray

To develop of x-ray beam, we need :

A vacuum tube

Electrons

Focusing cup

Metal filament

Target


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In conventional radiography, after passing thebody, x-ray will create an image directly onphotographic film.

The film is covered by a thin emulsion of SilverBromide (AgBr), which is very sensitive to x-raysand visible light, blackening the film after

having developed in liquid developer ( washingprocessing )


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Terms in conventional radiography

Darkness to brightness

Hyperradioluscent : free-air Radioluscent : lung, fat tissue

Intermediate : soft tissues,water/fluid

Radiopaque : Calsium, bone Hyperrariopaque : metal


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CT-Scan(Computerized Tomography Scan )

The greatest step forward since the discovery of

X-rays. First CT-Scan was introduced in 1972.

X-rays pass the patient and reach detectors ( not

on the film ) Only thin tissue slices are exposed by X-rays

high contrast resolution, no superimposition/

blurring of structures

Tissue and water/fluid can be distinguished ( in

conventional radiography can not be )


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Terms in CT

Hyperdense : blood, calcification, bone

Isodense/normodense : normal soft

tissues such as; brain, liver, spleen,etc

Hypodense : fluid, edema, fat, abscess,

tumor, etc


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HU=Hounsfield Unit


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Radionuclide Imaging

( Nuclear medicine )

Radioactive introduced into the body of the

patients orally or intravenously

Detection of radiation emittedfrom

radioactive tracer inside the patient

Radioactive tracers, termed

radiopharmaceuticals emit gamma rays.

Gamma camera is used to detect the rays

and produce image.


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Two major tomographic methods :

(1) SPECT ( single photon emission

computed tomography)

(2) PET ( positron emission tomography )


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Ultrasonography

Ultrasound (US) sound wave freq >20

KHz (above the human hearing range)

Commonly used : 2-10 MHz

No biologic effects


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Components

Transducer/probe which containpiezo-

electrical crystals ( the main component )

These crystals act as both

transmitter/produce ultrasound and

receiver (of echo)

Computer and dysplay

Printer


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The most important part is transducer

Transducer contains piezoelectric crystals

with two functions : transmitter of US and

receiver of echo

Echo returning to transducer generates

electrical signalscomputer image


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Terms in US

Hyperechoic = echorich brightness :

calcification, stone, gas

Isoechoic= normoechoic : normal soft

tissue; liver, spleen, etc

Hypoechoic = echopoor : tumor, abscess

Free-echoic = unechoic : fluid ;water,etc


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MRI


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MRI

( Magnetic Resonance Imaging )

The latest newcomer of radiological modalities

Exploits hydrogen nuclei (proton) of the human

body to develop signal

Images in any plane of any part of the body No ionizing radiation No biologic effects

Contraindication for patients with using

ferromagnetic material such as pacemaker More expensive, theoretically more difficult, and

technically more advanced


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Main Components

A very strong magnet ( 0.1-1.5 Tesla or > )

A radio transmitter

A radio frequency receiver coil A computer


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Terms in MRI

T1WI, T2WI, DWI, etc

(T1 Weighted Image)

Hyperintense : brightness Isointense : same with normal adjacent

tissue

Hypointense : darkness


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T2WI

T1WI


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Positioning in radiography

In conventional radiography, we should

familiar with the routine positions

PA : Postero-anterior

AP : Anterio-posterior

RLD : Right lateral decubitus

LLD : Left lateral decubitus etc


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Foto2


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Biologic effects

Come from X-rays and gamma-rays since

they can ionize atoms/molecules of human

tissue

Can be grouped into : immediately effects,

latent somatic effects, and manifest

genetic damage


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Principles of radiation protection

Should be apply to : patient, personnel,

and environment / around people

Work with : - shorten time,

- appropriate distance,

- use protective tools

Avoid and reduce somatic and geneticdoses to as low as possible ( ALARA, As

Low As Reasonably Achievable )


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Thank you


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Nama Radioaktif Energi

SinarGamma

( MeV )

Half - life

- Radium-226 0.029-2.43 1620 Th

- Caesium-137 0.662 30 Th- Cobalt- 60 1.17 & 1.33 5,3 Th

- Iridium-192 0.296 & 0.613 74 hari

- Iodine-131 0.364 & 0.637 8 hari

- Gold-198 0.411 2-7 hari

- Technetium-99m 0 140 6 jam

Basics Principles of Radiology

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