Life Goes On ~ The rays of light will always be there tomorrow

What is Xray? CR in KB!

In Suri Seri Begawan Hospital, finally have been installed the Computed radiography ( CR ) Unit!! Hehehe.. so kewl! Although slow, we can manipulate image we have acquired using the ‘special’ cassette before printing them!! How kewl is dat??!! Am waiting fer the DR ( Digital radiography system to be in RIPAS!! )


Heres my CPD ( Continuous Professional Development ) part for the department, which I have done for the visiting students in our department. Hope they understand!! Muahaha..

PHYSICS of the Radiology department


What is X – Ray?

 Is part of the electromagnetic spectrum.
 Is at the short – wavelength end of this electromagnetic spectrum with gamma rays.
 Has penetrating power.
 Not deflected in a magnetic field.

How is X – Rays produced?


2 ways:
• When fast moving electrons are decelerated resulting in the conversion of energy of some of its kinetic energy into X-Ray energy.

• Caused by the movement of an an electron between two inner shells in an atom with; difference between binding energies of these two shells emitting x-ray photon.

Both these processes occur in the target of an X-ray tube.


X – Ray tube
Design
 Glass envelope
 Vacuum
 Cathode
 Anode

Production of X-Ray

 Cathode filament releases electrons.
 Electrons are then accelerated across the tube by a high voltage applied between the filament and the anode.
 Electrons reach anode at high speed, they have high kinetic energy which is converted into X-rays and heat.

Properties of X-Rays
1. Florescence
2. Photographic effect
3. Penetrating
4. Ionisation and excitation
5. Produce chemical changes
6. Biological effects

Fluroscence
 X-Rays produce fluroscence in materials such as calcium thungstate, zinc cadmium sulphide and caesium iodide.
 This produce the visible pattern on the simple screen in X-ray fluroscopy.
Fluorescence refers to the luminescence; that is the emission of light instantaneously by various kinds of stimuli.

Photographic effects
 X-rays produce latent image on photographic film which can be developed to give a visible image as in an ordinary photographic latent image.
 Latent image is image which is not yet visible.
Only 5 % of the image is formed by the direct action of the X-rays; remaining 95% is due to the visible and ultraviolet emitted by the intensifying screens and to which the film is more sensitive

Penetration
 X-rays have penetrating power to substances that are opaque to visible light.
 They are gradually absorbed the farther they pass through the object.
 The amount of absorption depends on the atomic number, the density of the object ; also the energy of the x-rays

Ionization and excitation
 X-rays produce ionization and excitation of the atoms and molecules of the substances through which they pass.
 Experiment can be done by passing x-rays through air surrounding gold leaf electroscope.

Chemical changes
 X-Rays produce chemical changes in substances they pass.
 Oxidation of ferrous sulphate ( FeSO4 ) to forric sulphate is an example.
 It is a way to measure the x-radiation quantity being absorbed and also is the basis of the chemical system of dosimetry

Biological effects
 X-rays produce biological effects in living organisms, either by direct action on the cells or indirectly as a result of the chemical changes near to the cells.
 Cells can either be damaged or killed.
 Results in the organisms either injured or killed, or in the reproductive cells, the genes can undergo mutations resulting in inherited change in subsequent generations.

ULTRASOUND

 Ultrasound uses the principle of pulse – echo methods.
 Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used by submarines.

Pulse echo method

 A short pulse of utrasound is generated and directed as a narrow beam into the patients’ body.
 Sooner or later the beam will meet at an interface between different tissues and reflections will occur.
 If interface is oriented correctly at 90degrees, the reflections will return along the same path as the original pulse and maybe detected as an echo.

Components of a sonic imaging system

1. A transducer
2. An ultrasonic beam
3. A display method ( Television monitor or a cathode ray tube )

Events of ultrasound
In ultrasound, the following events happen:
 The ultrasound machine transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a probe.
 The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone).
 Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected.
 The reflected waves are picked up by the probe and relayed to the machine.
 The machine calculates the distance from the probe to the tissue or organ (boundaries) using the speed of sound in tissue (5,005 ft/s or1,540 m/s) and the time of the each echo's return (usually on the order of millionths of a second).
 The machine displays the distances and intensities of the echoes on the screen, forming a two dimensional image.





RADIATION PROTECTION
Protection in a diagnostic radiology is designed to achieved two ends;
1. Limit the exposure of the patient to the minimum that will produce satisfactory result ( ALARA principle )
2. To protect all other persons from the useful beam and from scattered and leakage radiation.


Some are achieved by:
 Limitation of field size ( Collimation )
 Directing the beam
 Careful preparation of patient
 Use of gonad shields
 Use of highest speed film emulsions and intensifying screens
 Presence of only essential staff in an X-ray room during radiological examinations
 Use of protective aprons or protective screens to wear or to stand behind
 Use of immobilizing devices for children and adults requiring support during an examination
 Provision of shielding in the walls of the X-ray room (equivalent to 1mm of lead )
 Presence of only essential staff in an X-ray room during radiological examinations
 Use of protective aprons or protective screens to wear or to stand behind
 Use of immobilizing devices for children and adults requiring support during an examination
 Provision of shielding in the walls of the X-ray room (equivalent to 1mm of lead)


Protection of early pregnancies
28 days rule
 Require the radiographer to ask the patient if there is any chance she may be pregnant.
 If answer is anthing other than a firm ‘no’, the date of the onset of her last menstrual period is established.
 If more than 28 days previously, Radiologist or requesting clinicians are consulted.
 PT – pregnancy test.

posted by akugafi @ 10:19:00 pm