Seminar on Radiology

8/3/2019 Seminar on Radiology

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Types of Radiation

The radioactive radiations are of three types (alpha), (beta) & (gama) rays. These weresorted out by Rutherford (1902) by passing twooppositely charged plates. The one bendingtoward the negative plate carried positive

charge & were named (alpha) rays. Thosebending towards the positive plate and carryingnegative charge were (Beta) rays. The thirdtype of radiation being uncharged passedstraight through the electric field & werenamed (gama) rays. (Alpha), (beta) &(gama) rays differ from each other in nature &properties. Their chief properties are a(

Velocity) (b) penetrating Power Ionization


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Principle of Radiological

Technique

All the radilogical technique are based on the radioactivedecay. Few radioactive details are :-

1. Decay by negatron emission: in this case neutron isconverted to a proton by the enjection of a negativelycharged beta () particles called a negatron (-ve)Neutron Proton+Negatron

6C14 7N

14+-ve

2. Decay by positron emission:- some isotopes decay byemitting positively charged particles referred to aspositron (+ ve). This occurs when a proton is convertedto a neutron.Proton Neutron+Positron

11Na22 10Ne

22++ve

3. Decay by alpha emission:- an alpha particle is a heliumnucleus in that it consist of two proton & two neutron

(2He4) Emission of - particles, therefore result in aconsiderable lightening of the nucleus of the nucleus, adecrease in atomic number of two & a decrease in themass number of four.

88Ra226 86Rn

222+ 2He4


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Detection & Measurement

of Radioactivity The radioactive radiation can be measured & detected by

a number of methods, which are as follows:- 1. cloud chamber :- This technique is used for detecting

radioactivity. The chamber contains air saturated with

water vapor, when the position is lowered suddenly, thegas expand & is super cooled, As an - or - particlespasses through the gas, ions are created along its path.These ions provide nuclei upon which droplets of watercondense. The trail or cloud thus produced marks thetrack of the particle. The track can be seen through the

window above & immediately photographed. Similarly an- or - particles from trail of bubbles as they passthrough liquid hydrogen. The bubble chamber methodgives better photograph of particle tracks .


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2. Ionization Chamber:- This is the

simplest chamber is fitted with two metalplates separated by air. When radiationpassed through this chamber, it knockselectron from gas molecules & positive ionsare formed. The free electrons migrate tothe anode & positive ions to the cathode.Thus a small passes between the plates.This current can be measured with anammeter & gives the strength of radiationthat passes through the ionizationchamber.


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3.Geigar- Muller Counter:- This device is usedfor detection & measuring the rate of emission ofa - or particles. It consist of a cylindricalmetal tube (cathode) & a central wire (anode).The tube is fitting with argon gas at reduced

pressure (0.1 atm). A potential difference of about1000 volts is applied across the electrodes. Whenan - or - particle enters the tube through themica window, it ionizes the argon atom along itspath.

The argon ions are drawn to the cathode &

electron to anode. Thus for a fraction of second, apulse of electric current flows between theelectrodes & completes the circuit around. Eachelectric pulse marks the entry of one - or -particle into the tube & is recorded in anautomatic counter.


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4.Scintillation Counter :- Rutherfordused spinthariscope for the detection &counting of- particles. The radioactive

substances mounted on the tip of thewire emitted -particles. Each particle onstriking the zinc sulphide screenproduced a flash of light. These flashes

of light (scintillation) could be seenthrough the eye-piece. With this device itwas possible to count -particles from 50to 200 per second.


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5. Applications ofradioisotopes in biologicalscience

A). Investigation of metabolic pathways:-.Radioactivity is located either by using a Geigerchromatogram scanner or by placing thechromatogram in contact with X-ray film for asuitable exposure time. By identifying the labeledcompounds, counting the radioactivity in each ofthem and plotting suitable graphs, it is possibleto obtain considerable information on themetabolic pathways involved.

B). Use of radioisotopes in studies ofabsorption and translocation:- Radioisotopeshave been very widely used in studying themechanism and rate absorption andtranslocation of inorganic and organiccompounds by both plants and animals.

C). Clinical applications of radioisotopes:-Radioisotopesare very widely used in medicinein particular of diagnosis tests. Lungs functiontests routinely made using 133 xenon (133xe) areparticularly useful in diagnosis of malfunctions oflung ventilation .

Iodohippuric acid are used in diagnosis ofkidney infections, kidney blockages or imbalanceof function between the two kidneys.Thyroid function tests using 131Iare employed inthe diagnosis of hypo- and hyperthroidism.


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D) Radio dating:- A Quite different usefor radioisotopes is in the dating ofrocks, fossils and sediments. For the

long dating, isotopoes with long halflives are necessary, such as 235U, 238M and40K whereas for shorter term dating 14Cis widely used.

E) Use of radioisotopes in sterilizationof food and equipment :- very shortgamma emitters are now widely used inthe food industry for sterilization of

prepacked foods such as milk andmeats. Normally either 60Co 137Ce isused.

60Co 137Ce are also used in

sterilization of plastic drugs which areadministered the injection.


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Conclusion

Radiological technique are those techniquewhich are based on the use of radioactivityelements or radioisotopes for variouspurposes like investigation of metabolic

pathways, radiodating, diagnosis ofdiseases etc. Radioisotopes are the unstableisotopes which undergo spontaneousnuclear changers accompanied by theemission of particulate & sometimes also

electromagnetic radiations. The radioactiveradiation are to three types (alpha) (beta)(gamma) rays. Some important methodsare Cloud Chamber Ionization Chamber,Geigar-Muller Counter, Scintillation

Counter & Film Badges. The range ofapplication of radioisotope is enormous &the data accrued from the use ofradioisotopes have a great contribution in

the biological science in the last fewdecades.

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Seminar on Radiology