artificially produced radioisotopes & its application

7/30/2019 Artificially Produced RadioIsotopes & Its Application

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Artificially Produced

RadioIsotopes & its Application


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Medical Application of Radionuclides

Therapeutic Application(Radiotherapy)

- Radionuclides are used as sourcesof ionising radiation to whichmalignant tissue is particularly

sensitive- Internally either by introduction of

sealed sources (small wires,needlesor capsule) into the tissue or byinjection of unsealed sources(usually in solution)

- Externally, by external beamtherapy (teletherapy), usingpowerful gamma ray emitters suchas Cobalt-60 or Caesium-137.

Diagnostic Application

- Radionuclides are used to helpdiagnose and monitor a patientsinjury or disease

- In Vitro Studies A sample of

patients tissue (e.g blood) isremoved and Radionuclide is usedto measure the level of one of itsconstituents.

- In Vivo Studies Radionuclide isinjected into the living patient for

1. Physiological Studies

2.Blood Volume Studies

3. Imaging Studies (RadionuclideImaging


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Artificially produced Radio-

Isotopes

Application

Caesium-137 Used for radiotracer techniquefor identification of sources of

soil erosion and deposition

Chromium-57 Used to label sand to study

coastal erosion

Cobalt-60 Used in gamma sterilisation,industrial radiography, used in

cancer treatment

Krypton-85 Used for industrial gauging

Manganese-54, Zinc-65 Used to predict the behaviour

of heavy metal components ineffluents from mining waste

water

Americium-241 Used in smoke detectors,

measuring ash content of coal


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Artificially produced Radio-

Isotopes

Application

Selenium-75, Ytterbium-169 Used in gamma radiography

and non destructive testing

Strontium-90, Thallium-204 Used for industrial gauging

Iridium-192 Used in gamma radiography to

locate flaws in metal

components

Nickel-63 Used to detect explosives and

in voltage regulators and

current surge protectors in

electronic devices, and in

electron capture detectors for

gas chromatographs


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Naturally occuringRadioisotopes

Application

Carbon-14 Used to measure the age of

water

Chlorine-36 Used to measure sources of

chloride and the age of waterLead-210 Used to date layers of sand

and soil


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Radio-Isotopes used in MedicineRadioIsotopes

Application

Molybdenum-99 Used as the parent in a generator to produce techetium-

99m

Technetium-99m Used to image the skeleton and heart muscle in

particular, but also for brain, thyroid, lungs (perfusion and

ventilation), liver, spleen, kidney (structure and filtration

rate), gall bladder, bone marrow, salivary and lacrimal

glands, heart blood pool, infection and numerousspecialised medical studies (SPECT)

Bismuth-213 Used for targeted alpha therapy

Chromium-51 Used to label red blood cells and quantify gastro-intestinal protein loss

Cobalt-60 Formerly used for external beam radiotherapy (treatment

of brain tumor)

Iodine-125, Palladium-103 Used in brachytherapy


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RadioIsotopes Application

Copper-64 Used to study genetic diseases affecting copper

metabolism such as Wilsons and Menkes diseases

Iodine-125 Used in cancer brachytherapy (prostate and brain), also

diagnostically to evaluate the filtration rate of kidneys

and to diagnose deep vein thrombosis in the leg

Iodine-131 Widely used in treating thyroid cancer and in imaging

the thyroid; also in diagnosis of abnormal liver function,

renal (kidney) blood flow and urinary tract obstruction. Astrong gamma emitter, but used for beta therapy.

Rhenium-186 Used for pain relief in bone cancer

Sodium-24 For studies of electrolytes within the body.

Strontium-89 Very effective in reducing the pain of prostate and bonecancer. Beta emitter.

Xenon-133 Used for pulmonary (lung) ventilation studies

Ytterbium-169 Used for cerebrospinal fluid studies in the brain


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RadioIsotopes Applications

Carbon-11, Nitrogen-13,

Oxygen-15, Fluorine-18

These are positron emitters used in PET for

studying brain physiology and pathology, in

particular for localising epileptic focus, and in

dementia, psychiatry and neuropharmacology

studies. Also in Cardiology

Gallium-67 Used for tumour imaging and localisation of

inflammatory lesions (infections).

Indium-111 Used for specialist diagnostic studies, eg brainstudies, infection and colon transit studies.

Phosphorous-32 Used in bone metastasis to control the pain

Iridium-192 Cancer therapy ,e.g. lung cancer, head and neck

cancer, tongue and mouth cancer, cancer of the

throat and treatment of stenosis

Yttrium-90 Therapy for arthritis

Erbium-169 Therapy for arthritis of smaller joints

Holmium-166 Development of therapy for liver cancer and

blood cancer


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RadioIsotopes Applications

Lutetium-177 it emits just enough gamma for imaging

while the beta radiation does the therapy on

small (eg endocrine) tumours.

Zinc-65 Brain Cancer Imaging, used as a tracer in

studies of zinc metabolismThallium-201 Cardiac Imaging (ideal tracer for detecting

myocardial Perfusion)

Gallium-68 Cardiac Imaging (PET)

samarium-153 used to kill cancer cells in the treatment

of lung cancer, prostate cancer, breast cancer& Osteosarcoma


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Particle Accelerators

It is a device which accelerates charged

particles such as protons, electrons, deuterons

where the acceleration is achieved by using

focused magnetic fields to route the beam of

particles through a sealed vacuum chamber

The exact design of the beam's path and

magnetic configuration determines the type ofparticle accelerator


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Cyclotron


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Cyclotron Fig 1


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Construction

It consists of two dees or D-shaped metal chambers D1

and

D2. The dees are separated by a small distance.

The Dees are connnected to a high frequency oscillator where

the frequency is of the order of 10^7 cycles per second and

potential difference is 10^4 volts.

The dees are enclosed within a large metal box containing a

gas at low pressure & are perfectly insulated from the box.

The whole apparatus is placed between the pole pieces of a

strong electromagnet.

The magnetic field is perpendicular to the plane of the dees


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Theory & Working

When a positive ion with a charge q is emitted from the source, it is

accelerated towards the dee having negative potential at that

instant.

Suppose that at any particular instant the alternating potential is in

the direction which makes D1 positive and D2 negative as shown in

fig1.

A positive ion starting from the source S will be attracted to the D2since there is a uniform magnetic field acts at right angles to the

plane of the dees . Therefore the ion is forced to move along a

semi-circular path inside the dee.

After it has traversed half a cycle, the ion comes to the edge of D2.

If in the meantime, the potential difference between D1 & D2 has

changed direction so that D2 is now positive and D1 negative.

The positive ion will receive an additional acceleration while going

across the gap b/w the dees D1 & D2, then travel in a circular path

of larger radius inside the D1 under the influence of magnetic field


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The frequency of the oscillator is adjusted such that the time

taken to describe the semi circle of the ion is equal to the

time for one half cycle. Here the ion will continue travelling in a semicircle of

increasing radii within the dees & will gain energy each time it

goes from D1 to D2 & from D2 to D1.

The ion executes a spiral path in the cyclotron. After the ionshave attained a very large velocity, an auxiliary electric field is

used to deflect them from their circular paths and make them

come out of a window .

The substance to be bombarded is placed near the window. Used to accelerate protons & ions

Refer the equation regarding cyclotron from the class notes


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Limitations of Cyclotron

Only when the speed of the circulating ion is lessthan 'c' the speed of light, we find the frequency ofrevolution to be independent of its speed.

At higher speeds, the mass of the ion will increaseand this changes the time period of the ionrevolution. This results in the ion lagging behind theelectric field and it eventually loses by collisionsagainst the walls of the dees.

The cyclotron is suitable for accelerating heavy

charged particles but not electrons. It is not suited for very high kinetic energy.


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Betatron Device used for accelerating electrons in a circular path by magnetic

induction Electrons with 300 Mev energy have been obtained.

Its operation is similar to the principle of transformer i.e., an

alternating current applied to primary coil induces an alternating

current with higher or lower voltages in the secondary coil

In Betatron, the secondary coil is replaced by a doughnut shaped

vacuum chamber or a tube.

The electrons are made to circulate in a doughnut shaped vacuum

chamber that is placed into the gaps between two magnet poles.

It may be considered an analogue of a transformer: the primarycurrent is the AC exciting the magnet & the secondary current is the

electron current circulating in the vacuum chamber

Electrons are produced by the electron gun or hot filament


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When an alternating magnetic field is applied parallel to the

axis of the tube, two effects are produced:

1. An emf is produced in the electron orbit by the changingmagnetic flux that gives an additional energy to the electrons

2. A radial force is produced by the action of magnetic field

whose direction is perpendicular to the electron velocity

which keeps the electron moving in a circular path. Alternating current of Frequency used is 50 Hz to 200 Hz

Refer the equation regarding betatron from the class notes


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Betatron figure


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Linear Accelerator (LINAC)

An electron, a proton or a heavy ionaccelerator in which the paths of the particlesaccelerated are essentially straight lines rather

than circles or spirals. LINAC consists of a long vacuum chamber

containing large number of cylindricalelectrodes.

The particles travel in straight lines along thewhole length of the tube.


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Consider a positively charged ion moving from left to right in

figure.

The ion after crossing the cylinder is accelerated in the gap

between the 1 and 2 when cylinder 2 isve.

The ion moves with constant speed in the cylinder 2 but

greater than the speed in the first cylinder

As soon as the ion reaches the end of the second cylinder, the

second cylinder becomes positive and the third cylinder

negative. The ion is accelerated in the gap of the 2 & 3

cylinders.

The process continues and the ion gains energy each time it

passes from one cylinder to the other.

The length of the cylinders increases with increase in their

number and in this way the ions are kept in phase with the

reversal of potential & increase in speed.


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Advantages of LINAC

Used to accelerate protons & electrons

No magnet is needed to guide the particles

The particles automatically emerge from it in awell collimated beam and can strike the target

directly.


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Medical LINAC


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artificially produced radioisotopes & its application

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