princip medicine nuclear

7/30/2019 princip medicine nuclear

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Principles of NuclearPrinciples of Nuclear

MedicineMedicine

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THE ATOMTHE ATOM

The nucleus has protons andThe nucleus has protons andneutrons.neutrons.

Protons are positively chargedProtons are positively chargedparticles.particles.

Neurons are particles without charge.Neurons are particles without charge.

Electrons orbit the nucleus inElectrons orbit the nucleus inprecisely defined shells and sub-precisely defined shells and sub-shells.shells.


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Atomic StructureAtomic Structure

Atom is smallest partAtom is smallest partof element thatof element thatretains chemicalretains chemicalproperties of thatproperties of that

elementelement Atoms are neutralAtoms are neutral

(no charge),(no charge),

but are divisible intobut are divisible intosmaller elementarysmaller elementaryor fundamentalor fundamentalparticlesparticles

Not to scaleNot to scale

NucleusNucleus


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Atom anatomyAtom anatomy

Electron Proton Neutron

Nucleons


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The AtomThe Atom

The symbol X is given to any atom.The symbol X is given to any atom.

A is the atomic mass number which isA is the atomic mass number which is

the total number of protons and neutrons.the total number of protons and neutrons.

Z is the atomic number which is theZ is the atomic number which is thenumber of protons. Atomic number definesnumber of protons. Atomic number definesthe atom.the atom.


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Atomic ShorthandAtomic Shorthand

II131131535353 Protons + 78 Neutrons = 131 Nucleons53 Protons + 78 Neutrons = 131 Nucleons

XXAA

ZZ

Atomic MassAtomic Mass

Atomic NumberAtomic Number

ElementElement


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ISOTOPESISOTOPES

If proton number Z changes, the atomIf proton number Z changes, the atomwill change (different element).will change (different element).

If neutron number change, the element willIf neutron number change, the element willbe the same, but we will have isotopes.be the same, but we will have isotopes.

By definition; all isotopes of a givenBy definition; all isotopes of a givenelement have the same number of protonselement have the same number of protonsand differ only in the number of neutrons.and differ only in the number of neutrons.

Example:Example: 5353II123123,, 5353II125125,, 5353II131131..

N F


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Nuc ear Fam es anuc ear am es anNomenclatureNomenclature

CC1212

66CC

1313

66CC

1414

66

Same number ofSame number of PProtons = Isotorotons = Isotoppeses


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Radioactive IsotopesRadioactive Isotopes

Some isotopes are stable (non-Some isotopes are stable (non-radioactive).radioactive).

Some isotopes are unstable (radioactive).Some isotopes are unstable (radioactive).


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UNSTABILITY AND DECAYUNSTABILITY AND DECAY

Unstable isotope seeks greater stability byUnstable isotope seeks greater stability bysome kind of radiation (decay).some kind of radiation (decay).


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IsotopesIsotopes


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Half-LifeHalf-Life

The time required for half of theThe time required for half of theradioactive isotope to undergo decay isradioactive isotope to undergo decay iscalled the half-life.called the half-life.

After 4 half-life's, the residual activityAfter 4 half-life's, the residual activitywould be 6.25% of original activity, whichwould be 6.25% of original activity, whichmeans there is no significant activity left.means there is no significant activity left.


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Types of RadiationTypes of Radiation

Particulate:Particulate:

Emission of beta particles (electrons)Emission of beta particles (electrons)

The isotope is converted into different element.The isotope is converted into different element.

Photonic (electromagnetic) : gamma rayPhotonic (electromagnetic) : gamma rayand x-rayand x-ray

Emission of photons (gamma ray or x-ray)Emission of photons (gamma ray or x-ray)

The isotope does not change.The isotope does not change.


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Types of radiationTypes of radiation


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Decay of RadioactiveDecay of Radioactive

Isotopes (electron emission)Isotopes (electron emission)


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Single Step RadioactiveSingle Step Radioactive

DecayDecay

II131131

5353

XeXe131131

5454(stable)(stable)

(unstable)(unstable)

.


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Decay of Radioactive IsotopesDecay of Radioactive Isotopes

(photon emission)(photon emission)


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PhotonsPhotons

Photon is electromagnetic wave.Photon is electromagnetic wave.

It is part of electromagnetic spectrum.It is part of electromagnetic spectrum.

Photons are used in imaging inPhotons are used in imaging inradiology (conventional radiographyradiology (conventional radiographyand CT scanning) and in nuclearand CT scanning) and in nuclear

medicine.medicine.


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101033 101022 101011 1010--11 1010--22 1010--33 1010--44 1010--22 1010--33 1010--44 1010--55 1010--66 1010--77 1010--88 1010--99 1010--1010

Radio/TVRadio/TV InfraredInfrared

VisibleVisible

UVUV XX--raysrays

GammaGamma

Wavelength (m)Wavelength (m)

4,000A4,000A7,000A7,000A

Electromagnetic SpectrumElectromagnetic Spectrum

Frequency (Hz)Frequency (Hz)

101055 101066 101077 101088 101099 1010101010101111 1010121210101313 10101414 10101515 10101616 10101717101018181010191910102020

Visual

Imaging

MRIX-ray

Imaging


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ElectromagneticElectromagnetic rradiationadiation

GAMMA

VISIBLE X-RAYS COSMIC

INFRARED ULTRAVIOLET

MICROVAVES

TV,RADIO Decreasing wave length

Increasing frequencyIncreasingphoton energy

IONIZINGRADIATON


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X-Ray and Gamma RayX-Ray and Gamma Ray

X-ray is emitted from outside the nucleusX-ray is emitted from outside the nucleus(electron shells).(electron shells).

Gamma ray is a photon emitted form someGamma ray is a photon emitted form some

isotopes in the process of their decay.isotopes in the process of their decay.


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XX--rays andrays and

gammagammaraysrays


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Ionizing RadiationIonizing Radiation

Radiation causes ionization of atoms andRadiation causes ionization of atoms andmolecules.molecules.

Ionization is the underlying mechanism forIonization is the underlying mechanism for

most radiation detectors and also ismost radiation detectors and also isresponsible for most radiobiologicalresponsible for most radiobiologicaleffects.effects.


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Biological Effect of RadiationBiological Effect of Radiation

Why should we protect ourselves fromWhy should we protect ourselves fromradiation?radiation?


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Radiation Effects at the MolecularRadiation Effects at the MolecularLevel - Direct ActionLevel - Direct Action

Direct molecularDirect molecularabsorption ofabsorption ofenergyenergy

DNA mostDNA mostsusceptiblesusceptible


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DNADNA llesions andesions and cchromosomehromosome

aaberrationsberrations

DNA SNGLE

STRAND BREAK

DNA DOUBLE

STRAND BREAK


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Indirect Action-Radiolysis of WaterIndirect Action-Radiolysis of Water

IonizationIonizationDissociationDissociation


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Free Radical Biological DamageFree Radical Biological Damage

Cause damage toCause damage to(DNA/RNA) which(DNA/RNA) whichbecome non-become non-functionalfunctional


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Somatic EffectsSomatic Effects

Acute or early (deterministic)Acute or early (deterministic) within dayswithin days dose dependentdose dependent Seen in accidents and nuclear warsSeen in accidents and nuclear wars Affects acutely bone marrow, GI tract andAffects acutely bone marrow, GI tract and

skin and less neurological system.skin and less neurological system. Latent or delayed (stochastic).Latent or delayed (stochastic).

not seen for yearsnot seen for years cancer, cataract, shortened life spancancer, cataract, shortened life span


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Principals of Radiation ProtectionPrincipals of Radiation Protection

TimeTime

DistanceDistance

ShieldingShielding


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TIMETIME

The total radiation exposure to anThe total radiation exposure to anindividual is directly proportional to theindividual is directly proportional to the

time he is exposed to the source.time he is exposed to the source.

Therefore, it is wise to spend no moreTherefore, it is wise to spend no moretime than necessary near the source oftime than necessary near the source of

radiation.radiation.


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DISTANCEDISTANCE

The intensity of radiation from a sourceThe intensity of radiation from a sourcevaries inversely with the square of thevaries inversely with the square of thedistance.distance.

Therefore, radiation workers shouldTherefore, radiation workers shouldmaximize the distance betweenmaximize the distance between

themselves and the radiation source.themselves and the radiation source.


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ShieldingShielding

Lead is most commonly used to shield photonsLead is most commonly used to shield photonsin diagnostic imaging.in diagnostic imaging.


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560 mGy/h

1 mGy/h

2 mm lead

Vial Shields


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Nuclear Medicine ImagingNuclear Medicine Imaging


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Technetium 99m (TcTechnetium 99m (Tc 99m)99m)

It is the main isotope used in nuclearIt is the main isotope used in nuclearmedicine imaging. It is used in more thanmedicine imaging. It is used in more than70-80% of cases.70-80% of cases.

It emits gamma ray only.It emits gamma ray only. Its half life is 6 hours.Its half life is 6 hours.

It can easily label different kind ofIt can easily label different kind ofpharmaceuticals.pharmaceuticals.

It is always given intravenously.It is always given intravenously.


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RadiopharmaceuticalsRadiopharmaceuticals

Pharmaceuticals are chemical compoundsPharmaceuticals are chemical compoundsthat have pharmacokinetics but do notthat have pharmacokinetics but do nothave pharmacological effects.have pharmacological effects.

They are usually labeled with Tc99m.They are usually labeled with Tc99m. For each organ there is certainFor each organ there is certain

radiopharmaceuticalsradiopharmaceuticals

In general, nuclear medicine images theIn general, nuclear medicine images thefunction (physiology), not the anatomy asfunction (physiology), not the anatomy asin conventional radiology.in conventional radiology.


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PharmaceuticalPharmaceutical


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Different PhrmaceuticalsDifferent Phrmaceuticals

f G


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Radio-labeling of Glucose withRadio-labeling of Glucose withradioactive Flourine-18radioactive Flourine-18


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The Gamma CameraThe Gamma Camera

It is a device that uses gamma rays toIt is a device that uses gamma rays tomake an image of radiopharmaceuticalmake an image of radiopharmaceuticaldistribution and uptake in patients.distribution and uptake in patients.

Its crystal has a chemical propriety that if itIts crystal has a chemical propriety that if itis hit by a photon it will scintillate.is hit by a photon it will scintillate.


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Nuclear ImagingNuclear Imaging

Not enough to detect just radioactive levelsNot enough to detect just radioactive levels

or concentrationsor concentrations

Need device to map the radioactiveNeed device to map the radioactive

distributiondistribution

External Radiation Detector


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Gamma camera-cont..Gamma camera-cont..

Scintillation means light production.Scintillation means light production.

The light is converted into electricalThe light is converted into electricalcurrent which then is stored in thecurrent which then is stored in thecomputer as a dot.computer as a dot.

S f G C


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Scintillation of Gamma CameraScintillation of Gamma Camera

Crystal

Gamma Ray

Light


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Gamma Camera Crystal (B)Gamma Camera Crystal (B)

NaINaI(Tl)(Tl)

1/41/4 -- 1/21/2**** thickthick

3/8 most popular3/8 most popular

1010-- 21 in diameter21 in diameter rectangular popularrectangular popular

Sensitive toSensitive tomoisture andmoisture and

temperaturetemperature


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Gamma CameraGamma Camera

StaticStaticImageImage

DyamicDyamicAcquisitionAcquisition

ImagesImages

MobileMobile

CameraCameraStationary DualStationary DualHead CameraHead Camera

Stationary SingleStationary SingleHead CameraHead Camera


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Gamma CameraGamma Camera

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