Nuclear Medicine.pdf

Table of Contents
Introduction
Radiopharmaceuticals
ProductionofRadionuclides
Conclusion
Nuclear medicine Vs Radiology
Definition and desirable features
General conclusion
Nuclear reactors, particle
accelerators and generators

Radiology began in 1895, when Wilhelm Rontgen
accidentally discovered x-rays.
At one point, his wife put her hand over the photographic
plate; the x-ray image showed the bones of her hand and the
ring she was wearing, surrounded by a faint outline created
by her flesh. It was the first x-ray of a human body part.
Radiology is an important part of medical care
today. The field developed relatively quickly in
the 20th Century, and thanks to computer
technology and artificial intelligence (AI), is still
advancing.
Introduction

In nuclear medicine clinical information is derived from
observing the distribution of a radiopharmaceutical
administered to the patient by noting the amount of
radioactivity present. These measurements may be carried
out either in vivo or in vitro.
In vivo : In these studies, radio-pharmaceutical material is
given to the patient through injection, consumption, or
inhalation, depending on the specific type of study.
In vitro : In vitro measurements are made on samples of
material taken from the patient, such as breath, blood,
urine, and feces, to determine the amount of radio-
pharmaceutical present.
What is Nuclear Medicine?
Introduction

Radioactive material
(tracer) is injected, ingested,
or inhaled
Images of the body show
where and how the tracer is
absorbed.
Shows function
(Biochemistry)
Used in diagnosis or
treatment
Beams of radiation pass
through the body
Images of the structure in
the body are produced
Shows structure (Anatomy)
Used in diagnosis
Nuclear
Medicine
Radiology
Introduction
Nuclear Medicine Vs Radiology

Radiopharmaceuticals are a group of sterile, pyrogen free
pharmaceutical drugs containing radionuclide or radioactively tagged
compounds administered to a patient for diagnostic, therapeutic or
sterilization purposes. A radiopharmaceutical has no pharmacological
effects because of the small amount of material administered.
Oral Nasogastric
Routes Of Administration

Desirable Features
For Therapeutic uses :
Radiopharmaceuticals should have a
long physical half-life.
For diagnostic uses : the effective half-
life time should also be equal to the
examination period.
The ideal radiopharmaceutical should have
a short or long physical half-life time
depending on what the property is being
used for.
Half-Life Time
Gamma ray or beta particle emission is
imperative to the diagnostic purposes of
radiopharmaceuticals. SPECT (single
proton computed tomography) scans, and
PET (positron emission tomography) scans,
are commonly used in diagnostics by
tracking the gamma ray emissions.
Gamma Ray Emission
For therapeutic purposes, Auger electrons
or alpha particles are emitted for molecular
nuclear therapies.
The radioactive emissions emit to the local
tissue only to cure or destroy the unhealthy
mass while leaving healthy tissues and
organs unharmed.
Auger Electrons or
Alpha Particles
Specific activity refers to the amount of
radioactivity per unit mass of the element or
compound. Typically, high specific activity
is ideal for radiopharmaceuticals to properly
localize to the receptor site.
Specific Activity
Radiopharmaceutical compounds should
largely gather in the localized treatment
area. This will not only specialize treatment
to the direct area needed, but it will also
keep healthy tissue and organs unaffected
by harmful radioactivity. Localizing to the
treatment area quickly also allows for the
treatment to take place faster, which is
often needed in diagnostics or life-saving
treatments such as tumor removal.
Localize Largely and
Quickly
The stability of radioisotopes can be affected by
light, temperature, and pH balances.If these
impacts are not taken into account during the
preparation and storing of compounds,
metabolically-decomposed
radiopharmaceuticals used in diagnostic
imaging can result in undesirable distribution of
radioactivity and decreased quality of the image,
makingdiagnosisdifficult.
Stability
Like any clinical trial or treatment, the
availability and cost of production play a
large role in creating beneficial
radiopharmaceuticals. Proper storage
availabilitymustbeaccountedforaswell.
Cost, Availability, and
Care
In radiopharmaceuticals specifically, the As Low
As Responsibly Achievable or ALARA principle
must be followed. This concept requires that
exposure to radiation is minimized as much as
possible, proper shielding from the radiation
source is present, and the maximum proper
distance between personnel and the radiation
sourceisachieved.
Safety

Radiopharmaceutical Type Storage Uses
Meta-iodobenzyl (I-131) injection Diagnostic Store frozen at ≤ 0 ℃ with proper shielding For imaging
Meta-iodobenzyl (I-131) injection Therapeutic Store frozen at ≤ 0℃ with proper shielding
To treat tumors of the adrenal or thyroid
glands
Samarium (Sm-153) ethylene diamine
tetramethylene phosphonate (EDTMP)
injection
Therapeutic Store at 2～8 ℃ with adequate shielding
For treatment of intense pain in advanced
stage due to metastatized form of lungs,
prostate and breast cancer
Sodium fluoride (F-18) injection Diagnostic
Store in sterile containers as single dose or
multiple doses with proper shielding
Bone imaging agent to define areas of
altered osteogenic activity
Sodium iodide (I-131) capsules Diagnostic
Store in a cool and dark place with proper
shielding
Diagnosis of thyroid function and
malignancies
Sodium iodide (I-131) capsules Therapeutic
Store in a cool and dark place with proper
shielding
Treating different types of thyroid tumors
EXAMPLES

Advantages and Disadvantages
Pros Cons
Effective therapeutic method
Safe diagnostic tool
Minimum radiation exposure
Detection of heart diseases
No accumulation of radiation in the
body
Determination of cancer status
Detection of bone metastasis
High cost of nuclear medicine
Need special considerations
May cause allergic reaction
Side effects as teeth failing
Not used in pregnant and breast
feeding woman
May need long time to obtain good
results
Requires highly trained personnel

Naturally occurring radionuclides are generally not suitable for diagnostic and therapeutic
procedures due to their typically long half-lives or less than ideal physical or chemical
characteristics;
The nuclides we use in nuclear medicine are produced either by bombarding stable atoms
or by splitting massive atoms. There are three basic types of equipment that are used to
make medical nuclides: generators, cyclotrons, and nuclear reactors.
RadionuclidesGenerators
Reactors
Cyclotrons
Production of Radionuclides

Nuclear reactors have for many years provided large quantities of radionuclides for
nuclear medicine. Some examples include I-131, Xe-133, and Mo-99.
The reactor radionuclides are produced either by introducing a target of stable
material into the neutron ﬂux found inside the reactor, or by separating out fission
products from the fuel rods or a uranium target.
So we have two processes to produce radionuclides with nuclear reactors :
Nuclear Reactor
Fission
Neutron activation

Nuclear Reactor : Fission
A nuclear reactor is a facility in which a fissile atomic nucleus of the fuel rods
absorbs a low-energy neutron and undergoes nuclear fission. In the process,
several fast neutrons are produced. The neutrons are slowed down in a
moderator and the slowed-down neutrons start new fission.
There is a very wide variety of nuclides that might be produced during
fission with mass numbers in the range 70 to 160.

I-131 is ～2.9 per cent per fission.
Mo-99 is ～6 per cent per fission.
During nuclear fission, the nucleus usually divides
asymmetrically rather than into two equal parts. Moreover,
every fission event of a given nuclide does not give the same
products; more than 50 different fission modes have been
identified for uranium-235, for example.
Consequently, nuclear fission of a fissile nuclide can never be
described by a single equation. Instead, as shown in the
Figure, a distribution of many pairs of fission products with
different yields is obtained.
The probability of producing :

Fission products always have an excess of
neutrons, these radionuclides therefore tend
to decay by β– emission.
Fission products may be carrier free , and therefore
radionuclides can be produced with high specific
activity by chemical separation.
The lack of specificity of the fission process is a
drawback that results in a relatively low yield of the
radionuclide of interest among a large amount of
other radionuclides.
Radionuclides produced by
the fission process have
the following general
characteristics :

Nuclear Reactor : Neutron activation
The high neutron flux associated with the fission reactions in
the reactor can be used to bombard other stable nuclides if
they are placed in the reactor.
Most neutron activation reactions result in the emission of a
gamma photon (n,γ). Following an (n, γ) reaction the
resulting radionuclide is an ‘isotope’ of the stable target which
produces chemically identical species.
It is possible to produce radionuclides that are elementally
different from the target using neutron, proton (n, p) and
neutron, alpha (n, α) particle reactions.

Because neutrons are added to the nucleus, the
products of neutron activation generally tend to
decay by β– emission.
The most common production mode is by the reaction
(n,γ) and the products are not carrier free . Removal
of carrier and impurities is an expensive process.
Only a very small fraction of the target nuclei actually
are activated. Thus an (n,γ) product may have very low
specific activity because of the overwhelming
presence of a large amount of stable carrier.
Radionuclides produced by
neutron activation have
the following general
characteristics:
Nuclear Reactor : Neutron activation

Charged particles, unlike neutrons, are unable to diffuse into the
nucleus, but need to have enough kinetic energy to overcome
the Coulomb barrier. Charged particles are readily accelerated
in particles accelerators that open up more reaction channels.
Particles Accelerators : Cyclotrons
A cyclotron is a type of compact particle accelerator
in which charged particles such as protons, deuteron
and alpha particles are accelerated in a spiral path
within a vacuum under the action of a static
magnetic field and an alternating electric field.

A resistive magnet that can create a magnetic field of 1–2 Tesla
A vacuum system down to 10-5 Pa.
A high frequency system.
An ion source that can ionize hydrogen to create free protons
as well as deuterium and eventually alpha-particles.
A cyclotron is composed by four systems:
In a cyclotron, two hollow “D” shaped electrodes are placed face to face
with a small gap, inside a vacuum chamber. An alternating voltage is
applied between the “D’s” across the gap. A uniform magnetic field is
applied perpendicular to the plane of the electrodes. The “D’s” have a
cylindrical space for the particles to move.

The charged particle will be attracted across the ‘gap’ toward the ‘D’
with the opposite charge. The magnetic field ensures the charged
particle travel in a circular path through the ‘D’ with the radius
dependent on the speed.
The charged particle then traverses the second ‘D’ in a circular arc
with a larger radius because the speed is higher. This process
continues until the charged particle reaches the target speed or
energy.
The frequency of the ac voltage must match with the cyclotron frequency
of the particles :
The kinetic energy for particles with speed v is therefore given by:

Pros Cons
The cyclotron uses the same accelerating gap,
which enables it to become compact and therefore
saves cost in many ways.
The accelerating particles can be taken to higher
energy states within the small space available.
Cyclotrons can produce the particle beam in a
continuous form.
It has only one electric driver. This makes it cost-
efficient because of less cost equipment and less
costly power.
The speed of a charged particle is increased by the
cyclotron device at a high rate, but much less than
that of the light wave.
It is very hard to maintain the same magnetic
field in a large space area for a cyclotron.
The mass of an electron is very small. Because of
this reason, the cyclotron device is incapable of
accelerating or speeding up the electron.
This device is also incapable of accelerating or
speeding up the particles which have no charge
(neutral particle).

Generators are units that contain a radioactive
“parent” nuclide with a relatively long half‐life that
decays to a short‐lived “daughter” nuclide which
can be chemically extracted when required.
They’re devices that allows a weekly supply of a
short lived radionuclide to be available on site.
Depending on the half-life of the parent/daughter,
regular separation and extraction of the daughter
from the parent can occur. Elution, also referred to
as ‘milking the generator’, can be repeated because
the parent replenishes the daughter by decay.
Radionuclides Generators

The most commonly used generator is the technetium‐99 generator, which consists of a heavily shielded column with
molybdenum‐99 (parent) bound completely and irreversibly to the alumina of the column due to its very high affinity for
alumina by adsorption in the generator as ammonium molybdate. Mo-99 then decays to its daughter radionuclide Tc-99m as
pertechnetate. The amount of pertechnetate grows as a result until a transient equilibrium is reached.
By drawing sterile saline (sodium chloride NaCl) through the column, the Tc-99m (daughter) is eluted due to its almost total
lack of affinity for alumina and get washed away into the vacuum vial as a solution of sodium pertechnetate which may now be
used to compound radiopharmaceuticals.
Radionuclides Generators : Mo-99/Tc-99m

Pros Cons
Available on site, no need for complicated
logistics
Mostly long shelf life
Easy to use
Trace contaminants of long-lived parent
nuclide in eluted product
Cost of the generator are relatively high
The in-house use must be timed, the generator
can't be stored for future use.
Radionuclides Generators

Conclusion
Nuclear medicine uses radiation to provide information about the functioning of a person's
specific organs, or to treat disease. In most cases, the information is used by physicians to make a
quick diagnosis of the patient's illness. The thyroid, bones, heart, liver, and many other organs
can be easily imaged, and disorders in their function revealed.
In addition to their use in the clinical practice of nuclear medicine and radiology and in the
research conducted in those medical fields, radioisotopes have found applications in a wide variety
of scientific fields such as nutrition, genetics, molecular biology, pharmacology, drug
development, nuclear physics, environmental chemistry, geology, and industrial manufacturing.

Nuclear Medicine.pdf

More Related Content

What's hot

Similar to Nuclear Medicine.pdf

Recently uploaded

Nuclear Medicine.pdf