Radiopharmaceutical: Uses, Production, and Effects

This document provides an overview of radiopharmaceuticals, including their uses in diagnosing and treating cancer. It explains the production of radioisotopes in reactors and cyclotrons, as well as the different types of radiation emitted by radiopharmaceuticals. The document also discusses the effects of radiation on the body and the somatic and genetic effects of exposure. Overall, it offers a comprehensive understanding of radiopharmaceuticals and their role in medical imaging and treatment.

Radiopharmaceutical

Table of Contents
1.1 a)............................................................................................................................................1
1.1 b)............................................................................................................................................1
1.2 a)............................................................................................................................................1
1.2 b)............................................................................................................................................1
1.3 a)............................................................................................................................................1
2.1 a)............................................................................................................................................2
2.1 b)............................................................................................................................................2
2.1 c)............................................................................................................................................2
2.2 a)............................................................................................................................................3
2.3 a)............................................................................................................................................3
2.3 b)............................................................................................................................................3
3.1 a)............................................................................................................................................4
3. 1 b)...........................................................................................................................................4
3.2 a)............................................................................................................................................4
3.3 a)............................................................................................................................................5
3.3 b)............................................................................................................................................5
3.3 c)............................................................................................................................................5
3.3 d)............................................................................................................................................5
3.3 e)............................................................................................................................................5
3.3 f).............................................................................................................................................5

1.1 a)
Radioisotope is defined as an atom in which the combination of neutrons and protons is
unstable or the energy in the nucleus is resent in excess. These can happen to occur either
naturally or after the occurrence of an artificial alteration in the atom.
1.1 b)
These are defined as radioactive medications which find their use in the diagnosis as well
as treatment of cancer. Radiopharmaceuticals can be administered to the patients in oral form as
well as intravenously. These can also be delivered interstitially.
1.2 a)
The production of radioisotope in reactors takes place on the basis of capture of neutron n
a target material. The fission of the target material on bombarding them with thermal neurons
then leads to the generation of radioisotopes. Beta decay is a characteristic feature of many of the
radio isotopes. it is for this reason that in a nuclear reactor, there is direct production of
radioisotopes. This is because, when the target nuclide captures the neutron, there is formation of
a radioactive or unstable product. Decay of this radioactive product takes place by beta emission.
1.2 b)
A cyclotron can be regarded as a particle accelerator which is in a compact form. It
produces radio isotopes which further find their application in imaging procedures. The
cyclotron ejects a beam of protons or charged particles in a circular path repeatedly. The non-
radioactive materials, also known as stable isotopes, lead to the formation of medical
radioisotopes when they are bombarded by protons. When there is an interaction between the
proton beam and stable isotopes, a nuclear reaction occurs. This reaction leads to the conversion
of the stable isotopes into radioactive isotopes or radioisotopes
1.3 a)
There is instability in the nuclei of radioisotopes. These nuclei undergo random
disintegration and lead to production of atoms of different elements. During this, they lead to the
emission of energetic subatomic particles. These are known as Alpha and Beta particles.
1

Half- life of each radioisotope is its characteristic feature. It is the time that a radio-
active isotope takes to reach half of its original value. The half- life of radio isotopes used for
medicine is short so that they are able to decay as soon as the imaging is complete.
The radioisotope used for diagnosis has a property of emitting gamma rays of sufficient
energy that helps it escape from the body.
2.1 a)
Following after the for organs in which a gamma camera is used for carrying out imaging tests:
 Thyroid
 Heart
 Lungs
 Kidney
2.1 b)
The most commonly used tracer for gamma camera is technetium -99 m. it is a
metastable isomer the reason behind choosing this tracer is its long half -life. Technetium -99m
(Tc – 99m) has a relatively longer half- life of six hours.
It also has the ability of being capable of incorporated in a variety of molecules. Due to
this property, it is able to target different systems within the body.
Moreover, technetium- 99m emits 140.5 KeV gamma rays. Due to this, medical
equipment is able to readily detect it in the body. These gamma rays emitted by Tc – 99m make
it possible for the medical practitioner to obtain an image of the internal organs of the body. It
also does not cause any radiation damage to the patient which the procedure for imaging is being
performed.
2

2.1 c)
Gamma camera is also known as a scintillation camera that finds its application in
imaging radioisotopes that emit gamma radiation. The gamma rays are emitted by a radioactive
marker. Scintillations produced by the gamma rays are detected by the gamma camera. When the
gamma rays impact sodium iodide crystal, it results in generation of scintillations that are
detected by the photomultipliers. Location of radioactive emitters can be done when a large
number of scintillations have been observed.
The gamma camera consists of a crystal of sodium iodide. The patient is injected with a
radioactive pharmaceutical. On leaving the patient’s body, the gamma photon hits the iodine
atom and knocks an electron loose from the crystal. This results in the production of a faint flash
of light when a minimal energy state is again found by the dislocated electron. These flashes of
light are detected by photomultiplier tubes. The flashes are counted by computer which then
produces a two dimensional image of the relative spatial count.
2.2 a)
When diagnosis of a disease is to be done, the radioisotopes are combined with scanning
machines such as CT scans, MRI and other machines. This assists in imaging and diagnosing
diseases. The radioisotopes are used in diagnostic imaging by putting them by putting them into
tracers. These are then injected, ingested or inhaled by the patient to be diagnosed.
Fluorodeoxyglucose (FDG) is a tracer that is used in imaging of cancer. It not only
diagnoses the cancer but also helps in assessment of the response of cancer. The reason for
choosing Fluorodeoxyglucose (FDG) as a tracer is that is has the ability to detect physiologic
changes within a tumor which are succeeded by anatomic changes.
PSMA is another tracer that is used for overall staging of prostate cancer. The reason for
choosing PSMA as a tracer is that it is more accurate at detecting metastatic tumors.
2.3 a)
The external source of radiation that is used for treatment of cancer is 3- D conformal
radiation therapy. It is the most common type of external therapy that makes use of radiation
3

beam. It is based on the use of images obtained from MRI, CT and PET scans. Thus the
treatment area can be precisely planned.
2.3 b)
Radiopharmaceuticals that are bone seeking provide systemic treatment options which
are effective for bringing improvement in the quality of life of patients. Moreover, another
advantage of them is that they decreased the morbidity in those patients who suffer from the
problem of painful skeletal metastases.
Another advantage of radiopharmaceuticals is that owing to their radioactivity external
monitoring can be done through non- invasive method. In this way, the biological processes of
the body are least affected.
As opposed to this, 3- D conformal radiation therapy causes side effects on the body.
These include tiredness, sickness and diarrhea. More severe side effects include inflammation of
the lungs.
3.1 a)
Three different radiations emitted by radiopharmaceuticals are:
 Alpha
 Beta
 Gamma
3. 1 b)
Alpha particles are positively charged helium nuclei and are characterized by high linear
energy transfer (LET). These radiations cause damage at the cellular level in the form of
breakage in DNA double strands which is irreparable. Often, a single hit by alpha particle has the
capability to induce cell death.
Gamma radiation causes oxidative damage and therefore, it is regarded as a potent
carcinogen. Due to it, a variety of lesions are caused in the DNA which lead to single and double
strand breaks. It also causes oxidized bases, abasic sites and DNA – Protein cross- links.
As compared to alpha particles, gamma particles are less ionizing.
4

3.2 a)
Somatic effects of radiation can be seen when its affects a significant amount of tissue. A
short term does of 200- 300 rads causes injuries which resemble those caused by sun burn. It also
leads to loss of hair. When the dose is above 1000 rads, the somatic affects comprise of nausea,
electrolyte imbalance and upset of gastrointestinal system. A dose of more than 5000 rads leads
to loss of coordination, internal bleeding, pressure in brain and shock in the nervous system.
Long term somatic effects comprise of tumors and cataracts.
Genetic effects of radiation are those that are that are inherited by the descendants of a
parent in whom the DNA has been modified due to exposure to radiation. Exposure of a pregnant
woman to radiation may lead to mental retardation as well as other serious conditions. this is
because the tissues in the fetus are developing and are vulnerable to these radiations.
Furthermore, radiation causes manage in the DNA. When his damage is caused in the male or
female reproductive cells (germ cells), it is likely to be transmitted to the next generation.
3.3 a)
Absorbed dose is defined as the amount of energy that is deposited in matter by ionizing
radiation per unit per mass.
3.3 b)
D = E
If E = .01 j
m = .31 Kg
absorbed dose, D= .032 Gy
3.3 c)
An effective dose is one which is used for the assessment of potential for long term effects that
might have an occurrence in the future.
3.3 d)
Effective Dose (mSv) = Absorbed dose (Gy) X Quality Factor (QF)
5
m

If absorbed dose = .032 Gy and quality factor = 20,
Effective dose = .64
3.3 e)
Relative biological effect is defined as the ratio of the doses with the help of which same level of
effect can be obtained by two radiations.
3.3 f)
RBE = Dx/Dr
If Dx = 1.5 Gy and Dr = 4.8 Gy
Then,
RBE = .003
6