Dear B.Sc MIT Students, Attached is an essential document featuring comprehensive Questions & Answers for Nuclear medicine 3 marks questions and answers. We encourage you to utilize this resource to deepen your understanding and excel in your studies. Wishing you all the success in your academic endeavors and future careers. Best regards,

1. NUCLEAR MEDICINE IMAGING
B.Sc Medidcal imaging technology – 3rd
year
Three Marks
QUESTIONS AND ANSWER
BY
2021 BATCH
ADHIL.PT
ADHILA.PT
DEREENA JOY
MOHAMMED SHAFI
ASWIN
Guided By
Mr. Yogananthem Dr. Harshavardhan B
B.Sc MIT course coordinator Head of Medical Technology Course

2. PAPER – 11: NUCLEAR MEDICINE IMAGING
Three Marks:
1. Difference between in-vivo and in-vitro dosimetry.
2. Define reactor-based radionuclide.
3. What are the Accelerators based Radionuclide?
4. Define photonuclear activation
5. What are the Equations for Radionuclide production?
6. What is Radionuclide Generators?
7. What are the operation principles for Radionuclide Generators?
8. Name any 4 usages of radiopharmaceuticals
9. What is a Blood Volume study?
10.What is the General concept of Radionuclide?
11.What is in-vivo dosimetry?
12.What is in-vitro dosimetry?
13.Define Radioactivity (UNIT - II)
14.Define Natural radioactivity
15.Define Artificial Radioactivity
16.Define Isotopes
17.Define gamma radiation
18.Define half-life
19.Define half-value layer
20.Define linear attenuation coefficient
21.What is the photoelectric effect?
22.Define Compton-scattering
23.Define pair production
24.What is total attenuation coefficient?
25.What is Rectilinear Scanner? (UNIT - III)
26.What is Anger Camera?
27.What is Pin hole collimator?
28.What are the Limitations of the Detector System?
29.What is the Principles of PET? (UNIT - IV)
30.Define Data Acquisition for PET

3. 31.What is Ionization Chamber?
32.What is Proportional Counter?
33.What is Geiger Muller counter?
34.Define Gas-filled detectors
35.What is a Photo multiplier tube?
36.What is Well counter?
37.Define Voltage amplifier
38.What is a liquid scintillation detector?
39.What are the Biological effects of Radiation? (UNIT - V)
40.Define somatic effects of radiation
41.Define hereditary effects of radiation
42.What are the effects of radiation on the embryo?
43.What are the maximum permissible dose levels?
44.What is absorbed dose?
45.Define the calculation of absorbed dose.
46.Define absorbed dose from diagnostic nuclear medicine procedures.
47.Define absorbed dose from therapeutic nuclear medicine procedures.
48.Define personnel monitoring devices.
49.What are the instruments used in radiation survey?
50.What are the instruments used in radiation monitoring?
Six Marks:
1. Write a short note on Unsealed Sources. (UNIT - I)
2. What is the Reactor-based Radionuclide and Accelerators based Radionuclide?
3. What are the Radionuclide Generators and their operation principles?
4. Write a short note on the production of Radionuclide used in Nuclear
Medicine.
5. Write a short note on Reactor-based Radionuclide and Accelerators based
Radionuclide.
6. Write a short note on various usages of radiopharmaceuticals.
7. Write a short note on Thyroid Uptake Measurements.
8. What are the General concepts of Radionuclide, imaging, and Historical
developments?
9. Write a short note on in-vivo and in-vitro dosimetry.
10.What is Radioactivity? Write a short note on its Discovery. (UNIT - II)

4. 11.What are the mechanisms of radioactive decay?
12.Write a short note on Radiation intensity & exposure.
13.Write a short note on the photoelectric effect and Compton-scattering.
14.Write a short note on gamma radiation.
15.Write a short note on Rectilinear Scanner and its operational principles. (UNIT
– III)
16.What are the Basic Principles and Design of the Scintillation Camera?
17.Write a short note on Different types of Collimators.
18.Write a short note on Image Display and Recording Systems in Radionuclide
Imaging.
19.Write a short note on Instrumentation of PET (UNIT - IV)
20.Write a short note on Construction and Principles of Proportional Counter.
21.Write a short note on Construction and Principles of Geiger Muller counter.
22.Write a short note on Voltage calibration of a Geiger Muller tube.
23.Write a short note on Construction and Principles of Photo multiplier tube.
24.Write a short note on Biological effects of Radiation (UNIT - V)
25.Write a short note on the induction of Radiation injury.
26.Write a short note on somatic and hereditary effects of radiation.
27.Write a short note on normal and abnormal human exposure to radiation.
28.Write a short note on absorbed dose and calculation of absorbed dose.
29.Write a short note on absorbed dose from diagnostic & therapeutic nuclear
medicine procedures.
30.Write a short note on instruments used in radiation survey and monitoring.
Ten Marks:
1. Describe the Positron Emission Tomography (PET) scan.
2. Briefly discuss the semiconductor detector.
3. Describe the liquid scintillation detector.
4. Write about instruments used in radiation survey and monitoring.

5. Answers
1. Difference between in-vivo and in-vitro dosimetry.
In-vivo Dosimetry in Nuclear Medicine:
 Definition: Measures radiation dose directly within living tissue or organs
during procedures.
 Application: Essential for estimating actual radiation exposure during
diagnostic or therapeutic nuclear medicine treatments.
 Instrumentation: Uses detectors like TLDs, diode detectors, or implantable
devices for real-time or near-real-time data.
 Purpose: Optimizes treatment plans, ensuring accurate therapeutic doses
while minimizing impact on healthy tissues.
In-vitro Dosimetry in Nuclear Medicine:
 Definition: Measures radiation dose outside living organisms, often in a
controlled laboratory setting.
 Application: Primarily used for research or studying properties of radioactive
materials before clinical use.
 Instrumentation: Utilizes standard detectors (ionization chambers,
scintillation detectors).
 Purpose: Aids in understanding radionuclide characteristics, decay properties,
and interactions with different materials, contributing to radiopharmaceutical
development.

6. 2.What is radionuclide
A radionuclide, also known as a radioactive nuclide, is an atom with an
unstable nucleus that undergoes radioactive decay. This decay process
involves the release of radiation in the form of alpha particles, beta particles,
and gamma rays. The transformation of a radionuclide's nucleus results in
the conversion of the unstable atom into a different element.
Examples: Common examples of radionuclides include technetium-99m
(used in medical imaging), iodine-131 (used in nuclear medicine and cancer
treatments), and uranium-235 (used in nuclear power plants).
3. What are the Accelerators based Radionuclide?
Accelerators can be used to produce radionuclides through the process of
nuclear reactions. In this context, a radionuclide is an atom with an unstable
nucleus that undergoes radioactive decay, emitting radiation. Accelerators
are devices that accelerate charged particles, such as protons or deuterons,
to high energies, and these particles are then used to induce nuclear
reactions. Some common accelerators and the radionuclides they can
produce include:

7.  Cyclotrons:
Fluorine-18 (^18F) and Carbon-11 (^11C)
 Linear Accelerators (Linacs):
Technetium-99m (^99mTc) and Iodine-123 (^123I)
 Van de Graaff Accelerators:
Carbon-14 (^14C) and Phosphorus-32 (^32P)
 Synchrotrons:
Copper-64
4 Define photonuclear activation
Photonuclear activation refers to the process by which a stable nucleus is
transformed into a radioactive one through the absorption of a high-
energy photon. This photon-induced nuclear reaction typically occurs when
a nucleus absorbs a gamma-ray photon with sufficient energy to overcome
the nuclear binding forces, leading to the ejection of a particle (usually a
neutron or a proton) and the creation of a radioactive isotope.
The basic reaction can be represented as follows:

8. where:
 γ represents a gamma-ray photon,
 A is the target nucleus (usually a stable isotope),
 X is the emitted particle (neutron or proton), and
 B is the resulting radioactive isotope.
5.what is the difference between stable and unstable nucleus
Stable Nucleus:
 Does not undergo spontaneous radioactive decay.
 Balanced forces within the nucleus maintain stability.
 Balanced ratio of protons and neutrons.
 Examples include carbon-12 (^12C) and iron-56 (^56Fe).
Unstable Nucleus:
 Undergoes spontaneous radioactive decay.
 Imbalance of protons and neutrons or energetically unfavorable state leads
to instability.
 Emits radiation (alpha particles, beta particles, gamma rays) to achieve a
more stable state.

9. 6. What is Radionuclide Generators
Radionuclide generators are devices used in nuclear medicine to produce
short-lived radioactive isotopes. They convert a long-lived parent isotope
decaying into a shorter-lived daughter isotope, which is used for medical
imaging or therapy. An example is the technetium-99m generator, which
uses molybdenum-99 decaying into technetium-99m, widely used in
medical imaging. These generators offer convenience, cost-effectiveness,
and reduced radiation exposure compared to traditional methods of
isotope production.

10. 7. What are the operation principles for Radionuclide Generators
Radionuclide generators work by loading a parent radionuclide into a
container. As it decays, it produces a daughter radionuclide, which is
separated and collected for use. This establishes equilibrium, ensuring a
continuous or on-demand supply. The daughter radionuclide is extracted
through an elution process, and quality control is crucial to ensure purity
and safety.
 Parent-Child Relationship: Radionuclide generators have a parent and
daughter radionuclide. The parent decays to produce the daughter.
 Parent Loading: The parent radionuclide is loaded into the generator.
 Separation Mechanism: The daughter radionuclide is selectively separated
from the parent using chemical or physical means.
 Continuous Decay and Collection: As the parent decays, the daughter is
continuously produced and collected.
 Equilibrium Establishment: A dynamic equilibrium is established between
parent and daughter, ensuring a steady production rate.
 Elution Process: The daughter radionuclide is extracted from the generator
using an eluent solution.
 Quality Control and Monitoring: Regular checks are done to ensure purity
and functionality of the generator.
8. Name any 4 usages of radiopharmaceuticals
Four uses of radiopharmaceuticals:
 Diagnostic Imaging: For visualizing and diagnosing medical conditions.
 Therapeutic Treatments: Targeted radiation therapy for cancer.
 Functional Studies: Assessing organ and tissue function.
 Research and Development: Supporting biomedical research and drug
development.

11. 9.What is a Blood Volume study?
A Blood Volume study, also known as a Red Blood Cell (RBC) Volume study
or an Erythrocyte Volume study, is a nuclear medicine procedure aimed at
measuring the volume of blood within the circulatory system. It involves
injecting a radiopharmaceutical tracer into the bloodstream and then using
gamma cameras or other imaging techniques to monitor the movement of
the tracer within the blood vessels. By analyzing the distribution of the
tracer over time, healthcare providers can assess parameters such as blood
volume, blood flow, and cardiac output. This study is particularly useful in
evaluating conditions such as heart failure, hypovolemia (low blood
volume), and certain types of anemia.
10. What is the General concept of Radionuclide
Radionuclides:
Definition: Atoms with unstable nuclei that emit radiation.
 Radioactive Decay: Spontaneous transformation into stable forms,
releasing radiation.
 Half-Life: Characteristic time for half of a sample to decay.
 Applications: Used in medicine, industry, research, and energy.
 Safety Considerations: Require careful handling and disposal to
minimize risks.

12. 11.What is in-vivo dosimetry in nuclear medicine ?
In nuclear medicine, in-vivo dosimetry refers to the measurement and
assessment of the radiation dose received by a patient's organs or tissues
during a diagnostic or therapeutic nuclear medicine procedure. These
procedures typically involve the administration of a radiopharmaceutical, a
radioactive substance that emits gamma rays or other forms of radiation.
In-vivo dosimetry utilizes various techniques, including:
Thermoluminescent Dosimeters (TLDs): Small detectors placed on the
patient's body to measure absorbed radiation, providing dose information
after treatment.
 b.Diode Detectors: Semiconductor devices offering real-time radiation
dose measurement during treatment often placed on or inside the
body.
 c.Metal-oxide-semiconductor field-effect transistor (MOSFET)
Dosimeters: Small electronic devices for real-time dose measurement,
useful in complex treatments.
 d.Radiochromic film: Films changing color upon radiation exposure,
placed on the skin or within the body to visualize dose distribution.
Techniques used for in-vivo dosimetry in nuclear medicine may
include
 External Radiation Detection: Using external radiation detectors,
such as thermoluminescent dosimeters (TLDs) or semiconductor
detectors, to measure radiation exposure at specific points on the
patient's body during or after the procedure.

13.  B.Internal Dosimetry: Calculating the radiation dose received by
internal organs or tissues based on the distribution of the radioactive
tracer or therapeutic agent within the body. This may involve imaging
techniques such as single-photon emission computed tomography
(SPECT) or positron emission tomography (PET), combined with
mathematical modeling to estimate organ doses.
 C.Patient-Specific Dosimetry: Tailoring the radiation dose to
individual patients based on factors such as body size, anatomy, and
clearance rates of the radioactive material. This ensures that each
patient receives an appropriate dose for their specific condition while
minimizing the risk of adverse effects.
In nuclear medicine, in-vivo dosimetry helps ensure the safety and
effectiveness of diagnostic and therapeutic procedures by monitoring
radiation exposure to patients and optimizing dose delivery. It allows
healthcare providers to adjust treatment protocols as needed to achieve
the desired diagnostic or therapeutic outcomes while minimizing radiation
risks.
12. What is in-vitro dosimetry?
In-vitro dosimetry involves measuring the radiation dose received by
biological samples or cells outside of a living organism, typically in a
laboratory setting. This method allows researchers to study the effects of
radiation on biological systems without involving humans or animals
directly. in-vitro dosimetry is a valuable tool for understanding the
biological effects of radiation exposure, assessing radiation safety, and
evaluating the efficacy of radiation-based treatments in a controlled
laboratory environment.

14. 13. Define Radioactivity
Radioactivity is the spontaneous emission of radiation, such as alpha
particles, beta particles, or gamma rays, from the nucleus of an unstable
atom. This emission occurs as the unstable nucleus undergoes radioactive
decay in an effort to achieve a more stable configuration. The process of
radioactive decay can result in the transformation of one element into
another, known as transmutation, as well as the release of energy in the
form of radiation.
14 Define Natural radioactivity.
Definition: Natural radioactivity is when certain elements found in nature
have unstable atomic nuclei and release energy in the form of radiation
spontaneously.
Examples of Naturally Radioactive Elements:
Uranium: Found in soil, rocks, and minerals like pitchblende.
Thorium: Present in rocks and minerals, often associated with uranium
deposits.
Potassium-40: A naturally occurring isotope found in bananas, potatoes,
and other foods.
15. Define Artificial Radioactivity
Artificial radioactivity is when humans create radioactive isotopes by
bombarding stable atoms with particles like protons or neutrons. This
process happens in places like laboratories or nuclear reactors.
Examples:
 Creating radioactive materials for medical treatments.
 Using radioactive isotopes in scientific experiments.
 Industrial applications like testing materials.
 Safety is crucial because these radioactive materials can be harmful if
not handled properly.

15.  Technetium-99m: Used in medical tests like bone scans and heart
scans.
 Iodine-131: Used to treat thyroid conditions and some types of
thyroid cancer.
 Cobalt-60: Used for radiation therapy to treat cancer.
 Fluorine-18: Used in PET scans to diagnose diseases like cancer and
heart conditions.
These isotopes are made in labs or nuclear reactors and have important
uses in medicine and other fields.
16.Explain isotope
An isotope is a variant of a chemical element that differs in the number of
neutrons within its nucleus while retaining the same number of protons.
This variation in neutron number results in isotopes having different atomic
masses but similar chemical properties.
In simple terms, isotopes have the same atomic number but different
atomic masses of the same element.
Hydrogen:
 Protium (¹H): 1 proton, 0 neutrons
 Deuterium (²H or D): 1 proton, 1 neutron
 Tritium (³H or T): 1 proton, 2 neutrons (radioactive)

16. Carbon:
 Carbon-12 (¹²C): 6 protons, 6 neutrons (stable)
 Carbon-13 (¹³C): 6 protons, 7 neutrons (stable)
 Carbon-14 (¹⁴C): 6 protons, 8 neutrons (radioactive)
16. Define gamma radiation
 Gamma rays are a type of electromagnetic radiation with extremely short
wavelengths and high frequencies.
 Gamma rays are produced through radioactive decay and nuclear reactions.
 Due to their exceptionally high energy, gamma rays can easily penetrate
dense materials such as metals and living tissue.
 This penetrating capability makes gamma rays highly valuable for various
practical applications in different fields.
 Examples of these applications include medical imaging, radiation therapy,
materials testing, quality control, sterilization, and astronomical
observations.

17. 17. Define half-life
The half-life of a radioactive substance is the time it takes for half of it to
decay or break down into another substance. For example, if you have a
radioactive material with a half-life of 1 hour, after 1 hour, half of it will have
changed into another substance. After another hour, half of what's left will
change, and so on.
19. Define half-value layer
The half-value layer (HVL) is a measure of the thickness of a material needed to
reduce the intensity of a beam of radiation, such as X-rays or gamma rays, by
half. It is typically expressed in units of length, such as millimeters or centimeters.
It represents the amount of shielding material required to halve the radiation
intensity. HVL is an important concept in radiology and radiation protection, as it
helps quantify the effectiveness of various shielding materials in reducing
radiation exposure.

18. 20. Define linear attenuation coefficient
The linear attenuation coefficient (μ) is a measure of how strongly a material
absorbs or scatters radiation as it passes through. It's calculated as the natural
logarithm of the ratio of the initial radiation intensity (I₀) to the intensity after
passing through a certain thickness (x) of the material, divided by that
thickness:
Here:
μis the linear attenuation coefficient (typically in units of cm⁻¹),
I0 is the initial radiation intensity,
I is the radiation intensity after passing through the material, and
x is the thickness of the material.
This coefficient helps in understanding how much radiation a material can
block or weaken, which is crucial in fields like radiation protection, medical
imaging, and industrial safety.

19. 21.What is the photoelectric effect?
The photoelectric effect refers to the emission of electrons from a material
when it's exposed to light. This phenomenon occurs when photons of
sufficient energy strike the material's surface, transferring their energy to
electrons and allowing them to break free from their atomic bonds. Key
points include the instantaneous nature of electron emission upon photon
absorption and the dependence of electron emission on the frequency (or
energy) of incident light, rather than its intensity. The photoelectric effect
has widespread applications in fields such as photovoltaics, photon
detection, and spectroscopy.
When light hits metals like cesium or potassium, it knocks out electrons,
creating an electric current. This helps in devices like photodiodes to sense
light and in solar panels to generate electricity from sunlight.

20. 22. Define Compton-scattering
Compton scattering occurs when a photon collides with a charged particle,
usually an electron. During this interaction, the photon transfers some of its
energy and momentum to the electron, causing the photon to lose energy
and scatter at a different angle. This process is significant in understanding
the behavior of X-rays and gamma rays, as it provides valuable information
about the properties of the scattering material, such as its atomic structure
and electron density. The Compton effect in X-ray imaging reveals internal
structures by analyzing how X-rays scatter off atoms in an object. By
measuring scattered X-rays, detailed images are created, helping detect
abnormalities like fractures or tumors.

21. Detailed comparison between stable and unstable atoms in tabular format:
Characteristic Stable Atom Unstable Atom
Nuclear
Composition
Contains a balanced ratio of protons
and neutrons, with the number of
protons equal to the number of
electrons, maintaining overall electrical
neutrality.
Exhibits an imbalance in the ratio of protons
and neutrons, often with excess energy. The
nucleus may contain an excess of protons or
neutrons, leading to instability.
Radioactivity
Typically not radioactive, as the nucleus
is held together by strong nuclear
forces, preventing decay.
Frequently radioactive, as the imbalance in
the nucleus leads to the emission of
particles or energy in order to achieve
stability.
Half-Life
Generally, stable atoms have long half-
lives, with some isotopes having half-
lives longer than the age of the
universe.
Unstable atoms have relatively short half-
lives, ranging from fractions of a second to
billions of years, depending on the degree
of instability.
Energy Level
Electrons occupy stable, low-energy
orbitals around the nucleus according
to the Aufbau principle.
Electrons may occupy higher energy orbitals
due to the presence of excess energy,
leading to more reactive behavior.
Chemical
Reactivity
Stable atoms exhibit predictable
chemical behavior, forming bonds with
other atoms to achieve a stable
electron configuration.
Unstable atoms may exhibit heightened
chemical reactivity, especially if they are
undergoing radioactive decay, leading to the
formation of new compounds or elements.
Common
Examples Carbon-12, Oxygen-16, Neon-20 Uranium-235, Carbon-14, Radon-222
Stability
Factors
Stable isotopes typically have an equal
or nearly equal number of protons and
neutrons, residing close to the line of
stability on the chart of nuclides.
Unstable isotopes often have an excess of
protons or neutrons, leading them to lie far
from the line of stability and undergo
radioactive decay to achieve a more stable
configuration.
Applications
Stable isotopes are used in various
applications such as medical imaging,
dating archaeological artifacts, and
studying chemical reactions.
Unstable isotopes are used in nuclear power
generation, radiometric dating, and medical
treatments like cancer therapy and
diagnostics.

22. 23. Define pair production
In pair production:
 A high-energy photon approaches a nucleus or an electric field.
 The photon disappears, converting its energy into mass.
 This mass is then used to create a particle-antiparticle pair, such as an
electron and a positron.
 The pair of particles created moves away from each other, typically with
high energy due to the momentum conservation principle.
 It has practical applications in areas such as medical imaging (e.g., positron
emission tomography, PET scans) and radiation therapy.

23. 24. What is total attenuation coefficient?
The total attenuation coefficient takes into account all mechanisms by which
radiation can be attenuated as it passes through a material. These mechanisms
may include:
1. Photoelectric Effect: Where photons are absorbed by atoms in the material,
resulting in the ejection of electrons.
2. Compton Scattering: Where photons lose energy and change direction after
colliding with electrons in the material.
3. Pair Production: Where high-energy photons can convert into particle-
antiparticle pairs in the presence of a nucleus.
Mathematically, the total attenuation coefficient (μ) can be expressed as the
sum of the individual attenuation coefficients for each process:

24. 25. What is Rectilinear Scanner?
 The rectilinear scanner is a device used in nuclear medicine imaging.
 It detects gamma rays emitted by radiopharmaceuticals administered to
patients.
 Gamma rays come from specific organs or tissues depending on the medicine
and medical condition.
 Unlike other scanners, rectilinear scanners have stationary detectors.
 These detectors move in a straight line over the patient's body.
 A collimator is used to focus gamma rays onto the detectors, improving image
quality.
 Data on gamma ray intensity and distribution is collected as detectors move
along the body.
 A computer processes this data to generate images showing medicine
distribution.

26. 26. What is Anger Camera?
Gamma cameras (also called scintillation cameras or Anger cameras) are the predominant nuclear
medicine imaging machine currently in use.
The Anger camera, named after its inventor Hal Anger, is a vital component in single-photon
emission computed tomography (SPECT) imaging, a technique used in nuclear medicine. Here are
some key points about the Anger camera:
 Function: Detects gamma rays emitted by radiopharmaceuticals in the body.
 Components: Includes a scintillation crystal (NaI or CsI) converting gamma rays into
visible light.
 Detection Mechanism: Uses photomultiplier tubes (PMTs) behind the crystal to detect
light photons.
 Image Reconstruction: Computer systems process PMT signals to reconstruct images
of radiopharmaceutical distribution.
 Clinical Importance: Crucial for diagnosing cancer, heart disease, and neurological
disorders by visualizing functional processes.

27. 27. What is Pin hole collimator?
A pinhole collimator is a type of collimator used in nuclear medicine imaging techniques
such as single-photon emission computed tomography (SPECT) and pinhole nuclear
scintigraphy. Its purpose is to limit the directionality of gamma rays emitted from a
radiopharmaceutical tracer and to focus them onto a gamma camera or detector.
Here's how a pinhole collimator works and its key features:
Collimation: A collimator directs radiation in specific directions. In a pinhole collimator, a
small aperture restricts gamma rays to a narrow beam.
Pinhole Design: The pinhole, usually made of dense materials like tungsten, is tiny,
enabling high-resolution imaging.
Focusing: Placed between the patient and the gamma camera, the pinhole collimator
allows only gamma rays from the region of interest to pass through due to its small size.
Spatial Resolution: Pinhole collimators offer excellent spatial resolution by narrowing
gamma ray paths, resulting in sharper images with detailed anatomical structures.
Magnification: Adjusting the distance between the pinhole collimator and the detector
controls image magnification, facilitating close examination of specific body areas.
Applications: Pinhole collimators excel in imaging small organs or structures like the
thyroid, joints, or tumors, and are useful in dynamic studies such as cardiac function or
joint movements.

28. 28.What are the Limitations of the Detector System in nuclear medicine
The detector system in nuclear medicine plays a crucial role in capturing and converting
emitted radiation from radiopharmaceuticals into images that can be interpreted by
healthcare professionals. However, like any technology, detector systems have their
limitations. Some of the common limitations include:
1. Spatial Resolution: Detectors struggle to precisely locate radiation sources,
affecting the clarity of images and making it harder to identify small
abnormalities.
2. Sensitivity: Despite their sensitivity to radiation, detectors may struggle to
detect faint signals, particularly in areas with low tracer uptake or deep within
the body.
3. Quantitative Accuracy: Detector measurements of tracer uptake may be
inaccurate due to factors like scattering, leading to potential errors in image
interpretation.
4. Artifacts: Detector systems can introduce unintended distortions in images
due to factors like patient movement or equipment malfunctions,
compromising diagnostic reliability.
5. Limited Anatomical Information: Nuclear medicine images offer functional
insights but lack detailed anatomical information, making it challenging to
precisely locate abnormalities or assess their relationship to surrounding
structures.
6. Radiation Exposure: Detectors expose patients and healthcare workers to
ionizing radiation, which poses risks with repeated or high-dose imaging
procedures.
7. Cost and Accessibility: High-resolution detector systems are expensive to
acquire and maintain, limiting their availability and potentially impacting
patient access to nuclear medicine imaging services.

29. 29.What is the Principles of PET (CT SCAN)
PET (Positron Emission Tomography) is a nuclear medicine imaging technique that
utilizes positron-emitting radiopharmaceuticals to visualize and quantify physiological
processes within the body. The principles of PET revolve around the detection of
positron-emitting radionuclides and the reconstruction of images based on the detected
signals. Here are the key principles of PET
1. Positron-Emitting Radionuclides: PET utilizes positron-emitting radiopharmaceuticals,
like , fluorodeoxyglucose (FDG) which emit positrons upon decay.
2. Positron Annihilation: Positrons emitted travel within tissue, annihilating upon
encountering electrons, emitting two gamma photons at 180 degrees apart, with energy
of 511 keV each.
3. Detection of Gamma Photons: PET scanners have rings of detectors composed of
scintillation crystals and PMTs. When gamma photons interact with crystals, they
produce light flashes detected by PMTs.
4. Coincidence Detection: PET scanners detect gamma photons emitted in coincidence by
detectors on opposite sides of the patient, localizing origin along the line of response
(LOR).
5. Image Reconstruction: Detected coincidence events are used to reconstruct images of
radiopharmaceutical distribution using algorithms like filtered back projection or OSEM.
6. Quantification and Analysis: PET images offer quantitative data on
radiopharmaceutical distribution, aiding in diagnosis and treatment monitoring through
SUVs or kinetic parameter analysis.

30. Aspect CT PET PET/CT
Imaging
Principle
Utilizes X-rays to produce
detailed cross-sectional images
of the body based on tissue
attenuation properties.
Relies on positron-emitting
radiopharmaceuticals to visualize
metabolic activity within tissues.
Integrates both CT and PET modalities
to provide anatomical and functional
information simultaneously.
Functional
Information
Provides anatomical information
(e.g., bone, soft tissue, organs)
based on X-ray attenuation.
Provides functional information
about metabolic activity, such as
glucose metabolism, within tissues.
Combines anatomical information
from CT with functional information
from PET for comprehensive
assessment.
Strengths
Excellent anatomical detail and
tissue characterization.
Sensitive to metabolic changes and
can detect abnormalities at the
cellular level.
Provides both anatomical and
functional information, offering
improved diagnostic accuracy and
localization of abnormalities.
Limitations
Limited sensitivity to functional
changes; may miss early
metabolic abnormalities.
Limited spatial resolution; may not
accurately localize abnormalities
without anatomical reference.
Radiation exposure from both CT and
PET components; higher cost
compared to standalone modalities.
Clinical
Applications
Commonly used for screening,
diagnosis, and staging of various
conditions, including trauma,
cancer, and vascular diseases.
Used for oncologic imaging,
staging, restaging, treatment
response assessment, and
localization of epileptic foci.
Widely employed in oncology for
accurate localization of tumors,
assessment of metastasis, and
treatment planning. Also used in
cardiology and neurology.
Image
Interpretation
Focuses on anatomical structures
and tissue characteristics (e.g.,
density, size, morphology).
Evaluates metabolic activity within
tissues, quantified using parameters
like standardized uptake value
(SUV).
Combines anatomical and functional
information for comprehensive
assessment, aiding in accurate
localization and characterization of
abnormalities.

31. 31.What is Ionization Chamber?
Aspect Description
Device
Structure
Consists of a gas-filled chamber.-
Contains two electrodes: an anode (positive) and a cathode (negative).
Functionality
Detects and measures ionizing radiation such as gamma rays or x-rays.
Operates based on the principle of ionization of gas molecules by incoming radiation.
Ionization
Process
Ionizing radiation enters the chamber, interacts with gas molecules.
This interaction leads to the creation of positively charged ions and free electrons.
Electric Field &
Current
An electric field exists between the electrodes. Positively charged ions move towards the
negatively charged cathode, and free electrons move towards the positively charged
anode. This movement generates an electric current proportional to the intensity of the
radiation.
Applications
Used for dosimetry, radiation monitoring, and quality control in nuclear medicine.
Provides accurate measurements of radiation dose. Often utilized alongside imaging
modalities like CT, PET, and SPECT to ensure safe radiation exposure levels for patients
and medical personnel.
Safety and
Monitoring
Essential for maintaining safe radiation levels in medical facilities. Helps in monitoring
radiation exposure for patients and medical staff.
Ensures compliance with safety regulations and standards in nuclear medicine practices.

32. 32. What is Proportional Counter?

33. Aspect Description
Structure
- Consists of a gas-filled chamber with a central anode wire surrounded by a cathode.
- Typically filled with a noble gas like argon, helium, or xenon.
Functionality
- Detects ionizing radiation such as alpha particles, beta particles, and gamma rays.
- Operates based on the proportional relationship between the number of ion pairs
produced in the gas and the energy deposited by radiation.
Principle of
Operation
- Radiation ionizes gas molecules, producing positively charged ions and free electrons.
- Electric field between anode and cathode causes ions and electrons to move towards
electrodes.
- High voltage applied to anode wire accelerates electrons, creating additional ion pairs
upon collision with gas molecules.
- Resulting avalanche of ions produces detectable electrical pulse at anode wire.
Proportional
Region
- Number of electron-ion pairs produced is directly proportional to energy of incident
radiation.
- Enables energy discrimination and determination of incoming radiation energy.
Applications
- Used in nuclear medicine for radiation detection, spectroscopy, and particle counting.
- Particularly useful for detecting low-energy radiation and precise energy
measurements.
Advantages
- High sensitivity to low-energy radiation.
- Excellent energy resolution, enabling accurate energy measurements.
Limitations
- Limited to detecting specific types of radiation (alpha, beta, gamma).
- Saturation effects may occur at high radiation intensities.
- Requires careful calibration and maintenance for accuracy.

34. 33.What is Geiger Muller counter?
Device Type Geiger-Müller counter, commonly known as a Geiger counter
Functionality Detects and measures ionizing radiation
Operating
Principle Ionization of gas molecules within a gas-filled tube
Components
Gas-filled tube, Anode (positively charged), Cathode (negatively
charged)and Detection circuitry
Radiation
Detection
Method
Ionization of gas molecules by incoming radiation creates free
electrons and positively charged ions. These ions are attracted to the
oppositely charged electrodes, producing a detectable pulse of
electrical current.
Signal Output
Audible clicks and/or visual signals (e.g., flashing light) are produced
each time radiation is detected.
Application
Areas
Nuclear medicine, Environmental monitoring, Radiological protection
and Geological surveying

35. 34.Define Gas-filled detectors
Gas-filled detectors in nuclear medicine:
1. Definition: Devices detecting ionizing radiation through ionization of gas
molecules.
2. Gas Used: Typically filled with inert gases like argon or helium at low pressure.
3. Principle: Radiation ionizes gas molecules, creating ion pairs within the gas
volume.
4. Common Type: Geiger-Mueller (GM) counter.
5. Operation: Radiation interacts with gas, producing measurable electrical
pulses.
6. Advantages:
 High sensitivity to alpha, beta, and gamma radiation.
 Wide dynamic range.
 Simple construction.
 Cost-effective.
7. Limitations:
 Limited energy resolution.
 Saturation at high radiation intensities.

36. 35. What is a Photo multiplier tube?
Construction
 Photocathode: Absorbs photons, emitting electrons.
 Dynodes: Amplify electron signal through secondary emission.
 Anode: Collects amplified electrons to generate output signal.
Operation:
 Photons hit photocathode, releasing electrons.
 Electrons accelerated, multiplied by dynodes.
 Amplified electron signal collected at anode for output.
Applications: Used in particle physics, medical imaging, fluorescence spectroscopy.
Advantages:
 High sensitivity.
 Fast response time.
 Wide spectral range capability.

37. 36.What is Well counter?
 A well counter is an instrument used in nuclear medicine and radiopharmaceutical
research.
 It consists of a lead-shielded chamber.
 The chamber contains multiple cylindrical wells or compartments.
 Each well is equipped with a detector.
 It is used to measure the radioactivity of samples placed in the wells.
 Well counters are commonly used in radioimmunoassays and other applications where
radioactive tracers are employed.
 They accurately quantify radioactivity levels in various samples including biological,
pharmaceutical, and environmental samples.
 Well counters are valuable tools in scientific and medical disciplines for research and
analysis purposes.

38. 37.Define Voltage amplifier.
Voltage Amplifier:
 An electronic device utilized in nuclear medicine.
 It is designed to amplify weak electrical signals.
 These signals are generated by radiation detectors.
 Common detectors include photomultiplier tubes or semiconductor
detectors.
 Detectors convert incident gamma rays into electrical pulses.
 Initial pulses are often too weak for effective processing.
 The voltage amplifier increases the strength of these weak signals.
 Amplification enables accurate measurement and analysis.
 Improves sensitivity and signal-to-noise ratio.
 Facilitates precise detection and analysis of radioactive emissions in
nuclear medicine imaging and research applications.

39. 38.What is a liquid scintillation detector?
What it is:
A liquid scintillation detector in nuclear medicine detects and measures radiation. It
comprises a container filled with a special liquid called a "liquid scintillator," typically
made of aromatic hydrocarbons like benzene, toluene, or xylene.
How it works:
 Radiation hitting the liquid scintillator causes it to glow, similar to a firefly.
 Photomultiplier tubes detect this glow emitted by the liquid scintillator.
What it detects:
 Primarily detects beta particles and low-energy gamma rays.
Common uses:
 Utilized in labs for radioimmunoassays and tracking radioactive tracers in the
body.
Why it's useful:
 Enables accurate measurement of small radiation amounts.
 Provides insight into the behavior of radioactive substances.

40. 39. What are the Biological effects of Radiation?
The biological effects of radiation explained simply:
1. Tissue Damage: Radiation can harm our body's cells, causing burns or making us sick.
2. Cancer: Radiation can damage our DNA, which may lead to cancer later on.
3. Genetic Changes: Radiation can cause changes in our genes, which might affect future
generations.
4. Radiation Sickness: Exposure to a lot of radiation can make us feel very sick, with
symptoms like nausea and weakness.
5. Blood Problems: Radiation can hurt our bone marrow, which makes blood cells, leading
to issues like infections or bleeding.
6. Eye Problems: High radiation exposure can cause cataracts, which blur vision.
7. Thyroid Issues: Radiation can affect the thyroid gland, leading to problems like cancer.
8. Long-Term Risks: Being around radiation for a long time might increase the chances of
getting certain cancers.

41. 40.Define somatic effects of radiation
Somatic effects of radiation refer to the health effects that occur in the individual
directly exposed to radiation. These effects primarily affect the person exposed and are
not passed on to future generations. Somatic effects can be acute, happening shortly
after exposure, or chronic, developing over time after exposure. Examples of somatic
effects include tissue damage, radiation sickness, cancer, and other health issues related
to the direct exposure to radiation. These effects can vary depending on factors such as
the type of radiation, the dose received, and the duration of exposure.
41.Define hereditary effects of radiation
Hereditary effects of radiation refer to the genetic changes or abnormalities that can be
passed on to future generations due to exposure to radiation. These effects occur when
radiation damages the DNA in reproductive cells (sperm or eggs), leading to mutations
that can be inherited by offspring. Unlike somatic effects, which affect the individual
directly exposed to radiation, hereditary effects impact future generations. Examples of
hereditary effects include birth defects, genetic disorders, and an increased risk of
certain diseases in the descendants of individuals exposed to radiation.

42. 42. What are the effects of radiation on the embryo?
The effects of radiation on the embryo are
1. Birth Defects: Radiation can cause problems in how the baby's body forms, leading to
birth defects like issues with the brain, heart, limbs, or face.
2. Organ Problems: Radiation can harm the development of organs in the baby, causing
them to form incorrectly or not work properly.
3. Slowed Growth: Radiation exposure might slow down the baby's growth, making them
smaller or causing delays in development.
4. Higher Cancer Risk: Babies exposed to radiation in the womb may have a higher
chance of getting cancer later in life because radiation can damage their cells.
5. Brain and Learning Issues: Radiation can affect the baby's brain development, leading
to problems with learning, behavior, and thinking.
6. Miscarriage or Stillbirth: Very high radiation doses can increase the risk of losing the
baby before birth.
43. What are the maximum permissible dose levels?
The maximum permissible dose is typically expressed in units of sieverts (Sv) or
millisieverts (mSv), which quantify the amount of absorbed radiation dose and its
potential biological effects on human tissues. It's essential to note that the MPD is not a
threshold for harm; instead, it represents a level at which the risk of adverse health
effects is considered acceptable based on available scientific evidence and risk
assessment.

43. 44.What is absorbed dose?
Absorbed dose refers to the amount of energy deposited by ionizing radiation per unit
mass of an absorbing material.
The relationship between exposure in air (measured in roentgens) and the amount of
charge produced (measured in coulombs) can be expressed as:
1 roentgen (R) = 2.58 x 10^-4 coulombs per kilogram (C/kg)
45.Define the calculation of absorbed dose.
The calculation of absorbed dose involves determining the amount of energy deposited
by ionizing radiation per unit mass of an absorbing material. This calculation is
fundamental in radiation dosimetry and is crucial for assessing the potential biological
effects of radiation exposure. Here's the basic formula for calculating absorbed dose:
Where:
 D is the absorbed dose,
 E is the energy deposited by ionizing radiation, and
 m is the mass of the absorbing material.
The absorbed dose D is typically expressed in the unit gray (Gy), where 1 gray is
equivalent to 1 joule of energy deposited per kilogram of mass (J/kg).

44. 46 Define absorbed dose from diagnostic nuclear medicine procedures.
Absorbed dose in diagnostic nuclear medicine procedures is the amount of ionizing
radiation energy absorbed per unit mass of tissue and is typically measured in grays (Gy)
or milligrays (mGy).
Formula: D=E/m
Where:
D is the absorbed dose (in grays, Gy or milligrays, mGy),
E is the energy deposited by ionizing radiation (in joules, J), and
m is the mass of the tissue (in kilograms, kg).
47. Define absorbed dose from therapeutic nuclear medicine procedures.
Absorbed dose in therapeutic nuclear medicine procedures refers to the amount of ionizing radiation
energy absorbed per unit mass of tissue in the human body due to the administration of radioactive
substances for therapeutic purposes. This absorbed dose is typically measured in units of gray (Gy) or
milligray (mGy).
Formula: D=E/m
Where:
D is the absorbed dose (in grays, Gy or milligrays, mGy),
E is the energy deposited by ionizing radiation (in joules, J), and
m is the mass of the tissue (in kilograms, kg).
Several types of equipment are used to detect absorbed dose.
1. Ionization Chambers: Measure electrical charge from radiation in a gas-filled chamber.
2. Thermoluminescent Dosimeters (TLDs): Crystals store radiation energy; heating emits
light proportional to dose.
3. Film Dosimetry: Radiographic films change density when exposed to radiation.
4. Scintillation Detectors: Materials emit light when hit by radiation; light intensity
indicates dose.
5. Semiconductor Detectors: Convert radiation into electrical signals for dose
measurement.
6. Chemical Dosimeters: Solutions or gels undergo chemical changes proportional to
radiation dose.

45. :
Aspect
Diagnostic Nuclear Medicine
Procedures Therapeutic Nuclear Medicine Procedures
Purpose
To diagnose various medical
conditions and diseases. To treat specific medical conditions or diseases.
Radiopharmaceuticals
Typically use low-radioactivity
radiopharmaceuticals. Use high-radioactivity radiopharmaceuticals.
Dosage
Low doses of radiation are
administered. High doses of radiation are administered.
Radiation Energy
Usually involves gamma rays for
imaging purposes. Can involve beta or alpha particles for therapy.
Absorbed Dose
Relatively low absorbed doses are
aimed for imaging. High absorbed doses are delivered for therapy.
Units
Measured in grays (Gy) or
milligrays (mGy). Measured in grays (Gy) or milligrays (mGy).
Methodology - Gamma cameras, PET scanners.
- Radioactive drugs delivered orally or
intravenously. External beam radiation therapy. <
Targeted radionuclide therapy.
Outcome
- Imaging for diagnostic
purposes, providing visual
information.
- Targeted destruction or alteration of specific
tissues or cells to treat the disease.

46. 49. What are the instruments used in radiation survey?
1. Geiger-Müller Counters: Portable devices for general radiation monitoring.
2. Ionization Chambers: Measure radiation by detecting gas ionization.
3. Scintillation Detectors: Detect radiation via light emission in certain
materials.
4. Dosimeters: Personal devices (TLD) to monitor individual radiation exposure.
5. Radiation Survey Meters: Handheld devices for quick radiation level
measurements.
6. Neutron Detectors: Specialized instruments for detecting and measuring
neutron radiation.
7. Environmental Monitoring Systems: Networks of sensors for continuous
radiation level monitoring in the environment.
50. What are the instruments used in radiation monitoring?
In radiation monitoring, various instruments are used to detect, measure, and
monitor radiation levels. Commonly used instruments include:
.Geiger-Müller Counters: Portable devices for general radiation monitoring.
 Ionization Chambers: Measure radiation by detecting gas ionization.
 Scintillation Detectors: Detect radiation via light emission in certain
materials.
 Dosimeters: Personal devices (TLD) to monitor individual radiation exposure.
 Radiation Survey Meters: Handheld devices for quick radiation level
measurements.
 Neutron Detectors: Specialized instruments for detecting and measuring
neutron radiation.
 Environmental Monitoring Systems: Networks of sensors for continuous
radiation level monitoring in the environment.

47. Aspect Radiation Monitoring Radiation Surveying
Purpose
Continuous monitoring of radiation levels over
time.
One-time or periodic assessment of radiation
levels in an area.
Focus Individual or specific locations. Wide-area or specific locations.
Instruments
Used
Dosimeters, continuous monitoring systems,
handheld meters.
Dosimeters, handheld meters, stationary
detectors, environmental monitoring
systems.
Application
Personal exposure monitoring, workplace
safety, environmental monitoring.
Environmental assessments, emergency
response, regulatory compliance.
Time Frame Ongoing and continuous.
Typically performed at specific intervals or as
needed.
Data
Collection Records individual exposure data over time.
Provides snapshot measurements at specific
times or locations.
Responsibility
Individual workers, radiation safety officers,
regulatory agencies.
Radiation safety officers, environmental
health and safety teams, regulatory agencies.
Examples
Personal dosimetry programs, workplace
monitoring systems, environmental radiation
monitoring networks.
Radiation surveys of nuclear facilities,
emergency response assessments,
environmental impact studies.