,Contents
Chapter 1 — Structure of Matter: ......................................................................................................... 3
Chapter 2 — Nuclear Transformations: ............................................................................................. 12
Chapter 3 — Production of X-rays: .................................................................................................... 21
Chapter 4 — Clinical Radiation Generators:..................................................................................... 30
Chapter 5 — Interactions of Ionizing Radiation: .............................................................................. 38
Chapter 6 — Measurement of Ionizing Radiation: ........................................................................... 45
Chapter 7 — Quality of X-ray Beams:................................................................................................ 53
Chapter 8 — Measurement of Absorbed Dose: ................................................................................. 61
Chapter 9 — Dose Distribution and Scatter Analysis: ...................................................................... 68
Chapter 10 — A System of Dosimetric Calculations: ........................................................................ 76
Chapter 11 — Treatment Planning I: Isodose Distributions: ........................................................... 84
Chapter 12 — Treatment Planning II: Patient Data Acquisition, Treatment Verification, and
Inhomogeneity Corrections:................................................................................................................. 92
Chapter 13 — Treatment Planning III: Field Shaping, Skin Dose, and Field Separation: ........... 99
Chapter 14 — Electron Beam Therapy: ........................................................................................... 107
Chapter 15 — Low-Dose-Rate Brachytherapy: ............................................................................... 115
Chapter 16 — Radiation Protection: ................................................................................................ 122
Chapter 17 — Quality Assurance: .................................................................................................... 130
Chapter 18 — Total Body Irradiation: ............................................................................................. 137
Chapter 19 — Three-Dimensional Conformal Radiation Therapy (3D CRT): ............................ 145
Chapter 20 — Intensity-Modulated Radiation Therapy (IMRT): ................................................. 153
Chapter 21 — Stereotactic Radiotherapy and Radiosurgery (SRS): ............................................. 161
Chapter 22 — Stereotactic Body Radiation Therapy (SBRT): ...................................................... 168
Chapter 23 — High-Dose-Rate Brachytherapy: .............................................................................. 176
Chapter 24 — Prostate Implants: Technique, Dosimetry, and Treatment Planning: .................. 184
Chapter 25 — Intravascular Brachytherapy: .................................................................................. 191
Chapter 26 — Image-Guided Radiation Therapy (IGRT): ............................................................ 199
Chapter 27 — Proton Beam Therapy: .............................................................................................. 207
Chapter 28 — Knowledge-Based Treatment Planning: .................................................................. 215
,Chapter 1 — Structure of Matter:
1. A clinical physicist is explaining atomic number and mass number to a new resident
while reviewing diagnostic isotope labels. If an atom has 26 protons and 30 neutrons,
which statement correctly identifies its atomic and mass numbers?
A. Atomic number = 30; Mass number = 26
B. Atomic number = 26; Mass number = 56
C. Atomic number = 56; Mass number = 26
D. Atomic number = 26; Mass number = 30
✅ Correct Answer: B. Atomic number = 26; Mass number = 56
Rationale: Atomic number (Z) equals the number of protons (26). Mass number (A) is
protons + neutrons = 26 + 30 = 56. The atomic number identifies the element; the mass
number distinguishes the isotope.
Keywords: Atomic number, mass number, isotope, protons, neutrons
2. During a TED-style teaching session, you present that the binding energy per nucleon
is a measure of nuclear stability. Which nucleus from the list below would you expect to
have the highest binding energy per nucleon (and thus be most stable)?
A. Deuteron (A = 2)
B. Iron-56 (A = 56)
C. Uranium-238 (A = 238)
D. Helium-3 (A = 3)
✅ Correct Answer: B. Iron-56 (A = 56)
Rationale: Nuclei around iron (A ≈ 56) have the largest binding energy per nucleon and
are the most tightly bound/stable. Light nuclei (A small) and very heavy nuclei (A large)
have lower binding energy per nucleon. This is fundamental to nuclear fission/fusion
energetics.
Keywords: Binding energy per nucleon, nuclear stability, iron peak
3. A radiotherapy dosimetrist reads a data sheet stating an isotope’s half-life is 12 hours.
Which of the following best describes what "half-life" means for that radioactive source?
,A. Time for activity to fall to one-quarter of its original value
B. Time for half the atoms to disintegrate, reducing activity to half the original value
C. Time for the dose rate to double due to decay products
D. Time for the activity to fall to zero
✅ Correct Answer: B. Time for half the atoms to disintegrate, reducing activity to
half the original value
Rationale: Half-life (t½) is defined as the time required for half the radioactive nuclei in
a sample to decay, which halves the activity. After one half-life activity = 0.5 · initial;
after two half-lives = 0.25 · initial.
Keywords: Half-life, radioactive decay, activity
4. A quality manager challenges a trainee: “If an electron in the K-shell has a binding
energy of 80 keV, which photon energy from the options below will definitely produce a
photoelectric absorption in that shell rather than pair production?”
A. 40 keV
B. 80 keV
C. 90 keV
D. 2.0 MeV
✅ Correct Answer: C. 90 keV
Rationale: Photoelectric absorption requires photon energy ≥ binding energy (80 keV) to
eject the bound electron; 90 keV meets that criterion. Pair production requires ≥1.022
MeV (in the vicinity of nucleus), so 90 keV cannot cause pair production. 40 keV is
below binding energy.
Keywords: Photoelectric effect, binding energy, pair production threshold
5. You are asked to compute nuclear binding energy from mass defect in a training
exercise. Given a hypothetical nucleus composed of 2 protons and 2 neutrons with
combined free nucleon mass = 4.031882 u and measured nuclear mass = 4.001506 u,
what is the total binding energy (use 1 u = 931.494 MeV/c²)?
A. ≈ 0.030376 MeV
B. ≈ 28.30 MeV
C. ≈ 3.04 MeV
D. ≈ 931.494 MeV
✅ Correct Answer: B. ≈ 28.30 MeV
,Rationale: Mass defect Δm = 4.031882 − 4.001506 = 0.030376 u. Binding energy = Δm
× 931.494 MeV/u ≈ 0.030376 × 931.494 ≈ 28.30 MeV. This demonstrates conversion of
mass defect to binding energy using E = mc².
Keywords: Mass defect, binding energy, atomic mass unit, E = mc²
6. A clinical physicist explains electron shells to therapists: which statement best
characterizes the relation between binding energy and atomic number (Z) for inner-shell
electrons?
A. Binding energy decreases with increasing Z for inner shells
B. Binding energy is independent of Z for inner shells
C. Binding energy increases roughly as Z² for inner shells (approximate trend)
D. Binding energy is determined only by the number of neutrons
✅ Correct Answer: C. Binding energy increases roughly as Z² for inner shells
(approximate trend)
Rationale: Inner-shell (e.g., K-shell) binding energies scale strongly with nuclear charge;
a simple approximate relation shows binding energy ∝ (Z − shielding)² for hydrogenic
approximations. So higher Z → much larger binding energies. Neutrons do not directly
determine electron binding.
Keywords: Binding energy, atomic number, K-shell, scaling with Z
7. An electronics engineer setting up a detector asks: “Which fundamental particle's
number determines the chemical identity of an atom and therefore affects cross sections
for photon interactions in matter?”
A. Neutrons
B. Protons (atomic number)
C. Electrons only
D. Neutrinos
✅ Correct Answer: B. Protons (atomic number)
Rationale: Chemical identity is set by the number of protons (atomic number, Z). Photon
interaction probabilities (photoelectric effect especially) depend acutely on Z. Neutrons
influence isotopic mass and nuclear properties, but Z governs electron cloud and photon
interaction cross sections.
Keywords: Atomic number, protons, photon interactions, Z dependence
, 8. A trainee must convert an electron binding energy of 0.5 keV to joules for a detector
calibration. Which conversion is correct? (1 eV = 1.602 × 10⁻¹⁹ J)
A. 0.5 keV = 8.01 × 10⁻¹⁶ J
B. 0.5 keV = 8.01 × 10⁻¹⁷ J
C. 0.5 keV = 8.01 × 10⁻²⁰ J
D. 0.5 keV = 3.20 × 10⁻¹⁶ J
✅ Correct Answer: A. 0.5 keV = 8.01 × 10⁻¹⁶ J
Rationale: 0.5 keV = 500 eV. Multiply by 1.602 × 10⁻¹⁹ J/eV: 500 × 1.602e-19 = 8.01e-
17? Wait — recalc: 500 × 1.602e-19 = 8.01e-17 J. Hmm check options: A = 8.01 × 10⁻¹⁶
J, B = 8.01 × 10⁻¹⁷ J. Correct is 8.01 × 10⁻¹⁷ J. (Correction: B is correct.)
✅ Correct Answer (amended): B. 0.5 keV = 8.01 × 10⁻¹⁷ J
Rationale (corrected): 0.5 keV = 500 eV. 500 × 1.602×10⁻¹⁹ J = 8.01×10⁻¹⁷ J. My earlier
crack at the arithmetic misstated the exponent — 8.01×10⁻¹⁷ J is correct. Always check
unit prefixes carefully.
Keywords: eV to joules, unit conversion, calibration
9. In a lecture on electron configuration and radiation interactions, which mechanism
most directly depends on the presence of bound electrons and their binding energies?
A. Pair production
B. Compton scattering
C. Photoelectric effect
D. Neutron capture
✅ Correct Answer: C. Photoelectric effect
Rationale: Photoelectric effect involves the photon being completely absorbed by a
bound electron, which is ejected if photon energy ≥ binding energy. Compton scattering
involves loosely bound or free electrons; pair production involves creation of e⁻/e⁺ and a
nuclear field; neutron capture involves nucleus.
Keywords: Photoelectric effect, bound electrons, binding energy
10. A dosimetry workshop includes a problem: A monochromatic photon beam of 511
keV interacts with tissue. Which interaction becomes energetically possible at this energy
that is impossible at 100 keV?
A. Compton scattering
Chapter 1 — Structure of Matter: ......................................................................................................... 3
Chapter 2 — Nuclear Transformations: ............................................................................................. 12
Chapter 3 — Production of X-rays: .................................................................................................... 21
Chapter 4 — Clinical Radiation Generators:..................................................................................... 30
Chapter 5 — Interactions of Ionizing Radiation: .............................................................................. 38
Chapter 6 — Measurement of Ionizing Radiation: ........................................................................... 45
Chapter 7 — Quality of X-ray Beams:................................................................................................ 53
Chapter 8 — Measurement of Absorbed Dose: ................................................................................. 61
Chapter 9 — Dose Distribution and Scatter Analysis: ...................................................................... 68
Chapter 10 — A System of Dosimetric Calculations: ........................................................................ 76
Chapter 11 — Treatment Planning I: Isodose Distributions: ........................................................... 84
Chapter 12 — Treatment Planning II: Patient Data Acquisition, Treatment Verification, and
Inhomogeneity Corrections:................................................................................................................. 92
Chapter 13 — Treatment Planning III: Field Shaping, Skin Dose, and Field Separation: ........... 99
Chapter 14 — Electron Beam Therapy: ........................................................................................... 107
Chapter 15 — Low-Dose-Rate Brachytherapy: ............................................................................... 115
Chapter 16 — Radiation Protection: ................................................................................................ 122
Chapter 17 — Quality Assurance: .................................................................................................... 130
Chapter 18 — Total Body Irradiation: ............................................................................................. 137
Chapter 19 — Three-Dimensional Conformal Radiation Therapy (3D CRT): ............................ 145
Chapter 20 — Intensity-Modulated Radiation Therapy (IMRT): ................................................. 153
Chapter 21 — Stereotactic Radiotherapy and Radiosurgery (SRS): ............................................. 161
Chapter 22 — Stereotactic Body Radiation Therapy (SBRT): ...................................................... 168
Chapter 23 — High-Dose-Rate Brachytherapy: .............................................................................. 176
Chapter 24 — Prostate Implants: Technique, Dosimetry, and Treatment Planning: .................. 184
Chapter 25 — Intravascular Brachytherapy: .................................................................................. 191
Chapter 26 — Image-Guided Radiation Therapy (IGRT): ............................................................ 199
Chapter 27 — Proton Beam Therapy: .............................................................................................. 207
Chapter 28 — Knowledge-Based Treatment Planning: .................................................................. 215
,Chapter 1 — Structure of Matter:
1. A clinical physicist is explaining atomic number and mass number to a new resident
while reviewing diagnostic isotope labels. If an atom has 26 protons and 30 neutrons,
which statement correctly identifies its atomic and mass numbers?
A. Atomic number = 30; Mass number = 26
B. Atomic number = 26; Mass number = 56
C. Atomic number = 56; Mass number = 26
D. Atomic number = 26; Mass number = 30
✅ Correct Answer: B. Atomic number = 26; Mass number = 56
Rationale: Atomic number (Z) equals the number of protons (26). Mass number (A) is
protons + neutrons = 26 + 30 = 56. The atomic number identifies the element; the mass
number distinguishes the isotope.
Keywords: Atomic number, mass number, isotope, protons, neutrons
2. During a TED-style teaching session, you present that the binding energy per nucleon
is a measure of nuclear stability. Which nucleus from the list below would you expect to
have the highest binding energy per nucleon (and thus be most stable)?
A. Deuteron (A = 2)
B. Iron-56 (A = 56)
C. Uranium-238 (A = 238)
D. Helium-3 (A = 3)
✅ Correct Answer: B. Iron-56 (A = 56)
Rationale: Nuclei around iron (A ≈ 56) have the largest binding energy per nucleon and
are the most tightly bound/stable. Light nuclei (A small) and very heavy nuclei (A large)
have lower binding energy per nucleon. This is fundamental to nuclear fission/fusion
energetics.
Keywords: Binding energy per nucleon, nuclear stability, iron peak
3. A radiotherapy dosimetrist reads a data sheet stating an isotope’s half-life is 12 hours.
Which of the following best describes what "half-life" means for that radioactive source?
,A. Time for activity to fall to one-quarter of its original value
B. Time for half the atoms to disintegrate, reducing activity to half the original value
C. Time for the dose rate to double due to decay products
D. Time for the activity to fall to zero
✅ Correct Answer: B. Time for half the atoms to disintegrate, reducing activity to
half the original value
Rationale: Half-life (t½) is defined as the time required for half the radioactive nuclei in
a sample to decay, which halves the activity. After one half-life activity = 0.5 · initial;
after two half-lives = 0.25 · initial.
Keywords: Half-life, radioactive decay, activity
4. A quality manager challenges a trainee: “If an electron in the K-shell has a binding
energy of 80 keV, which photon energy from the options below will definitely produce a
photoelectric absorption in that shell rather than pair production?”
A. 40 keV
B. 80 keV
C. 90 keV
D. 2.0 MeV
✅ Correct Answer: C. 90 keV
Rationale: Photoelectric absorption requires photon energy ≥ binding energy (80 keV) to
eject the bound electron; 90 keV meets that criterion. Pair production requires ≥1.022
MeV (in the vicinity of nucleus), so 90 keV cannot cause pair production. 40 keV is
below binding energy.
Keywords: Photoelectric effect, binding energy, pair production threshold
5. You are asked to compute nuclear binding energy from mass defect in a training
exercise. Given a hypothetical nucleus composed of 2 protons and 2 neutrons with
combined free nucleon mass = 4.031882 u and measured nuclear mass = 4.001506 u,
what is the total binding energy (use 1 u = 931.494 MeV/c²)?
A. ≈ 0.030376 MeV
B. ≈ 28.30 MeV
C. ≈ 3.04 MeV
D. ≈ 931.494 MeV
✅ Correct Answer: B. ≈ 28.30 MeV
,Rationale: Mass defect Δm = 4.031882 − 4.001506 = 0.030376 u. Binding energy = Δm
× 931.494 MeV/u ≈ 0.030376 × 931.494 ≈ 28.30 MeV. This demonstrates conversion of
mass defect to binding energy using E = mc².
Keywords: Mass defect, binding energy, atomic mass unit, E = mc²
6. A clinical physicist explains electron shells to therapists: which statement best
characterizes the relation between binding energy and atomic number (Z) for inner-shell
electrons?
A. Binding energy decreases with increasing Z for inner shells
B. Binding energy is independent of Z for inner shells
C. Binding energy increases roughly as Z² for inner shells (approximate trend)
D. Binding energy is determined only by the number of neutrons
✅ Correct Answer: C. Binding energy increases roughly as Z² for inner shells
(approximate trend)
Rationale: Inner-shell (e.g., K-shell) binding energies scale strongly with nuclear charge;
a simple approximate relation shows binding energy ∝ (Z − shielding)² for hydrogenic
approximations. So higher Z → much larger binding energies. Neutrons do not directly
determine electron binding.
Keywords: Binding energy, atomic number, K-shell, scaling with Z
7. An electronics engineer setting up a detector asks: “Which fundamental particle's
number determines the chemical identity of an atom and therefore affects cross sections
for photon interactions in matter?”
A. Neutrons
B. Protons (atomic number)
C. Electrons only
D. Neutrinos
✅ Correct Answer: B. Protons (atomic number)
Rationale: Chemical identity is set by the number of protons (atomic number, Z). Photon
interaction probabilities (photoelectric effect especially) depend acutely on Z. Neutrons
influence isotopic mass and nuclear properties, but Z governs electron cloud and photon
interaction cross sections.
Keywords: Atomic number, protons, photon interactions, Z dependence
, 8. A trainee must convert an electron binding energy of 0.5 keV to joules for a detector
calibration. Which conversion is correct? (1 eV = 1.602 × 10⁻¹⁹ J)
A. 0.5 keV = 8.01 × 10⁻¹⁶ J
B. 0.5 keV = 8.01 × 10⁻¹⁷ J
C. 0.5 keV = 8.01 × 10⁻²⁰ J
D. 0.5 keV = 3.20 × 10⁻¹⁶ J
✅ Correct Answer: A. 0.5 keV = 8.01 × 10⁻¹⁶ J
Rationale: 0.5 keV = 500 eV. Multiply by 1.602 × 10⁻¹⁹ J/eV: 500 × 1.602e-19 = 8.01e-
17? Wait — recalc: 500 × 1.602e-19 = 8.01e-17 J. Hmm check options: A = 8.01 × 10⁻¹⁶
J, B = 8.01 × 10⁻¹⁷ J. Correct is 8.01 × 10⁻¹⁷ J. (Correction: B is correct.)
✅ Correct Answer (amended): B. 0.5 keV = 8.01 × 10⁻¹⁷ J
Rationale (corrected): 0.5 keV = 500 eV. 500 × 1.602×10⁻¹⁹ J = 8.01×10⁻¹⁷ J. My earlier
crack at the arithmetic misstated the exponent — 8.01×10⁻¹⁷ J is correct. Always check
unit prefixes carefully.
Keywords: eV to joules, unit conversion, calibration
9. In a lecture on electron configuration and radiation interactions, which mechanism
most directly depends on the presence of bound electrons and their binding energies?
A. Pair production
B. Compton scattering
C. Photoelectric effect
D. Neutron capture
✅ Correct Answer: C. Photoelectric effect
Rationale: Photoelectric effect involves the photon being completely absorbed by a
bound electron, which is ejected if photon energy ≥ binding energy. Compton scattering
involves loosely bound or free electrons; pair production involves creation of e⁻/e⁺ and a
nuclear field; neutron capture involves nucleus.
Keywords: Photoelectric effect, bound electrons, binding energy
10. A dosimetry workshop includes a problem: A monochromatic photon beam of 511
keV interacts with tissue. Which interaction becomes energetically possible at this energy
that is impossible at 100 keV?
A. Compton scattering
