RTT – RADIATION THERAPY TECHNOLOGIST | EXAM QUESTIONS
AND CORRECT ANSWERS | VERIFIED RADIATION THERAPY
CERTIFICATION
RTT - Radiation Therapy Technologist
1. Who discovered X-rays and when? — Wilhelm Conrad Roentgen,
November 1895.
2. Who discovered natural radioactivity? — Henri Becquerel, 1896
(uranium salts).
3. Who discovered radium and polonium? — Marie and Pierre Curie, 1898.
4. Who won the first Nobel Prize in Physics? — Roentgen (1901).
5. Speed of light? — ~3 × 10⁸ m/s.
6. Electron rest-mass energy? — 0.511 MeV.
7. Elementary charge? — 1.602 × 10⁻¹⁹ C.
8. Atomic number (Z)? — Number of protons in the nucleus.
9. Mass number (A)? — Protons + neutrons.
10.Isotopes? — Same Z, different A.
11.Isobars? — Same A, different Z.
12.Isotones? — Same neutron number, different Z.
13.Nuclear isomers? — Same Z and A, different energy states (e.g., Tc-99m).
14.Force that binds the nucleus? — Strong nuclear force.
,15.Mass–energy equivalence equation? — E = mc².
16.Photon energy formula? — E = hf = hc/λ.
17.1 eV equals? — 1.602 × 10⁻¹⁹ joules.
18.K-shell binding energy of tungsten? — 69.5 keV.
19.Standard anode target material? — Tungsten (Z = 74).
20.Dominant x-ray production process at megavoltage? — Bremsstrahlung
(>95%).
21.Define bremsstrahlung. — "Braking radiation" emitted when electrons
decelerate near nuclei.
22.Characteristic radiation? — Discrete-energy photons from outer-shell
electrons filling inner-shell vacancies.
23.Energy needed for tungsten K-characteristic x-rays? — Incident energy >
69.5 keV.
24.Fraction of x-ray tube energy that becomes heat? — ~99%.
25.What does tube current (mA) control? — Photon quantity.
26.What does tube voltage (kVp) control? — Photon quality/penetration
(and quantity).
27.Annihilation radiation? — Two 0.511 MeV photons emitted 180° apart
from positron–electron annihilation.
28.Pair production threshold? — 1.022 MeV; cross-section ∝ Z².
29.Triplet production? — Pair production in an orbital electron's field;
threshold 2.044 MeV.
30.Photoelectric effect dependence? — ∝ Z³/E³; dominant at low energies
and high Z.
31.Compton effect dependence? — Scales with electron density; nearly Z-
independent per gram; dominant in the therapy range.
32.Rayleigh (coherent) scattering? — Elastic low-energy scattering with no
energy deposition.
33.Photodisintegration threshold? — ~8–10 MeV; produces neutrons
(shielding concern above 10 MV).
, 34.Interaction responsible for diagnostic image contrast? — Photoelectric
effect.
35.Dominant interaction in therapeutic radiotherapy? — Compton (Co-60
to ~25 MV).
36.Define half-life. — Time for half the radioactive atoms to decay.
37.Activity units? — Becquerel (s⁻¹); 1 Ci = 3.7 × 10¹⁰ Bq.
38.Mean (average) life? — 1.44 × half-life.
39.Effective half-life? — 1/T_eff = 1/T_physical + 1/T_biological.
40.Electron capture? — Nucleus captures an orbital electron; proton
converts to neutron (competes with β⁺ decay).
Section 2: Equipment & Beam Physics (41–75)
41.Main linac components? — Electron gun, RF accelerating waveguide,
bending magnet, treatment head (target, flattening filter, monitor
chamber, collimators).
42.How does a linac accelerate electrons? — High-frequency RF waves
(~2856 MHz, S-band) in the accelerating waveguide.
43.Role of the bending magnet? — Turns the beam (270° achromatic
design) into the treatment head and focuses/selects energies.
44.Purpose of the flattening filter? — Makes photon fluence uniform across
the field.
45.Electron-mode component replacing target/flattening filter? — Double
scattering foils.
46.Monitor chamber function? — Transmission ionization chamber
measuring dose (MU) and dose rate with redundant channels.
47.Standard MU calibration convention? — 1 MU ≈ 1 cGy at Dmax for a 10 ×
10 cm² field at SSD 100 cm.
48.Typical clinical dose rates? — 100–600 MU/min; FFF modes up to ~2400
MU/min.
AND CORRECT ANSWERS | VERIFIED RADIATION THERAPY
CERTIFICATION
RTT - Radiation Therapy Technologist
1. Who discovered X-rays and when? — Wilhelm Conrad Roentgen,
November 1895.
2. Who discovered natural radioactivity? — Henri Becquerel, 1896
(uranium salts).
3. Who discovered radium and polonium? — Marie and Pierre Curie, 1898.
4. Who won the first Nobel Prize in Physics? — Roentgen (1901).
5. Speed of light? — ~3 × 10⁸ m/s.
6. Electron rest-mass energy? — 0.511 MeV.
7. Elementary charge? — 1.602 × 10⁻¹⁹ C.
8. Atomic number (Z)? — Number of protons in the nucleus.
9. Mass number (A)? — Protons + neutrons.
10.Isotopes? — Same Z, different A.
11.Isobars? — Same A, different Z.
12.Isotones? — Same neutron number, different Z.
13.Nuclear isomers? — Same Z and A, different energy states (e.g., Tc-99m).
14.Force that binds the nucleus? — Strong nuclear force.
,15.Mass–energy equivalence equation? — E = mc².
16.Photon energy formula? — E = hf = hc/λ.
17.1 eV equals? — 1.602 × 10⁻¹⁹ joules.
18.K-shell binding energy of tungsten? — 69.5 keV.
19.Standard anode target material? — Tungsten (Z = 74).
20.Dominant x-ray production process at megavoltage? — Bremsstrahlung
(>95%).
21.Define bremsstrahlung. — "Braking radiation" emitted when electrons
decelerate near nuclei.
22.Characteristic radiation? — Discrete-energy photons from outer-shell
electrons filling inner-shell vacancies.
23.Energy needed for tungsten K-characteristic x-rays? — Incident energy >
69.5 keV.
24.Fraction of x-ray tube energy that becomes heat? — ~99%.
25.What does tube current (mA) control? — Photon quantity.
26.What does tube voltage (kVp) control? — Photon quality/penetration
(and quantity).
27.Annihilation radiation? — Two 0.511 MeV photons emitted 180° apart
from positron–electron annihilation.
28.Pair production threshold? — 1.022 MeV; cross-section ∝ Z².
29.Triplet production? — Pair production in an orbital electron's field;
threshold 2.044 MeV.
30.Photoelectric effect dependence? — ∝ Z³/E³; dominant at low energies
and high Z.
31.Compton effect dependence? — Scales with electron density; nearly Z-
independent per gram; dominant in the therapy range.
32.Rayleigh (coherent) scattering? — Elastic low-energy scattering with no
energy deposition.
33.Photodisintegration threshold? — ~8–10 MeV; produces neutrons
(shielding concern above 10 MV).
, 34.Interaction responsible for diagnostic image contrast? — Photoelectric
effect.
35.Dominant interaction in therapeutic radiotherapy? — Compton (Co-60
to ~25 MV).
36.Define half-life. — Time for half the radioactive atoms to decay.
37.Activity units? — Becquerel (s⁻¹); 1 Ci = 3.7 × 10¹⁰ Bq.
38.Mean (average) life? — 1.44 × half-life.
39.Effective half-life? — 1/T_eff = 1/T_physical + 1/T_biological.
40.Electron capture? — Nucleus captures an orbital electron; proton
converts to neutron (competes with β⁺ decay).
Section 2: Equipment & Beam Physics (41–75)
41.Main linac components? — Electron gun, RF accelerating waveguide,
bending magnet, treatment head (target, flattening filter, monitor
chamber, collimators).
42.How does a linac accelerate electrons? — High-frequency RF waves
(~2856 MHz, S-band) in the accelerating waveguide.
43.Role of the bending magnet? — Turns the beam (270° achromatic
design) into the treatment head and focuses/selects energies.
44.Purpose of the flattening filter? — Makes photon fluence uniform across
the field.
45.Electron-mode component replacing target/flattening filter? — Double
scattering foils.
46.Monitor chamber function? — Transmission ionization chamber
measuring dose (MU) and dose rate with redundant channels.
47.Standard MU calibration convention? — 1 MU ≈ 1 cGy at Dmax for a 10 ×
10 cm² field at SSD 100 cm.
48.Typical clinical dose rates? — 100–600 MU/min; FFF modes up to ~2400
MU/min.
