70 Questions
What is the energy range of ionizing photons in the UV range?
Between 10 eV and 33 eV
What is the primary mechanism of direct hit in ionizing radiation?
Breakage of DNA molecules by direct interaction with EM or particulate radiation
What is the time frame for observing short-term effects of ionizing radiation?
Within 3 months of exposure
What is the unit of measurement for radiation exposure in conventional units?
Roentgen
What is the effect of long-term low-dose ionizing radiation on the human eye?
Cataracts
What is the effect of ionizing radiation on the reproductive system?
Mutations to the genes of the reproductive cells
What is the time frame for observing long-term effects of ionizing radiation?
Between 10-15 years after exposure
What is the unit of measurement for radiation dose in SI units?
Coulombs/kg
What is the result of a neutron being converted into a proton, an electron, and an antineutrino in β− decay?
An electron and an antineutrino are emitted
What is the process by which an inner shell electron is drawn into the nucleus and combines with a proton, forming a neutron and a neutrino?
Electron capture
What is the type of radiation that occurs as a result of attenuation of the incident beam to the patient's body?
Scatter radiation
What is the time it takes for the radioactivity of a specified isotope to decay to half its original value?
Half-life
What is the result of an alpha particle emission from an atom of Uranium 238?
The atomic number decreases by 2 and the atomic mass decreases by 4
What is the process by which a proton is converted into a neutron, a positron, and a neutrino?
Positron emission
What is the type of scatter radiation that occurs when an incident photon collides with an atom?
Coherent scatter
What is the fraction of atoms remaining after seven half-lives?
1/128
What is the result of an incident photon colliding with an inner shell orbital electron in photoelectric scatter?
The electron is ejected and an outer orbital electron moves to the inner orbit, emitting a new photon.
What is the energy range of X-rays in electron volts?
100eV – 100KeV
What is the unit of energy used to measure the penetrating abilities of ionizing radiation?
Electron volts (eV)
What is the result of an incident photon colliding with an outer orbital electron in Compton scatter?
The electron is ejected and the photon is deflected from its original path with decreased energy.
What is the difference between ionizing and non-ionizing radiation?
Ionizing radiation has a higher energy, while non-ionizing radiation has a lower energy.
What is the energy range of gamma rays in electron volts?
300KeV – 10MeV
What is the effect of ionizing radiation on cell structures?
It causes severe cellular damage by ionizing cell structures, organelles, and DNA.
Which type of radiation has a velocity of approximately 5% of the speed of light?
Alpha particle
What is the primary purpose of wearing devices such as dosimeters or film badges in occupational exposure?
To monitor the cumulative doses received by an individual
What does the acronym ALARA stand for in radiation safety practices?
As Low As Reasonably Achievable
What is the primary purpose of shielding equipment in radiation safety practices?
To reduce radiation exposure to personnel
What is the difference between PET and SPECT scans?
PET uses a beta emitter, while SPECT uses a gamma emitting radioisotope
What is the primary advantage of PET/CT scans over PET scans?
PET/CT combines anatomical and functional information in one test
What is the principle behind MRI technology?
Magnetic field aligns hydrogen molecules, which are then disturbed by radiofrequency pulses
What is the difference between ionizing and non-ionizing radiation tests?
Ionizing tests use higher energy radiation, while non-ionizing tests use lower energy radiation
What is the purpose of the fluorine-18 tag in PET scans?
To tag glucose molecules for uptake in cells
What advantage does TEE have over TTE?
Closer proximity of the heart to the esophagus, reducing tissue interference
Why is sedation or general anesthesia required for TEE?
To facilitate the passage of the transducer through the esophagus
What is the primary mechanism of ultrasound imaging?
Reflection of high-frequency sound waves
Why is manipulation of the transducer necessary for optimal ultrasound visualization?
To change the direction of the sound waves
Which type of needle is commonly used for regional anesthesia and reflects sound energy away from the transducer?
Smooth needles
What is the benefit of using echogenic needles in ultrasound-guided nerve blocks?
They reflect sound energy towards the transducer
What is the purpose of the piezoelectric crystal in the ultrasound transducer?
To generate high-frequency sound waves
What is the advantage of ultrasound in regional anesthesia?
It provides real-time visualization of the needle
What is the minimum energy required for an incident photon to ionize an atom or molecule?
100eV
What is the energy range of X-rays that can cause ionization of cell structures?
100eV – 100KeV
What is the result of an outer orbital electron moving to an inner orbit to fill a vacated space in photoelectric scatter?
The emission of a new photon with decreased energy
What is the boundary between ionizing and non-ionizing EM radiation in the UV range?
Not sharply defined
What is the effect of ionizing radiation on DNA?
It causes severe cellular damage
What is the energy range of gamma rays that can cause ionization of cell structures?
300KeV – 10MeV
What is the result of a proton being converted into a neutron, a positron, and a neutrino?
A proton is converted into a neutron, a positron, and a neutrino
What is the purpose of the half-life concept in radioactivity?
To measure the time it takes for the radioactivity to decay to half its original value
What is the type of radiation that occurs when an incident photon collides with an atom and the energy is momentarily absorbed?
Coherent scatter
What is the result of an electron being captured by the nucleus and combining with a proton to form a neutron?
A neutrino is emitted from the nucleus
What is the result of an alpha particle emission from an atom of Uranium 238?
A helium nucleus is emitted from the atom
What is the relationship between the number of half-lives and the remaining atoms of a radioactive isotope?
The number of remaining atoms is halved for each half-life
What is the equivalent dose of a worker who receives 10rads of alpha particles and 5rads of x-rays if the radiation weighting factor for alpha particles is 20 and for x-rays is 1?
205 rem
What is the unit of measurement for absorbed dose in SI units?
Gray
What is the relationship between the units of measurement for equivalent dose and absorbed dose?
1 Sv = 100 rem and 1 Gy = 100 rad
If a worker receives 2.05 Sv of equivalent dose, what is the equivalent dose in rem?
20.5 rem
What is the purpose of the radiation weighting factor in calculating equivalent dose?
To account for the difference in biologic effects of different types of radiation
What is the unit of measurement for radiation exposure in conventional units?
Roentgen
What is the primary advantage of using TEE over TTE?
Better visualization of heart structures due to fewer tissues between the esophagus and heart
What is the purpose of the piezoelectric crystal in the ultrasound transducer?
To generate high frequency sound waves
What is the reason for manipulating the transducer during ultrasound imaging?
To optimize the visualization of internal structures
Why are echogenic needles used in ultrasound-guided nerve blocks?
To increase the reflection of sound energy
What is the reason for sedation or general anesthesia during TEE?
To ensure the patient remains still during the procedure
What is the characteristic of the sound waves used in ultrasound imaging?
High frequency and low amplitude
What is the primary mechanism of indirect hit in ionizing radiation?
H2O breakage into H+ + OH- free radicals, which then chemically damage DNA
What is the purpose of measuring radiation dose in Coulombs/kg (C/kg) in SI units?
To quantify the amount of ionizing radiation absorbed by a material
What is the result of long-term low-dose ionizing radiation on the human body?
Cancer and shortened life span
What is the advantage of using the Sievert (Sv) unit in measuring radiation dose?
It takes into account the biological effects of radiation
What is the result of mutations to the genes of the reproductive cells due to ionizing radiation?
Mutations carried over to progeny
What is the difference between the Roentgen (R) and Gray (Gy) units of measurement?
Roentgen (R) is a unit of measurement for radiation exposure, while Gray (Gy) is a unit of measurement for radiation dose
Study Notes
Radiation Physics
- Ionizing radiation carries enough energy to free electrons from atoms or molecules, thereby ionizing them.
- Penetrating energies are measured in electron volts (eV), with:
- Alpha particles: 5MeV
- Beta particles: 1.6 MeV
- X-rays: 100eV – 100KeV
- Gamma rays: 300KeV – 10MeV
- Penetrating energies are measured in electron volts (eV), with:
- Non-ionizing radiation is below UV in the EM spectrum, with no damage, including:
- Visible light
- Infrared
- Microwaves
- Radio waves
Radioactive Decay
- Alpha decay: atom of Uranium 238 emits an alpha particle (Helium nucleus)
- Atomic mass (A) and atomic number (Z)
- Beta radiation:
- β− decay (electron emission): neutron → proton + electron + antineutrino
- β+ decay (positron emission): proton → neutron + positron + neutrino
- Electron Capture Decay (“K-capture”): inner shell e- is drawn into the nucleus and combines with a proton
- Half-Life (t1/2): time it takes for radioactivity to decay to half its original value
Scatter Radiation
- Occurs as a result of attenuation of the incident beam to the patient’s body
- Three types:
- Coherent scatter (Thompson scatter)
- Compton scatter
- Photoelectric scatter
Radiation Measurements
- Rad (rad): unit of Absorbed Dose (D)
- Equal to 100 erg (unit of energy)
- Rem (rem): unit of Equivalent Dose (EqD)
- Corresponding SI unit is the Sievert (Sv)
- Radiation Weighting Factors (WR) assigned to each type of radiation
Radiation Biology
- Two types of cell interactions from ionizing radiation:
- Direct hit: breakage of a DNA molecule
- Indirect hit: H2O breakage into H+ + OH- free radicals
- Biologic effects:
- Somatic effects:
- Short-term (hematologic, GI, CNS)
- Long-term (“latent”): cataracts, cancer, shortened life span
- Genetic effects: mutations to reproductive cells
- Somatic effects:
Medical Imaging
- Ionizing tests:
- X-rays
- CT
- Nuclear scans
- Non-ionizing tests:
- Ultrasound
- MRI
- Medical uses of radiation: diagnostic and therapeutic
Test your understanding of different types of radioactive decay, including alpha decay, beta decay, and electron capture. Learn about the changes in atomic mass and atomic number during these processes.
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