Quiz Questions Flashcards
(40 cards)
Which material results in the highest number of photon interactions?
Metal
Metal is dense and has a high atomic number, interacting with most incident photons.
What materials will result in the highest x-ray attenuation reading?
Metal
Metals are effective at attenuating x-rays due to their density and atomic structure.
During a CT scan with a radiation dose of approx 3,000 mGy, which two effects may occur?
Epilation, cancer
Deterministic effects like cataracts and decreased fertility can occur at this dose if specific areas are directly exposed.
Which radiation interaction does not result in ionization of an atom?
Coherent Scattering
Ionization is the process through which an electron interacts with a photon and is ejected out of th atom. Coherent scattering changes the direction of the incoming photon but no ionization takes place
Which dose quantity is most useful for projecting the risk of radiation-induced cancer?
Effective dose
Effective dose is commonly used to project the risk of radiation-induced cancer from radiology procedures. This is possible because effective dose is calculated using the tissue weighting factor, which is based on radiosensitivity of individual tissues. If a tissue has a high risk of developing cancer, this results in a higher tissue weighting factor and larger effective dose.
Effective dose and equivalent dose are measured in which units?
Sieverts (Sv) or Millisievert (mSv)
What is absorbed dose?
The most basic measurement of radiation dose absorbed in a person, referring to the energy of radiation absorbed by the person, measured in gray (Gy) which equals 1 joule per kilogram (J/kg) of tissue.
Absorbed dose is crucial for understanding the effects of radiation on human tissue.
Radiation exposure is calculated in units of?
Coulombs/Kilogram (C/kg).
Exposure measures the amount of ionization created in air from x-ray, with roentgen being a familiar unit in traditional systems.
What effect does a low atomic number have on attenuation?
Results in minimal attenuation.
Materials with low atomic numbers allow most photons to pass through without interaction.
What results from photoelectric absorption?
Total absorption of the photon, leaving no photon to be scattered.
This process is significant in radiology for understanding how x-rays interact with matter.
What happens when kilovoltage peak (kVp) is increased for a CT procedure?
Decreased attenuation.
Increasing kVp reduces the percentage of photons attenuated but increases the total number of absorbed photons due to higher beam intensity.
What is a likely reason for a CT examination exceeding the dose notification value?
Increased milliamperage (mA).
The CTDI used for the scan is affected by high mA, leading to dose alerts.
What should a technologist do upon receiving a ‘dose alert’ during a CT scan?
Review the exposure parameters.
This ensures safety and compliance with dose notification values.
How does increasing kilovoltage peak (kVp) affect patient dose?
Increased patient dose.
Higher kVp can lead to greater radiation exposure for the patient.
What does automatic dose modulation with variable milliamperage (mA) depend on?
Patient attenuation readings acquired during the scout images.
This allows the scanner to adjust mA throughout the scan for optimal dosing.
What is the main purpose of traditional lead shielding?
To reduce scatter radiation absorption outside of the exposure field.
Lead shielding is essential for protecting patients and personnel from unnecessary radiation exposure.
What is attenuation in the context of x-ray beam?
Attenuation refers to any interaction in which the x-ray beam decreases in intensity.
Attenuation can occur due to various interactions, including coherent scattering, Compton scattering, and photoelectric absorption.
Which three processes can cause attenuation of the x-ray beam?
- Coherent scattering
- Compton scattering
- Photoelectric absorption
These processes remove photons from the useful beam and lead to attenuation.
What do Bremsstrahlung and characteristic radiation refer to?
Bremsstrahlung and characteristic radiation refer to the x-ray production processes in the x-ray tube.
They are not interaction mechanisms in matter.
How is the number of ionization events in air described?
Exposure.
Exposure is a measure of ionization events caused by x-rays in air.
What does Air Kerma refer to?
The energy of ions created in air from x-rays.
KERMA stands for kinetic energy released per unit mass.
What does the acronym KERMA stand for?
Kinetic Energy Released per unit mass.
KERMA is measured in Gray (Gy) and Milligray (mGy).
What is the unit of measurement for KERMA?
Gray (Gy) and Milligray (mGy).
