Unit 3 - Radiation Electronics and Detection Flashcards
What are the units for Rontgens?
C/kg
What are rontagens measuring?
Exposure
Define exposure?
The intensity of radiation upon the surface of an object (i.e. the number of ionized electrons)
What is the units for Gry and what is it measuring?
J/Kg-measuring the absorbed dose
How do you count the x ray photons before they are absorbed by an attenuator?
Find their number of photons by recording the ionizations that take place in air near the material that is being attenuated
What is exposure (i.e. Rontgens) useful for measuring?
The intestisity of the “raw” x ray beam emmited from the tube
Is the measurement of rontgens useful for measuring the biological imact of radiation exposure? Why or why not?
No
1. Air and soft tissue have diff. densities therefore the dose absorbed by the patient is different with varying tissue types
2. P.E. effect contributes most to dose, and we cannot tell the difference in a measurement between P.E. and scatter.
True or false?
All radiation detection instruments have a transducer? What is a transducers purpose?
True. Transducer measures the # of ionizations that are occuring.
What are the 2 different ways that radiation detectors operate based off of?
- # Ionizations of atoms
- The excitation of electrons
How do detectors that operate on the basis of excitation of electrons count the number of photons?
As the e- returns to the pre-excitation stage, they release energy which is captured and transferred into an electrical current which is then measured.
How do detectors that operate on the basis of the ionizations of atoms count the number of photons?
Free e- that have been knocked out of orbit travel to a positive anode plate that creates a charge that can be measured.
What factors determine whether ionization or excitation is favored?
- The physical state of the transducer
- The denisty of the transducer
The transducer is coupled to an ___________ where the radiation is converted into a useful electronic signal
Electronic component
What are the 3 functions that radiation detectors can preform?
- Can detect radiation
- Can measure radiation
- Can do both
What is the function of pulse or rate mode detectors?
Detect the presence of radiation (and general intensity)
Can pulse mode detectors measure radioactivity without a meter or a counter?
No
When using a pulse mode detector, how do we know that radiation is present?
When radiation is present, a clicking/beeping/ticking will occur and the meter will move to indicate the general amount of radiation present
What type of mode is a geiger counter?
It is a pulse mode detector
What is rate mode measuring?
The rontgens present per hour
In order for a rate mode detector to be useful, what enviroment must it be in?
-Useful when there is a steady flow of radiation
True or false?
Rate mode detectors are useful for detecting natural sources of radioactivity. Why or why not?
False, natural sources of radioactivity have varying rates which does not allow for an accurate reading
What is them most useful mode of detectors?
Integrate mode
What does integrate mode measure?
The number of ionizations per set unit of time
True or false?
Integrate mode is accurate.
True, they can count events at an extremely high speed and with great accuracy