Radioactivity Flashcards
Define activity
The rate at which the nuclei within the sample undergo transition and can be expressed in terms of the number of transitions per second
What are the two units for activity?
- becquerel (Bq)
2. curie (Ci)
What is becquerel equivalent to?
1 tps
What is curie equivalent to?
3.7 x 1010 tps
What was curie first introduced as ?
activity of 1g of radium
What are some useful conversions?
1 Ci = 3.7 x 1010 Bq
1 mCi = 37 MBq
1 MBq = 27 µCi
What are two quantities used in clinical nuclear medicine related to?
- the number of radioactive (untransformed) nuclei in the sample
- Elapsed time
What is the lifetime of radioactive material?
Time between formation of a radioactive nucleus and its radioactive transition
What is the fundamental characteristic of radioactivity?
All nuclei, even of the same radioactive nuclide, do not have the same life time
What is it possible to determine of a nucleus?
Average lifetime of the nuclei of a specific radioactive nuclide
What is a unique characteristic of each specific nuclide?
The average lifetime
What is the half-life?
Time required for one-half of the nuclei to undergo transition
What is the specific relationship of half-life and average life?
T1/2 = 0.693 Ta, or
Ta = 1.44 T1/2
What is proportional to average life?
Half-life
What is another way to express life-tine characteristic of a radioactive substance?
Transformation constant - delta
decay constant
What does the transformation constant actually express?
The probability that a nucleus will undergo a transition in a stated period of time
What is the value of transformation constant inversely related to?
Lifetime
What is the relationship between the transformation constant and lifetime?
T1/2 = 0.693/l .
What is 0.693 a natural logarithm of?
number 2 and appears in relationship involving half-life
What is the transformation constant 1 a reciprocal of?
- Average life
2. l = 1/Ta .
What can a characteristic lifetime be expressed in?
- Half-life
- Average life
- Transformation constant
What can the transformation constant, lambda be related the activity to?
The number of nuclei in a sample
What is the equation of activity?
1 x N
What is the amount of radioactive material?
Quantity of radioactive nuclei or atoms in a sample
activity is inversely related to half-life
Activity = 0.693 x N / T1/2
Number of nuclei = 1.44 x Activity x T1/2
Define cumulated activity?
The quantity of radioactive nuclei that undergo transition in a period of time
relationship between cumulated activity, Ã, and the initial activity of a collection of radioactive material, A
à (mCi-hr) = 1.44 x A (mCi) x T1/2 (hr).
What is one of the most important characteristic of a radioactive material ?
Quantity and activity constantly change with time
What happens during transition?
One atom is removed from the parent radioactive material and converted into the daughter product
Define radioactive decay
Both quantity and activity decrease continuously with elapsed time
What is the build up of radioactivity a mirror image of?
Radioactive decay
What does radioactive build up never reach?
saturation
