Midterms | Unit 1: Half-life Flashcards
The radioactive matter is not here one day and gone the next. Rather, radioisotopes disintegrate into a (1) of different elements at a (2) rate so that the quantity of radioactive material never quite reaches zero.
- stable isotope
- decreasing
Radioactive material is measured in —
becquerels
1 Bq is equal to the disintegration of —
1 atom each second
The rate of decay of radionuclides
Decay constant (λ)
Formula for λ
λ= (ln(2) / T1/2)
Unit of measurement for the original amount, amount decaying, and remaining amount of the time elapsed
milliCurie (mCi)
Original amount, amount decaying, and remaining amount after 1 second
Original amount: 100 mCi
Amount decaying: 25 mCi
Remaining amount: 75 mCi
Original amount, amount decaying, and remaining amount after 2 seconds
Original amount: 75 mCi
Amount decaying: 19 mCi
Remaining amount: 56 mCi
Original amount, amount decaying, and remaining amount after 3 seconds
Original amount: 56 mCi
Amount decaying: 14 mCi
Remaining amount: 42 mCi
Types of half-life
- Radioactive/ Physical Half-Life (T½)
- Biological Half-Life (Tb)
- Effective Half-Life (Te)
The time required for a quantity of Radioactivity to be reduced to one-half its original value
Radioactive/ Physical Half-Life (T½)
Every radioactive material has its unique half-life value
Radioactive/ Physical Half-Life (T½)
All Radioactivity never disappears
Radioactive/ Physical Half-Life (T½)
The time required for the body to eliminate one-half of the administered dose of any substances by biological processes (perspiration, urine, feces, exhalation)
Biological Half-Life (Tb)
Examples of biological processes
perspiration
urine
feces
exhalation
Most radiopharmaceuticals are also cleared from organs by various physiologic processes
Biological Half-Life (Tb)
In Biological Half-Life (TB), most radiopharmaceuticals are also cleared from organs by various — processes
physiologic
Encompasses both T1/2 and Tb
Effective Half-Life (Te)
Effective Half-Life (Te) must always be — than T1/2 and Tb
shorter
The time required for a radioactive elimination in the body to be diminished by 50% as a result of the combined action of radioactive decay and biological elimination.
Effective Half-Life (Te)
ln(2) = —
.693
Drugs that emit radiation and are eliminated through biological processes
Radiopharmaceuticals
Radioactivity remaining after 0 half-life (% and fraction)
100%
1
Radioactivity remaining after 1 half-life (% and fraction)
50%
1/2
Radioactivity remaining after 2 half-lives (% and fraction)
25%
1/4
Radioactivity remaining after 3 half-lives (% and fraction)
12.5%
1/8
Radioactivity remaining after 4 half-lives (% and fraction)
6.25%
1/16
Radioactivity remaining after 5 half-lives (% and fraction)
3.125%
1/32
Radioactivity remaining after 6 half-lives (% and fraction)
1.56%
1/64
Radioactivity remaining after 7 half-lives (% and fraction)
0.78%
1/128
Half-life of 99Tc
6 hours
Half-life of 131I
8 days
Half-life of 123I
13 hours
Half-life of 223Ra
11 days
Half-life of 226Ra
1600 years
Half-life of 14C
5730 years
Half-life of 192Ir
74 days
Half-life of 60Co
5.26 years
Half-life of 137Cs
30 years
Half-life of 90Sr
28 years
Half-life of 99Mo
66 hours
equation for n (no. of half-life)
n= Time elapsed (T) / Half-life (T1/2)
