RADIOACTIVITY. LAW OF RADIOACTIVE DECAY Activity units: 1 Ci = 3.7 × 1010 Bq 1. Nuclear decay law: N = Noe-At The law of radioactive decay gives the quantitative relationship between the original number of nuclei present at time zero No and the number N at a later time t (sec), where e = 2.71828... is the base of the natural logarithm, and 2 is the decay constant for the nuclide (1/s). 2. Relationship between decay constant 1 and isotop half-life T1/2: In(2) 0.693 Modality Radioisotope Carbon-11 Half-life T1/2 where 1 is decay constant (1/s), T1/2 is isotope half- life (s). T1/2 20 minutes PET Fluorine-18 110 minutes PET 12.7 hours Copper-64 Gallium-67 PET 3. Activity or decay rate of a radioactive source A: ΔΝ 78.3 hours SPECT Gallium-68 68 minutes PET = AN Technetum-99m 6.02 hours SPECT Δt where A is activity or decay rate of a radioactive source (Bq), N is number of nuclei present at time t (s ), A is decay constant (1/s). 4. Activity A of a radioactive source at a time t: Indium-111 67.3 hours SPECT lodine-123 13.22 hours SPECT Thallium-201 72.9 hours SPECT A = A̟e¬dt = A,2 T1/2 A, is initial activity (Bq), T1/2 half life time of an isotope (s). 5. Relationship between mass and number of nuclei: т м NA m is mass (kg), M is molar mass (kg/mole), N is number of nuclei, N, = 6.022 · 1023 mole- is Avogadro's constant. 10. Iodine-120 has a half life of 1.35 hours. If you start off with a sample which has an activity of 1.0 Ci, how long is it before the activity drops to the following values: (a) 0.50 Ci; (b) 9.77x104 Ci; (c) 9.31×1010 Ci.
RADIOACTIVITY. LAW OF RADIOACTIVE DECAY Activity units: 1 Ci = 3.7 × 1010 Bq 1. Nuclear decay law: N = Noe-At The law of radioactive decay gives the quantitative relationship between the original number of nuclei present at time zero No and the number N at a later time t (sec), where e = 2.71828... is the base of the natural logarithm, and 2 is the decay constant for the nuclide (1/s). 2. Relationship between decay constant 1 and isotop half-life T1/2: In(2) 0.693 Modality Radioisotope Carbon-11 Half-life T1/2 where 1 is decay constant (1/s), T1/2 is isotope half- life (s). T1/2 20 minutes PET Fluorine-18 110 minutes PET 12.7 hours Copper-64 Gallium-67 PET 3. Activity or decay rate of a radioactive source A: ΔΝ 78.3 hours SPECT Gallium-68 68 minutes PET = AN Technetum-99m 6.02 hours SPECT Δt where A is activity or decay rate of a radioactive source (Bq), N is number of nuclei present at time t (s ), A is decay constant (1/s). 4. Activity A of a radioactive source at a time t: Indium-111 67.3 hours SPECT lodine-123 13.22 hours SPECT Thallium-201 72.9 hours SPECT A = A̟e¬dt = A,2 T1/2 A, is initial activity (Bq), T1/2 half life time of an isotope (s). 5. Relationship between mass and number of nuclei: т м NA m is mass (kg), M is molar mass (kg/mole), N is number of nuclei, N, = 6.022 · 1023 mole- is Avogadro's constant. 10. Iodine-120 has a half life of 1.35 hours. If you start off with a sample which has an activity of 1.0 Ci, how long is it before the activity drops to the following values: (a) 0.50 Ci; (b) 9.77x104 Ci; (c) 9.31×1010 Ci.
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11th Edition
ISBN:9781305952300
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Chapter1: Units, Trigonometry. And Vectors
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Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...
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![RADIOACTIVITY. LAW OF RADIOACTIVE DECAY
Activity units:
1 Ci = 3.7 × 1010 Bq
1. Nuclear decay law:
N = Noe-At
The law of radioactive decay gives the quantitative relationship between the original number
of nuclei present at time zero No and the number N at a later time t (sec), where e = 2.71828...
is the base of the natural logarithm, and 2 is the decay constant for the nuclide (1/s).
2. Relationship between decay constant 1 and isotop half-life T1/2:
In(2)
0.693
Modality
Radioisotope
Carbon-11
Half-life
T1/2
where 1 is decay constant (1/s), T1/2 is isotope half-
life (s).
T1/2
20 minutes
PET
Fluorine-18
110 minutes
PET
12.7 hours
Copper-64
Gallium-67
PET
3. Activity or decay rate of a radioactive source A:
ΔΝ
78.3 hours
SPECT
Gallium-68
68 minutes
PET
= AN
Technetum-99m
6.02 hours
SPECT
Δt
where A is activity or decay rate of a radioactive
source (Bq), N is number of nuclei present at time t
(s ), A is decay constant (1/s).
4. Activity A of a radioactive source at a time t:
Indium-111
67.3 hours
SPECT
lodine-123
13.22 hours
SPECT
Thallium-201
72.9 hours
SPECT
A = A̟e¬dt = A,2 T1/2
A, is initial activity (Bq), T1/2 half life time of an isotope (s).
5. Relationship between mass and number of nuclei:
т
м
NA
m is mass (kg), M is molar mass (kg/mole), N is number of nuclei, N, = 6.022 · 1023 mole-
is Avogadro's constant.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F3b2af8a3-7e8b-4bac-b9c5-0042b40b7957%2Fc2146e96-4efb-4cae-ab3d-0e5efef73f8e%2F7y67tyh.png&w=3840&q=75)
Transcribed Image Text:RADIOACTIVITY. LAW OF RADIOACTIVE DECAY
Activity units:
1 Ci = 3.7 × 1010 Bq
1. Nuclear decay law:
N = Noe-At
The law of radioactive decay gives the quantitative relationship between the original number
of nuclei present at time zero No and the number N at a later time t (sec), where e = 2.71828...
is the base of the natural logarithm, and 2 is the decay constant for the nuclide (1/s).
2. Relationship between decay constant 1 and isotop half-life T1/2:
In(2)
0.693
Modality
Radioisotope
Carbon-11
Half-life
T1/2
where 1 is decay constant (1/s), T1/2 is isotope half-
life (s).
T1/2
20 minutes
PET
Fluorine-18
110 minutes
PET
12.7 hours
Copper-64
Gallium-67
PET
3. Activity or decay rate of a radioactive source A:
ΔΝ
78.3 hours
SPECT
Gallium-68
68 minutes
PET
= AN
Technetum-99m
6.02 hours
SPECT
Δt
where A is activity or decay rate of a radioactive
source (Bq), N is number of nuclei present at time t
(s ), A is decay constant (1/s).
4. Activity A of a radioactive source at a time t:
Indium-111
67.3 hours
SPECT
lodine-123
13.22 hours
SPECT
Thallium-201
72.9 hours
SPECT
A = A̟e¬dt = A,2 T1/2
A, is initial activity (Bq), T1/2 half life time of an isotope (s).
5. Relationship between mass and number of nuclei:
т
м
NA
m is mass (kg), M is molar mass (kg/mole), N is number of nuclei, N, = 6.022 · 1023 mole-
is Avogadro's constant.
![10. Iodine-120 has a half life of 1.35 hours. If you start off with a sample which has an
activity of 1.0 Ci, how long is it before the activity drops to the following values: (a) 0.50 Ci;
(b) 9.77x104 Ci; (c) 9.31×1010 Ci.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F3b2af8a3-7e8b-4bac-b9c5-0042b40b7957%2Fc2146e96-4efb-4cae-ab3d-0e5efef73f8e%2Fhqfgb2f.png&w=3840&q=75)
Transcribed Image Text:10. Iodine-120 has a half life of 1.35 hours. If you start off with a sample which has an
activity of 1.0 Ci, how long is it before the activity drops to the following values: (a) 0.50 Ci;
(b) 9.77x104 Ci; (c) 9.31×1010 Ci.
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