Biomedical Engineering Reference
In-Depth Information
If
3 × 10
8
disintegrations occurred in compartment
b
between
t
= 0
and
t
= 200
d, how much activity was initially
taken into compartment
a
?
(c)
41.
Use the two-compartment model described in Section 16.6 for
ingestion of a nuclide that emits a single 5.5-MeV alpha particle
per transformation and has a radioactive half-life of 8.6 d. No
other radiation is emitted. The metabolic half-life in the body
fluids (compartment
a
) is 0.25 d, and that in compartment
b
is
3.5 d. The fraction of the radionuclide that goes to
b
when it
leaves
a
is 0.80. Assume that 100% of the ingested nuclide goes
directly into the body fluids and that compartment
b
receives a
negligible dose as a result of the activity in
a
. The mass
associated with compartment
b
is 1800 g.
(a)
Calculate the specific effective energy, SEE (
b
b
).
←
(b)
Calculate the number of transformations in
compartment
b
over the 50-y period following ingestion of
1 Bq of activity at time
t
0.
=
(c)
What is the committed equivalent dose in
b
per Bq of
ingestion?
(d)
If the organ weighting factor for
b
is 0.05, determine the
ALI for ingestion for this radionuclide.
42.
Why is bone dosimetry of particular importance?
43.
What are the target tissues for bone?
44.
Why is the dosimetric model for submersion in a radioactive
gas cloud different from the model for the respiratory system?
Calculate the equivalent-dose rate in air in Sv h
-1
due to 1 Bq
of
14
C per gram of air.
45.
46.
Estimate the equivalent-dose rate at the surface of the skin of a
person immersed in air (at STP) containing
2.4
10
3
Bqm
-3
×
of
14
CO
2
.
47.
Calculate the equivalent-dose rate in a large air volume (at STP)
that contains a uniform distribution of
2
10
3
Bqm
-3
of
137
Cs.
×
48.
Why is the DRAC for tritiated water so much smaller than that
for elemental tritium?
49.
(a)
What activity of tritium, distributed uniformly in the soft
tissue of the body (reference man), would result in an
equivalent-dose rate of 0.05 Sv y
-1
?
(b)
What would be the total mass of tritium in the soft tissue?
50.
Estimate the time it takes for the body to expel by normal
processes 95% of the tritium ingested in a single intake of
tritiated water. Would the retention time be affected by
increasing the intake of liquids?
51.
What fraction of the iodine in the total body of reference man
is in the thyroid?
