Biomedical Engineering Reference
In-Depth Information
(b)
At a higher level of survival (lower dose), is the RBE larger
or smaller?
(c)
Give a reason to explain your answer to (b).
43.
What factors can modify dose-effect relationships?
44.
Figure 13.19 shows the surviving fraction of cells as a function
of dose when exposed to either X rays or carbon ions in an
experiment. From the curves, estimate the RBE of the carbon
ions for 1% survival and for 50% survival. What appears to
happen to the RBE as one goes to lower and lower doses?
45.
Explain why radiation is used in cancer therapy, even though it
kills normal cells.
46.
Estimate the oxygen enhancement ratio from the cell-survival
curves in Fig. 13.18.
47.
Are the curves in Fig. 13.18 more typical of results expected
with high-LET or low-LET radiation? Why?
13.17
Answers
4.
4.9 Å
26.
3.3
µ
m
2
1
-7
s
5.
1.3
×
31.
0.706
7.
2.4 Å
41.
(a)
0.117
4.68
µ
m
3
8.
5.2 Å
(b)
11.
3.3
(c)
0.373
12.
2.3
42.
(a)
1.3
15.
0.89
(b)
Larger
2.83 × 10
14
17.
44.
2.7, 5.3
18.
17,500
46.
2.0
