1468 / 1708
to or encompassed by the CTV. The IMPT provided further
normal tissue sparing for most structures.
Figure 3shows axial views of the IMRT, proton, and IMPT
plans for treatment of an infratentorial ependymoma. Dose
distributions are shown at the level of the cochlea and tempo-
ral lobes. For the infratentorial plan, the left cochlea received
a mean dose of 37 Gy with IMRT, 2 CGE with protons, and
less than 0.1 CGE with IMPT. Mean dose received by the
Table 2. Comparison of plans (IMPT, protons, and IMRT) for a representative patient with a supratentorial ependymoma
IMPT
Protons
IMRT
Mean
D
5
D
50
D
90
Mean
D
5
D
50
D
90
Mean D
5
D
50
D
90
Whole-brain CTV 5
27
0
<0.1
7
37
0.2 <0.1
12
45
3
0.5
Temporal lobe
8
19
8
<0.1
11
30
14
<0.1
23
47
23
3
Brainstem
21
57
4
<0.1
22
56
7
<0.1
23
58
8
2
Pituitary
<0.1 <0.1 <0.1 <0.1 <0.1
0.1 <0.1 <0.1
2
3
2
2
Optic chiasm
<0.1 <0.1 <0.1 <0.1
0.1
0.3 <0.1 <0.1
3
4
3
2
Left cochlea
<0.1 <0.1 <0.1 <0.1 <0.1
0.1 <0.1 <0.1
3
4
3
2
Right cochlea
<0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
2
2
2
1
Hypothalamus
15
47
13
0.3
22
49
20
4
22
50
22
6
CTV
56
57
56
56
56
57
56
56
57
58
57 56
GTV
57
57
57
56
56
56
56
56
57
58
57 56
Abbreviations:
IMPT = intensity-modulated proton therapy; IMRT = intensity-modulated radiation therapy; CTV = clinical tumor volume;
GTV = gross tumor volume; D
x
= Dose in gray to structures for x% of tissue volume.
Fig. 1. Comparison dose–volume histogram (DVH) for intensity-
modulated radiation therapy (IMRT), proton (3DC proton), and in-
tensity-modulated proton therapy (IMPT) plans for infratentorial
ependymoma: (A) clinical tumor volume (CTV), temporal lobes
(TL), pituitary (PT), hypothalamus (HT), (B) gross tumor volume
(GTV), right cochlea (RC), left cochlea (LC), brainstem (BS), and
whole brain (WB).
Fig. 2. Comparison dose–volume histogram (DVH) for intensity-
modulated radiation therapy (IMRT), proton (3DC Prot.), and inten-
sity-modulated proton therapy (IMPT) plans for supratentorial
ependymoma: (A) clinical tumor volume (CTV), brainstem (BS),
whole brain (WB), (B) gross tumor volume (GTV), temporal lobes
(TL), pituitary (PT), and hypothalamus (HT).
982
I. J. Radiation Oncology
d
Biology
d
Physics
Volume 71, Number 4, 2008