Dosimetric Comparison of Lung-Sparing Radiation Therapy between Volumetric Arc Therapy and Helical Tomotherapy for Unresectable Malignant Pleural Mesothelioma
Table 2
Dose volume parameters for planning target volumes and organs at risk.
Characteristics
VMAT median (range)
HT median (range)
value
PTV45, Gy
Dmax
53.9 (52.2–59.2)
48.4 (47.1–49.8)
0.001
Dmin
38.8 (30.7–43.3)
37.5 (19.4–43.7)
0.81
Dmean
49.2 (48.1–52.1)
45.8 (45.6–46.1)
<0.001
PTV54, Gy
Dmax
64.3 (61.9–69.9)
57.8 (56.2–59.2)
<0.001
Dmin
46.8 (37.2–52.1)
45.4 (26.7–51.7)
0.65
Dmean
58.6 (56.3–61.9)
55.0 (54.7–55.2)
0.001
Ipsilateral lung
Mean dose, Gy
38.2 (20.8–51.4)
33.5 (18.0–40.1)
0.007
V5 (%)
100 (96.2–100)
99.7 (98.0–100)
0.59
V10 (%)
100 (77.2–100)
95.1 (68.2–100)
0.028
V20 (%)
92.0 (43.6–100)
80.2 (41.2–100)
0.10
Contralateral lung
Mean dose, Gy
11.8 (5.2–18.1)
6.7 (5.3–8.1)
0.018
V5 (%)
67.8 (33.2–90.0)
30.6 (21.4–49.0)
0.001
V10 (%)
51.4 (3.9–100)
29.6 (11.9–49.0)
0.009
V20 (%)
3.5 (0–55.0)
0.5 (0–14.3)
0.002
Total lung
Mean dose, Gy
19.8 (17.8–33.0)
16.1 (10.5–24.4)
0.003
V20 (%)
36.2 (25–69.0)
29.3 (13.08–45.5)
0.021
Spinal cord, Gy
Dmax
39.3 (31.9–44.2)
33.2 (22.5–34.2)
0.005
Heart
Mean dose, Gy
33.3 (12.1–54.9)
25.8 (7.3–45.7)
0.006
V25 (%)
57.9.0 (7.21–100)
43.5 (4.1–95.3)
0.002
V30 (%)
50.9 (4.45–100)
34.8 (1.4–88.9)
0.001
Mean kidney dose, Gy
Ipsilateral
2.5 (1.3–11.2)
1.6 (0.7–6.4)
0.28
Contralateral
1.9 (0.3–8.9)
2.0 (0.2–5.2)
0.27
Liver
Mean dose, Gy
13.1 (6.3–33.6)
15.1 (8.3–31.4)
0.31
V30 (%)
11.0 (0.0–59.2)
13.3 (0–50.8)
0.67
Esophagus
Dmean
38.6 (16.2–57.8)
29.9 (8.3–44.2)
0.001
V35
57.2 (0.9–100)
42.3 (0–100)
0.017
V50
40.3 (0–98.9)
29.6 (0–97)
0.024
Dosimetric indices
Conformity index
0.96 (0.93–0.99)
0.98 (0.97–0.99)
0.74
Homogeneity index
1.1 (1.1–1.1)
1.036 (1.03–1.05)
<0.001
Treatment duration
Monitor units, per fr
529 (471–765)
6590 (6185–7116)
<0.001
Treatment time (min/fr)
2.5 (2.1–3.0)
7.4 (6.9–7.8)
<0.001
PTV: planning target volume; VX: volume receiving X Gy; Dmax: maximum dose; Dmin: minimum dose; Dmean: mean dose; fr: fraction.
