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Song, Kim, Jeong, Yoon, Ahn, Chung, and Nam: Evaluation of Dose Distributions Recalculated with Per-field Measurement Data under the Condition of Respiratory Motion during IMRT for Liver Cancer
Original Article

Progress in Medical Physics 2014;25(2):79-88.

Published online: 20 June 2014

DOI: https://doi.org/10.14316/pmp.2014.25.2.79

Evaluation of Dose Distributions Recalculated with Per-field Measurement Data under the Condition of Respiratory Motion during IMRT for Liver Cancer

Ju-Young Song†, Yong-Hyeob Kim∗, Jae-Uk Jeong∗, Mee Sun Yoon†, Sung-Ja Ahn†, Woong-Ki Chung†, Taek-Keun Nam†,

∗Department of Radiation Oncology, Chonnam National University Hwasun Hospital, Hwasun, Korea

†Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea

Correspondence:Taek-Keun Nam (tknam@chonnam.ac.kr) Tel:82-61-379-7224, Fax:82-61-379-7249

Received 8 May 2014       Revised 3 June 2014       Accepted 9 June 2014

Copyright © 2014 Korean Society of Medical Physics

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The dose distributions within the real volumes of tumor targets and critical organs during internal target volume-based intensity-modulated radiation therapy (ITV-IMRT) for liver cancer were recalculated by applying the effects of actual respiratory organ motion, and the dosimetric features were analyzed through comparison with gating IMRT (Gate-IMRT) plan results. The ITV was created using MIM software, and a moving phantom was used to simulate respiratory motion. The doses were recalculated with a 3 dose-volume histogram (3DVH) program based on the per-field data measured with a MapCHECK2 2-dimensional diode detector array. Although a sufficient prescription dose covered the PTV during ITV-IMRT delivery, the dose homogeneity in the PTV was inferior to that with the Gate-IMRT plan. We confirmed that there were higher doses to the organs-at-risk (OARs) with ITV-IMRT, as expected when using an enlarged field, but the increased dose to the spinal cord was not significant and the increased doses to the liver and kidney could be considered as minor when the reinforced constraints were applied during IMRT plan optimization. Because the Gate-IMRT method also has disadvantages such as unsuspected dosimetric variations when applying the gating system and an increased treatment time, it is better to perform a prior analysis of the patient's respiratory condition and the importance and fulfillment of the IMRT plan dose constraints in order to select an optimal IMRT method with which to correct the respiratory organ motional effect.

Keywords: Respiratory organ motion, IMRT, Internal target volume (ITV), Gating system, 3DVH

References

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Fig. 1.
MapCHECK2 laid on the dynamic moving phantom for the per-field measurement of ITV-IMRT under the condition of respiratory motion.
pmp-25-79f1.tif
Fig. 2.
Diagram of the overall study process.
pmp-25-79f2.tif
Fig. 3.
Example of PTV and OARs in ITV-IMRT plan delineated in MIM program reflecting the respiratory motional effect.
pmp-25-79f3.tif
Fig. 4.
Volume increase rate of PTV and OARs in ITV-IMRT plan compared with the volume in Gate-IMRT plan.
pmp-25-79f4.tif
Fig. 5.
Example of the DVH comparison between the recalculated dose in the ITV-IMRT beam delivery and the DVH of Gate-IMRT plan.
pmp-25-79f5.tif
Fig. 6.
Differences of PTV's DVH values between the ITV-IMRT beam delivery and Gate-IMRT plan at the major points.
pmp-25-79f6.tif
Fig. 7.
Comparison of homogeneity index (HI) between the beam delivery of ITV-IMRT and Gate-IMRT plan.
pmp-25-79f7.tif
Fig. 8.
Differences of liver's DVH values between the ITV-IMRT beam delivery and Gate-IMRT plan at the major points.
pmp-25-79f8.tif
Fig. 9.
Differences of kidney's DVH values between the ITV-IMRT beam delivery and Gate-IMRT plan at the major points. (a) Left kidney. (b) Right kidney.
pmp-25-79f9.tif
Fig. 10.
Differences of maximum dose and mean dose of spinal cord between the ITV-IMRT beam delivery and Gate-IMRT plan.
pmp-25-79f10.tif
Table 1.
Volume comparison of PTV and OARs between ITV-IMRT plan and Gate-IMRT plan with information on the period and range of respiratory motion in each patient.
Patients PTV [cm3] Liver [cm3] Lt-kidney [cm3] Rt-kidney [cm3] Respiration period [sec] Respiratory motional range [cm]
Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT
A 642.0 711.2 1785.9 1965.9 238.8 270.2 196.8 221.2 9.0 1.7
B 273.8 327.8 1846.3 2073.9 145.8 170.7 141.9 155.7 5.0 1.8
C 49.5 58.7 1325.3 1471.7 161.3 191.5 153.0 174.5 6.0 1.2
D 573.0 612.5 1053.3 1261.6 240.3 271.5 185.6 214.8 7.0 1.5
E 2021.9 2100.3 2506.2 2752.3 187.2 215.8 175.1 183.1 7.0 1.3
F 683.2 762.5 2005.1 2148.9 418.6 478.9 213.5 238.7 4.0 1.4
G 1133.9 1286.2 1453.4 1618.6 220.5 251.7 231.7 258.4 5.0 1.5
H 465.8 529.9 1326.1 1518.1 167.6 189.6 154.4 184.8 5.0 1.5
I 433.4 532.0 938.1 1115.9 201.2 239.9 165.2 199.5 7.0 1.8
J 440.6 527.8 1438.6 1726.8 147.5 190.4 156.2 196.8 6.0 1.2
Table 2.
Comparison of PTV's DVH on the specific points between the beam delivery of ITV-IMRT and Gate-IMRT plan.
Patients PTV mean-dose [Gy] PTV max-dose [Gy] PTV V47.5Gy [%vol]
Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT
A 51.19 50.95 53.21 55.14 99.66 99.40
B 50.78 52.84 52.62 55.46 99.94 100.00
C 51.92 55.04 53.53 56.89 100.00 100.00
D 50.53 51.24 52.86 54.49 99.82 99.29
E 49.61 50.61 53.67 59.21 98.33 97.63
F 49.56 51.74 53.52 57.74 88.95 98.87
G 48.95 49.81 52.22 55.26 94.88 95.75
H 50.13 50.75 52.37 55.22 99.02 90.23
I 49.64 51.19 54.83 61.36 67.32 73.57
J 51.28 52.47 53.29 56.83 99.88 99.70
Table 3.
Comparison of liver's DVH on the specific points between the beam delivery of ITV-IMRT and Gate-IMRT plan.
Patients Liver mean-dose [Gy] Liver max-dose [Gy] Liver D30% [Gy]
Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT
A 13.46 15.68 51.63 52.36 19.22 19.97
B 21.92 25.80 52.62 56.41 29.08 33.26
C 7.46 9.56 53.13 56.43 7.43 12.90
D 8.05 11.10 52.13 53.24 9.23 14.83
E 40.83 42.26 53.67 56.55 49.61 50.64
F 30.40 34.02 53.52 57.74 46.95 50.27
G 23.29 25.23 52.17 54.70 27.79 29.52
H 21.57 22.78 54.43 55.14 30.37 31.18
I 28.91 30.40 54.83 61.36 48.78 50.12
J 27.83 28.80 53.29 56.83 35.80 37.04
Table 4.
Comparison of kidney's DVH on the specific points between the beam delivery of ITV-IMRT and Gate-IMRT plan.
Patients Lt-kidney mean-dose [Gy] Lt-kidney max-dose [Gy] Lt-kidney D20% [Gy]
Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT
A 22.72 26.07 52.52 54.18 39.48 42.39
B 5.54 6.92 24.17 29.21 7.58 9.09
C 1.52 2.24 14.14 16.81 1.12 3.03
D 15.71 16.54 44.53 46.69 18.86 20.05
E 7.09 8.09 24.38 24.55 18.22 19.05
F 0.79 1.45 5.42 6.80 0.90 3.38
G 12.57 14.31 43.48 46.17 19.35 20.07
H 7.57 8.25 29.53 31.00 13.46 13.91
I 0.74 1.22 7.11 11.28 0.89 1.93
J 2.58 2.94 19.14 19.28 5.16 5.43
Patients Rt-kidney mean-Dose [Gy] Rt-kidney max-Dose [Gy] Rt-kidney D20% [Gy]
Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT
A 15.98 17.10 28.68 31.63 19.33 20.27
B 11.87 14.21 34.53 35.21 16.92 17.85
C 5.27 6.40 20.96 23.14 14.65 16.36
D 14.40 15.51 46.97 49.73 19.07 20.67
E 10.56 13.38 51.32 53.00 19.14 23.55
F 5.81 8.33 31.05 34.17 12.64 18.60
G 14.88 15.94 50.80 52.25 18.79 19.70
H 12.44 13.52 48.35 51.68 19.03 20.45
I 6.75 7.55 25.16 26.89 17.34 17.70
J 2.58 3.00 35.47 35.29 2.24 3.21
Table 5.
Comparison of cord's maximum dose and mean dose between the beam delivery of ITV-IMRT and Gate IMRT plan.
Patients Cord mean-dose [Gy] Cord max-dose [Gy]
Gate-IMRT ITV-IMRT Gate-IMRT ITV-IMRT
A 17.59 20.02 38.84 41.91
B 9.32 11.27 22.16 23.21
C 2.60 3.43 18.08 19.75
D 27.51 29.67 40.72 42.47
E 18.21 19.25 38.11 39.27
F 11.35 11.96 28.84 27.14
G 19.76 22.64 41.81 42.49
H 18.30 19.06 40.41 40.63
I 8.21 9.33 41.33 43.85
J 9.53 10.15 30.31 32.10
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