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Yea: Comparison of the Dose Distributions with Beam Arrangements in the Stereotactic Body Radiotherapy (SBRT) for Primary Lung Cancer
Original Article

Progress in Medical Physics 2014;25(2):110-115.

Published online: 20 June 2014

DOI: https://doi.org/10.14316/pmp.2014.25.2.110

Comparison of the Dose Distributions with Beam Arrangements in the Stereotactic Body Radiotherapy (SBRT) for Primary Lung Cancer

Ji Woon Yea

Department of Radiation Oncology, Yeungnam University College of Medicine, Daegu, Korea

Correspondence: Ji Woon Y ea (yjw1160@ynu.ac.kr) Tel: 82-53-620-3371, Fax:82-53-624-3599

Received 30 April 2014       Revised 26 May 2014       Accepted 2 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

To compare 2 beam arrangements, circumferential equally angles (EA) beams or partially angles (PA) beams for stereotactic body radiation therapy (SBRT) of primary lung cancer for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques with respect to target, ipsilateral lung, contralateral lung, and organs-at-risk (OAR) dose-volume metrics, as well as treatment delivery efficiency. Data from 12 patients, four treatment plans were generated per data sets (IMRTEA, IMRTPA, VMATEA, VMATPA). The prescribed dose (PD) was 60 Gy in 4 fractions to 95% of the planning target volume (PTV) for a 6-MV photon beam. When compared with the IMRT and VMAT treatment plan for 2 beams, conformity index, homogeneity index, high dose spillage, D2 cm (Dmax at a distance ≥2 cm beyond the PTV), R50 (ratio of volume circumscribed by the 50% isodose line and the PTV), resulted in similar. But Dmax of the Organ at risk (OAR), spinal cord, trachea, resulted in differ between four treatment plans. Especially HDSlocation showed big difference in 21.63% vs. 26.46%.

Keywords: Dose distribution, Equal angle, Partial angle, Stereotatic body radiotherapy (SBRT)

References

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Fig. 1.
Comparisons of the IMRT and VMAT with equally ((a); (c)) or partially ((b); (d)) beam arrangements. (a) IMRTEA; (b) IMRTPA; (c) VMATEA; (d) VMATPA.
pmp-25-110f1.tif
Table 1.
환자 특성.
나이 42∼86 (중간값=72)
성별  
  　남자 10
  　여자 02
종양크기  
  　육안적 종양체적 0.4 cc∼44.3 cc
    평균 9.8 cc
  　계획용 표적체적 7.6 cc∼137.3 cc
    평균 39.7 cc
  종양위치  
　우상엽 1
  　우중엽 1
  　우하엽 6
  　좌상엽 3
  　좌하엽 1
총수 12
Table 2.
Plan evaluation table for HDSvolume, D2cm, R50 in the RTOG9).
PTV volume (cc) Ratio of prescription isodose volume to the PTV volume Ratio of 50% prescription isodose volume to the PTV volume, R50% Maximum dose (in % of dose prescribed) @ 2 cm from PTV in any direction, D2cm (Gy) Percent of lung receiving 20 Gy total or more, V20 (%)
Deviation Deviation Deviation Deviation
None Minor None Minor None Minor None Minor
1.8 ＜1.2 ＜1.5 ＜5.9 ＜7.5 ＜50.0 ＜57.0 ＜10 ＜15
3.8 ＜1.2 ＜1.5 ＜5.5 ＜6.5 ＜50.0 ＜57.0 ＜10 ＜15
7.4 ＜1.2 ＜1.5 ＜5.1 ＜6.0 ＜50.0 ＜58.0 ＜10 ＜15
13.2 ＜1.2 ＜1.5 ＜4.7 ＜5.8 ＜50.0 ＜58.0 ＜10 ＜15
22.0 ＜1.2 ＜1.5 ＜4.5 ＜5.5 ＜54.0 ＜63.0 ＜10 ＜15
34.0 ＜1.2 ＜1.5 ＜4.3 ＜5.3 ＜58.0 ＜68.0 ＜10 ＜15
50.0 ＜1.2 ＜1.5 ＜4.0 ＜5.0 ＜62.0 ＜77.0 ＜10 ＜15
70.0 ＜1.2 ＜1.5 ＜3.5 ＜4.8 ＜66.0 ＜86.0 ＜10 ＜15
95.0 ＜1.2 ＜1.5 ＜3.3 ＜4.4 ＜70.0 ＜89.0 ＜10 ＜15
126.0 ＜1.2 ＜1.5 ＜3.1 ＜4.0 ＜73.0 ＜91.0 ＜10 ＜15
163.0 ＜1.2 ＜1.5 ＜2.9 ＜3.7 ＜77.0 ＜94.0 ＜10 ＜15
Table 3.
Comparisons of PTV, HI, CI, RTOG plan evaluation's parameter and MU between the equally angles and the partially angles for the beam arrangements.
    IMRTEA IMRTPA Difference (%) VMATEA VMATPA Mean diff (%)
    Mean±SD Mean±SD IMRTPA − IMRTEA ×100 IMRTPA Mean±SD Mean±SD IMRTPA − IMRTEA ×100 IMRTPA
PTV Dmax (Gy) 71.57±2.59 71.31±2.42 −0.37 70.13±2.73 70.40±2.55 0.38
  Dmean (Gy) 65.37±1.64 65.29±1.51 −0.13 64.94±1.67 64.90±1.63 −0.06
  Dmin (Gy) 52.09±2.12 52.36±1.97 0.51 53.91±2.87 53.27±1.85 −1.22
HI & CI rDHI 0.73±0.04 0.74±0.04 0.88 0.77±0.06 0.76±0.05 −1.62
  mDHI 0.92±0.21 0.86±0.02 −6.29 0.81±0.23 0.87±0.02 6.89
  CI 0.74±0.07 0.70±0.10 −5.56 0.68±0.08 0.67±0.07 −1.89
RTOG HDSlocation 1.61±1.26 2.05±1.13 21.63 3.63±4.55 4.93±5.30 26.46
  HDSvolume 1.09±0.12 1.10±0.12 −5.56 0.68±0.08 0.67±0.07 −1.89
  D2cm 0.74±0.07 0.70±0.10 −5.56 0.68±0.08 0.67±0.07 −1.89
  R50 0.74±0.07 0.70±0.10 −5.56 0.68±0.08 0.67±0.07 −1.89
MU   5287±1117 4493±998 −17.67 3565±715 3030±539 −17.68

IMRTEA: Intensity-modulated radiotherapy arranged by equally beam angles, IMRTPA: Intensity-modulated radiotherapy arranged by partially beam angles, VMATEA: Volumetric-modulated arc therapy arranged by equally beam angles, VMATPA: Intensity-modulated radiotherapy arranged by partially beam angles, SD: standard deviation, rDHI: radical dose homogeneity index, mDHI: moderate dose homogeneity index, CI: conformity index, HDSlocation: location of the high dose spillage described by the RTOG, HDSvolume: volume of the high dose spillage described by the RTOG, D2cm: location of the low dose spillage described by the RTOG, R50: volume of the low dose spillage described by the RTOG, and MU: monitor units.

Table 4.
Dose difference analysis according to the equally angles and the partially angles for the beam arrangements.
Structure Parameter IMRTEA IMRTPA Difference (%) VMATEA VMATPA Difference (%)
Mean±SD Mean±SD IMRTPA − IMRTEA × IMRTPA ×100 Mean±SD Mean±SD IMRTPA − IMRTEA ×100 IMRTPA
Both MLD (Gy) 4.61±1.39 4.19±1.29 −10.04 4.69±1.51 4.55±1.43 −3.02
  lung V5 (%) 20.35±5.66 17.21±5.57 −18.28 19.62±7.49 16.57±7.49 −18.36
    V12.5 (cc) 407.49±224.81 321.68±224.81 −26.68 370.03±206.62 347.51±190.34 −6.48
    V13.5 (cc) 375.44±214.44 302.32±162.60 −24.19 350.48±201.25 329.11±186.05 −6.49
    V20 (%) 6.40±3.04 6.20±2.65 −3.14 7.18±3.35 7.05±3.24 −1.82
    V25 (%) 4.39±2.26 4.51±2.09 2.69 4.80±2.49 5.34±2.68 10.04
Ipsilateral MLD (Gy) 7.40±2.42 7.26±2.36 −1.95 8.03±2.78 7.98±2.78 −0.69
  lung V5 (%) 30.12±7.47 29.77±7.72 −1.18 31.61±7.81 31.54±7.92 −0.23
    V10 (%) 23.18±7.44 21.98±8.05 −5.45 24.80±8.55 23.85±8.46 −3.99
    V20 (%) 12.63±6.26 12.48±5.60 −1.24 14.51±7.17 14.25±6.90 −1.86
    V30 (%) 7.24±3.76 7.29±3.58 0.67 8.34±4.50 8.64±4.67 3.47
Contralateral MLD (Gy) 1.75±0.77 1.15±0.50 −51.89 1.39±0.58 1.17±0.45 −18.70
  lung V5 (%) 10.28±4.88 4.30±4.88 −139.34 7.50±8.30 3.93±4.63 −91.08
    V10 (%) 5.40±2.50 0.11±0.27 −4645.17 0.33±0.72 0.17±0.36 −96.82
PRVSpinal cord Dmax (Gy) 13.36±0.85 10.37±2.56 −28.81 10.69±1.43 9.59±1.82 −11.46
OARTrachea Dmax (Gy) 11.78±10.31 9.08±8.02 −29.75 10.34±9.56 10.67±8.96 3.14
OARHeart Dmax (Gy) 23.53±12.39 18.85±13.63 −24.84 18.84±12.96 19.34±13.19 2.58

V5/10/20/25/30 (%): percentage volumes that received 5, 10, 20, 25 and 30 Gy, respectively, V12.5/13.5 (cc): absolute volumes that received 12.5 and 13.5 Gy, respectively, MLD: Mean Lung Dose.

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