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Chung, Eom, Kim, Kim, Lee, Hong, Kim, Park, Kang, and Suh: Comparison of Anisotropic Analytic Algorithm Plan and Acuros XB Plan for Lung Stereotactic Ablative Radiotherapy Using Flattening Filter-Free Beams
Original Article

Progress in Medical Physics 2014;25(4):210-217.

Published online: 20 January 2014

DOI: https://doi.org/10.14316/pmp.2014.25.4.210

Comparison of Anisotropic Analytic Algorithm Plan and Acuros XB Plan for Lung Stereotactic Ablative Radiotherapy Using Flattening Filter-Free Beams

Jin-Beom Chung∗, Keun-Yong Eom∗, In-Ah Kim∗, Jae-Sung Kim∗, Jeong-Woo Lee†, Semie Hong†, Yon-Lae Kim‡, Byung-Moon Park†, Sang-Won Kang§, Tae-Suk Suh§

∗Department of Radiation Oncology, Seoul National University Bundang Hospital, Seongnam, Korea

†Department of Radiation Oncology, Konkuk University Medical Center, Seoul, Korea

‡Department of Radiologic Technology, Choonhae College of Health Sciences, Ulsan, Korea

§Department of Biomedical Engineering, The Catholic University of Korea, Seoul, Korea

Correspondence:Jeong-Woo Lee (polirain@naver.com) Tel:82-2-2030-5393, Fax:82-2-2030-5383

Received 8 December 2014       Revised 16 December 2014       Accepted 19 December 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

This study investigated the dosimetric effects of different dose calculation algorithm for lung stereotactic ablative radiotherapy (SABR) using flattening filter-free (FFF) beams. A total of 10 patients with lung cancer who were treated with SABR were evaluated. All treatment plans were created using an Acuros XB (AXB) of an Eclipse treatment planning system. An additional plans for comparison of different alagorithm recalcuated with anisotropic analytic algorithm (AAA) algorithm. To address both algorithms, the cumulative dose-volume histogram (DVH) was analyzed for the planning target volume (PTV) and organs at risk (OARs). Technical parameters, such as the computation times and total monitor units (MUs), were also evaluated. A comparison analysis of DVHs from these plans revealed the PTV for AXB estimated a higher maximum dose (5.2%) and lower minimum dose (4.2%) than that of the AAA. The highest dose difference observed 7.06% for the PTV V105%. The maximum dose to the lung was also slightly larger in the AXB plans. The percentate volumes of the ipsilateral lung (V5, V10, V20) receiving 5, 10, and 20 Gy were also larger in AXB plans than for AAA plans. However, these parameters were comparable between both AAA and AXB plans for the contralateral lung. The differences of the maximum dose for the spinal cord and heart were also small. The computation time of AXB plans was 13.7% shorter than that of AAA plans. The average MUs were 3.47% larger for AXB plans than for AAA plans. The results of this study suggest that AXB algorithm can provide advantages such as accurate dose calculations and reduced computation time in lung SABR plan using FFF beams, especially for volumetric modulated arc therapy technique.

Keywords: Anisotropic analytical algorithm, Acuros XB, Stereotactic ablative radiotherapy, Lung cancer

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Fig. 1.
An example of dose distribution between AAA (a) and AXB (b) plan for PTV when 48 Gy was prescribed at the isoceneter.
pmp-25-210f1.tif
Fig. 2.
Cumulative dose-volume histogram of the PTV using AAA and AXB in all plans.
pmp-25-210f2.tif
Table 1.
Target coverage, homogeneity, and conformity in lung SABR plans between the AAA and AXB.
Coverage indices Algorithm
AXB (Mean±SD) AAA (Mean±SD) Relative difference (%) (AXB−AAA)/ AAA×100
PTV V95% (%) 92.35±5.53 95.01±0.35 −2.89
PTV V100% (%) 82.25±6.81 86.50±1.33 −4.91
PTV V105% (%) 3.08±2.58 2.87±1.05 7.06
CTV V95% (%) 99.90±0.83 100.01±0.36 −0.11
CTV V100% (%) 98.58±1.23 98.93±0.63 −0.35
PTV      
Maximum dose (Gy) 53.63±2.98 51.37±2.13 4.40
Mean dose (Gy) 47.98±1.51 48.16±1.49 −0.37
Minimum dose (Gy) 39.36±3.79 41.52±3.25 −5.20
CTV      
Maximum dose (Gy) 52.53±2.11 51.07±1.79 2.86
Mean dose (Gy) 48.99±1.53 48.63±1.55 0.74
Minimum dose (Gy) 45.59±3.04 46.32±2.71 −1.58
HI      
PTV sigma index (Gy) 3.89±0.52 2.52±0.31 54.37
CTV sigma index (Gy) 1.28±0.33 1.05±0.13 21.90
CI      
LCF 0.89±0.12 0.92±0.10 −3.26
HTCI 0.87±0.19 0.88±0.21 −0.68
CN 0.77±0.15 0.81±0.09 −4.94

HI: homogeneity indices, CI:　conformity indices, LCF: lesion coverage factor, HTCI: health tissue conformity index, CN: conformity number V95%, V100%, V105%: the volumes receiving 95%, 100%, and 105% of the prescribed dose, respectively.

Table 2.
Comparison of OARs dosimetric data in lung SABR plans between the AAA and AXB.
Coverage indices Algorithm
AXB(Mean±SD) AAA (Mean±SD) Relative difference (%) (AXB−AAA)/ AAA×100
Ipsilateral lung      
V5 (%) 24.60±6.13 23.11±5.61 6.45
V10 (%) 12.37±4.31 11.41±3.69 8.41
V20 (%) 3.86±1.53 3.63±1.36 6.34
MLD (Gy) 4.26±1.14 4.14±1.20 2.90
Contralateral lung      
V5 (%) 12.28±3.73 12.07±3.70 1.74
V10 (%) 5.86±2.44 5.76±2.43 1.74
V20 (%) 2.97±2.02 2.92±2.01 1.71
MLD (Gy) 2.40±0.66 2.39±0.65 0.42
Spinal cord      
Maximum dose (Gy) 8.40±2.19 8.24±1.73 1.94
Heart      
Maximum dose (Gy) 12.32±9.58 12.45±9.47 −1.04

MLD: mean lung dose. V5, V10, V20: the percentage volumes receiving 5, 10, and 20 Gy dose, respectively.

Table 3.
The average computation time of AAA and AXB for 10 lung SABR plans using VMAT technique.
  AXB(Mean±SD) AAA Rel(Mean±SD) Rlative difference (%)(XB−AAA)/AAA×100
Time (Sec) 529.5±49.4 4 613.9±76.5 −13.7
Table 4.
The percentage difference of total MUs in the two different calculation algorithms.
Algorithm Patients [MUs]
1 2 3 4 5 6 7 8 9 10 Mean
AXB 2857 2894 2396 3340 3005 2698 2652 2525 2811 2951 2812.9
AAA 2698 2760 2412 3118 2936 2658 2555 2458 2739 2825 2715.9
DMU (%) 5.89 4.86 −0.66 7.12 2.35 1.50 3.80 2.73 2.63 4.46 3.47

MUs: monitor units, DMU (%): percentage difference in MUs

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