https://digitalcommons.wpi.edu/ourmutualfriend/1001/thumbnail.jp

Hegi-Johnson, F.

Unicomb, K.

West, K.

Small, K.

White, S.

Barber, J.

Van Tilburg, K.

Yeghiaian-Alvandi, R.

F. Hegi-Johnson

K. Unicomb

K. West

K. Small

S. White

J. Barber

K. Van Tilburg

R. Yeghiaian-Alvandi

Crossref

Radiotherapy and Oncology

PD-0473: Comparing VMAT with IMRT and 3D-CRT for stereotactic body radiotherapy in early lung cancer

Elsevier - Publisher Connector 

S184  2nd ESTRO Forum 2013	
PD-0473   
Comparing VMAT with IMRT and 3D-CRT for stereotactic body 
radiotherapy in early lung cancer. 
F. Hegi-Johnson1, K. Unicomb1, K. West1, K. Small1, S. White1, J. 
Barber1, K. Van Tilburg1, R. Yeghiaian-Alvandi2 
1Nepean Hospital, Radiation Oncology Network Nepean Cancer Care 
Centres, Sydney NSW, Australia  
2Westmead Hospital, Radiation Oncology Network Nepean Cancer Care 
Centres, Sydney NSW, Australia  
 
Introduction: Stereotactic body radiotherapy(SBRT) for early lung 
cancer results in excellent local control and potentially improved 
survival,but demands high levels of dose conformality. To achieve this 
with 3D-conformal radiotherapy(3D-CRT) and intensity modulated 
radiotherapy (IMRT) large numbers of beams, and non-coplanar 
techniques are often required. Hence treatment times are long, 
increasing the risk of patient motion. Volumetric arc therapy(VMAT) 
may result in improved dosimetric outcomes, and reduce treatment 
time. We report on a planning study comparing VMAT to coplanar (CP) 
and non-coplanar (NCP) 3D-CRT and IMRT, and our initial clinical 
results.  
Materials and Methods: Pinnacle VMAT, and CP and NCP 3D-CRT and 
IMRT plans for delivery on Elekta Linacs of 5 patients were 
compared.The following dosimetric characteristics were assessed: 
target coverage(coverage with the prescribed dose and 98% coverage 
of the PTV), dose conformality (100% conformity indices, D2cm and 
volume of tissue outside PTV receiving high dose, defined as >105% of 
prescription dose) and V20 (volume of lung receiving 20 Gy). A 
minimum of 10-12 beams were used for IMRT and 3D-CRT plans. VMAT 
plans were single arc with 4 degree spacing. Plans aimed to deliver 
the prescription dose to at least 98% of the volume, with a V20 ≤ 8% . 
All patients had peripheral tumours and received 48 Gy in 4 fractions.  
Results:  
Dosimetric Outcomes 
VMAT achieved equivalent radiotherapy target coverage to 3D-CRT 
and IMRT (>98.2%). However, 3D-CRT plans had a large volume of 
surrounding normal tissue receiving a high dose (24.0% and 21.3% of 
the PTV volume for CP and NCP respectively) when compared to VMAT 
and IMRT plans (3.9% and 4-5% of the PTV volume respectively). 100% 
conformity indices were lowest for VMAT and NCP IMRT (1.1 for both) 
and highest for 3D-CRT (1.5 and 1.4 for CP and NCP respectively). 
D2cm was also lowest for VMAT and NCP IMRT (26.1 Gy and 25.3 Gy) 
and highest for 3D-CRT plans (29.4 Gy and 28.7 Gy for CP and NCP 
respectively). V20 was between 4.4 and 6.1% for all plans. 
Clinical outcomes 
Clinical VMAT treatment time takes 35 minutes, and beam-on time is 8 
minutes. With short follow-up (range 4 weeks to 6 months), 1 patient 
has developed worsening dyspnoea, due to a chest infection. No other 
Grade 2 or greater toxicity was seen in the other 4 patients.  
Conclusions: Clinical implementation of VMAT was successfully 
demonstrated, and has resulted in fast treatment times for our SBRT 
lung patients. VMAT plans are similar in quality to NCP IMRT, but are 
much faster to deliver due to reduced gantry and couch movements. 
3D-CRT plans were unable to deliver equivalent dose conformality, 
and a much larger region of normal tissue was exposed to a high dose 
when equivalent PTV coverage was achieved.  
 
 
PD-0474   
Fiducial markers for liver SBRT using helical tomotherapy MVCT 
K. Muller1, Q. Ruiter de1, J. Jacobs1, I. Niehoff1, A. Minken1, R. 
Westendorp1 
1RISO, Radiation Oncology Department, Deventer, The Netherlands  
 
Purpose/Objective: To assess the visibility of various fiducial markers 
for the application in stereotactic body radiation therapy of colorectal 
liver metastases. Breathing dynamics were mimicked with a 4D 
phantom and evaluated with helical tomotherapy MVCT. 
Materials and Methods: Initially, fifteen types of markers were 
imaged in a static water environment with MVCT. Poor visible markers 
on MVCT were eliminated leaving six markers for further evaluation in 
dynamic conditions.  
A 4D motion phantom was developed and validated to perform these 
measurements. A repetitive motion on the studied markers was 
applied in a water environment. Peak-to-peak amplitude and 
frequency was varied to analyze the effect of dynamic conditions on 
the marker detectability on MVCT of a helical tomotherapy system. A 
conventional 4D kVCT unit was used as reference. 
The detectability was quantified by analyzing the contrast of the 
fiducial markers on the obtained images. Also, the artifacts on the 
images caused by the moving markers were analyzed with respect to 
the amplitude and frequency of the movements.  
Results: Best contrast on MVCT was generated by the 'gold sphere' 
marker, but this marker generated unacceptable artifacts on kVCT. 
The ‘gold anchor’ marker provided the least artifacts on kVCT; 
however, visibility on MVCT was limited. All studied fiducial markers 
had good agreement between the average geometric position and the 
observed position on MVCT under the studied conditions. 
The size and number of the observed artifacts on MVCT were 
dependent on type of marker and specific dynamic conditions. 
Artifacts on MVCT improved the marker detectability and helped the 
observer to determine the center of the markers.  
Conclusions: Good detectability of all observed fiducial markers was 
obtained for the studied dynamical conditions. Good agreement was 
observed between the geometrical average position of the moving 
markers with respect to the observed position on MVCT. Artifacts 
generated by the MVCT-image processing can help in determining the 
position of the markers. 
   
PD-0475   
Multi-atlas fusion methods for segmentation of head and neck 
lymph nodes for radiotherapy planning 
S. Gorthi1, M. Bach Cuadra2, J. Villafruela Vicario3, P.A. Tercier3, J.P. 
Thiran1, A.S. Allal3 
1École Polytechnique Fédérale de Lausanne (EPFL), Institute of 
Electrical Engineering (IEL), Lausanne, Switzerland  
2University Hospital Center (CHUV) and University of Lausanne (UNIL), 
Department of Radiology, Lausanne, Switzerland  
3Hôpital Fribourgeois, Service de Radio-oncologie, Fribourg, 
Switzerland  
 
Purpose/Objective: Intensity Modulated Radiotherapy (IMRT) 
treatment planning for head and neck (H&N) cancer requires accurate 
delineation of target volumes, and these volumes could include 
several lymph node levels. Manual contouring of lymph nodes, in each 
CT slice, is a laborious and time consuming task; instead, it is more 
efficient to first perform automated segmentations and then followed 
by manual corrections if needed. It is shown in many recent works 
that the automated segmentations obtained by merging segmentation 
results obtained from multiple atlases are more accurate and robust 
than the results from a single atlas. In this work, we evaluate state-
of-the-art atlas fusion methods and our recently proposed fusion 
method for H&N lymph nodes segmentation. 
Materials and Methods: The fusion methods compared in this work 
are: (i) Majority Voting (MV), (ii) Global Weighted Voting (GWV), (iii) 
Local Weighted Voting (LWV), (iv) Shape Based Averaging (SBA), (v) 
Simultaneous Truth And Performance Level Estimation (STAPLE), and 
(vi) a Markov Random Field (MRF) based LWV method that we have 
proposed recently, which performs simultaneously both fusion and 
smoothing (LWV+MRF). In this evaluation, we consider 10 lymph node 
structures for automated segmentations: (i) IB-Left, (ii) IB-Right, (iii) 
IIA-Left, (iv) IIA-Right, (v) IIB-Left, (vi) IIB-Right, (vii) III-Left, (viii) III-
Right, (ix) IV-Left and (x) IV-Right. The dataset contains 12 atlas 
images and 8 patients' images to be segmented. For each image to be 
segmented, results obtained from 12 atlases are merged using all the 
above methods. 
Results: The quantitative evaluation is performed over the entire 
dataset, using two metrics; (i) Dice Similarity Measure (DSM): This is a 
commonly used metric that computes the measure of overlap (in %) 
between the ground truth and automated segmentations. (ii) Number 
of connected regions per label: The output segmentations of each 
lymph node should ideally contain a single contiguous region. Hence, 
we evaluate the fusion algorithms also based on the number of 
connected regions it creates per structure. Figure 1 presents box plots 
of average DSM computed across all lymph nodes. Among all fusion 
schemes, our LWV+MRF method provided the best results followed by 
LWV, GWV, MV, SBA and STAPLE respectively. Table 1 presents the 
average values of number connected regions per structure. Notice 
that LWV+MRF provided the best results, in terms of both these 
metrics. We also performed Wilcoxon signed rank test, and it is found 
(with p= 0.05) that the improvements in DSM from LWV+MRF when 
compared to the rest of the methods are statistically significant. 
 
 
Parameter  VMAT  3D-CRT 
CP  
3D-CRT 
NCP  
IMRT 
CP*  
IMRT- 
CP*  
PTV Coverage  98.2%  98.2%  98.3%  98.4%  98.4%  
V20  4.82%  5.1%  3.9%  5.4%  4.6%  
Mean Lung Dose  4.3 Gy 3.9 Gy  4.2 Gy  4.2 Gy  4.4 Gy  
High dose Spillage (% 
PTV volume)  
3.9%  24.02%  21.3%  5.2%  4.6%  
D2Cm 26.1 
Gy 
29.4 Gy 28.7 Gy 30.7 Gy 25.3 Gy 


PD-0473: Comparing VMAT with IMRT and 3D-CRT for stereotactic body radiotherapy in early lung cancer 

https://digitalcommons.wpi.edu/cgi/viewcontent.cgi?article=1008&amp;context=ourmutualfriend

PD-0473: Comparing VMAT with IMRT and 3D-CRT for stereotactic body radiotherapy in early lung cancer

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