Kouijzer, M.

Mast, M.

Petoukhova, A.

Struikmans, H.

Verbeek- de Kanter, A.

Willems, M.

Elsevier - Publisher Connector 

S888                                                                                                                                         3rd ESTRO Forum 2015 
 
facility; a longer training with this mask system could lead to 
a reduction of translational shifts and rotations.  
   
 
Electronic Poster: RTT track: Pre-treatment imaging and 
volume definition  
 
 
EP-1620   
An audit of breast cancer ct protocols in radiation therapy 
to establish national dose reference levels 
S. O'Connor1, O. McArdle2, L. Mullaney1 
1Trinity College Dublin, Discipline of Radiation Therapy, 
Dublin 8, Ireland Republic of  
2St Luke’s Radiation Oncology Network at Beaumont 
Hospital, Department of Radiation Oncology, Dublin 9, 
Ireland Republic of  
 
Purpose/Objective: Computed tomography (CT) scanning 
delivers ionising radiation doses that may increase the 
stochastic risk of malignancy. The implementation of dose 
reference levels (DRLs) for imaging procedures using ionising 
radiation is mandated by European Commission directive 
97/43 EURATOM. DRLs have yet to be established for 
radiation therapy (RT) localisation CT scans. The purpose of 
this research is to establish if CT dose variation occurs for 
breast cancer localisation CT scans between Irish RT 
departments; to investigate the factors contributing to this, 
and to propose DRLs for this procedure.  
Materials and Methods: All Irish RT departments were invited 
to complete a dose audit survey for 10 average-sized breast 
cancer patients undergoing a CT localisation scan. The data 
requested included: Computed Tomography Dose Index: 
Volume (CTDIvol), Dose Length Product (DLP), current-time 
product (mAs), tube potential (kVp), scan length, slice 
thickness, scanning margins, use of automated exposure 
control, and scanner technology. 
Results: Data was collected on 60 scans from six 
departments, representing 67% of the national departments. 
Significant variations in mean CTDIvol and DLP were observed 
between departments (p<0.0001). Mean scan lengths and 
mean mAs also differed significantly between departments 
(p<0.0001). CTDIvol was more positively correlated with DLP 
than scan length. Proposed DRLs for breast localisation CT 
scans is 26mGy and 732mGy cm for CTDIvol and DLP 
respectively.  
Conclusions: The variation in dose between departments 
suggests a large potential for optimisation of this procedure. 
CT dose variation between RT centres may be more 
influenced by factors affecting CTDIvol than scan length. 
Baseline national figures for breast cancer RT localisation CT 
DRLs are provided. 
   
EP-1621   
Evaluation of the reconstruction of image acquired from 
CT simulator to reduce metal artifact 
J.H. Choi1 
1Seoul National Univ. Bundang Hospital, radiation oncology, 
Seongnam Gyeonggi-Do, Korea Republic of  
 
Purpose/Objective: This study presents the usefulness 
assessment of metal artifact reduction for orthopedic 
implants(O-MAR) to decrease metal artifacts from materials 
with high density when acquired CT images. 
Materials and Methods: By CT simulator, original CT images 
were acquired from Gammex and Rando phantom and those 
phantoms inserted with high density materials were scanned 
for other CT images with metal artifacts and then O-MAR was 
applied to those images, respectively. To evaluate CT images 
using Gammex phantom, 5 regions of interest(ROIs) were 
placed at 5 organs and 3 ROIs were set up at points affected 
by artifacts. The averages of standard deviation(SD) and CT 
numbers were compared with a plan using original image. For 
assessment of variations in dose of tissue around materials 
with high density, the volume of a cylindrical shape was 
designed at 3 places in images acquired from Rando phantom 
by Eclipse. With 6 MV, 7-fields, 15 × 15 cm2 and 100 cGy per 
fraction, treatment planning was created and the mean dose 
were compared with a plan using original image. 
Results: In the test with the Gammex phantom, CT numbers 
had a few difference at established points and especially 3 
points affected by artifacts had most of the same figures. In 
the case of O-MAR image, the more reduction in SD appeared 
at all of 8 points than non O-MAR image. In the test using the 
Rando Phantom, the variations in dose of tissue around high 
density materials had a few difference between original CT 
image and CT image with O-MAR. 
Conclusions: The CT images using O-MAR were acquired 
clearly at the boundary of tissue around high density 
materials and applying O-MAR was useful for correcting CT 
numbers.  
 
EP-1622   
Delineation of the CTV-breast performed by RTTs and 
radiation oncologists: a comparative study 
M. Kouijzer1, M. Willems1, M. Mast1, A. Petoukhova1, A. 
Verbeek- de Kanter1, H. Struikmans1 
1Radiotherapy Centre West, Radiotherapy, The Hague, The 
Netherlands  
 
Purpose/Objective: Radiation oncologists currently delineate 
the Clinical Target Volume (CTV)-breast (glandular breast 
tissue) in patients referred for whole breast irradiation. To 
optimize the efficiency of this process, it would be useful to 
know whether the RTTs can adequately delineate the CTV-
breast. We therefore, compared the delineated CTVs of the 
RTTs with those of the radiation oncologists. The aim of this 
study was to assess if the conformity index of the CTV-breast 
was >0.8 for both groups. We also examined if it would be 
feasible for the RTTs to delineate the CTV-breast and what 
would be the best procedure. 
Materials and Methods: Ten RTTs and 2 radiation oncologists 
delineated the CTV-breast of 5 patients: 3 left-sided cases 
and 2 right-sided cases. The RTTs were previously trained by 
the specialized radiation oncologist so they would not start 
from scratch. 
The delineations of the RTTs and radiation oncologists were 
compared with each other in MatLab. This program calculates 
the conformity index (CI of two CTVs is defined by the ratio 
of the intersecting volume and the encompassing volume). 
The CI is represented by a number between 0 and 1. When 
the CI is 0, there is no similarity at all between the two 
compared volumes. When the CI is 1, the two delineated 
volumes are completely identical.  
3rd ESTRO Forum 2015                                                                                                                                         S889 
 
For this study the CI of the CTV-breast needed to be >0.8. 
Furthermore, we used the same method as Struikmans et al. 
to compare the derived CIs for all RTTs with those of the 
delineation of the 2 radiation oncologists [1]. 
Results: The mean CI for each single patient was higher than 
0.8 for the RTTs and radiation oncologists together. In both 
separate groups the mean CI was higher than 0.8 as well, the 
values are indicated in table 1. 
Conformity Index  
   
 
RT oncologists + 
RTTs 
RTTs 
RT 
oncologists 
Patient 1 
Patient 2 
Patient 3 
Patient 4 
Patient 5 
0.901 
0.904 
0.875 
0.912 
0.920 
0.901 
0.911 
0.872 
0.911 
0.918 
0.898 
0.867 
0.876 
0.926 
0.923 
Average of the pts 0.902 0.903 0.898 
Standard 
deviation 
0.017 0.018 0.027 
Table 1. Conformity Indices 
 
The results show that the CI of the CTV-breast for the RTTs 
and radiation oncologists do not differ significantly. In 
addition we noted that the visual differences are mainly 
located on the lateral, medial and dorsal side of the breast. 
This is shown in the figure below.  
 
 
Figure 1. patient no.2 and no.3, delineations of RTTs and 
radiation oncologists 
 
Conclusion : With a mean CI of about 0.9 for both groups, 
the CIs were >0.8 for the five delineated patients.  
Recommendations: We recommend that RTTs will delineate 
the CTV-breast in our radiotherapy department. When the 
RTTs delineated the CTV-breast, this will be supervised by 
the radiation oncologists. Both the RTTs and the radiation 
oncologists need to work according to the delineation 
guidelines. The final approval must be done by the radiation 
oncologist. 
Based on the average number of 100 patients treated with 
breast conserving radiotherapy per year we recommend that 
five RTTs need to be trained to delineate the CTV-breast in 
breast conserving radiotherapy. In our opinion it is enough 
when the five RTTs delineate at least twenty patients a year.  
[1] H Struikmans et al., Radiother Oncol. 2005 
   
 
 
 
 
EP-1623   
Contouring of critical organs in pelvis area in postoperative 
radiotherapy - problems and solutions 
P. Tsenov1, L. Iliev1, A. Antonova1, I. Payanova1, N. 
Djankova1, E. Stoyanova1, A. Vesselinova1, R. Lazarov1 
1Tokuda Hospital, Radiotherapy, Sofia, Bulgaria  
 
Purpose/Objective: Contouring organs at risk is generally 
performed by the RTTs. These organs in the lower pelvis have 
large variations, especially in patients undergone surgical 
treatment. The objective of the study is to analyze the 
contouring process of organs at risk in lower pelvis in patients 
undergoing postoperative radiotherapy, to present the most 
frequently observed problems and to point out the solutions 
to overcome them. 
Materials and Methods: Postoperative treatment was applied 
to 157 patients in 'Tokuda Hospital Sofia' in the period 
XI.2009 – XI.2014. From the total number 28 patients were 
operated due to prostate carcinoma and 129 patients due to 
carcinoma uteri. Patients were scanned on a CT 
LifgtSpeedTMRT16 with the protocol for Pelvis scanning without 
intravenous contrast. The patients were prepared for CT 
scanning and irradiation with empty bladder. The protocol 
Helical full, 1,0 sec rotation speed, pitch 0.938:, 
thickness/interval 0.5 mm; Large FOV; Auto mA. A planning 
system ERGO++ was used to contour organs at risk. Obtained 
data were CT processed using Microsoft ExcelTM. 
Results: It was found in 10% of male patients have expressed 
atony of the bladder and 30% showed severe incontinence. 
Within the female patients 30% showed atonia and only 10% 
have incontinence, but at considerably lower level. Within 
prostate cancer patients there were no cases showing 
lymphocele. Among the patients operated from carcinoma 
uteri 20% were found with significant degree of lymphocele, 
as in 5% of them additional surgical treatment was applied. In 
one patient bilateral aneurism of the common iliac arteries 
was found. 
Conclusions: The knowledge of the normal anatomy of lower 
pelvis and the capabilities for contouring organs at risk has 
been incorporated into the modern planning algorithms and 
allows reduction the dose in the organs at risk. There are 
often considerable aberrations in the anatomic localization, 
shape and size of the organs at risk in the patients undergone 
surgery. This requires high level of knowledge of those 
variations, individual approach and very often directing the 
patient for additional surgical treatment. Such requirements 
raise creativity in the skills of RTTs at a new higher level. 
Thus, the team working capabilities of RTTs together with 
the physicians are improved and patients are provided with 
best choice of treatment. 
    
EP-1624   
A one-stop palliative treatment with a CBCT as planning-CT 
L.J. Mesch1, R. Martens1, S. Hol1, N. Marmouk1, W.J.M. De 
Kruijf1, G. D'Olieslager1 
1Dr. Bernard Verbeeten Instituut, Radiotherapy, Tilburg, The 
Netherlands  
 
Purpose/Objective: Institute Verbeeten is located in 3 cities, 
Tilburg, Breda, and 's-Hertogenbosch. Only in Tilburg we have 
access to a planning-CT scan. As patients have to travel for 
the CT scan a method has been developed to use the CBCT as 


EP-1622: Delineation of the CTV-breast performed by RTTs and radiation oncologists: a comparative study 

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EP-1622: Delineation of the CTV-breast performed by RTTs and radiation oncologists: a comparative study

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