ESTRO 36 Abstract Book

563 / 1082

S548 ESTRO 36 2017
_______________________________________________________________________________________________
delineating method for delineating the CTV of the regional
lymph nodes of breast cancer patients due to the increase
of the CIgen combined with the shortest delineation time
and the smallest standard deviation per delineating
direction. We also recommend performing second reading
to improve the concordance between radiation
oncologists. Finally, further research is required because
the CIgen did not reach a level higher than 0.8.
PO-1002 Comparison of Best Commercial Model and
Atlas based segmentation with CT and MR in brain
cancer.
J.Y. Woo1, T.Y. KIM2, J.Y. SEOK3, T.M. KIM1, Y.W. CHO1,
S.Y. KIM1, J.G. BAEK 1, J.H. KIM1, J.H. CHO1
1 Yonsei Cancer Center, Radiation Oncology, Seoul, Korea
Republic of
2 National Cancer Center, Radiation Oncology, Gyeonggi-
do, Korea Republic of
3 Seoul National University Bundang Hospital, Radiation
Oncology, Gyeonggi-do, Korea Republic of
Purpose or Objective
It is important to accurately delineate critical organ such
as optic chiasm, pituitary gland and brainstem when
radiation therapy is delivered in brain cancer. MR images
were usually used to delineate critical organ accurately in
most brain cases. But manually delineated contours by
different users sometimes have different shape and region
in the same planning CT. Even if different users delineate
contours, we would expect to get more accurate and
regular critical organ if using auto contouring method.
Recently there are many commercial auto contouring
softwares including model based segmentation (MBS) and
atlas based segmentation (ABS) softwares even supporting
MR images. This study aims to compare auto contouring
methods to delineate critical organ accurately and to have
certain shape and region.
Material and Methods
It is multi-center study. We selected 10 patients. We used
three MBS software solutions and ABS software solution
(MIM_software ver. 6.5.5.) to generate the automatic
contouring on the planning CT. All MBS software just made
contours without any preparation, and we chose the best
result among 3 MBS solutions for comparison. But ABS
software should have subjects (who are already registered
for ABS to work on auto contouring and also they are not
the patients involved in this study). We made two groups
of atlas, 60 subjects of CT based and 20 subjects of MR
based. We used two matching techniques for MR based
ABS, Majority-vote and STAPLE. We analyzed auto
contouring with 4 classified groups - best MBS (BM), CT
based ABS for 60 subjects (CA), and MR based ABS using
Majority-vote (MR_MV) and MR based ABS using STAPLE
(MR_ST). We gained brain stem, optic chiasm, and
pituitary gland contours. Average Dice Similarity
Coefficients (DSC) was calculated for each structure to
compare against 'gold” standard contours which are
manually defined of 4 groups respectively. Values closer
to 1 indicate higher accuracy.
Results
MR_ST was significantly more accurate than other group
according to DSC of 0.646 ± 0.094 compared to 0.564 ±
0.102, 0.298 ± 0.109, 0.39 ± 0.254 respectively for MR_MV,
CA and BM in optic chiasm. DCS scores in pituitary gland
were following, 0.624 ± 0.055 in MR_ST, 0.582 ± 0.052 in
MR_MV, 0.514 ± 0.140 in CA and 0.28 ± 0.24 in BM
respetively. Brainstem was showed similar DSC score as
0.89 ± 0.021, 0.892 ± 0.017, 0.842 ± 0.038 and 0.73 ± 0.156
respectively for MR_ST, MR_MV, CA and BM.
Conclusion
Most of auto delineated contours was smoothened in
advance. Among 4 groups, DSC of MR based was the
highest. Even though auto contouring is conducted by
different users, it shows certain shape and included
similar region when we use same subject’s data. ABS
software takes more effort and time to use in the first
place. However, MR based ABS would have better auto
contouring accuracy compared with MBS and CT based ABS
in brain cancer. In addition STAPLE has provided better
results for smaller volumes based on my study.
PO-1003 A analysis of safety of whole brain
radiotherapy with Hippocampus avoidance in brain
metastasis
Y. Han1, J. Chen1, G. Cai1, X. Cheng 1, Y. Kirova2, W. Chai3
1Shanghai Jiao Tong university-ruijin hospital, radiaton
oncology, Shanghai, China
2Institute Curie- Paris- France, Department of Radiation
Oncology, Paris, France
3Shanghai Jiao Tong university-ruijin hospital,
Department of Radiology, Shanghai, China
Purpose or Objective
Purpose: Whole brain radiotherapy (WBRT) remains
reference treatment in patients with brain metastasis
(BM), especially with multiple lesions. Hippocampus
avoidance in WBRT (HA-WBRT) offers the feasibility of less
impaired cognitive function than conventional WBRT and
better intracranial control than SBRT. Oncological safety
is critical in defining the proper role of HA-WBRT. The
study aims to investigate the frequency of intracranial
substructure involvement based on large series of
radiological data and to optimize the margin definition in
treatment planning.
Material and Methods
Methods: Consecutive patients with diagnosis of BM from
enhanced MRI between 03/2011 and 07/2016 diagnosed
and treated in RuiJin Hospital were analyzed. Lesions of
each patient were confirmed by a senior radiologist and
the closest distances from tumor to the hippocampal area
were measured and analyzed by radiation oncologist.
Results
Results: A total of 226 patients (pts) (115 males and 111
females) with 1080 metastatic measurable lesions have
been studied. The distribution of the primary tumours was
as following: 72.6% lung cancers (LC) (n=164), 19.9% breast
cancer (BC) patients (n=45) and 7.5% from other
malignancies (n=17). Seventy-one pts were diagnosed with
BM before or simultaneously with their primary
malignancy. In the case of others 155 pts, the latency of
BM appearance was as following: 14 months in LC pts
(n=100), 59 months in BC pts (n=42). Totally, 758 (70.2%)
lesions were situated beyond the tentorium. The median
diameter of the lesions was 10 mm (1.2mm-162mm). The
situation of the lesions was as following: 322 (29.8%) in the
cerebellum, 268 (24.8%) in the frontal lobe, 168 (15.6%) in
the temporal lobe, 128(11.9%) in the parietal lobe, 131
(12.1%)in the occipital lobe, 45 (4.2%)in the thalamus and
18 (1.6%) in the brainstem. After measuring the closest
between the lesions and the Hippocampus in every case,
the pts with lesions close to this zone (n=45) were
classifed into 3 catogories: 7 (3.1 %) at 5 mm or less, 13
(5.7%) within 10 mm or less and 19 (8.4%) at 20 mm or less
(Fig1). 45 patients received WBRT only and 18 of 45
patients who had complete radiological follow-up after
WBRT in the same hospital were founded progress of BM.
The median follow-up was 11 months. Only one new lesion