510 / 1096
S495
ESTRO 36
_______________________________________________________________________________________________
Conclusion
In patients who underwent RT for prosta te cancer
treatment, an increase in signal intensity of t he internal
obturator muscles was observed. Specifi cally, this
enhancement was concentrated in the area near the
prostate, likely to be included in high dose regions. This
evidence was present both in T2w and T1w post CA
injection MRI and can be compatible with an inflammatory
status that normally follows RT. This inhomogeneous
structural variation may be explained by the spatial dose
distribution. Moreover, correlations with toxicity scores
should be investigated, considering the involvement of the
pelvic floor muscles in the urinary dysfunctions.
PO-0897 Atlas-based auto-segmentation of heart
structures in breast cancer patients
R. Kaderka
1
, R. Mundt
1
, A. Bryant
1
, E. Gillespie
1
, B.
Eastman
1
, T. Atwood
1
, J. Murphy
1
1
University of California San Diego, Department of 858-
822-4842, San Diego, USA
Purpose or Objective
Radiation therapy deposited in the heart increases the risk
of ischemic heart disease, and sudden cardiac death.
Reproducible contouring of the heart on CT imaging
represents a critical component of treatment planning,
though the literature demonstrates substantial variability
in contouring among providers. In this study we assess the
accuracy of an atlas-based auto-segmentation approach of
the whole heart and the left anterior descending artery
(LAD).
Material and Methods
We randomly selected a cohort of 38 breast cancer
radiotherapy patients treated between 2014 a nd 2016.
For all patients the whole heart and LAD were manually
contoured according to guidelines published by Feng et al.
(2011). The patients were divided into a training dataset
(N=18), and a test dataset (N=20). We used the training
dataset to create a contouring atlas using commercially
available imaging software (MIM Vista, Cleveland OH). On
the test dataset the agreement between the manually
drawn gold standard contours and atlas-based auto-
segmented contours was measured with a Dice-
coefficient. To determine the impact of auto-segmented
contours on dosimetry calculations we determined the
mean radiation dose for the manual contours and the auto-
segmented contours for left-sided breast cancer patients.
Differences in dose between the two contours were
expressed with mean absolute errors.
Results
Within the test dataset the atlas-based auto-segmentation
approach accurately delineated the heart with a Dice-
coefficient of 0.87 ± 0.06 (mean ± standard deviation).
Auto-segmentation was much less accurate for the LAD
with a Dice-coefficient of 0.05 ± 0.06. Among left-sided
breast cancer patients the mean heart dose was 1.2 ± 0.9
Gy for the manually contoured heart, and 2.7 ± 0.9 Gy for
the manually contoured LAD. The auto-segmented mean
heart dose was similar to the manually contoured mean
heart dose, with a mean absolute error of 0.1 ± 0.2 Gy
(range 0.0 - 0.7 Gy). The auto-segmented mean LAD dose
differed moderately from the manual contoured mean LAD
dose, with a mean absolute error of 1.0 ± 1.2 Gy (range
0.0 – 1.7 Gy). There were no statistically significant
differences between the manual contours and the
automated-contours for either the whole heart (p=0.78 by
Wilcoxon-rank sum test), or the LAD (p=0.85).
Conclusion
This study demonstrates that atlas-based auto-
segmentation accurately delineates the whole heart,
though less accurately captures the LAD. The high
concordance in mean heart dose between the manual
contours and automated contours suggests that atlas-
based auto-segmented contours could play a role in
radiation treatment planning.
PO-0898 Automated segmentation for breast cancer
radiation therapy based on the ESTRO delineation
guideline.
A.R. Eldesoky
1,2
, E.S. Yates
3
, T.B. Nyeng
3
, M.S. Thomsen
3
,
H.M. Nielsen
1
, P. Poortmans
4
, C. Kirkove
5
, M. Krause
6,7
,
C. Kamby
8
, I. Mjaaland
9
, E.S. Blix
10,11
, I. Jensen
12
, M.
Berg
13
, E.L. Lorenzen
14,15
, Z. Taheri-Kadkhoda
16
, B.V.
Offersen
1
1
Aarhus University Hospital, oncology, Aarhus, Denmark
2
Mansoura University, Clinical Oncology and Nuclear
Medicine, Mansoura, Egypt
3
Aarhus University Hospital, Medical Physics, Aarhus,
Denmark
4
Radboud University Medical Center, Radiation Oncology,
Nijmegen, The Netherlands
5
Catholic University of Louvain, Radiation Oncology,
Louvain, Belgium
6
OncoRay- University Hospital Carl Gustav Carus-
Technische Universität Dresden- and Helmholtz-Zentrum
Dresden-Rossendorf, Radiation Oncology, Dresden,
Germany
7
German Cancer Consortium DKTK Dresden and German
Cancer Research Center DKFZ Heidelberg, Radiation
Oncology, Dresden, Germany
8
Rigshospitalet, Oncology, Copenhagen, Denmark
9
Stavanger University Hospital, Oncology, Stavanger,
Norway
10
University Hospital of North Norway, Oncology,
Tromsø, Norway
11
Institute of Medical Biology- UiT The Arctic University
of Norway, Immunology Research group, Tromsø, Norway
12
Aalborg University Hospital, Medical Physics, Aalborg,
Denmark
13
Hospital of Vejle, Medical Physics, Vejle, Denmark
14
University of Southern Denmark, Institute of Clinical
Research, Odense, Denmark
15
Odense University Hospital, Laboratory of Radiation