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RAD AB, Sweden) and compared to a reference scan taken
at the beginning of each session. The Catalyst
TM
system
works through an optical surface scanning with LED light
(blue: λ = 450 nm) and reprojection captured by a CCD
camera (green: λ = 528 nm; red: λ = 624 nm), which
provide target position control during treatment delivery.
For 3D surface reconstruction, the system uses a non-rigid
body algorithm to calculate the distance between the
surface and the isocenter and using the principle of optical
triangulation. Three-dimensional deviations and relative
position differences during the whole treatment fraction
were calculated by the system and analyzed statistically.
Results
Overall, the magnitude of the deviation vector showed a
mean change of 1.3 mm +/- 0.4 mm (standard deviation)
and a median change of 1.1 mm during dose application
(beam-on time only). Along the lateral and longitudinal
axis changes were quite similar (0.9 mm +/- 0.3 mm vs.
0.9 mm +/- 0.5 mm), on the vertical axis the mean change
was 1.1 mm +/- 0.3 mm. The mean net beam-on time of
radiation therapy was 2.8 minutes. There was no linear
correlation between the length of the fraction and the
magnitude of deviation. Pearson’s correlation coefficient
between mean time and mean magnitude of deviation
vector over all patients was 0.25 (p-value= 0.175).
Conclusion
Mean real-time intrafraction motion was within two
millimeters in all directions and is therefore of minor
clinical relevance in postoperative radiotherapy of breast
cancer.
EP-1187 Heart dose evaluation in two free-breathing
and deep-breathing modes of breast cancer patients
R. Anbiae
1
, A.R. Taji
1
, A. Ahmari
1
, Z. Siavashpour
2
, M.
Beigi
1
1
Shahid Beheshti Medical University, Radiation Oncology,
Tehran, Iran Islamic Republic of
2
Shahid Beheshti University, Medical Radiation
Engineering, Tehran, Iran Islamic Republic of
Purpose or Objective
To investigate how much respiratory manner of breast
cancer patients during external beam radiotherapy would
affect their heart dose.
Material and Methods
21 patients with left breast cancer underwent CT
simulation without contrast in one day and two positions;
breath hold and free breathing, prospectively. Two CT
image sets were imported to treatment planning system
(Eclipse, version 6). Volumes of PTV (that included breast
and chest wall), heart and ipsilateral lung in both image
sets were contoured by an individual radiation oncologist.
An experienced physicist designed the plans for both CTs.
Prescribed dose was 50 Gy in 25 fractions for all included
cases. Plans were then confirmed by the oncologist and
heart and lung dose volume parameters were
exported. Lung and heart Volumes, their V30 and V22.5
and also mean heart dose (MHD) in two condition were
studied and analyzed.
Results
Mean age of patients was 46.9±12.1.Twelve patients had
done MRM and 9 of them had done BCS. Mean heart
volume, its V30, V22.5 and MHD in two breathing
conditions, breath hold and free breathing, were 519±108
and 526±107 (P=0.545), 1.89±2.41 and 62.88±2.04
(P=0.030) , 2.41±2.68 and 4.35±3.42 (P=0.048) and
0.98±0.7 and 1.42±0.5 (P=0.002), respectively. Also left
lung volume and V30 of lung in breath hold and free
breathing modes were 1763±315 and 1114±219 (P<0.001)
and 8.72±3.27 and 8.92±4.29 (P=0.819) respectively.
Person correlation did not show linear relation between
lung volume and its mentioned DVH parameters; for MHD
obtained r=-0.421 (P=0.057), for heart V30 and V22.5
obtained r=-0.500 (P=0.021) and obtained r=-0.371
(P=0.097) and also, for heart volume r=0.032 (P=0.889).
Conclusion
All MHD and heart V30 and V22.5 variables were
significantly higher with deep breathing in our study. It
was shown that irritated heart volume was reduced
significantly in this condition. V30 of lung were lower in
deep breathing so deep breathing can be efficient method
in
left
breath teletherapy.
EP-1188 DIBH radiotherapy in left-sided breast cancer
patients using an optical surface scanning system
S. Schönecker
1
, M. Pazos
1
, P. Freislederer
1
, D. Reitz
1
, H.
Scheithauer
1
, S. Corradini
1
, C. Belka
1
1
LMU University of Munich, Radiation Oncology, Munich,
Germany
Purpose or Objective
There is a potential for adverse cardiovascular effects in
long-term breast cancer survivors following adjuvant
radiotherapy (RT). For this purpose, the deep inspiration
breath-hold technique (DIBH) has been introduced into
clinical practice, to maximally reduce the radiation dose
to the heart. In the present study radiotherapy in DIBH was
applied using the optical surface scanning system
Catalyst
TM
/Sentinel
TM
.
Material and Methods
A total of 38 patients with left-sided breast cancer
following breast conserving surgery were analysed.
Normofractionated and hypofractionated radiotherapy
protocols were eligible for this prospective clinical trial.
Patient surface data and respiratory parameters were
acquired using the laser surface scanner Sentinel
TM
(C-RAD
AB, Uppsala, Sweden) during CT acquisition in free
breathing (FB) and DIBH. Dual treatment plans were
created and dosimetric output parameters of organs at
risk were compared using Wilcoxon signed-rank test. For
treatment application the optical surface scanner
Catalyst
TM
(C-RAD AB, Uppsala, Sweden) was used and
gating control was performed with an individual audio and
video glasses-based feedback system. The Catalyst
TM
is
interconnected to the LINAC systems via a gating interface
and allows for a continuous and touchless surface
scanning.
Results
Following initial patient training and treatment setup,
radiotherapy in DIBH with the Catalyst
TM
/Sentinel
TM
system
was time-efficient and reliable. 30 of 38 patients were
treated using normofractionated treatment protocols. In
these patients, the reduction of the mean heart dose for
DIBH compared to FB was 43.2 % (2.45 to 1.39 Gy; p <
0.001). The maximum doses to the heart and LAD were
reduced by 47.2 % (41.3 to 21.8 Gy; p < 0.001) and 61.7 %
(31.2 to 11.9 Gy; p < 0.001), respectively. For 8
hypofractionated regimes the reduction of the mean heart
dose for DIBH compared to FB was 50.1 % (2.13 to 1.06 Gy;
p = 0.012). The maximum doses to the heart and LAD were
reduced by 49.7 % (38.8 to 19.5 Gy; p = 0.012) and 77.3%
(29.9 to 6.8 Gy; p = 0.012), respectively. Overall, also the
mean lung dose and the V20 of the ipsilateral lung were
significantly lower (-16.1 % and -17.8 %) for DIBH (Lung
Mean
6.64 Gy; Lung V
20
= 11.7 %) compared to FB (Lung
Mean
7.92
Gy; Lung V
20
= 14.2 %; p each <0.001).
Conclusion
The Catalyst
TM
/Sentinel
TM
system enabled a fast and
reliable application and surveillance of DIBH in daily
clinical routine. Furthermore, the present data confirm
that using the DIBH technique during RT could significantly
reduce high dose areas and mean doses to the heart.