1017 / 1096
S1001
ESTRO 36
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Results
IMRT and VMAT significantly improved the conformity to
the Planning Target Volume (PTV) and increased the
volume of PTV covered with 50Gy. This effect was clearly
illustrated in the region of the lateral field edges since it
is difficult to achieve in 3D-CRT due to the dose building
up effect. The lung volume received 20Gy in IMRT and
VMAT were higher than that of 3D-CRT but the result was
found to be not significant. The treatment time in terms
of number of monitor unit (MU) was found to be
significantly lower in 3D-CRT but the time required for
setting up the patient to the treatment position was
almost doubled to other two techniques.
Conclusion
IMRT and VMRT are well-accepted techniques and able to
provide encouraging dosimetric results for bilateral breast
irradiation. VMAT could further reduce the overall
treatment time because of the simple setup procedure
and the relatively small number of MU. This study
suggested that VMAT technique is feasible and is
recommended for bilateral breast irradiation.
EP-1828 Mean Dose in healthy lung for chest tumors
treated with Stereotactic Body Radiation Therapy
(SBRT)
J.l.Monroy Anton
1
, M. Asensio Martinez
2
, V. Borreda
Talon
2
, J. Hernandis Barbera
2
, M. Marco Collado
2
1
Hospital universitario de la ribera, radiation oncology,
alzira, spain
2
hospital universitario de la ribera, radiation protection
and radiophysics dpt, Alzira, Spain
Purpose or Objective
Stereotactic body radiotherapy (SBRT) is considered
treatment of choice in patients with pulmonary lesions not
candidates for surgical treatment.
High doses of radiation, both total and per fraction
,
requires a dose limitation in healthy organs at risk
(contralateral lung, heart, spine)
Our
objectives
were:
-- To evaluate the mean dose (Dm) received by the
contralateral lung in SBRT for thoracic lesions.
-- To analyze if PTV volume and/or total dose (TD) are
related to the Dm achieved
in the contralateral lung.
Material and Methods
A total of 26 pulmonary lesions treated with SBRT were
evaluated. Simulation was performed with CT 4D
respiratory gating and customized immobilization devices.
PTV was designed with an isotropic margin of 0.5 cm from
the GTV. Treatment was delivered with Linear Accelerator
( CLINAC, Varian), and verification done with internal
fiducial markers surrogates.
Results
Total Dose (TD) (Gy): range 20 – 45 Gy. Most cases (18;
69%) received a TD of
45Gy.
Dose/fraction: range 10-20 Gy/fr. The most frequent
fractionation was 15 Gy (20; 77%).
PTV volumen (cc): range between 10.18 - 99.33cc, with a
mean: 36.14cc ; median:
26.65cc
Healthy lung Dm (Gy): range 0.23 - 9.8 Gy; mean: 1.75Gy;
median: 1.25Gy
The increase in PTV volume did not associate an increase
in the average dose to the contralateral lung. Fig 1
An increase in total dose not involved an associated
increase in the dose to the healthy lung. Fig. 2
Conclusion
The Mean Dose received by the contralateral healthy lung
is
minimal.
No relationship was found between the increase in total
dose and increased in contralateral lung Dmean
No relationship was found between the volume of PTV and
Dmean reached in contralateral
lung
The parameters PTV and TD do not appear to relate to the
dose received to the contralateral
lung.
We can conclude that SBRT technique can be applied
safely largely preserving the healthy lung.
EP-1829 Dose delivery accuracy in total body
irradiation delivered with Step and Shoot IMRT
T. Berlon
1
, L. Specht
1
, P.M. Petersen
1
, L.S. Fog
1
1
Rigshospitalet, Clinic of Oncology- Department of
Radiotheraphy, Copenhagen, Denmark
Purpose or Objective
In total body irradiation (TBI) delivered with step and
shoot IMRT (SS IMRT), the dose conformity is considerably
improved compared with the more widely used TBI
delivered with open fields. This conformity is achieved
through the use of multiple fields defined by multileaf
collimators (MLCs). We aim to quantify the accuracy with
which TBI patients treated at our clinic were positioned,
and to determine the effect any positioning errors may
have had on the delivered dose.
Material and Methods
Images acquired as a routine part of the patient treatment
with the Theraview ™ (Theraview Technology, Leuden,
The Netherlands) imaging system were used to determine
the positioning shift in the cranio-caudal direction.
Images for 11 consecutive patients, each receiving 6
fractions, were analysed and the shifts recorded (figure
1). For 3 of the patients, only images for 5 of the 6
fractions were available.