Physica Medica: European Journal of Medical Physics - Volume 32 - Supplement 1 - February 2016

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Results: The protocol warranties a higher accuracy showing a reduced error
in patient setup after the first five treatments. Systematic errors are reduced
but differences are observed across number of fractions and different pa-
thologies. In breast treatment the vertical orientation is affected of major
errors. After the first 5 treatments the errors in all directions are signifi-
cantly reduced for every pathology.
Conclusions: Results suggest introducing a new setup correction around
the 20th treatment in order to maintain the error in patient setup under
4 mm. The protocol reduce the systematic error in all pathology treated
and warranty a reduction of 44% of CB CT’s, reducing the imaging dose (in
the longest treatment as prostate, from 750 mSv to 420 mSv) and CB time
by the same percentage.
A.107
CATALYST SYSTEM IN BREAST CANCER RADIATION THERAPY: FEASIBILITY
STUDY AND PERFORMANCE ASSESSMENT
M. Haller S. Hofer P. Ferrari M. Maffei a Azienda Sanitaria dell’Alto
Adige – Servizio Aziendale di Fisica Sanitaria, Bolzano, Italy; b Azienda Sanitaria
dell’Alto Adige – Servizio di Radioterapia Oncologica del Comprensorio Sanitario
di Bolzano, Bolzano, Italy
Introduction: The patient positioning standard procedure in the Radia-
tion Therapy Department in Bolzano during breast cancer treatment was
based on iViewGTTM (Elekta AB, Stockholm, Schweden) orthogonal fields
EPID acquisition. The patient was centred using marker draws on skin and
position checked by iViewGT acquisition. The proposed study is a retro-
spective analysis to assess the performance of the new technology
CatalystTM-System (C-RAD AB, Schweden) aiming to substitute the draws
on patient in the positioning procedure and limiting the numbers of the
iViewGTTM. We compare the CatalystTM positioning versus draws on skin
positioning observing the numbers of false-negative and comparing the po-
sitioning errors. The new equipment is less time consuming during the
positioning given an on line feedback of the patient position.
Material and Methods: Two groups of patients are considered. 1236 patient
are positioned with draws and 589 patients with CatalystTM. Every patient
position in both groups was verified by iViewTM orthogonal fields EPID ac-
quisition, in order to identify the false negative and the relative error. Percent
of false-negative, standard deviation and mean in the three orientations
were calculated and compared respectively between the two groups. T-test
was used to compare intra-group standard deviation.
Results: Results showed comparable efficacy of the new procedure
CatalystTM versus the draws positioning with a percentage of false-
negative equal to 12%. Position errors are comparable in longitudinal and
lateral direction and significantly (p < 1.08E −6) reduced in vertical direc-
tion of 50% using CatalystTM.
Conclusions: The new equipment CatalystTM can be considered an im-
provement in patient position during breast cancer radiation therapy,
warranting a comparable efficacy respect the standard procedure, improve
the precision in vertical direction and results to more practice, time-
saving and warranting an on line feedback in the patient position limiting
the errors during treatment.
A.108
DOSIMETRIC COMPARISON BETWEEN FOUR IRRADIATION TECHNIQUES
FOR BREAST CANCER
M. Iacco C. Zucchett M. Marcantonini A.C. Dipilat V. Lancellott
C. Aristei R. Tarducci a Medical Physics Department, Santa Maria della
Misericordia Hospital, Perugia, Italy; b Radiation Oncology Department, Santa
Maria della Misericordia Hospital, Perugia, Italy
Introduction: The purpose of this work was to compare the dosimetric
results of treatment plans using 3D Conventional Radiation Therapy (3DCRT),
Intensity Modulated Radiation Therapy (IMRT) linac-based, with Helical
Tomotherapy (HT) and Direct Tomotherapy (DT) in breast cancer pa-
tients, who required irradiation of the chest wall/breast and draining nodes.
Materials and Methods: 30 breast cancer patients (17 right, 13 left) were
enrolled. Four plans (3DCRT, IMRT linac-based, HT and DT) were created
for each patient. Dose prescription was 50 Gy in 25 fractions to the PTV
retracted 2 mm from the skin (PTV eval).
Results: Plans were compared in terms of doses to the PTV, homogeneity
index (HI) and doses to OARs. The non-parametric Friedman test for paired
data and the Conover post-hoc analysis were used to compare the differ-
ent irradiation techniques. D98%, D95%, D50% and mean doses (Dmean) of
target increased significantly for IMRT techniques particularly for
tomotherapy treatments. HI was significantly higher for HT, compared with
the other techniques. V5 Gy and V20 Gy of the ipsilateral lung and V5 Gy
of the contralateral lung increased significantly with the IMRT tech-
niques. The heart received significantly lower mean and maximum doses
(D2%) with 3DCRT for right-sided treatments; significantly lower D2% and
V25 Gy of heart results were achieved with HT techniques in left-sided treat-
ments, but the Dmean was higher. The contralateral breast was better spared
with 3DCRT.
Conclusions: IMRT techniques significantly improved the HI and the
minimum doses to the target. However, this result was achieved at the cost
of a greater exposure of all OARs (lungs, heart in right-sided and left-
sided treatment and contralateral breast) to low and medium doses. With
regard to left-sided treatments, HT resulted to be the better performing
technique for the sparing of the heart.
A.109
PRE-TREATMENT DQA USING ARCCHECK FOR CRANIOSPINAL
IRRADIATION WITH HELICAL TOMOTHERAPY
G. Iacoviello *, B.F. Abbate, V. Caputo, F. D’Alia, K.K. Gallias, M. Spano’. ARNAS
– Ospedale Civico – UOC Fisica Sanitaria, Palermo, Italy
Introduction: The aim of this work is to analyze two pre-treatment dose
verification methods using the ArcCheck diode array for craniospinal ir-
radiation (CSI) with helical tomotherapy (HT).
Materials and Methods: The Sun Nuclear diode array, ArcCheck, is a cy-
lindrical acrylic phantom that can be used for dose verification of fields
up to 20 cm. Some radiotherapy techniques, however, as craniospinal ir-
radiation or total marrow irradiation, require fields longer than 20 cm. To
overcome this limitation, we followed a double procedure. In the first one
we split the verification plan in two DQA plans, calculated at the head level
and at the middle dorso-lumbar level, on two different kVCT Data Set of
ArcCheck obtained with the phantom oriented with electronics toward gun
and toward target respectively. In the second one we calculated one single
DQA plan on a virtual CT of a longer ArcCheck (50 cm), downloaded from
the Sun Nuclear Support web page, delivered in two steps with different
ArcCheck orientation and then analysed using the merging function in the
SNC Patient software. In both cases the DQA plans were created with “fine”
grid calculation and with the PMMA ArcCHECK cavity insert.
Results: The comparison between calculated and measured dose was per-
formed in 3D Absolute Dose Mode on 15 DQA plans with a 3%/3 mm gamma
analysis criterion according to Van Dyk with a 10% threshold. The average
gamma passing rate for splitted DQA plans was 99.1% ± 0.8% (range 99.7–
98.3%) for the head region and 99.4% ± 0.4% (range 99.8–99.1%) for the dorso-
lumbar region. For the single DQA plan we obtained 97.1% ± 0.6% (range
96.1–97.5%).
Conclusions: In our institution a DQA plan is accepted if 95% of the points
“pass” the 3%–3 mm gamma evaluation criterion and this result has been
obtained for both methodologies. Due to limited number of cases we cannot
assess any statistical difference between the two methods.
A.110
CLINICAL IMPLICATIONS AFTER A CHANGE IN THE DOSE CALCULATION
ALGORITHM IN VMAT TREATMENTS OF NASOPHARYNGEAL TUMORS
A. Ianiro F. Deodato G. Macchia C. Digesu P. Viola M. Craus
M. Ferro V. Picardi M. Nuzzo A. Piermattei V. Valentini
A.G. Morgant S. Cilla a Fondazione di Ricerca e Cura Giovanni Paolo II-
Università Cattolica del S. Cuore, Campobasso, Italy; b Policiinico Universitario
A. Gemelli – Università Cattolica del S. Cuore, Roma, Italy; c DIMES Università
di Bologna – Ospedale S.Orsola Malpighi, Bologna, Italy
e32 Abstracts/Physica Medica 32 (2016) e1–e70