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

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A.58
EXPLOITING THE MACHINE LOG FILES FOR VMAT AND IMRT TREATMENT
VERIFICATION
V. D’Errico * A. Sarnelli D. Bianchini E. Menghi E. Mezzenga
F. Marcocci L. Strigari M. Benassi a Medical Physics Department, IRCCS
Istituto Scientifico Romagnolo per lo Studio e la Cura dei tumori, Meldola, Italy;
b Laboratory of Medical Physics and Expert Systems, National Cancer Institute
Regina Elena, Roma, Italy
Introduction: The rotational-volumetric treatments are more complex than
the traditional IMRT; as more degrees of freedom are involved during treat-
ment delivery, a greater potential for delivery errors is associated to the
treatment section. Investigation and improvements of QA methods are man-
datory to avoid that potential errors are masked.
Materials and methods: A tool to capture the machine parameters stored
in the log file is developed and implemented. All the machine parameters
are compared with the planned ones in order to quantify delivery errors.
A new treatment plan including all the parameters extracted from the
machine log file output is the input for Pinnacle 9.10 and is used for the
re-calculation of the dose distribution. The re-calculated dose distribu-
tion is the actual delivered dose distribution. Action levels based on DVH
analysis and radiobiological quantities are proposed to evaluate the good-
ness of the delivered dose. Five left breast treatments and five prostate
treatments are considered. The deviations between calculated dose dis-
tribution and the delivered one were evaluated. The comparison included
evaluations of DVHs and radiobiological quantities.
Results: For the targets the discrepancy between the calculated and de-
livered dose distributions is less than 2%; the largest deviations occur in
correspondence of the highest dose. The discrepancy between the TCP values
is less than 5%. For the organs of interest near the targets, the discrepan-
cy between the dose distributions could reach 10%, while the discrepancy
between the NTCP values is less than 5%. The histograms of the planned
and delivered machine parameters are within the tolerances expected.
Conclusions: The machine log file analysis allows to verify that machine
parameters are consistent as planned. DVH analysis and radiobiological quan-
tities are a promising tool to evaluate the goodness of a treatment and
overcomes the limitations of the gamma index analysis.
A.59
WEB-INTERFACEDMONTE CARLO SIMULATION FOR QUALITY ASSURANCE
IN RADIATION THERAPY
F. Dalmasso F. Bourhaleb G. Russo N. Franza S. Spot A. Attili
a Istituto Nazionale di Fisica Nucleare, Torino, Italy; b Università degli Studi,
Torino, Italy; c Internet Simulation Evaluation Envision (I-SEE), Torino, Italy;
d DosimETrICA, Nocera Inferiore, Italy
Introduction: The increasing complexity of radiotherapy equipment (e.g.
IMRT) requires increasing accuracy in QA procedures. The system used to
verify the adherence between planned and delivered dose should be in-
dependent of the treatment planning system. Monte Carlo (MC) algorithms
are the reference choice. They allow computing the dose taking into account
patient heterogeneities and dosimetric effects generated by multi-leaf col-
limators (MLCs). In line with these motivations, we developed a MC-
based tool for dosimetric purposes and the independent verification of
planned dose distributions.
Materials and methods: The tool is built exploiting the Geant4 MC simu-
lation package. Any LINAC can be modelled, provided that the manufacturer
discloses its specifications. The simulation is performed in two stages. First,
the phase space above the secondary collimator is derived simulating the
traversal of the patient-independent part of the LINAC head. Then, the ra-
diation field generated from the phase space is propagated through the
secondary collimators, the MLCs and into the patient, where the dose dis-
tribution is scored. We run the simulations on a cluster, implementing an
automatic way to distribute the computations of events, monitor their pro-
gress and gather the outputs. We provide the user with a remote web-based
interface that eases the management of the workflow and the inspection of
the results.
Results: We tested the tool simulating the Varian Clinac iXmachine. For dif-
ferent energies and field sizes, the simulations and measurements in water
agreed to within 1.0% for percentage depth doses and 2.0% for dose profiles.
We then simulated a daily QA irradiation of a homogeneous phantom and
obtained that more than 90% of the points passed the 3%/3 mm γ-index
criterion.
Conclusions: Our MC tool provides a way to independently verify planned
dose distributions. The use of a web interface makes MC distributed com-
putations accessible to clinical users and allows one to run the computations
and inspect the results from any location.
A.60
A SIMPLIFIED INTENSITY-MODULATED RADIOTHERAPY TECHNIQUE FOR
THE BREAST TO REDUCE POSTERIOR PART OF THE AXILLA IRRADIATION
R. Di Benedetto *, C. Guida, D. Barzaghi, O. Cristiano, M. Elmo, S. Ancona,
A. Buonavita, A. Iacobelli, V. Lampognara, D. Spiniello, C. Iervolino.
Radiotherapy Department, A.O. S.G. Moscati, Avellino, Italy
Introduction: The breast irradiationwith conventional technique (CN-C) poses
a clinical difficulty in treating pendulous breast in patients with unfavor-
able anatomy of chest, causing an overdosage of posterior part of the axilla.
The aims of the study are to implement and to quantify the benefits of a sim-
plified IMRT technique using a set of beams with optimal orientations (SI-O).
Materials and methods: The patients included in the study were 55 con-
secutive patients in which the distance (d), calculated from the posterior
entrance of the lateral tangent beam to the target, was greater than 3.5 cm
on axial slices during the CT simulation.
SI-O plan is an extension of CN-C plan that uses the same tangent pair of
beams but with additional segments oriented on the CTV geometry. The
additional lateral tangent beam is split into two segments (s-C and s-D).
The segment s-D, parallel to lateral tangent beam, is generated on the BEV
view closing the collimator Y2 on the portion of the target identified as
the portion with a 95% isodose’s distribution compliant to CTV. s-C is gen-
erated in the same way on BEV, closing the collimator Y1 on the portion
of the target identified as the portion with overdosage on the posterior part
of the patient’s axilla. It has a different angle (about 13°) of lateral tangent.
The overlap between s-C and s-D has been done so that no hot spot is caused.
Results: Although we reached equal dosimetric and geometric index in the
comparison of the treatment plans, we found a significant difference for
CIRTOG (p < 0.05). The average CI is 1.38 ± 0.03 vs 1.45 ± 0.03 for the SI-O
and CN-C plans, respectively.
Conclusions: Using the SI-O technique, we have a significant sparing of the
posterior part of the axilla in patients with a particular breast anatomy.
The SI-O technique ensures a better CI with equal potential damage induced
on OARs, such as heart, lung, and contralateral breast.
A.61
RADIOTHERAPY IN ASSOCIATIONWITHHYPERTHERMIA: OUTCOME AND
TOXICITY IN THE TREATMENT OF SUPERFICIAL RECURRENT/METASTATIC
TUMORS
A. Di Dia E. Garibaldi E. Delmastr G. Bell M. Gatti G. Cattari
A. Salatino S. Squint A. Mirant M. Poli P. Gabriele M. Stasi
a Medical Physics, FPO-IRCCS, Candiolo Cancer Institute, Candiolo, TO, Italy;
b Radiotherapy Department, FPO-IRCCS, Candiolo Cancer Institute, Candiolo,
TO, Italy
Introduction: The aim of this work is to evaluate the outcome/toxicity of
radiotherapy-hyperthermia (RT-HT) in the treatment of superficial recurrent/
metastatic tumors.
Materials and methods:Twenty-nine patients (mean [range]: 69 years [49–
93], 17 breast carcinoma, 5 head and neck cancer, 2 malignant melanoma,
2 sarcomas, 1 uterine adenocarcinoma, 1 hepatocarcinoma, 1 squamous
skin cancer) were evaluated. Patients underwent radiotherapy treatment
using 3D-conformal radiotherapy (10/29) or helical tomotherapy (19/29).
External beam radiotherapy was delivered (1.8–5 Gy, 6–27 fractions, total
dose 20–57.5 Gy (mean dose: 41 Gy). Hyperthermia is performed with an
electromagnetic superficial applicator operating at the frequency of 434MHz.
HT session was delivered once/twice weekly (mean[range]: 5[1–9] ses-
sions), 1 hour after radiotherapy. Average (Tmean), maximum (Tmax) and
e18 Abstracts/Physica Medica 32 (2016) e1–e70