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

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The analysis of the dose reconstruction at the isocenter was performed by
DISO software, developed by INFN and the University Cattolica del Sacro
Cuore.
The CBCT calibration and the 2D and 3D gamma analyses are performed
by a toolkit software called GADD-23 developed in Matlab and Bash lan-
guage, interacting with two open source software, Elastix and CERR. GADD-
23 has been developed in our Radiotherapy Department.
Results and conclusions: The method developed is able to focus on sys-
tematic anatomical changes that some patients can have during the
treatment; in these cases, it is essential to replan, or to underline random
type errors, on which it may be useful to conduct the attention of the ra-
diotherapist, although is not necessarily a replanning.
A.11
SBRT OF PROSTATE AND SEMINAL VESICLES WITH TOMOTHERAPY:
FEASIBILITY AND DOSIMETRIC RESULTS
L. Berta L. Vigna S. Aimonetto A. Peruzzo Cornetto F. Migliacci
A. Fozza F. Muno T. Melon a Azienda USL Valle d’Aosta – Fisica Sanitaria,
Aosta, Italy; b Azienda USL Valle d’Aosta – Radioterapia, Aosta, Italy; c Azienda
USL Valle d’Aosta – Radiologia Diagnostica E Interventistica, Aosta, Italy
Introduction: We present preliminary data of a feasibility study for a SBRT
(stereotactic body radiotherapy) protocol for low and intermediated risk
prostate cancer that delivers 36.25 Gy to the prostate and 31.6 Gy to the
seminal vesicles (SV) in 5 fractions.
Materials and methods: Ten consecutive patients previously treated with
a moderate hypofractionated scheme were considered. The original pre-
scription was 70.2 Gy (2.7 Gy/fraction) to the prostate gland (PTV1.1) and
61.1 Gy (2.35 Gy/fraction) to the SV (PTV1.2). Seven millimeter margins were
posteriorly added to the CTV and 10 mm in all other directions to create
PTVs. Patients were instructed to follow a low fiber diet and an “ad-hoc”
protocol for rectal and bladder filling. A knee–feet device immobilization
was used during CT simulation. For each patient, new plans were created
using the same CT images and contours with prescriptions of 36.25 Gy to
PTV1.1 and 31.6 Gy to PTV1.2 in 5 fractions. All plans were elaborated in
helical tomotherapy platformwith technical settings used for standard plans
(pitch 0.215, field width 2.5 cm, modulation factor 2.5).
Results: Mean target coverage (V95%) and maximum dose (D2%) were
97.4 (96.5–99.4%) and 103% (103%–106%) of the prescription dose. Maximum
doses (D1cc) and V32.6Gy for the rectum were 36.25 Gy and 10% (6%–
14%). V18Gy were on average 46% and 47% for rectum and bladder
respectively. Values of V18Gy greater than 45% for bladder were ob-
served for patients with a bladder volume lower than 200 cc. V14.5 Gy
for femoral heads was 1.8% and the average value of D50 for penile bulb
was 29.7 Gy (12.3 Gy–36.5 Gy). The average treatment time was 12.3
minutes.
Conclusions: SBRT of prostate and SV with tomotherapy is feasible. The
main dosimetric goals can be achieved with default technical settings in a
reasonable delivery time. Superior dose distributions to organs at risk are
expected if a dedicated SBRT protocol is used in order to reduce CTV-PTV
margins and different technical settings are considered to increase dose
conformation.
A.12
RADIOTHERAPY INTER-FRACTION BLADDER SETUP VARIATIONS FOR
CERVICAL CANCER PATIENTS ASSESSED WITH A CBCT
C. Bianch F. Tanzi R. Novari L. Pozzi , D. Doino a S.C. Fisica Sanitaria,
Ospedale Di Circolo e Fondazione Macchi, Varese, Italy; b Dipartimento di
Biotecnologie e Scienze della vita, Università dell’Insubria, Varese, Italy; c S. C.
Radioterapia, Ospedale Di Circolo e Fondazione Macchi, Varese, Italy
Introduction: For cervical cancer patients, bladder filling variations may
be very important in EBRT target coverage and optimization treatment plan-
ning process. For a group of 21 patients who received filling bladder
instructions, inter-fraction variations and time trends in bladder volume
were quantified with a CBCT.
Materials and methods: Patients were treated in supine positions on
Posirest-2 Arm Support and Combifix cushion; the dose prescription was
50.4 Gy in 28 fractions, and all treatment plans were delivered with 6 MV
photon beam Rapidarc. CBCT images were acquired during treatment (mean
10 CBCT for patient) to verify the bladder filling.
Results: The population mean bladder volume at planning of 162.9 ± 50.6 cc
(1 SD) was reduced to 128 ± 85.5 cc (1 SD) in about 6 weeks, a reduction
of 48%, revealing an inter-fraction time trend. Intra-patient variation bladder
volume during RT was 162.8 cc (1 SD = 85.1 cc), range 60.9–329.5 cc.
Conclusions: We have tested for all patients the DVH-bladder consisten-
cy; for this purpose, we performed a statistical analysis (chi-square test)
considering the DVHs at planning compared to those obtained from CBCT
during therapy and evaluating for each patient, the volume receiving 10,
20, 30, 40, 50 Gy. We have observed that, for 50% of the patients, the volume
receiving 50 Gy is the only one for which the volume differences has a p
value < 0.05 in the chi-square test.
A.13
DOSIMETRICAL EVALUATIONS BY CALCULATING EQD2, EUD AND NTCP
IN IMAGE GUIDED VAGINAL HDR BRACHYTHERAPY
C. Bianchi F. Tanz L. Pozz *, R. Novario D. Doin a S.C. Fisica Sanitaria,
Ospedale Di Circolo e Fondazione Macchi, Varese, Italy; b Dipartimento di
Biotecnologie e Scienze della vita, Università dell’Insubria, Varese, Italy; c S. C.
Radioterapia, Ospedale Di Circolo e Fondazione Macchi, Varese, Italy
Introduction: We evaluate EQD2 differences, for rectum and bladder,
between DVHs obtained with the TPS for the first fraction and DVHs cal-
culated by re-planning at each fraction for HDR adjuvant vaginal treatments.
21 patients with endometrial ADK who had radical surgery were treated
with exclusive HDR BT with this fractionation scheme: 6 Gy fraction/36 Gy,
6.5 Gy fraction/39 Gy, 7 Gy fraction/35 Gy; BED10 from 57.6 Gy to 67.9 Gy.
Material and methods: We compared the EQD2 calculated from D2cc, using
the geometry of the first fraction, with the EQD2 calculated by re-planning
each BT fraction on new CT images.
Results showed percentage differences for bladder from −38.17% to +34.75%,
for rectum from −83.49% to +45.00%.
EQD2 differences for each OAR of all patients were tested using t-test for paired
data: differences were not statistically significant. We calculated EUD and
NTCP from DVHs by using EUDMODEL software running in Matlab. We used
values for the parameters α/β for rectum and bladder taken from “Applied
Radiobiology” (a = 6.0; γ50 = 3.0; TD50bladder = 80.3; TD50rectum = 80.0).
Results: We found that re-planning at each fraction by TC gives advan-
tages because EQD2 is very different if calculated without taking into account
each fraction set-up. This is because all planned fractions were calculated
so that the D2cc is the highest possible (value nearest the recommended
ESTRO limit).
Conclusions: EQD2, EUD and NTCP are very different for each fraction setup,
allowing a better description of the results of the treatment in terms of
organ sparing.
A.14
BONE TEXTURE ANALYSIS AS PREDICTIVE FACTOR OF RADIATION-
INDUCED DAMAGE IN PELVIC RADIOTHERAPY TREATMENT
M. Biondi V. Nardone A. Bogi L.N. Mazzoni E. Vanzi
G.M. Belmonte G. De Otto P. Tini L. Pirtoli A. Guasti
F. Banci Buonamici a Department of Medical Physics, University Hospital of
Siena, Siena, Italy; b Department of Radiotherapy, University Hospital of Siena,
Siena, Italy; c Department of Medical Physics, U.S.L. 7, Siena, Italy
Introduction: To assess the potential role for a CT-based, bone texture anal-
ysis as a predictive factor of bone radiation damage in patients undergoing
radiotherapy (RT) for pelvic malignancies.
Materials and methods: Patients were selected from those treated with
RT for pelvic malignancies from January 2010 to December 2014. CTs ac-
quired for RT planningwere collected and analyzedwith a homemade ImageJ
macro. Two ROIs were selected: the L5 vertebral body and the femoral heads.
Texture analysis (TA) parameters were evaluated: mean (M), standard de-
e4 Abstracts/Physica Medica 32 (2016) e1–e70