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

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viation (SD), skewness (SK), kurtosis (K), entropy (E) and uniformity (U).
24 patients who developed bone RT-related damages during the follow-up
constitute the study patient (SP) group. TA data were collected for a com-
parative analysis also in a control group of 48 patients (CP) not developing
bone damages. The CPs were matched taking into account: age, sex, type
of tumor, intent of postoperative treatment, comparable doses to the con-
sidered organs-at-risk. A univariate analysis (Pearson correlation) and a
multivariate analysis (logistic regression) using the SPSS software 17.0 were
performed.
Results: In the comparison between SP and CP groups, the univariate anal-
ysis showed a significant correlation of the ROI parameters of L5: SD (p:
0.012); K (p < 0.001), E (p: 0.001); U (p: 0.008); and of the femoral head:
M (p < 0.001); SD (p < 0.001), with the development of bone damage. The
logistic regression highlighted a significant correlation with the ROI pa-
rameters of L5: E (p: 0.004); U (p: 0.014), and femoral head M (p: 0.022)
and SD (p: 0.042), with an overall model Nagelkerke R2 of 0.590.
Conclusions: These results and those reported in previous related studies
deserve some interest, since the knowledge of predictive factors of bone ra-
diation damagemight help in patient selection for pelvic RT and in identifying
suitable dose constraints for the bony pelvis in RT planning for patients at
risk.
A.15
HIFU GENERATED FAST HYPERTHERMIA AS A NEW OPTION FOR
GLIOBLASTOMA TREATMENT
G. Borasi G. Russo A. Nahu Q. Zhan M.C. Gilardi a CNR–IBFM,
Milano, Italy; b The Clatterbridge Cancer Centre NHS Foundation Trust,
Bebington, UK; c Radiation Oncology Department, University of Nebraska
Medical Center, Omaha, NE, USA
Introduction: Glioblastoma (GBM) is a highly aggressive tumor of the central
nervous system, corresponding to grade IV of the World Health Organiza-
tion histological classification (Louis et al., 2007). High grade gliomas are the
most common primary brain tumor in adults, with an incidence of 3.1 per
100,000 person-year in the USA and themedian survival times of 14.6months
(Stupp et al., 2005) after first occurrence and 11.9 after the first re-resection
(Quick et al., 2014). Against to this pathology, we proposed (Borasi et al., 2014)
the use of high intensity focused ultrasound (HIFU).
Material and methods: The first brain tumor ablation treatments with the
magnetic resonance (MR) guided HIFU (Exablate Neuro), recently de-
scribed (Coluccia et al., 2014), revealed the power limitation of the system
in penetrating the skull bone so that only a small tumor volume could be
ablated. We then concentrate ourselves on the use of this HIFU device for
administering, on a larger possible volume, a low power “fast hyperther-
mia”, coupled with a standard EBRT protocol. We simulated the combined
effect of radiotherapy (EBRT) and fast hyperthermia (FH) in the mathe-
matical frame of Fisher–Kolmogorov equation. A new formulation of the
synergistic effect has been developed.
Results: The EBRT plus FH should be able to overcome the main problem
of GBM treatments, that is, the progressive modification to a more aggres-
sive and resistant entity, due to a subset of glioma cells that share many
characteristics with stem cells (Galli et al., 2004; Singh et al., 2004). These
cells are generally resistant to RX and TMZ and are considered a cause of
recurrence (Bao et al., 2006; Chen et al., 2012).
Conclusion: The assumption that hyperthermia can sensitize glioma stem-
like cells to radiation has been recently verified by Man et al. (2015). The
EBRT plus (HIFU generated) FH treatments deserve, in our opinion, a large
scale trial to give a new therapeutic perspective to this devastating pathology.
Acknowledgment – In memoriam: The authors would like to dedicate this
presentation to the memory of Doctor L. Andreucci.
A.16
COMPARISON OF STATIC AND ROTATIONAL IMRT TECHNIQUES IN THREE
DOSE LEVEL PLANS FOR HEAD AND NECK CANCER
M. Bougtib M.R. Malisan M. Cresp C. Foti M. Guernier E. Morett
a International Master on Medical Physics, Trieste, Italy; b Medical Physics
Department, AOU SMM Udine, Udine, Italy
Purpose: The aim of this study is to optimize the performance of triple-
arc VMAT (TAV) against conventional IMRT for 3 dose level irradiation of
HN cancer.
Methods: A planning study was conducted on 10 patients previously treated
with IMRT for HN cancer with 3 dose levels (70, 63, 56 Gy/35 fractions)
delivered by a SIB technique. Optimization was done in a Varian Eclipse
TPS. IMRT plans included 7 beams using SW technique. Three TAV plans
were generated for each patient: 3 full-arc plan, 3F (collimator angles (CA)
0°, 20°, 340°); 2 full + partial arc plan, 2FP0 (CA 20°, 340°; 0° for partial arc);
2 full + partial arc plan, 2FP90 (CA 20°, 340°; 90° for partial arc). Dose nor-
malization was D(95%) = 70 Gy for primary tumour and involved nodes
(PTV70), while objective was D(95%) > 95% of prescription dose for PTV63
and PTV56. OARs were brainstem, spinal cord, parotids, oral mucosa, larynx,
mandible, vertebrae, and thyroid. Plan comparison included PTV cover-
age, dose homogeneity and conformity, OAR sparing, healthy tissue integral
dose (HTID) and MUs.
Results: Similar coverage of all PTVs is obtained in all techniques. TAV plans
show better homogeneity and conformity in PTV70 compared to IMRT, al-
though the difference is significant only for the 2FP90 technique. For spinal
cord and vertebra the 2FP90 plans show significantly lower maximum dose.
No significant changes are observed in mean dose to parotids or maximum
dose to mandible, while oral mucosa and thyroid result better spared with
TAV techniques. Although smallest for IMRT, the mean HTID is not signifi-
cantly different from the TAV techniques. Finally, MUs for all TAV techniques
are significantly lower than for IMRT.
Conclusion: TAV techniques allow the same PTV coverage and OAR sparing
as 7-field IMRT, with one third of MUs and better dose homogeneity. HTID
results were lowest in IMRT, but the difference is not significant. As for the
optimal TAV configuration, 2FP90 including one partial arc with a 90° col-
limator angle seems to spare best spinal cord and brainstem.
A.17
TOWARDS ADAPTIVE TOMOTHERAPY: ASSESSMENT OF PLANNING CT TO
MVCT DEFORMABLE IMAGE REGISTRATION RELIABILITY FOR “DOSE OF
THE DAY” CALCULATION IN HEAD AND NECK
M. Branchini * S. Broggi M.L. Belli C. Fiorino G.M. Cattane
L. Perna R. Calandrino a IRCCS San Raffaele Scientific Institute, Milan, Italy;
b Scuola di Specializzazione in Fisica Medica, Università degli Studi di Milano,
Milan, Italy
Introduction: The aim of this study was to report the results of the vali-
dation of a developed method for dose of the day calculation in head and
neck (HN) tomotherapy based on deformable image registration (DIR) of
the planning CT to MVCT.
Material and methods: kVCT/MVCT images of ten HN patients treated
with helical tomotherapy (HT) with a simultaneous integrated boost
(54/66/69 Gy/30 fractions) were retrospectively analysed. For each patient
the planning kVCT (CT-plan) was elastically registered (DIR) to the MVCT
acquired at the 15th therapy session (MVCT15) with a B-Spline deforma-
tion algorithm using Mattes mutual information (open-source software
3D Slicer), resulting in a deformed CT (CTdef). At the same day
a kVCT was acquired with the patient in the same treatment position
(CT15) and taken as reference. The original HT plans were recalculated
both on CTdef and CT15 in the HT planning station. Dose distributions on
CTdef and CT15 were compared; local dose differences < 2% of the pre-
scribed dose (DD2%) and global gamma-index values (2%-2 mm; with a
threshold dose level equal to 20% of the prescribed one) were assessed
for all the available transversal slices (step6 mm) with Mapcheck SNC
patient software.
Results: The results of DIR were qualitatively satisfactory when comparing
CTdef against CT15. On average, 94.4% ± 0.9% of points passes the gamma
analysis test and 87.9% ± 1.1% of the body’s voxel was found for DD2% (on
average 27 sliceswere available for each patient). If excluding 3 patientswhere
a relevant number of slices were cut due to the narrow FOV of the MVCT15,
the valueswere further improved respectively to 95.7% ± 0.8% and 89.1%± 1.3%.
Conclusions: This study represents the first proof of the dosimetric accu-
racy of DIR from kVCT to MVCT for calculating the dose of the day in HT
treatments. The suggested method is sufficiently quick and reliable to be
e5 Abstracts/Physica Medica 32 (2016) e1–e70