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

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IBDQ5 <−3, quartile value) was the endpoint. Correlations between diarrhea
and clinical/dosimetric parameters were assessed by logistic analyses.
Results: Pts without basal score and with D-IBDQ5 <−3 were excluded: 23/
77 pts showed acute GI toxicity.
No correlation emerged for sigmoid colon, while volumes of intestinal loops
receiving more than 5 to 40 Gy were correlated with D-IBDQ5 <−3 (p < 0.03).
Multivariate analysis confirmed a leading role of dosimetric variables, while
no significant correlation for clinical parameters was found.
The best cut-off values (assessed by ROC) discriminating pts with/without
D-IBDQ5 <−3 were: V20 < 250 cc, V30 < 150 cc and V40 < 90 cc. The overall
incidence equal to 10% and 50% resulted for the group of pts with DVH pa-
rameters lower/higher than thresholds, respectively (p = 0.0028, OR = 4.9,
AUC = 0.68).
Conclusion: Low–medium IMRT doses to intestinal loops were corre-
lated to diarrhea symptoms at the half/end of RT. Based on these results,
dose–volume constraints for the bowel have been proposed.
A.209
SPINAL LESION TREATMENT USING THE CYBERKNIFE: A SINGLE FRACTION
RADIOSURGICAL TECHNIQUE
C. Siragusa A. Brogn F. Midil V. Mongell A. Di Pasquale A. Micali
I. Bonapart M.C. Angiocch G. Fet A. Pontoriero G. Iat S. Pergolizz
I. Ielo a A.O.U. Policlinico G. Martino – U.O.C. di Fisica Sanitaria, Messina, Italy;
b Università degli Studi di Messina – Scuola di Specializzazione in Fisica Medica,
Messina, Italy; c A.O.U. Policlinico G. Martino – U.O.C. di Radioterapia Oncologica,
Messina, Italy
Introduction: The CyberKnife is an image-guided frameless stereotactic
radiosurgery system that allows radiosurgical treatments of spinal lesions.
This study evaluated the feasibility and effectiveness of the treatment of
spinal lesions with a single-fraction radiosurgical technique using the
CyberKnife with spinal cord sparing.
Material and Methods: CyberKnife system uses the coupling of an or-
thogonal pair of X-ray cameras to a dynamically manipulated robot-
mounted linear accelerator with six degrees of freedom that guides the
therapy beam to the intended target with the use of a simple frame-based
fixation. Real-time imaging allows the tracking of patient movement. Cer-
vical and lower spinal lesions were located and tracked with Xsight spine
tracking method. In this prospective cohort evaluation of a spine radio-
surgery technique, 21 spinal lesions were treated with a single-fraction
radiosurgery technique. The dose prescription was 8 Gy at isodose [50–
60%] to the whole vertebra (CTV) in order to obtain a [13–16 Gy] SIB to the
clinical tumor (GTV). Each treatment was elaborated using Multiplan TPS
(ver. 4.6.0 3.5.2 accuray) that uses sequential algorithm as the optimiza-
tion method (based on Pareto-solution). Objective function consists of
different steps and absolute constraints for CTV/GTV and OARs respectively.
Results: The analysis of results shows a good coverage of CTV with dose
escalation to the GTV, maintaining the dose constraints of OARs, particu-
larly creating a dose hole on the spinal cord as demonstrated by cumulative
DVH tables.
Conclusions: The CyberKnife allows treatment of spinal lesions, deliver-
ing high dose prescription and high dose gradient, with good results verified
by patients follow-up.
However, in order to achieve the clinical objectives, the associated plan-
ning phase could be complex and time consuming.
A.210
INNOVATIVE APPROACH IN IORT SARCOMA ASSESSMENT USING A
DEDICATED TREATMENT PLANNING SYSTEM
A. Soriani * A. Ciccotelli S. Carpino Mg Petrongari M. D’Andrea
G. Iaccarin G. Felici M. Benassi G. Sanguinet R. Biagini L. Strigari
a Laboratory of Medical Physics and Expert Systems, Regina Elena Cancer
Institute, Roma, Italy; b R&D Dept, S.I.T. Sordina IORT Technologies S.p.A., Aprilia,
LT, Italy; c Radiation Oncology Dept, Regina Elena Cancer Institute, Roma, Italy;
d Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori IRST, Meldola,
FC, Italy; e Orthopaedic Surgery Dept, Regina Elena Cancer Institute, Roma, Italy
Introduction: In this study, the IORT dedicated Treatment planning system
(CSRAD+), already validated on simple geometries, has been used to perform
calculation on sarcoma cancer patients and to compare the measured and
the calculated dose distribution in a clinical configuration In sarcoma IORT
treatments, the air gap between target and applicator and the extended
dimensions are critical parameters that must be fully taken into account.
Material and Methods: Twenty six patients with sarcoma cancer have been
treated using NOVAC 7 with energy from 7 to 9 MeV, an applicator diam-
eter from 40 to 100 mm, delivering a dose from 10 to 16 Gy. In vivo
dosimetric data collected during IORT using Gaf films have been used as
the gold standard for testing the accuracy of the algorithms implemented
in the TPS. CT images of five representative patients have been used to re-
produce the surgery room scenario, using the collected data and taking into
account tissue removal during the surgery procedure. Then, the CT images
were imported in the TPS and used in order to perform an accurate dose
calculation. The dose distributions have been compared with the in vivo
dosimetry in order to perform a sensitivity analysis.
Results: CSRAD + permits to make a virtual docking, to delineate the target
ROI, and to evaluate the dose distribution and the dose volume histo-
gram. The sensitivity analysis revealed potential setup uncertainties (up
to 80%) due to the manually performed alignment procedure in the sur-
gical room and inaccuracy on target thickness when blood and air are present
during the docking.
Conclusion: The developed CSRAD+ shows a good agreement with exper-
imental data and could replace the time consuming MC absolute dose
calculation, becoming a potential on-line aid for physicians and physi-
cists in the surgical room. The CSRAD+ could represent a training tool for
IORT staff and could provide a provisional plan that also includes DVH and
MU calculation.
A.211
COMPARISON OF THREE DIFFERENT SYSTEMS FOR GAMMA INDEX
EVALUATION IN IMRT TREATMENTS
S. Spampinato *, L. Raffaele, A. Gueli. Scuola di Specializzazione in Fisica
Medica, Università di Catania, Catania, Italy
Introduction: The Gamma Index (GI) method has become a gold stan-
dard for the comparison between measured and calculated dose distributions
in inverse radiotherapy planning. However, the methods to verify GI are
several, depending on the needs of the radiotherapy unit. This work in-
volves the comparison of three different instruments used for the GI
verification: an array of diodes, EBT3 films and a software that uses the
EPID system of the radiotherapy LINAC.
Materials and Methods: The array of diodes (MapCHECK2, SunNuclear)
allows a direct comparison between the measured dose map and that cal-
culated by TPS. Although this method is fast and direct, it is limited by
angular dependence and low spatial resolution. The second system (DoseLab,
Mobius) allows comparing maps calculated by the TPS which those ac-
quired with EBT3 films. The method has the advantage of excellent spatial
resolution, but it is expensive and time consuming. The last system
(DosimetryCheck, Mathworks) uses the information contained in DICOM
RT files of IMRT plans sent from the TPS and the portal images of the treat-
ment fields acquired with the EPID that are used to extract information
on fluence. In this way it is possible to obtain a 3D reconstruction of the
dose in the CT scan and to verify the GI and other parameters (isodoses,
DVHs, etc.). The system has the advantage of taking into account angular
dependence and different densities within the patient, but is based on a
recalculation and takes time for processing. The three methods were com-
pared for different anatomical regions to test and evaluate differences.
Results: The methods have been proven, in the limits of experimental error,
suitably comparable. DosimetryCheck allows a better knowledge of po-
tential over- or under-dosing, while EBT3 allow to better estimate regions
with a high dose gradient.
Conclusion: The methods allow a more or less accurate estimate of the
GI, but great care must be taken with complex plans with high dose
gradients.
e62 Abstracts/Physica Medica 32 (2016) e1–e70