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

80 / 146

B.250
GAMMA-TOOLS: A MULTIPURPOSE PHANTOM FOR QUALITY ASSURANCE
IN GAMMA KNIFE STEREOTACTIC RADIOSURGERY TREATMENTS
S. Calusi L. Noferini M. Casat L. Marrazzo C. Arill A. Compagnucci
C. Talamonti S. Scoccianti D. Greto L. Bord L. Livi S. Pallotta
a University of Florence, Department of Clinical and Experimental Biomedical
Sciences -Mario Serio, Firenze, Italy; b Health Physics Unit AOU Careggi, Firenze,
Italy; c Medical Physics Unit AOU Careggi, Firenze, Italy; d Radiotherapy Unit
AOU Careggi, Firenze, Italy; e Neurosurgery Unit AOU Careggi, Firenze, Italy
Introduction: Geometrical and dosimetric accuracy are relevant param-
eters in SRS treatments. For this purpose we designed, realized and tested
a novel multipurpose phantom to assess the accuracy of dose delivery in
treatments with Gamma Knife.
Materials and Methods: The γTOOLS is a multipurpose modular phantom
for complete end-to-end tests. The phantom consists of two PMMA cylin-
ders screwed one above the other. The image deformation module is
composed by 12 removable PMMA foils hosted in the cylinders that realize
a 3D grid of points for image distortion measurements and for the verifi-
cation of MRI/CT image fusion accuracy. In the dose plan verification module
the PMMA foils form cavities where inserts with targets and inhomoge-
neities can be included in different positions and with different orientations.
Radio chromic films can be fixed between the inserts to measure the dis-
tributions of dose delivered to the target; inserts with inhomogeneities can
be used to estimate their impact on the delivered doses. The geometrical
accuracy of the image deformation and dose plan verification modules were
estimated. Delivered and calculated dose maps were compared for simple
and complex plans. The distortions of MR images for a commonly used se-
quence were mapped.
Results: The geometrical accuracy of the image deformation and dose plan
verification modules resulted <0.2 mm in both cases. Comparing calcu-
lated and measured dose distributions for simple shots (16, 8 and 4 mm),
we obtained gamma passing rates ranging from 71% to 85% with 1%/
1 mm and from 96% to 100% with 2%/2 mm (10% th, local approach). From
the dose comparison of a plan composed by 22 shots, we obtained a gamma
passing rate of 65.5% 1%/1 mm, and of 99.6% with 2%/2 mm (10% th, local
approach). Distortion regions in MR images were individuated in periph-
eral areas.
Conclusion: The outcome of the tests proved the capability of the phantom
to perform quality assurance with sufficient accuracy.
B.251
CLIMATE CHANGE IMPACTS ON RADIOLOGICAL RISK MANAGEMENT IN
HOSPITALS
G.M. Contessa V. Cannatà E. Genovese S. Sandri a ENEA, Italian
National Agency for New Technologies, Energy and Sustainable Economic
Development, Roma, Italy; b Ospedale Pediatrico Bambino Gesù, Roma, Italy
Introduction: The impacts of climate change (cc) are more and more bur-
densome, not only because extreme events are increasing in frequency and
intensity, but also because the severity of the impact also depends on the
vulnerability of the system. The accident at Fukushima Daiichi nuclear power
plant (NPP) has brought new attention on the matter of adaptation of NPPs
due to external events related to natural causes, but NPPs are not the only
situations in which the use of ionizing radiation is affected by the impact
of cc. In particular also at the hospitals the radiological risks due to cc
extreme events and disasters have to be considered and managed.
Materials and Methods: The impact of cc is analyzed regarding all the hos-
pital units in which the radiological risk is present, e.g. the areas in nuclear
medicine departments for the storage of radioactive waste, the prepara-
tion of radiopharmaceuticals, the brachytherapy treatment and the blood
irradiation devices.
Different scenarios are considered related to extreme weather events, in-
cluding the case of fire and in particular severe floods, which are increasingly
occurring in Europe over the last decade and have been recognized as one
of the most threatening disasters.
Results and Conclusions: Adaptation strategies are necessary to deal with
emerging changes in climate and weather, and both hard (design or struc-
tural methods) and soft (operating procedures) measures are presented to
be included in the hospital safety analysis and in the intervention plans
(DL 230/95, art 115-ter) in order to ensure adequate protection against severe
external hazards, according to the principle of optimization of radiologi-
cal protection.
In particular, the risk management has to focus on emergency prepared-
ness and response.
B.252
PATIENT RADIATION DOSE IN INTERVENTIONAL PROCEDURES FOR
INTRACRANIAL ANEURYSMS: FIRST RESULTS OF A MULTI-CENTER
EXPERIENCE
L. D’Ercole F. Lisciandr N. Paruccin A. Radic L. Riccard A. Turra
L. Manc E. Laf P. Remida F. Causin O. Marcello a Fondazione IRCCS
Policlinico San Matteo, Pavia, Italy; b A.O. San Gerardo, Monza, Italy; c Istituto
Oncologico Veneto IOV IRCCS, Padova, Italy; d Arcispedale Sant’Anna, Ferrara,
Italy; e Azienda Ospedaliera Padova, Padova, Italy
Introduction: Cerebral embolizations are considered high dose proce-
dures. The aim of this work is to compare and report, among four different
centers, the exposure data of patients undergoing these procedures, per-
formed by experienced operators using flat panel angiographic systems,
since we didn’t find similar experiences nationally.
Materials and Methods: We studied a sample of 199 therapeutic proce-
dures for intracranial aneurysms which were performed on four Philips Xper
Allura angiographic systems: two monoplanar (A and B) and two biplanar
(C and D), one of the latter equipped with a new technology for dose re-
duction (Clarity). We compared cumulative air kerma area product (PKA),
fluoroscopy time and cumulative air kerma.
Results: The median values of the four centers for fluoroscopy time and
PKA were the following: 44,3 (A); 21,6 (B); 20 (C) and 65,7 (D) min; 230
(A); 161,7 (B); 160,2 (C) and 118,4 (D) Gy*cm2. For the two biplanar systems,
the median values for cumulative air kerma are 1226,6 (C) and 877,10 (D)
mGy (Frontal); 600,54 (C) and 455,40 (D) mGy (Lateral), while for the two
monoplanar the median cumulative air kerma are 3134,3 (A) and 1741,9
(B) mGy. The data analysis showed that the Clarity system brings a PKA
reduction in the range 35 ÷ 94%.
Conclusions: The studied procedures can result in clinically significant ra-
diation dose to the patients, even when performed by trained operators
with use of dose-reducing technology and modern fluoroscopic equip-
ment. From this comparison, the need of exposure optimization for one
center has arisen. The substantial difference may be due to the utilization
of higher dose modes and to a non-optimized geometry.
In order to confirm these first results, the number of procedures per center
has to be made comparable; it is also advisable to collect the data values
for PKA-CINE or for the number of images, to analyze in more detail the
complexity of the procedures and the operating modes.
B.253
ITERATIVE RECONSTRUCTION COMPARISON IN CT: MODEL BASED (MBIR-
VEO), ADAPTIVE STATISTICAL (ASIR) AND NEW ADAPTIVE STATISTICAL
ITERATIVE (ASIR-V)
P. De Marco M. Guernieri D. Origgi a Istituto Europeo di Oncologia,
Milano, Italy; b Azienda Ospedaliero Universitaria Santa Maria della
Misericordia, Udine, Italy
Introduction: The aim of this work is to investigate the effect on physical
CT parameters of the new adaptive statistical iterative algorithm ASIR-V
in comparison to the currently used ASIR and the fully iterative recon-
struction (VEO).
Methods and Materials: A phantom (CATPHAN 500) and a water phantom
were scanned on a GE Discovery 750 and a GE Revolution at 120 kV, 0.5 s/
rot, 40 mm collimation, pitch close to 1, 0.625 mm slice thickness and mA
selected to obtain a CTDIvol of 1, 2, 4, 7 and 15 mGy. Reconstructions were
performed on the GE Discovery 750 with ASIR (40%–60%–100%) and VEO
and on the GE Revolution with ASIR-V (40%–60%–100%). Images were also
reconstructed on both scanners with FBP. Noise Power spectra (NPS) were
calculated with 4 ROIs on 80 water slices, MTF was evaluated on the
e75 Abstracts/Physica Medica 32 (2016) e71–e96