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

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to 15 × 12 cm). Different dose indicators were evaluated: KAP, cumulative
air kerma at the isocenter (Kair), cone beam dose index (CBDI) and central
cumulative dose evaluated in a single and in a stack of three adjacent CTDI
phantoms. TLDs and radiochromic films positioned in an anthropomor-
phic Rando phantom were used to measure organ and effective doses (E).
Results: For radiotherapy CBCT, the triple body phantom setup provided
values about 33% greater in the central position and about 8% greater at
the peripheral in comparison with single phantom measurements. CBDI
values were on average 10% lower than central cumulative doses. In phantom
dose indexes provided better correlation with organ doses than Kair and
KAP, with average ratios in the range 0.9–1.1 and variations for different
organs and protocols below 20%.
Measurements of in phantom dose indicators were more critical for dental
CBCT, due to asymmetric and partial exposure. Good correlations were ob-
served between KAP and E, with variable ratios for different FOVs from
0.09 μSv mGy−1 cm−2 to 0.15 μSv mGy−1 cm −2.
Conclusion: All in phantom dose indicators for radiotherapy CBCT pro-
vided similar information about organ doses for a standard patient size.
For dental CBCT a good correlation of E vs KAP was assessed, whereas large
organ dose variations were observed with constant dose indicators and dif-
ferent patient positioning.
B.301
EFFECTIVENESS EVALUATIONS OF AN ORGAN BASED MODULATION
SYSTEM FOR COMPUTED TOMOGRAPHY
O. Rampado S. D’Angelo F. Marchisio P. Isoard A. Izzo G. Gandin
R. Ropolo a S.C. Fisica Sanitaria, A.O.U. Città della Salute e della Scienza, Torino,
Italy; b S.C. Radiodiagnostica Universitaria, A.O.U. Città della Salute e della
Scienza, Torino, Italy
Introduction: Recent developments in CT dose reduction tools included the
use of organ dose modulation (ODM) systems. The purpose of this study was
the evaluation of dose reduction and image quality variations obtained by
the application of an ODM system provided with a new CT equipment.
Materials andMethods: Measurements were performed on a GE OPTIMA 660
for different protocols and acquisition parameters. Angular distribution of current
modulation was evaluated by means of a dose temporal sampling with a solid
state dosimeter. Radiochromic films positioned over an anthropomorphic
phantomwere used to compare patient organ doses in presence and in absence
of the ODM system. Noise variations were evaluated on images of geometri-
cal and anthropomorphic phantoms. Nominal tube current and dose indicators
variations were recorded for 30 patient examinations.
Results: A tube current reduction between 30% and 40% was observed over
anterior 120° for small FOV and 180° for large FOV. Dose reductions up to
59% for thyroid and up to 37% for breast were measured. Radiochromic films
highlighted the non uniform dose distribution consequent to spiral acqui-
sition and current modulation. Noise variations were below 20% for most
cases. Tube current variations recorded during actual examinations con-
firmed phantom observations, whereas associated dose indexes reductions
were about 10%. The application of the ODM did not interfere with rou-
tinely activity and did not add significant time to the procedure execution.
Conclusion: Our results confirmed that ODM is an effective dose reduc-
tion system for CT, with an acceptable impact on image quality. The
associated dose reduction is assessable by means of real time or large area
dosimeters, whereas related dose indexes registration do not provide useful
information about ODM effective use.
B.302
USE OF A COMMERCIAL SOFTWARE TO MANAGE DOSES FROM
RADIOLOGICAL PROCEDURES IN A MULTI-SITE ENVIRONMENT:
PRESENTATION AND EARLY EXPERIENCE OF A PROJECT FROM AIFM
L. Riccardi * M. Gabusi F. Cretti L. D’Ercole A. Gambirasio
F. Lisciandr S. Loi P. Marini M. Mangiarotti S. Pin M. Quattrocch
E. Rinald E. Trevisio A. Turra G. Zatelli D. Zefiro S. Zucc G. Catoll
L. Begnozz M. Paiusc a Istituto Oncologico Veneto IOV IRCCS, Padova, Italy;
b Ospedale Papa Giovanni XXIII, Bergamo, Italy; c Fondazione IRCCS Policlinico
S. Matteo, Pavia, Italy; d AO G. Brotzu, Cagliari, Italy; e ASL Sassari, Sassari, Italy;
f ASL Firenze, Firenze, Italy; g Tecnologie Avanzate, Torino, Italy; h Ospedale S.
Luigi, Orbassano (To), Italy; i Azienda Ospedaliera Sant’Anna, Ferrara, Italy; j ASL
5 Spezzino, La Spezia, Italy; k Azienda ULSS 9 Treviso, Treviso, Italy; l Azienda
USL 2 Lucca, Lucca, Italy
Introduction: The radiological protection of patients against risks from ion-
izing radiation in medical practice has assumed great relevance in the last
years, in light of the ICRP recommendations, which promotes optimiza-
tion of procedures and definition of Diagnostic Reference Level (DRL). Patient
dose monitoring is the first step of the optimization process, including dose
reporting, tracking and data analysis. The so-called “Dose Archive and Com-
munication Systems” (DACS) are software packages designed to fulfill these
tasks. This work reports the early experience of managing CT data in a
multicentre study, using a DACS.
Materials and Methods: The project started in the year 2015 under the
purview of the Italian Society of Medical Physics (AIFM). It is supported
by a company (Tecnologie Avanzate®, Torino, Italy), which supplies tem-
porary licenses of a DACS (Radiation Dose Monitor®, Medsquare, France).
The trial is structured in 2 sessions, involving 21 institutions. Each center
can collect data from 3 radiological devices, for 6 months. After software
setup and tests, each center extracts dose histograms for selected proto-
cols. These data are gathered and statistical indexes of the overall distribution
are found. Institutions are then provided with feedback reports compar-
ing their data to aggregate results. A web platform was specifically created
to perform survey and data collection in a dynamic way. The first analysis
includes 12 CT units, 23 protocols.
Results: The comparison between local and global dose histograms high-
lighted some non-optimal situations and triggered local optimization actions.
Effectiveness of dose optimization tools was proved by intercomparison.
The standardization of CT scan protocols turns to be a critical issue, as in-
consistencies were detected by all centers and had to be corrected for the
statistical analysis.
Conclusion: Implementing a DACS in a multicentre framework can be a
powerful strategy to improve dose optimization in daily practice.
B.303
CT IMAGE QUALITY RECONSTRUCTED BY ITERATIVE ALGORITHMS: IS IT
TIME TO CHANGE STANDARD ANALYSIS METHODS?
R. De Vincolis, V. La Monaca, D. Leanza, S. Mele, F. Platania, N. Romeo *.
Azienda Sanitaria Provinciale di Messina, UOC Radioterapia, Taormina (ME),
Italy
Introduction: Iterative reconstruction algorithms are widely used in CT di-
agnostic radiology and have the potential to reduce radiation dose.
Worldwide more than 220 million CT examinations annually performed,
are responsible for being high contributors of the total collective dose from
X-ray examinations (around 50%) so that radiation dose has become a major
concern.
Iterative algorithms modify the noise contents of a FBP image so that stan-
dard analysis methods (Signal to Noise Ratio, Contrast to Noise Ratio, . . .)
may result in limited utility.
The aim of this work is to assess if and how the ASIR iterative reconstruc-
tion algorithm from GE company improve the quality of an image (for a
predefined dose level) evaluated through the Radiology Department “di-
agnostic capability”.
Material and Methods: Low contrast details in a phantom have been
scanned at 120KV with 11 different exposure levels; images have been re-
constructed with 3 different ASIR percentage: 0% (classical FBP), 50% and
100%. 11 Radiologists were asked to find and locate low contrast details
in a set of 132 images. Radiologist’s answers were analyzed by the Receiv-
er Operating Characteristic (ROC) curve methodology.
Results: ASIR algorithm seems to improve slightly the correct response rate
(7% increase) and seems to improve more evidently the wrong response
rate (15% decrease). It is possible to assess the level of dose reduction using
ASIR vs FBP for each level of correct response percentage the Radiology De-
partment is ready to accept. In our experiment we evaluated the following
capabilities:
e89 Abstracts/Physica Medica 32 (2016) e71–e96