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

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B.243
DUAL ENERGY CT IMAGING FOR BONE MARROW EDEMA DETECTION
M. Biondi A. Bog L.N. Mazzon E. Vanz G.M. Belmonte G. De Otto
D. Guerrieri A. Maiolino L. Guerrini A.E. La Rocca A. Guasti
F. Banci Buonamici a Department of Medical Physics, University Hospital of
Siena, Siena, Italy; b Department of Medical, Surgical and Neurosciences,
University of Siena, Siena, Italy; c Department of Diagnostic Imaging, University
Hospital of Siena, Siena, Italy; d Department of Medical Physics, U.S.L. 7, Siena,
Italy
Introduction: After the introduction of modern dual energy computed to-
mography in clinical application many studies aim to validate this method
in the detection of diseases previously not detected with standard ct. In
this optics a new approach for detection of bone marrow edema not based
on HU quantification has been investigated.
Materials and Methods: Ten traumatic patients with bone marrow edema
previously detected with MRI exam (GE, Signa HDxT 1.5 T MRI) were scanned
with DECT (GE, Discovery 750 CT). The anatomies investigated were: knee,
ankle, elbow, hips and spine. All exams were processed using Dual Energy
CT software (GE, GSI Viewer) performing a 2 material density decompo-
sition for the evaluation of water (W) and calcium (Ca) concentration in
each voxel. The mass attenuation coefficient needed for the decomposi-
tion of these materials was taken from the NIST curves. ROIs were placed
considering MRI results correspondingly to cortical bone (CB), normal bone
marrow (NBM) and edema (ED). Scatter plots of concentrations (mg/cm3 )
of W and Ca in each ROI were made.
Results: For each exam the values found in edema regions were well sepa-
rated from the ones found in NBM and CB. Concentrations (expressed in
mg/cm3) were: 750–900 (W) and 100–750 (Ca) in ED; 800–1000 (W) and
0–250 (Ca) in NBM; 0–400 (W) and 1000–2000 (Ca) in CB. Choosing edema
concentration values in the scatter plot the software can build a colored
concentration map to superimpose over the CT images for a fast and better
visualization.
Conclusions: DECT images with colored maps superimposed show a good
congruency with the MRI images in all the exams performed. These results
are very promising because in case of traumatic patients, especially aged
people, DECT is preferable to MRI because is possible to detect infraction
and bone marrow edema with a short exam duration.
B.244
MONTE CARLO (MC) CODE APPLICATION TO MAMMOGRAPHY:
EVALUATION OF THE COEFFICIENTS FOR THE ESTIMATION OF THE
AVERAGE GLANDULAR DOSE (AGD)
F. Badino, F. Bisi *, R. Rosasco, N. Canevarollo. Fisica Sanitaria-ASL3 Genovese,
Genova, Italy
Introduction: In this work MC simulations have been carried out by means
of the EGSnrc/BEAMnrc software, initially conceived for radiotherapy, here
applied in mammography.
The purpose was to evaluate the AGD parameters (as defined in EUREF pro-
tocol) for a realistic mammography unit.
Materials and Methods: Using as reference the geometry of a commer-
cial model, a mammographic standard unit has been defined with realistic
X-ray tube characteristics, not matching to any specific mammographic
unit.
The breast tissue has been figured by means of standard homogeneous phan-
toms with different glandularities (from 0,1% to 100% by step of 25%) and
thicknesses (20 ÷ 110 mm).
Then it has been considered the use of heterogeneous patterns in place of
the homogeneous ones. They show a discrete and spread distribution of
glandular and adipose voxels.
Even if the heterogeneous phantom does not represent the real distribu-
tion of glandular tissue within the breast, where the glandular tissue is
usually gathered in specific regions, this geometry is more reliable com-
pared to the homogeneous model. Furthermore to estimate AGD, since it
is an average value, such geometry results to be relevant not focusing on
specific areas inside the breast.
Results: The values of AGD factors have been calculated for each
glandularities in homogeneous phantoms for the 28 kV energy spectrum.
Analogous simulations have been carried out only in the 50 mm hetero-
geneous phantom.
The results point out that AGD differences between the homogeneous and
heterogeneous phantom become significant, around 10%, for low values of
glandularity (less than 50%).
Conclusions: A procedure to calculate AGD and related conversion factors
has been outlined. According to the geometry features and the defined pro-
cedure, it is possible to estimate the AGD and the connected parameters
for any kinds of device. The use of the heterogeneous phantoms implies
more accuracy in spite of a more elaborated procedure to determine the
EUREF factors.
B.245
PATIENT DOSE EVALUATION IN DIGITAL BREAST TOMOSYNTHESIS
THROUGH A MATLAB SCRIPT
R. Bona * C. Marchioni F. Pinna A. Poggiu M. Tamponi
G.B. Meloni P.G. Marin a ASL 1 Sassari, Sassari, Italy; b AOU Sassari, Sassari,
Italy
Introduction: The communication of dosimetric data to patients will soon
be mandatory, as required by Directive 2013/59/Euratom. To this end, we
present the results of the computation of average glandular dose (AGD) on
a group of patients undergoing 2D plus tomo examinations in Sassari Hos-
pital. We implemented a MatLab (MathWorks, Natick, MA) script to simply
extract patient data from DICOM images.
Material and Method: To make the computation we combined Quality
Control data (i.e. filtration, output in clinical setup) and actual exposure
data stored in the DICOM header of mammographic images. An auto-
mated way to extract data (mAs, kV, body part thickness, machine AGD)
was developed in the MatLab environment and used to estimate AGD as
recommended in EUREF protocols. Calculated AGD was then compared to
AGD reported in DICOM information, coming from the configuration of the
company owner.
We have analyzed images of 100 patients made with Hologic Selenia
Dimension.
Results: AGD was calculated for all projection and examinations of 100 pa-
tients. Both 2D (average = 4.95 ± 0.75 mGy for the 4 projections CC and MLO)
and 3D AGDs (average = 1.86 ± 0.49 mGy for the whole exposition) are below
the achievable limits of EUREF guidelines.
The comparison of the calculated data and the ones by the system showed
a good agreement (δmax = 9%).
Conclusion: The MatLab tool lets you extract and analyze data quickly,
without opening the images, to make statistical evaluations of a large
number of patients and to combine different variables.
The comparison with the data of the system gave a good result, which allows
to state that the Hologic data is reliable. We must remember, however, that
AGD estimate is always approximate because we lack data on the actual
composition of the breasts.
B.246
APPLICATION OF THE EUREF PROTOCOL FOR ACCEPTANCE TEST OF
THREE DIGITAL BREAST TOMOSYNTHESIS SYSTEMS
P. Bonfanti M. Invernizzi A. Martinott I. Redaelli F. Ria A. Vai
A. Bergantin a Centro Diagnostico Italiano, Milano, Italy; b Scuola di
Specializzazione in Fisica Medica, Milano, Italy; c Fondazione Bracco, Milano,
Italy
Introduction: Quality assurance program for three Hologic Selenia Di-
mensions systems, with both conventional 2D Full Field Digital
Mammography (FFDM) and Digital Breast Tomosynthesis (DBT) capabili-
ties, has been implemented in accordance to European guidelines (2006)
and EUREF protocol (2015), respectively. Acceptance tests performed on
DBT systems are described in this study, emphasizing critical aspects in ap-
plying the European Protocol.
Materials and Methods: DBT images are acquired in full-field geometry.
Several tests require usage of stationary mode at zero degree angle mo-
dality, in which DBT exposure parameters are replicated but x-ray tube
e73 Abstracts/Physica Medica 32 (2016) e71–e96