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

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Conclusions: The DMS has supported the implementation of iterative re-
construction system, to reduce CT dose. A systematic control of patient dose,
using dose monitoring software in Radiology Service, supports the process
of optimization of radiological practice.
B.279
EFFECT OF THE PEDIATRIC PATIENT POSITIONING AND MANAGEMENT
ON CT AEC
A. Mari E. Cerquetell S. Maggi A.O.U. Ospedali Riuniti, Ancona, Italy;
b Universita’ Politecnica Delle Marche, Ancona, Italy
Introduction: Because of the high radiosensitivity in pediatrics it is nec-
essary to optimize CT exams and know which would be the impact of the
patient positioning on the AEC.
Materials and Methods: We evaluated the dose on a GE Lightspeed 16 slices
on a pediatric anthropomorphic phantom (10 years old, AARON model 705-
D, Atom Inc.) varying the following parameters: 80–100 kV,10–15–20 NI,
10–20 cm collimation. We changed patient offset (±5 cm AP and LR) and
scout order. For all the acquisitions SmartAm and AutoAm (GE’s AEC) were
used. The dose was calculated from mAs/slice multiplied by a factor from
QC. We calculated the % difference in CTDI between correct and mis-
aligned position.
Results: For vertical misalignment at 100 kV (AP-LL scout) analysis shows
a mean CTDI variation of 10% without a clear trend, more variations are
present on morphological and density discontinuity (40%), for higher NI
and small collimation that trend increase of less than 5%. When scout is
LL-AP the trend is more clear and scans with patient positioned +5 cm have
of dose of meanly +15%, patient placed −5 cm have CDTI/slice −20% respect
patient at isocenter. Dose delivery is more stable for low NI and small col-
limation. At 80 kV dose delivery follows the same trends of 100 kV scans
with 5% of more difference (in each direction) and more variability. With
lateral misalignment dose varies (until 20%) for LL/AP scans but without
difference between the two positions, when the second scout is the lateral
the difference is about ±10% but less stable, inverting scouts the differ-
ence between the two position is evident but not always higher or lower
respect the isocentric position, values variations reach the 30%.
Conclusions: Alignment and scout order may change significantly dose de-
livery for the same exam on the same patient. Protocols must be carefully
applied and configured, when is not possible to place correctly the patient
that variations must be taken in account and corrected by protocol set up.
B.280
PATIENT CT DOSIMETRY: USE OF THE DICOMSR PROTOCOL FOR
CALCULATION AND MONITORING OF DRL AND RELEVANT PARAMETERS
A. Martignano *, A. Valentini. Department of Medical Physics, Azienda
Provinciale per i Servizi Sanitari, APSS, Trento, Italy
Introduction: The Dicom Structured Report (DicomSR) is a format capable
of carrying several types of information. Of particular interest is the pos-
sibility to associate structured dosimetric information to each diagnostic
exam. The data from the CT scanners of the APSS capable of sending DicomSr,
are collected and analyzed in order to obtain useful information about the
use of the scanners and the dose received by the patients.
Materials and Methods: An Excel software was written to organize and
analyze the data. The program recollects all extracted data, separates them
on the basis of several parameters and performs statistical and dosimet-
ric analysis. Annual reports are written. The reports show statistics on the
number of patients and dose events, the scanned anatomic region, the
number of scans per exams for different anatomic regions, the average
CTDIvol and the DRL of the DLP value. The Excel software calculates the
mean effective dose on the basis of EC 2000 dose model. DLP values are
compared to DRL limits.
Results: 41,712 exams and 144,252 dose events were analyzed in 3 years
on 5 CT. The mean effective dose per dose event was 2.1 mSv and the mean
effective dose per patient was 7.2 mSv. An incorrect protocol without current
optimization was identified and corrected on the basis of a difference in
the DLP value with respect to the other scanners. DLP DRL values per dose
event were lower than the limit values for all types of exams.
Conclusions: The DicomSr format showed to be a very useful tool to re-
trieve and analyze dosimetric information, giving the possibility to perform
analysis and identify issues. However a software is needed to manage the
data. An Excel software was written to perform statistical analysis and cal-
culate effective doses to the patients. Annual reports with the main
information are written and sent to the involved professionals in order to
optimize the diagnostic process.
B.281
THE SYRMA-CT PROJECT FOR BREAST COMPUTED TOMOGRAPHY WITH
SYNCHROTRON RADIATION: IMAGE QUALITY AND DOSE EVALUATION
G. Mettivier *. Università degli Studi di Napoli Federico II, Napoli, Italy
Introduction: The SYRMA-CT project (INFN, ELETTRA Synchrotron Radi-
ation Facility, Trieste University Hospital) is a pilot study for 3D breast
imaging with Synchrotron Radiation (SR) monochromatic X-rays, via prop-
agation based phase-contrast X-ray CT of the pendant breast. This project
aims at producing the first high-resolution phase-contrast in vivo images
of the breast, for improved visualization of breast cancer lesions, at dose
levels comparable to that of two-view mammography.
Materials and Methods: In SR breast CT the patient is in prone position
with her breast freely pending without compression from a hole in the bed.
The SR beam is incident horizontally and irradiates a thin section of the
breast. For acquiring multiple views, the patient bed rotates around a hor-
izontal axis: for a scan of a thick section of the breast the bed translates
vertically. The SR laminar beam has a size of 210 × 3 mm2 and the photon
energy was 38 keV. The detector is at about 2 m away from the isocenter.
The single-photon counting detector is PIXIRAD-8, a 0.65-mm thick CdTe
hybrid detector (25 × 2.5 cm2 sensitive area) with 60-μm pixel pitch on a
hexagonal 2D arrangement. A breast specimen of about 9 cm diameter was
imaged, as well as test objects for image quality evaluation. CT slices were
reconstructed via FBP or iteratively both in attenuation and after phase re-
trieval using the homogeneous transport-of-intensity algorithm.
Discussion and Conclusion: First CT attenuation images and phase images
have been produced of the breast specimen, at glandular dose levels in the
irradiated slice of 5–20 mGy. Phase retrieval increased the signal-to-
noise ratio with respect to attenuation CT; iterative reconstruction allowed
to reduce significantly the dose with a limited reduction of the contrast-
to-noise ratio. The limiting spatial resolution was over 2.5 mm-1 after phase
retrieval. SR phase-contrast breast CT is technically feasible at dose levels
comparable to two-view mammography.
B.282
CT-BASED MONITORING OF MICROWAVE THERMAL ABLATION
S. Minosse D. D’Alessi . Loprest . Pinto . Farina . Cavagnaro
L. Strigari a Post Graduate School of Medical Physics, Sapienza University of
Rome, Rome, Italy; b Medical Physics Laboratory, Regina Elena National Cancer
Institute, Rome, Italy; c ENEA, Division of Health Protection Technologies,
Casaccia Research Center, Rome, Italy; d Department of Information Engineering,
Electronics and Telecommunications, Sapienza University of Rome, Rome, Italy
Introduction: Microwave thermal ablation (MWA) is a therapeutic tech-
nique which exploits the absorption of electromagnetic energy at microwave
frequencies to induce an irreversible coagulation necrosis in the target tissue
through a temperature increase higher than 55–60°C. Recent research has
been focused on increasing the efficiency of MWA procedures and reduc-
ing the tumors recurrence rate through a full control of the thermally ablated
region. The combination of CT imaging and MWA is used to examine spatial
evolution of the thermally ablated volume during treatment.
Materials and Methods: A plastic box with a regular grid of holes on its
walls was designed to contain tissue samples and to insert lead fiducial
markers and an antenna applicator. A CT system was used for real-time
monitoring of density variation during the ablation procedure and of the
movements of the lead markers. A software was developed in LabView, syn-
chronized with the CT acquisition, for automatic remote control of the MWA
e83 Abstracts/Physica Medica 32 (2016) e71–e96