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

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Conclusion: For some isotopes the knowledge of the calibrator behavior
with different geometry is essential to evaluate accurately the activity value.
With 123I the measure is significantly affected by composition and thick-
ness of container; with 90Y the volume correction is essential.
C.336
PERFORMANCE CHARACTERISTICS OF BIOGRAPH MCT TOF-PET/CT
SCANNER
I. Bonetti G. Sceni E. Cefalì S. Morano V. Scaffidi M. Guerrisi
a Section of Medical Physics, School of Medical Physics – University of Rome
Tor Vergata – Faculty of Medicine, Roma, Italy; b Department of Medica Physics,
A.O. Bianche Melacrino Morelli, Reggio Calabria, Italy; c Department of Nuclear
Medicine, A.O. Bianche Melacrino Morelli, Reggio Calabria, Italy; d Section of
Medical Physics, Department of Biomedicine and Prevention, University of Rome
Tor Vergata-Faculty of Medicine, Roma, Italy
Introduction: The aim of this work is to characterize the physical
properties of the Biograph mCT – TOF PET/CT scanner recently
installed at Nuclear Medicine Department in Ospedali Riuniti Reggio
Calabria.
Materials and Methods: The Biograph mCT scanner combines a 64-slice
CT scanner (Siemens SomatomDefinition AS) with an LSO PET scanner which
incorporates Time of Flight (TOF) reconstruction and has TrueV Option. The
PET component is configured with 32,448 LSO crystals arranged in 4 rings
of 48 detector blocks in a matrix 13 × 13 of 4 mm × 4 mm × 20 mm. This
configuration covers an axial field-of-view (FOV) of 21.8 cm correspond-
ing to 109 image planes with a slice thickness of 2 mm. Performance
characteristics of PET component have been evaluated according to NEMA
NU-2 2007 standards by means of Siemens NEMA kit (NEMA PET Self-
Test-mCT) provided with the scanner.
Results: Preliminary data analysis confirms that the values of measured
major machine parameters (sensitivity, spatial resolution stability, count
rate performance, scatter fraction, image quality) are in agreement with
manufacturer specification.
Conclusions: In this work we have assessed the performance character-
istics of Biograph mCT PET/CT scanner according to NEMA NU-2 2007
standard test.
Preliminary results confirm the good performance of the system in agree-
ment with recent publications on similar devices.
C.337
AUTOMATIC GTV CONTOURING APPLYING ANOMALY DETECTION
ALGORITHM ON DYNAMIC FDG PET IMAGES
C. Bracco F. Verdoj M. Grangett A. Di Dia M. Racca T. Varett
M. Stas a Medical Physics Department, Candiolo Cancer Institute – FPO- IRCCS,
Candiolo, Italy; b Computer Science Department, University of Turin, Turin, Italy;
c Nuclear Medicine Department, Candiolo Cancer Institute – FPO- IRCCS,
Candiolo, Italy
Introduction: The aim of this work is to show the results of GTV auto-
matic segmentation based on dynamic PET acquisition. With respect to
single voxel segmentation the temporal information is used to improve
quality of GTV delineation. The segmentation algorithm proposed ex-
ploits the theoretic assumption that FDG uptake over time in cancer cells
is very different from the one in normal tissues and therefore in this
study anomaly detection is used to look for tumor peculiar-anomalous
TACs.
Material and Methods: For each patient two list mode datasets of images
were acquired. The first one scan (basal) was acquired one hour after FDG
injection and reconstructed as static frame. The last one (delayed) was ac-
quired half one hour after the first scan and reconstructed as dynamic scan.
Two delayed scans were registered to the basal scan. A modified version
of the RX Detector was used. RX Detector usually works in RGB, but in this
study its use on TACs has been explored passing the three grayscale images
in place of the three channels of RGB. The resulting single image, which
actually is a matrix of Mahalanobis distances, presents values that are very
high for voxels whose TAC has anomalous temporal behavior. Finally, thresh-
old segmentation is performed on the distance matrix. On a dataset of 10
patients segmentation techniques present in the literature working on single
PET scan have been implemented as well as segmentation techniques based
on RX Detector output.
Results: Spatial overlap index (SOI) was used as metric to evaluate the seg-
mentation accuracy. All of the segmentation algorithms implemented on
RXD output show better SOI (0.507 ± 0.158) than algorithm based on SUV,
i.e. Brambilla, SOI 0.278 ± 0.236. A manual contour drawn by experienced
Nuclear Physician was the reference.
Conclusion: Although a small dataset, the segmentation of dynamic PET
images based on RXD output seems to be promising.
C.338
BREATHING MOTION CORRECTION IN DOSIMETRY OF LIVER LESION
BASED ON 90Y-PET/CT IMAGING
G. Iaccarino, A. Cacciatore *, S. Ungania, M. Cazzato, M. D’Andrea,
L. Strigari. Istituto Nazionale Tumori Regina Elena, Roma, Italy
Introduction: A degrading factor in quantitative PET imaging is internal
organ motion due to respiration which is a primary cause of image blur-
ring. The aim of this work was to investigate a method to correct PET images
for breathing artifacts in order to improve the dosimetry of liver
radioembolization with 90Y microspheres.
Materials and Method: PET/CT images were acquired in list mode
modality (LM) with an acquisition time of 30 minutes due to the low
branching ratio of 90Y. The breath curve was constantly monitored
by an external monitor system. The respiratory signal was generated
from a small load cell placed in an elastic belt which was fastened just
below the diaphragm on the patient’s abdomen. The trigger signal sent
by the device to the PET was used to perform the synchronization of
the LM and the respiratory curve. Using a Matlab script, the LM file
was split into sub-files, each corresponding to a different breath ampli-
tude. Images corresponding to each breath amplitude were recon-
structed correcting for scatter, attenuation and system resolution. All
images were finally co-registered to the end-exhale position at which the
CT scan was acquired. Dose distribution was then calculated by convolv-
ing the activity distribution with a Monte Carlo 90Y-kernel. Different volumes
of interest were contoured by gradient and threshold methods and dose
volume histograms were calculated with and without breathing
correction.
Results: Depending on lesion size and breathing amplitude, the correc-
tion incremented both mean and maximum doses. In the most dramatic
case a patient with an amplitude of about 3.2 cm and a lesion size of 2.7 cm
showed a difference of about 50% in mean dose estimation.
Conclusion: Our study shows that taking into account organ motion
is mandatory for an accurate dose evaluation. In particular absence of
breathing correction always causes dose underestimation. The magni-
tude of correction strongly depends on lesion size and respiratory
amplitude.
C.339
THE IMPACT OF EANM (2013) FORMALISM FOR RADIOIODINE DOSIMETRY
IN HYPERTHYROIDISM DISEASE: A COMPARATIVE EVALUATION OF
THERAPEUTIC ACTIVITY
M. Cacciatori G. Frigerio M. Duchini A. Bresolin A. Ostinelli
a Department of Medical Physics, Sant’Anna Hospital, Como, Italy; b Physics
Department, University of Milan, Milano, Italy
Introduction: The treatment of choice in most of hyperthyroidism cases
is the radioiodine therapy. An accurate assessment of the pathological
volume and an individual dosimetry procedure implementation prior to
therapy are mandatory by Council Directive 97/43/Euratom. The aim of this
study is to assess the differences arising in the 131I therapeutic activity
depending on whether the SIE-AIMN-AIFM (2005) or EANM (2013) for-
malism is used.
e99 Abstracts/Physica Medica 32 (2016) e97–e115