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

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Introduction: Radio-guided surgery (RGS) is a technique that helps the
surgeon to perform a complete lesion resection. Currently, RGS uses γ
emitting tracers, to mark the cancerous tissue from the healthy organs, and
a γ radiation detection probe. To overcome the limitations due to the high
penetration of γ radiation, a novel approach based on β-radiation has been
developed (Sci Rep. 2014;4:4401), allowing to include cases with high uptake
of nearby healthy organs, and to benefit of a low medical team exposure.
Material and Methods: Feasibility studies for meningioma, glioma and NETs
were performed assuming administration of 90Y-DOTATOC, utilizing a sim-
ulation code based on the biodistribution estimated in 68Ga-DOTATOC-
PET scans (JNuclMed. 2015;56(1):3–8). Experimental phantoms have been
prepared to tune the simulations and finally ex-vivo tests on patient speci-
mens after surgery of meningioma have been performed to validate in
clinical setting the features of the probe.
Results: Considering typical tumor uptakes ranging from 0.1 to 1% of the
injected activity, preclinical tests and simulations estimated that about
3 MBq/kg administered to the patient is enough to identify in 1 s a tumor
volume <0.1 mL. The exposure of surgeon was estimated to be 0.04 μSv/h
on the whole body, 0.35 μSv/h on the hands. Phantom measurements con-
firmed the simulations. Ex-vivo tests showed excellent agreement between
experimental and expected rates for lesions and healthy tissues: e.g. the
bulk tumor showed signals of ~100 cps, 0.2 mL residual signals of ~40 cps
and healthy tissues of less than 5 cps. Furthermore, exposure measure-
ments confirmed the low level of radioactivity in the surgical environment
(<1 μSv/h at 10 cm from patient abdomen).
Conclusions: The proposed RGS using β-radiation has a wide range of ap-
plications and succeeded in the first clinical test. The future goal is to study
the efficiency of the probe to other radio-tracers to further extend applicability.
C.357
A QUALITY CONTROL PROTOCOL FOR ROUTINE TESTS ON THE PHOSPHOR
IMAGER CYCLONE PLUS
R. Errico * R. Bampi M. Riondato A. Chimenz O. Ferrando
F. Foppiano a Department of Physics, University of Genova, Italy; b Medical
Physics Department, St. Andrea Hospital, Asl5 Spezzino, La Spezia, Italy; c Nuclear
Medicine Department, St. Andrea Hospital, Asl5 Spezzino, La Spezia, Italy
Aims: The aim of this study was to define a set of tests to establish a routine
quality control procedure for the Cyclone Plus, a digital autoradiography
system. In recent years the use of this device has widely spread in nuclear
medicine for the quantitative imaging of the radioactivity distribution, to
investigate the presence of impurities in radiopharmaceuticals. As there
are no standardized protocols concerning the quality controls of such a
system, we have developed a home made quality control protocol to val-
idate the device.
Methods and Materials: To analyze the active components of the Cyclone
Plus (phosphor screen and photometer) the following tests were per-
formed: integral uniformity (IU) and differential uniformity (DU) in a useful
field of view (UFOV) and in a central field of view (CFOV), resolution and
geometric linearity of the screen. Integral and differential uniformity were
measured irradiating strips for thin layer chromatography (TLC) with a point
source of 99mTc. Resolution and geometric linearity of the phosphor screen
were measured using a 2 mm thick lead plate with a hole matrix (2 mm
hole diameter at a distance of 10 mm). Integral and differential uniformi-
ty of the photometer were measured scanning a white paper (A4 format)
while photometer resolution was determined scanning a paper with a set
of black lines of different widths (0.5 mm–2 mm).
Results: Screen IU was (12.33 ± 3.9)% (UFOV) and (7.4 ± 1.0)% (CFOV); screen
DU was (8.7 ± 2.7)% (UFOV) and (7.5 ± 1.6)% (CFOV) and screen resolution
measured as full width at half maximum (FWHM) of the lead plate holes
was (1.97 ± 0.07) mm. Photometer IU was (12.2 ± 1.5)% (UFOV) and (7.5 ± 2.2)%
(CFOV); photometer DU was (7.1 ± 1.6)% (UFOV) and (4.8 ± 0.6)% (CFOV). Pho-
tometer resolution was 0.49 ± 0.04 mm.
Conclusions: The results obtained by the tests suggest that the proposed
methodology could be an accurate, simple, fast and cheap tool to ensure
the proper operation of the device.
C.358
90Y-PET/CT IMAGING QUANTIFICATION IN PEPTIDE RECEPTOR
RADIONUCLIDE THERAPY (PRRT)
G. Sarti V. Mattone M. Cas F. De Laur S. Sanniti N. Bartolini
G. Gentili C. Fabbri a Medical Physics and Clinical Engineering Unit, AUSL
Romagna, Cesena, Italy; b Nuclear Medicine Unit, AUSL Romagna, Cesena, Italy;
c Medical Physics Unit, Ospedali Riuniti Marche Nord, Pesaro, Italy
Purpose: We evaluated the possibility to assess 90Y-PET/CT imaging quan-
tification in 90Y-Peptide Receptor Radionuclide Therapy (PRRT).
Materials and Methods: Tests were performed by Discovery 710 Elite (GE)
PET/CT equipment. Image Quality, NU-2 Phantom containing radioactive-
coplanar-spheres was filled with 90Y-water solution to reproduce different
signal-to-background-activity-ratios (S/N).
We studied Minimum Detectable Activity concentration (MDA), Contrast-
to-Noise Ratio (CNR) and Full-Width-at-Half-Maximum (FWHM).
Subsequently, three Recovery Coefficients (RC)-based correction ap-
proaches were evaluated: Maximum-RC, Resolution-RC and Isovolume-RC.
The analysis of the volume segmentation thresholding method was also
assessed in order to derive a relationship between the true volume of the
targets and the threshold to be applied to the PET images.
90Y-PET/CT imaging quantification was then achieved on 10 patients ad-
ministered with 90Y-DOTATOC activity ranging from 1.5 to 2.5 GBq and
related with preclinical tests. Moreover activity concentration and mean
absorbed dose evaluations were obtained in targets and kidneys.
Results: CNR value was greater than 5 if the MDA was greater than 0.2 MBq/
mL with no background activity and 0.5–0.7 MBq/mL with S/N ranging from
3 to 6. FWHM was equal to 7 mm.
An exponential fitting of isovolume RCs-based correction technique was
adopted for activity quantification.
Adaptive segmentation thresholding exponential curves were deter-
mined and applied for target volume identification in three signal-to-
background-activity-ratios.
Imaging quantification study in clinical cases was feasible. Targets activi-
ty concentration was ranging from 0.3 to 2.2MBq/mL corresponding to mean
absorbed doses ranging from 3.3 to 32.4 Gy/GBq. Kidneys activity concen-
tration was almost equal to the MDA.
Conclusions: 90Y-PET/CT imaging quantification is possible both in phan-
toms and in patients. Clinical applications are strongly related to targets
activity concentration.
C.359
EVALUATION OF FDG-PET/CT ROLE IN RADIOTHERAPY TREATMENT OF
HEAD AND NECK CANCER
O. Ferrando A. Ciarmiello T. Scolaro F. Foppiano a Medical Physics
Department, St. Andrea Hospital, Asl5 Spezzino, La Spezia, Italy; b Nuclear
Medicine Department, St. Andrea Hospital, Asl5 Spezzino, La Spezia, Italy;
c Radiotherapy Department, Felettino Hospital, Asl5 Spezzino, La Spezia, Italy
Aims: The present study aims to compare modification of gross tumour
volumes and radiotherapy treatment of head and neck cancer by FDG-PET/
CT with respect to conventional CT.
Methods and Materials: A set of 25 patients with histological diagnosis
of head and neck cancer who underwent conformal-3D Radiotherapy was
analysed. Gross tumour volumes were delineated on CT images blinded to
PET data and successively on PET/CT fused images. The CT and PET/CT
volumes were compared. The study also analysed how the therapeutic
scheme in terms of total dose and irradiated volumes can be changed by
PET information.
Results: 22% of patients had the nodal stage changed from N0 to N + when
small lymph nodes identified on CT scans as insignificant were found to be
FDG avid on PET/CT. 5% of patients had negative PET/CT, and for 5% of pa-
tients PET reveals distantmetastasis. In 11% of patients gross tumour volumes
should not be identified without PET information. Mean values of PET/CT
gross tumour volumes were smaller than CT volumes: 109 ± 110 cm3 versus
130 ± 98 cm3 (p < 0.015). The mismatching fraction between CT volumes
and PET/CT volumes was 0.41. In 87% of patients the total therapeutic dose
was not changed by PET data but the irradiated volumes in PET-CT based
treatment and CT-based treatment were different. 13% of patients had the
e105 Abstracts/Physica Medica 32 (2016) e97–e115