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

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Results: In the evaluation of sensitivity factor no differences were noted
in the values evaluated with the Petri versus point source; while signifi-
cant differences were noted in the values with and without scatter correction.
The sensitivity factors (with Petri dish and with scatter correction) for Tc99m
and I131 were 71.4 and 26.1 counts/MBq s, respectively. The mean SUV values
measured in homogeneous phantoms were 1.08 (4 it, 10 sub) for Tc99m
and 0.75 (2 it, 10 sub) for I131. Recovery coefficient varied from 0.88
(26.5 mL) to 0.27 (1.15 mL) for Tc99m and from 0.53 (26.5 mL) to 0.10
(1.15 mL) for I131.
Conclusion: Our results suggest that this method can be applied on clin-
ical SPECT-CT and the use of Q.Metrix software permitted us to work more
precisely and with higher repeatability than manually.
C.350
QUANTITATIVE 177LU SPECT IMAGING USING ADVANCED CORRECTION
ALGORITHMS IN NON-REFERENCE GEOMETRY
M. D’Arienzo M.L. Cozzella A. Fazio M. Cazzato S. Ungania
G. Iaccarin M. D’Andrea K. Schmidt S. Kimiae L. Strigar a ENEA,
National Institute of Ionizing Radiation Metrology, Rome, Italy; b Department
of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, La
Sapienza University, Rome, Italy; c Laboratory of Medical Physics and Expert
Systems, Regina Elena National Cancer Institute, Rome, Italy; d ABX-CRO
advanced pharmaceutical services Forschungsgesellschaft m.b.H., Blasewitzer
Straße 78-80 D, 01307 Dresden, Germany
Introduction: Peptide receptor therapy with 177Lu-labelled somatosta-
tin analogues is a promising tool in the management of patients with
inoperable or metastasised neuroendocrine tumours. The aim of this
work was to perform accurate absolute activity quantification of 177Lu in
challenging anthropomorphic geometry using advanced correction
algorithms.
Materials and Methods: A cylindrical PMMA insert was manufactured and
fixed into the liver of an anthropomorphic phantom to simulate a hepatic
lesion. Measurements at the 208 keV peak were performed with a Philips
IRIX gamma camera using three tumour to background activity concen-
tration ratios (6:1, 9:1, 14:1). Attenuation correction was performed using
μ-maps derived from CT data and co-registered with SPECT images, while
scatter correction was performed using the transmission-dependent con-
volution subtraction method. Both the scatter function and the scatter
fraction were experimentally determined. SPECT acquisitions were cor-
rected for dead time and septal penetration. Recovery coefficients were
evaluated using a NEMA phantom. Image analysis was performed using the
commercially available QSPECT software.
Results: For all acquisitions, the recovered total activity was within 12%
of the calibrated activity both in the background region and in the tumour.
Using a 6:1 tumour/background ratio the recovered total activity was within
2% in the tumour and within 5% in the background. Because of partial volume
effects, the ability to recover activity in the NEMA phantom depends on
the ROI size. An ROI size as large as the physical radius of the sphere + 1 cm
margin provided activity values correct to within a few per cent in spheres
with diameter >2.2 cm.
Conclusions: Accurate activity quantification of 177Lu can be obtained in
the clinical practice if activity measurements are performed with equip-
ment traceable to primary standards, advanced correction algorithms are
used and acquisitions are performed at the 208 keV photopeak.
C.351
MICROSPHERES THERAPY OF LIVER TUMORS: CALCULATIONS AND
MEASUREMENTS OF ABSORBED DOSES FOR NON-UNIFORM ACTIVITY
DISTRIBUTIONS VIA 90Y-PET/CT IMAGING
M. D’Arienzo * M.L. Cozzella M. Tapner E. Spezi N. Patterson
P. Chiaramida L. Filippi A. Fisher T. Paulu O. Bagni M. Pimpinella
A.S. Guerr M. Capogni a ENEA, National Institute of Ionizing Radiation
Metrology, Rome, Italy; b Department of Anatomical, Histological, Forensic
Medicine and Orthopedic Sciences, La Sapienza University, Rome, Italy; c Sirtex,
North Sydney, NSW 2060, Australia; d Cardiff University, Cardiff, UK;
e Department of Medical Physics, Velindre Cancer Centre, Cardiff, UK; f GE
Healthcare Medical Systems, Milano, Italy; g Nuclear Medicine Department,
Santa Maria Goretti Hospital, Latina, Italy; h Philips Technologie GmbH
Innovative Technologies, Research Laboratories, Pauwelsstr. 17, 52074 Aachen,
Germany
Introduction: In recent years there has been an intensifying debate on the
most accurate dosimetric approach for dosimetry in molecular radiother-
apy. The aim of the present work is to evaluate the absorbed dose to lesions
from 90Y-PET images using different calculation algorithms including: (I)
Direct Monte Carlo (MC) using Raydose; (II) Kernel-convolution using Philips
Stratos; (III) Local deposition; (IV) MCNP, assuming uniform activity dis-
tribution; and (V) MIRD approach. Absorbed doses calculated using MC codes
were compared with those obtained performing measurements with
LiF:Mg,Cu,P TLDs inside a cylindrical phantom filled with a homogenous
90YCl solution.
Materials and Methods: An anthropomorphic phantom was used in the
present study. A home-made cylindrical PMMA insert was manufactured
and fixed into the liver cavity to simulate a hepatic lesion. Measurements
in anthropomorphic geometry were performed using a GE Discovery ST PET/
CT scanner with a 6:1 tumor to background activity concentration ratio.
The first scan was performed with an activity concentration of 5.5 MBq/
mL for the lesion insert and 0.89 MBq/mL for the liver background. The
anthropomorphic phantom was then acquired at days 4, 5, 6 and 12 down
to an activity concentration of 0.31 MBq/mL for the lesion insert and 50 kBq/
mL for the liver background.
Results: All dose algorithms provided acceptable results, the worst case
scenario providing an agreement between absorbed dose evaluations within
20%. Measured doses were consistent with absorbed doses calculated using
full MC techniques with an agreement within 3%, well within the stated
uncertainties.
Conclusions: Although all dose calculation algorithms provided compa-
rable average dose values, heterogeneous activity distributions were obtained
from 90Y-PET data, where a uniform activity distribution was supposed to
be. Additional work is needed toward the development of specific 90Y-
PET reconstruction protocols to allow proper image quantification for
dosimetry.
C.352
INTERNAL DOSE ASSESSMENT IN MOLECULAR RADIOTHERAPY: TIME FOR
AN AGREED DOSIMETRY PROTOCOL?
M. D’Arienzo * M. Capogni V. Smyth M. Cox L. Johansson
A. Fenwick J. Solc C. Bobin H. Rabus L. Joulaeizadeh a National
Institute of Ionizing Radiation Metrology, ENEA-INMRI, C.R. Casaccia, Rome,
Italy; b Department of Anatomical, Histological, Forensic Medicine and
Orthopedic Sciences, La Sapienza University, Rome, Italy; c National Physical
Laboratory (NPL), Hampton Road, Teddington, Middlesex, TW11 0LW London,
UK; d Czech Metrology Institute (CMI), Inspectorate for Ionising Radiation,
Radiova 1, CZ-102 00 Prague, Czech Republic; e Commissariat a l’Energie
Atomique (CEA) Bt 476, Pt Courrier 142, CEA-Saclay, FR-91191 Gif-sur-Yvette
Cedex, Paris, France; f Physikalisch-Technische Bundesanstalt (PTB), Bundesallee
100, D-38116 Braunschweig, Germany; g VSL, Dutch Metrology Institute,
Thijsseweg 11, P.O. Box 654, NL-2629 JA Delft, The Netherlands
Introduction: Molecular radiotherapy (MRT) is conventionally pre-
scribed on the basis of administered activity. The major drawback is that
uptake and retention differ appreciably from patient to patient and so the
absorbed dose to the target can vary significantly between patients for the
same administered activity.
Material and Methods: Despite the growing trend toward developing
patient-specific dosimetry models based on quantitative data, progress in
this area has been hindered by the lack of (a) appropriate standards for cali-
brating the imaging systems and (b) a clinically accepted dosimetry protocol.
Consequently, it is generally accepted that quantitative imaging (QI) and
dosimetry in MRT suffer from considerable inaccuracy.
Results: By analogy with external beam radiotherapy, the EMRP MetroMRT
project addressed these issues by formulating MRT dosimetry as a mea-
surement chain traceable to primary standards with known uncertainty:
(I) measurement of administered activity, (II) measurement of activity within
e103 Abstracts/Physica Medica 32 (2016) e97–e115