113 / 146
Materials and Methods:
Measurements were performed with a PerkinElmer
2470 WIZARD Gamma Counter. Instrument performance was verified with
a 129-I source to control the absence of any systematic trends or large
random deviations. A background acquisition was performed to correct the
measurements. A homogeneous solution of liquid 131-I with a high ac-
tivity (greater than 37 MBq) was prepared. The activity was measured with
a Capintec CRC-25R dose calibrator. From the master solution, I-131 cali-
bration sources with different low activities (in the range from 1 kBq to
1400 kBq) and with the same geometry of the blood samples were ob-
tained by subsequent dilution. The activity of the calibration sources was
determined with accuracy by measuring the weight of the solution with
a SAUTER AR 1014 precision balance and knowing the activity concentra-
tion of the master solution.
Results:
131-I calibration sources of low activities were used to construct
a calibration curve, needed to determine the activity corresponding to the
measured counts in the 131I-blood sample taken from patient undergo-
ing radiometabolic therapy.
Conclusions:
A simple method to measure with accuracy low activities of
radioactive sources is here reported. By implementing this method, low ac-
tivity radioactive sources can be produced and used in calibration of a RIA
gamma counter for blood sample measurements, needed for red marrow
dosimetry.
http://dx.doi.org/10.1016/j.ejmp.2016.01.372C.367
QUALITY ASSURANCE FOR PET/CT SYSTEM: NEMA NU2-2012 PROTOCOL
ON THE NEW SIEMENS BIOGRAPH MCT FLOW
L. Manco
* , a ,E. Tonini
a ,A. Barbon
i a ,A. Turr
a a ,L. Fegg
i b ,C. Cittant
i b .a
Medical
Physics Unit, Arcispedale S.Anna Hospital, Ferrara, Italy;
b
Nuclear Medicine
Unit, Department of Diagnostic Imaging, Arcispedale S.Anna University Hospital,
Ferrara, Italy
Introduction:
The purpose of this work is to apply the methodology of the
standard NEMA NU2-2012 to a new generation of PET-CT: Siemens Biograph
mCT Flow installed, for the first time in Italy, at Nuclear Medicine Unit,
Sant’Anna Hospital in Ferrara.
Materials and Methods:
Our PET/CT equipment uses TOF and PSF tech-
nologies to image reconstruction and it also has the fourth ring of detectors,
so the axial FOV is of 22.1 cm. NEMA kit for QA included different phan-
toms, capillary, tubing and all that is needed to perform quality checks. The
preparation of radioactive source is an integral part of PET acceptance testing,
and requires accurate recording of times of assays and scan start times. Ac-
ceptance testing includes spatial resolution, sensitivity, image quality and
accuracy of attenuation and scatter fraction, count losses and random
measurements.
Results:
Scatter fraction at peak NECR (Noise Equivalent Count Rate) is 37%,
sensitivity of 10.2 cps/kBq and spatial resolution axial/transverse of 4.7/
4.5 mm. The results of all quality controls are conformal to the system
specifications.
Conclusions:
The acceptance test is only one step of the quality assur-
ance program established by Medical Physicist according to Nuclear
Physician. Quality control schedules allow verifying the performance of PET/
CT scanner and monitoring that over time but Medical Physicist contribution
is also to work with the Nuclear Physician for optimization of clinical pro-
tocols to the needs of the individual patient.
http://dx.doi.org/10.1016/j.ejmp.2016.01.373C.368
NON-RIGID DEFORMATION OF MULTIPLE PET SERIES AND DOSE
DISTRIBUTIONS FOR EVALUATING HEAD AND NECK CANCER RESPONSE
TO RADIOTHERAPY
P. Mancosu
*
, L. Paganini, A. Fogliata, C. Franzese, A. Gaudino, F. Lobefalo,
G. Maggi, V. Palumbo, G. Reggiori, A. Stravato, F. Zucconi, S. Tomatis,
M. Scorsetti, L. Cozzi.
Humanitas Research Hospital, Humanitas Cancer Center,
Istituto Clinico Humanitas, Rozzano (Milano), Italy
Introduction:
The possibility to link PET series acquired pre and post ra-
diotherapy (RT) treatments to non-rigid dose deformation was investigated
for evaluating the RT efficacy and the toxicities prediction in the head and
neck region.
Material and Methods:
Twenty patients with pharyngeal or laryngeal
tumours, treated between 2011 and 2013, were retrospectively selected.
All patients underwent a simulation PET (PETsim) and a second PET 3(
±
1)
months after the end of the treatment (PETpost). The treatment dose pre-
scription was 69.96 Gy over 33 fractions on target and positive nodes, and
54.45 Gy on elective nodes with simultaneous integrated boost. Contours
and dose matrices were non-rigidly propagated from CTsim to PETsim and
PETpost using Velocity (Varian Medical Systems). SUVpre (standardised
uptake value from PETsim), SUVpost (from PETpost), and treatment doses
were analysed for all the delineated contours. Normalised delta SUV (defined
as difference between SUVpost and SUVpre relative to the SUVpre) was cal-
culated for each voxel using a home-made Matlab code. Tumour response
and toxicities were evaluated in correlation with dose and normalised delta
SUV.
Results:
Regarding the target, BTV (biological target volume), GTV_t (gross
tumour volume) and GTV_n (gross nodal-tumour volume) resulted in a mean
reduction of SUV of 4.4
±
6.3%, 4.0
±
7.2%, and 2.0
±
3.8%, respectively. Re-
garding the organs at risks, an increase of SUV was shown due to logistic
effects. Variations in mean SUV correlated with mean doses to constrictor
muscles and deep parotid for dysphagia and xerostomia toxicities,
respectively.
Conclusions:
This analysis showed how normalised delta SUV could cor-
relate with tumour response and toxicity. The medical physicists’ skills of
linking data analysis and data interpretation using home-made tools were
fundamental to obtain these results. Aprospective controlled study is ongoing.
http://dx.doi.org/10.1016/j.ejmp.2016.01.374C.369
NOISE STRUCTURE ANALYSIS IN [F-18]FDG-PET IMAGING: A MULTICENTER
PHANTOM STUDY
R. Matheoud
*
, a ,M. Lecch
i b ,D. Lizio
a ,B. Isiak
a a ,C. Scabbio
b ,C. Rodella
c ,L. Indovina
d ,M. Brambilla
a ,O. Zoccarato
e .a
Medical Physics Dep-Aou
Maggiore della Carità, Novara, Italy;
b
Health Sciences University of Milan and
Nuclear Medicine Unit San Paolo Hospital, Milano, Italy;
c
Health Physics Unit,
Spedali Civili, Brescia, Italy;
d
Medical Physics Dep, Polyclinic Agostino Gemelli,
Roma, Italy;
e
Nuclear Medicine Unit, S. Maugeri Foundation, Veruno (NO), Italy
Introduction:
New PET reconstruction algorithms with point spread func-
tion (PSF) modeling seem to be very attractive to obtain superior image
quality in 18FDG oncological studies. Nonetheless, PSF is known to sig-
nificantly increase noise variability. Our aim was to evaluate the impact
of PSF on noise structure of iterative reconstructed (IR) images, also when
time of flight (TF) is applied.
Materials and Methods:
An anthropomorphic phantom (Data Spectrum
Corporation) with inserts (lungs, liver, heart, mediastinum) filled with 18FDG
clinical activity was acquired for 20 min on Biograph-mCT (Siemens) and
Discovery690 (General Electric) PET/CT scanners. Overall, 96 datasets were
obtained by varying reconstruction modalities (RM
=
IR, TF, PSF, TF
+
PSF),
frame (128,256), iterations number (IT
=
63,270), and Gaussian Filter
(GF
=
2,4,6 mm).
To limit the problem of noise correlation, 6 groups of 5 concentric ROIs (r
=
8;
10; 13; 16; 19 mm) were drawn on 3 liver slices. For each slice and ROI size,
the signal variation was defined SV%
=
100*SD/M, where SD and M are the
standard deviation and the mean of the mean count in each of the 6 ROIs.
Results:
For both PET scanner, SV decreases with ROI size and GF, and in-
creases with IT. Moreover, SV depends on RM, but in different ways on the
two PET scanners.
For mCT the highest and lowest SV were observed for PSF and TF and for
GF
=
2,4,6 mm the mean (range) values were: 7.8% (5.1–10.6); 5.7% (3.1–
8.5); 4.5% (2.5–6.7) and 4.5% (2.7–6.4); 3.8% (2.4–5.4); 3.2(2.2–4.5),
respectively.
For D690 the highest and lowest SV were observed for PSF
+
TF and IR and
for GF
=
2,4,6 mm the mean (range) values were: 8.3% (6.8–10.5); 8.1% (6.7–
10.2); 7.9% (6.6–9.7) and 5.1% (3.5–8.2); 4.5% (3.1–7.0); 4.2% (3.2–6.2),
respectively.
The same trend is observed for the range of SV values.
Conclusions:
Both mCT and D690 showed different behavior of noise struc-
ture in relation to RM. An increased SV could lead to a degradation of
e108
Abstracts/Physica Medica 32 (2016) e97–e115