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

116 / 146

We assessed whether this method actually leads to significant differences
in the evaluation of the activity to be administered than the simplified
methods reported in the AIMN-AIFM guidelines, which provide the eval-
uation of T1/2eff from linear fit of the uptake at 24 and 72 h (or longer),
and in the ICRP 53, which considers a standard 132 hours T1/2eff. In both
of these simplified methods Umax is considered at 24th hour.
The results are concerned with the first 7 patients (administered activi-
ties range from 102 to 303 MBq).
Results: The results show that both simplified methods can give quite dif-
ferent results in the assessment of activity to be administered (maximum
overestimation >40% and maximum underestimation close to 40%) if com-
pared to the tool.
Conclusions: The use of simplified methods can lead to an incorrect as-
sessment of the activity to be administered and it should therefore be limited
to special cases.
Reference
[1]
C.377
USE OF CUMULATIVE SUV VOLUME HISTOGRAM AS A NEW TOOL TO
RADIOTHERAPY TREATMENT MONITORING
P. Pisciotta * A. Stefano G. Russo M.G. Sabini L.M. Valastro
T. Licciardello C. D’Arrigo F. Marletta D. D’Urso G. Borasi
M. Ippolit M.G. Gilard a Istituto di Bioimmagini e Fisiologia Molecolare,
Consiglio Nazionale delle Ricerche (IBFM CNR), Cefalù (PA), Italy; b Università
degli Studi di Catania, Catania, Italy; c Dipartimento di Ingegneria Chimica,
Gestionale, Informatica, Meccanica (DICGIM), Università degli Studi di Palermo,
Palermo, Italy; d Azienda Ospedaliera per l’Emergenza Cannizzaro, Catania, Italy
Introduction: This study investigated the biological evolution of tumor
volume using [11C]-Methionine-PET (MET-PET) images. MET-PET diagnos-
tic exams provide metabolic information about brain lesions impossible
to obtain using other imaging techniques. Similar to the radiotherapy Dose–
Volume Histogram (DVH), the Cumulative SUV–volume Histogram (CSH)
represents the percentage of tumor metabolic volume higher than an SUV
threshold, variable from 0 to the maximum SUV value.
The aim of this study was to evaluate how the CSH could be used as a tool
for the treatment monitoring in stereotactic radiosurgery.
Materials and Methods: The patients selected for this study presented one
or more brain metastases. The lesions were studied using metabolic MET-
PET imaging before and after 3 months of the Gamma Knife treatment. The
Radiotracer distribution changes were evaluated using the CSH param-
eters, that is: Area under the CSH, Uptake Intensity, etc. The CSH parameters
were calculated for 14 patients using a homemade MATLAB tool.
Results: According to the literature, the area under the CSH curve was con-
sidered as a quantitative index of the heterogeneity in the MET uptake inside
the lesion volume. The percentage change of CSH was obtained as follows:
δCSH(post vs pre) = 100*(CSHpost − CSHpre)/CSHpre, and this value was com-
pared with the Nuclear Medicine physicians qualitative assessment. These
CSH variations were in agreement with qualitative observation of MET-
PET/CT images.
Conclusions: The CSH could be a new tool to monitor the treatment follow-
up for stereotactic radiosurgery. The CSH parameters seem to be correlated
with the tumor response and permit a more accurate early assessing of
therapy response. Future studies are needed to evaluate the threshold of
the CSH parameter changes to discriminate between responders and
non-responders.
C.378
NEW PROMISING SCINTILLATION CRYSTALS FOR MOLECULAR IMAGING
APPLICATIONS: CRY018 AND CRY019
C. Polito M.N. Cinti R. Pellegrini R. Pani a SAIMLAL Department,
Sapienza University of Rome, Rome, Italy; b Department of Molecular Medicine,
Sapienza University of Rome, Rome, Italy; c INFN Roma I Section, Rome, Italy;
d Department of Sciences and Medical and Surgical Biotechnologies, Sapienza
University of Rome, Rome, Italy
Introduction: A detailed investigation of new scintillation crystals, pro-
duced by CRYTUR spol. s r.o. (Czech Republic), is presented. Pulse height
distributions have been measured as a function of photon energy, in order
to evaluate the Energy Resolution. The crystals have shown promising per-
formances for gamma ray imaging applications as the short scintillation
decay time that makes these scintillation crystals attractive for the im-
provement of a wide range of applications in Nuclear Medicine, like PET
and SPECT instrumentations.
Materials and Methods: A couple of new mixed rare-earth silicate single
crystal scintillation materials (CRY018 and CRY019) have been studied. The
crystals have round shape and white painting on all sides, except on the
one in contact with Photomultiplier Tubes. Their size is proper of a small
Field of View gamma imager (50 mm diameter and 6 mm thickness). The
crystals were irradiated with radioactive source with different photon energy
in order to characterize their Energy Resolution. Subsequently the Spatial
Linearity and Spatial Resolution were quantified with a scanning of the crys-
tals surface with a 1 mm Tc99m point source. The fast decay time allows
combining the crystals with fast timing applications (i.e. Silicon
Photomultiplier).
Results: The Energy Resolution is close to 16.3% for CRY019 and 12.4% for
CRY018 at 122 keV (comparable with one of NaI:Tl that is 12%). About spatial
linearity, the CRY019 crystal shows the worse linearity but the greater ef-
ficiency respect to the CRY018. Finally, the intrinsic spatial resolutions were
1.6 mm and 2 mm for CRY018 and CRY019 respectively.
Conclusion: The satisfactory results in terms of Energy and Spatial Reso-
lution suggest the employment of these crystals in many different
applications. Moreover these materials are not hygroscopic, this means that
they do not need to be contained in a sealed casing. Finally, all these great
performances make the crystals attractive also for dual modality applications.
C.379
RED MARROW AND BLOOD DOSIMETRY IN 131I TREATMENT OF
METASTATIC DIFFERENTIATED THYROID CARCINOMA: 7 YEARS
EXPERIENCE AT MAURIZIANO HOSPITAL OF TURIN
E. Richetta * C. Cutaia S. Valzano M. Pasquino G. Lo Moro
G. Brusasco R.E. Pellerito M. Stas a S.C. Fisica Sanitaria, AO Ordine
Mauriziano di Torino, Torino, Italy; b S.C. Medicina Nucleare, AO Ordine
Mauriziano di Torino, Torino, Italy
Introduction: Radioiodine treatment of metastatic differentiated thyroid
cancer is limited by red marrow toxicity. In our institution dosimetry to
red marrow and blood is performed before and after therapy to individ-
ually determine the maximum tolerable 131I activity. The study shows the
results obtained comparing different dosimetric methods, pre- and in-
therapy dosimetry and doses to patients with repeated treatment.
Material and Methods: Since 2008, 665 dosimetries were performed adopt-
ing the AIFM protocol. Pre-treatment dosimetry was performed 7 days before
therapy with a 131I tracer activity: 4 blood samples were acquired and AP-
PA whole body measurements were performed (2 h, 24 h, 48 h, 96 h). For
in-therapy dosimetry a detector placed on patients’ bed provided AP counts
(every 2 h). From blood and WB residence times, derived from the activity–
time curves, doses to red marrow (AIFM and Traino methods) and to blood
(EANM) were calculated. 62 pre and in-therapy doses per activity were com-
pared. The dosimetric results of 83 repeated treatments were analyzed to
investigate the possibility of using the first dosimetry as a reference.
Results: In-therapy (7.8 ± 3.1 cGy/GBq) versus pre-therapy (7.2 ± 2.4 cGy/
GBq) red marrow doses showed a mean percentage difference of −2% ± 16%
[range −36% to 31%]. In 57% of cases in-therapy red marrow doses were
lower than pre-therapy ones. 61% of patients subjected to two treat-
ments showed difference in dose per activity lower than 20% and only 12%
greater than 40% (D2 = 0.84 D1). T-test for paired samples did not show a
significant difference. The different dosimetric methods showed similar
results. No dose correlation with thyroid hormones was found.
Conclusions: Pre and in-therapy red marrow and blood dosimetry may rep-
resent an important tool to personalize metastatic thyroid cancer treatment,
e111 Abstracts/Physica Medica 32 (2016) e97–e115