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

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exceeding the limit of the fixed activity approach and prescribing higher
131I activity in safety.
C.380
RADIOIODINE 131I TREATMENT OF DIFFERENTIATED THYROID CANCER
IN PATIENTS UNDERGOING DIALYSIS: DOSIMETRY, RADIATION
PROTECTION AND PRACTICAL ASPECTS
E. Richetta M. Pasquino C. Cutai S. Valzano S. Berutti C. Vital
R.E. Pellerit M. Stasi a S.C. Fisica Sanitaria, AO Ordine Mauriziano, Torino,
Italy; b S.C. Nefrologia, AO Ordine Mauriziano, Torino, Italy; c S.C. Medicina
Nucleare, AO Ordine Mauriziano, Torino, Italy
Introduction: 131I therapy is a standard treatment of differentiated thyroid
cancer. In dialysis patients, the impaired renal function makes the deter-
mination of the optimal activity difficult. Here we compare radioiodine
uptake measurements in patients treated with different dialysis regi-
mens. Red marrow and blood doses and individual workers’ effective dose
were also evaluated.
Materials and Methods: Patient 1 (papillary, pT4) was treated for abla-
tion (2.7 GBq) in 2002; 24 h p.a. standard haemodialysis (HD, 4 h) was
performed. Patient 2 (papillary, pT3N1) was treated in 2014 (2.59 GBq) and
in 2015 (5.54 GBq). Immediately after administration, continuous
haemodiafiltration (CVVHDF, 8 h, equivalent to a renal clearance of 70 mL/
min) was performed and repeated after 48 h. To evaluate activity distribution,
whole-body measurements were performed with a detector placed on pa-
tients’ beds every 2 h. WB curves were normalised and residence times were
evaluated. A comparison with a normal patient is reported as reference.
Blood samples were acquired (2, 24, 48, 96 h p.a.) to perform red marrow
and blood dosimetry. Nurses conducting dialysis sessions were provided
with individual dosimeters to evaluate effective doses.
Results: Patient 1 showed a maximum uptake until dialysis started at 24 h,
then it decreased to 24%: residence time was about 41 h. In Patient 2 the
uptake decreased progressively during first dialysis (100%, 68%, 42%, 29%
in 8 h) and remained almost constant until next treatment at 48 h (20%,
16%, 13%, 11%, 8% in 8 h). Similar residence times were observed in both
treatments (2014: 18.5 h, 2015: 21.8 h). Normal patient’s residence time
was about 19.5 h. Red marrow and blood doses were 0.39 and 0.50 Gy re-
spectively. Effective doses to workers ranged from 78 to 96 microSv per
dialysis session.
Conclusions: CVVHDF allowed a more predictable removal of 131I than
standard HD, similar to normal patient, with safe radiation protection for
patient and workers.
C.381
RED MARROWDOSIMETRY IN DIFFERENTIATED THYROID CANCER (DTC):
COMPARISON BETWEEN PREVISIONAL AND POST THERAPY DOSE FOR
MULTITREATED PATIENTS AND FOLLOW-UP
G. Rossi * M. Camarda P. D’Avenia E. Di Nicola L. Montani
C. Bartolozzi A.M. Dente F. De Angelis N. Gasparrini E. Brianzon
S. Fattori a Medical Physic, Macerata Hospital, AV3 ASUR Marche, Macerata,
Italy; b Nuclear Medicine, Macerata Hospital, AV3 ASUR Marche, Macerata, Italy
Introduction: In multi treated DTC patients (pts) it is desirable to make
dosimetry to establish the maximum tolerated dose (MTD) to avoid
complicances to the red marrow (RM), to verify the effective absorbed dose,
to evaluate the clinical utility and define the correct staging.
Materials and Methods: We enrolled 46 pts (25 M, 21 F) with DTC, 9 pts
with 2 evaluations and 1 with 3, for a total of 56 calculations. All pts were
in thyroid hormone withdrawal. On the first day, TSH, hTG, AbhTG, Ioduria
and aematochemical routine were evaluated then 131I was administered
(median 18 MBq, range 8–21), fasting and no urine excretion for 2 hours.
According to the AIFM protocol we collected blood sample (BS) and whole
body (WB) counts at 2-24-48-96-120 h. We calculated tau (SAAMII) and
the MTD (OLINDA/EXM) after blood/RM approximation considering the 2 Gy/
RM limit and 2960 MBq of WB retention at 48°h (if pulmonary metastases).
Then considering dosimetry we administered the 131I-therapy MTD (range
1019–9334 MBq) sometimes modulated. In therapy we repeated the data
collection and calculations. Pts have made every 20 days for three months
aematochemical routine.
Results: No pts overcame 2 Gy/RM. The pre-post comparison shows dif-
ferences greater than 50% for WB in 14/56 pts (26%, 9 m, 5 f, 7 lower and
7 higher), for the RM in 18/56 (32%, 8 m, 10 f, 3 higher and 15 lower). The
absorbed RM dose range is 0.17–1.9 Gy. In the 9 multidosimetry pts we found
big deviation between different dosimetric evaluation: for 2/9 more than
400% (19–21 months between treatments), for 7 dosimetries from 3% to
76% for WB and from 2% to 53% for RM (6–12 months). There was no side
effect of elevated grade for the aemathological syneresis.
Conclusions: The previsional dosimetry allows to avoid to overcome 2 Gy/
RM. High variation pre-post often is due to a significative modification of
the staging at the WB scan post treatment. It is then desirable to repeat
dosimetry for further treatment and to study metastases to modulate the
following one.
C.382
8F-FDG WHOLE BODY PET/CT DOSE EVALUATION IN PEDIATRIC PATIENTS
L. Rossi F. Zito G. Galetta L. Florimont E. Orunesu M. Castellan
C. Canzi F. Voltini R. Benti a Medical Physics Department, Fondazione IRCCS
Cà Granda Ospedale Maggiore Policlinico, Milan, Italy; b Medical Physics
Specialization School, Milan, Italy; c Nuclear Medicine Department, Fondazione
IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
Introduction: A retrospective analysis of 18F-FDG PET/CT absorbed dose
in pediatric patients is presented with the purpose to optimize CT acqui-
sition parameters and to improve protection for high-radiation-sensitive
young population.
Material & Methods: Eight pediatric patients (1–7 years) were evalu-
ated. 18F-FDG activity was scaled according to PET scanner sensitivity and
body weight (~5 MBq/kg, 37 MBq as minimum injected activity). PET whole-
body (WB) was performed with the Biograph TruePoint system (Siemens)
with 3 min/bed. All CT scans were carried out with automatic control of
tube current, with 90mAs as reference. Four patients were scanned at 120 kV
and the other four at 100 kV. PET effective dose was assessed by multiply-
ing the injected MBq with the ICRP 80 18F-FDG factors (mSv/MBq),
interpolated to each patient age. Based on AAPM report 204, patient-
specific CTDIvol index (CTDIvol_AAPM) was calculated by measuring on
CT the effective diameter and correcting the scanner CTDIvol with AAPM
factor. ImPACT dosimetry calculator estimated CT effective dose (ImPACT).
ImPACT values, referred to adult patients, were scaled to pediatric age. Two
expert physicians scored CT image quality with a 3 level scale: sufficient,
good or excellent.
Results:Patients scanned at 100 kV had on average 40% reduction of CTDIvol
with respect to those at 120 kV, without changing on CT image qualities.
CTDIvol_AAPM, based on the patient specific size, doubled CTDIVol which
is calculated with the standard 32 cm phantom. For two patients, scanned
at 120 kV, CT effective dose, assessed with ImPACT, overcame PET dose. For
the remaining patients, CT dose was on average half PET dose. CT image
quality scores were sufficient and good in 5 and 3 cases, respectively, in-
dependent of tube kV.
Conclusion: The importance of patient-specific size use in exposure dose
estimation for 18F-FDG PET/CT has been reported. In our PET/CT unit, ef-
fective dose is used as more relevant parameter for WB scan exposure and
100 kV is set for young patient CT scans.
C.383
A PROCEDURE TO QUANTIFY RADIONUCLIDE PURITY OF [18F]FDG BY
MEANS OF GAMMA RAY SPECTROMETRY
S. Calusi P. Saletti L. Capacciol a Department of Clinical and Experimental
Biomedical Sciences, University of Florence, Mario Serio, Florence, Italy; b Health
Physics Unit, AOU Careggi, Florence, Italy
Introduction: Radionuclide purity is a fundamental parameter that de-
termines the quality of a radiopharmaceutical. European and national laws
e112 Abstracts/Physica Medica 32 (2016) e97–e115