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

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Results: The mean absorbed dose and standard deviation for 4 lesions (mean
[σ%]) were: 434 mGy [15%] and 516 mGy [21%] for right and left humeral
heads, 1205 mGy [14%] and 781 mGy [8%] for right and left glenoids. The
total absorbed dose after the whole treatment, considering the relative-
biological-effectiveness of alpha particles (RBE = 5), yielded a DRBE range
of 13–36 Gy. TNT showed an overall reduction in two cases (−42% and −48%),
but for most lesions it remained fairly constant.
Conclusion: The inter-fraction variability of dosimetric assessments indi-
cates that dosimetry would be advisable more than once, for a more accurate
estimation of the total absorbed dose. TNT constancy highlights that 223Ra-
dichloride therapy tends to prevent further progression of the osseous
disease, leading to chronicity of the metastatic status.
C.343
LESIONS DOSIMETRY FOR 223RA THERAPY OF BONE METASTASES FROM
CASTRATION-RESISTANT PROSTATE CANCER
M. Pacilio B. Cassano G. Ventroni G. De Vincenti R. Pellegrini
E. Di Castro V. Frantellizzi G.A. Follacchio L. Lorenzo P. Ialong
L. Mango R. Pani a Department of Medical Physics, Azienda Ospedaliera San
Camillo Forlanini, Roma, Italy; b Postgraduate School of Medical Physics,
Sapienza University of Rome, Roma, Italy; c Department of Nuclear Medicine,
Azienda Ospedaliera San Camillo Forlanini, Roma, Italy; d Department of
Radiological, Oncological and Anatomo Pathological Sciences, Sapienza
University of Rome, Roma, Italy; e Department of Molecular Medicine, Sapienza
University of Rome, Roma, Italy; f Department of Radiology, Azienda Ospedaliera
San Camillo Forlanini, Roma, Italy
Introduction: 223Ra-dichloride is an alpha-emitting radiopharmaceuti-
cal used in the treatment of bone metastases from castration-resistant
prostate cancer. The aim of this study was to perform lesions dosimetry
by in-vivo quantitative planar imaging, assessing the absorbed dose to lesions
with the MIRD approach.
Materials and Methods: The study included 11 patients and 27 lesions.
The treatment consisted of 6 injections of 50 kBq per kg of body weight.
Gamma-camera calibrations for 223Ra included measurements of sensi-
tivity and transmission curves. Patients were statically imaged for 30 min,
using an MEGP collimator, double-peak acquisition, and Wiener filtering
to improve the image quality. Lesions were delineated on 99mTc-MDP
whole-body images, and the ROIs superimposed on the 223Ra images after
image coregistration. The activity was quantified with background, atten-
uation, and scatter correction. Absorbed doses were assessed deriving the
S values from the S factors for soft-tissue spheres of OLINDA/EXM, evalu-
ating the lesion volumes by delineation on the CT images.
Results: The optimal timing for serial acquisitions was between 1 and 5 h,
18–24 h, 48–60 h and 7–15 days, but the first early acquisition affects poorly
dosimetric assessments and could be skipped. The mean effective half-
life of 223Ra (mean [range]) was 7.8 [4.3–11.4] days. The absorbed dose
after the first injection was 0.6 [0.2–1.9] Gy. Considering the Relative Bi-
ological Effectiveness for alpha particles (RBE = 5), DRBE/Aadm to lesions
was 891 [340–2450] mGy/MBq.
Conclusion: In-vivo quantitative imaging and lesions dosimetry in 223Ra
therapy resulted feasible. The DRBE to lesions per unit injected activity was
much higher than that of other bone-seeking radiopharmaceuticals, but
considering a standard administration of 21 MBq (six injections of 50 kBq/
kg to a 70-kg patient), the mean cumulative value of DRBE was about 21 Gy,
and was therefore in the range of those of other radiopharmaceuticals.
C.344
PET SCANNER CLINICAL TRIAL QUALIFICATION WITH 68GE-FILLED
NEMA/IEC IMAGE QUALITY PHANTOM OUTPERFORMS WITH RESPECT TO
18F
S. Chauvie F. Bergesio F. Fioron M. Brambill a Medical Physics Unit,
ASO S. Croce e Carle, Cuneo, Italy; b School of Medical Physics, University of
Torino, Torino, Italy; c Medical Physics Unit, ASO S. Maria Nuova, Reggio Emilia,
Italy; d Medical Physics Unit, ASO Maggiore della Carità, Novara, Italy
Introduction: The quantitative reading of Positron Emission Tomography
(PET) scan by standardized uptake value and derived parameters is exper-
imentally studied in several clinical trials. Since scanners give different
quantitative readings, a program for clinical trial qualification (CTQ) is man-
datory to guarantee a reliable and reproducible use of quantitative PET in
prospective multi-center clinical trials and in every-day clinical life.
Materials and Methods: Under the auspices of Italian Foundation on Lym-
phoma (FIL) we set-up a CTQ program consisting on the PET/CT scan
acquisition and analysis of 18F and 68Ge NEMA/IEC image quality phan-
toms for the reduction of inter-scanner variability. Variability was estimated
on background activity concentration (BAC) and sphere to background ratio
(SBR).
Results: Seventy-four sites equipped with 83 PET/CT scanners partici-
pated in the 18F phantom CTQ program. Sixty-three out of 83 (76%) scanners
fulfilled the CTQ requirements, 14 (17%) did not because of a lack of phan-
toms or trained personnel, while CTQ is still ongoing on 6 (7%) scanners.
For qualified scanners the CTQ was reached at the first round in 28% of
the cases, while in 18%, 17% and 13%, two, three or more than three itera-
tions were required, respectively. The use of 68Ge phantom allowed reducing
the inter-scanner variability at 95% confidence level among different
scanners from 39.2% to 10.6% in BAC and from 23.6% to 9.4% in SBR with
respect to the one based on 18F phantom. The CTQ criteria were fulfilled
at first round in 100% and 28% of PET scanners with 68Ge and 18F
respectively.
Conclusions: The 68Ge-filled phantom is a reliable tool for CTQ and permits
to reduce inter-scanner variability with respect to 18F-filled one.
C.345
TRULY DOSIMETRIC TREATMENT PLANNING WITH 99M-TC MAA SPECT
PROLONGED OVERALL SURVIVAL IN RADIOEMBOLIZATION OF
HEPATOCARCINOMA WITH 90-Y GLASS MICROSPHERES
C. Chiesa *, M. Mira, M. Maccauro, A. Facciorusso, C. Spreafico, R. Romito,
C. Sposito, A. Brusa, B. Padovano, M. Migliorisi, A. Marchianò, F. Crippa,
V. Mazzaferro. Fondazione IRCCS Istituto Nazionale Tumori, Milano, Italy
Aim: To estimate the impact of truly dosimetric treatment planning in
radioembolization of hepatocarcinoma (HCC) with 90Y glass microspheres.
Materials and Methods: 2 cohorts of intermediate/advanced HCC pa-
tients were treated. 52 patients had been enrolled in cohort 1 with strict
inclusion criteria. Activity was chosen according to the pamphlet indica-
tion of 120 Gy to the target liver lobe. Retrospective 99mTc-MAA SPECT
dosimetry was based on local deposition method and patient relative cal-
ibration. In the 43 Child A patients, analysis of liver toxicity had shown
an NTCP = 14% at 75 Gy (mean absorbed dose on the whole parenchyma).
TCP 50% had been determined at 250 Gy for small lesions (<10 cc) and at
1300 Gy for larger lesions (>10 cc).
189 patients were enrolled in cohort 2 with loose criteria. For a meaning-
ful comparison, the subcohort 2 was selected applying to cohort 2 the
same inclusion criteria of cohort 1. The 90Y activity was chosen after per-
sonalized 99mTc-MAA SPECT planning using the above mentioned
thresholds.
Results: planning modified the activity in 73% of patients with respect to
pamphlet indications. Activity was increased/decreased in 47%/25% of pa-
tients (mean +100%/−30%). The standard deviation of parenchyma dose was
strongly reduced (16.5 Gy vs 30 Gy). In Child A patients of subcohort 2, liver
toxicity incidence (11/71 = 15.5%) was as in cohort 1 (6/43 = 14%), as planned;
overall survival was prolonged (17 m, 95% C.I. [13–19] versus 15 m, 95%
C.I. [12–18]), also in patients with portal vein thrombosis (15 m, 95% C.I.
[10–17] versus 13 m, 95% C.I. [9–17]).
Conclusion: In HCC Child A patients, truly dosimetric treatment planning
resulted in strongly personalized administration, reduced inter-patient
spread of parenchyma dose, identical toxicity incidence and prolonged sur-
vival, with respect to the 120 Gy to lobe prescription. Treatment planning
should be implemented for ethical reasons, but legally might appear in con-
flict with the pamphlet indications.
e101 Abstracts/Physica Medica 32 (2016) e97–e115