An international quantitative SPECT/CT imaging exercise for assessment of Ba-133 as surrogate for I-131
Tran-Gia, J. Robinson, A. P. Bobin, C. Calvert, Nicholas Collins, S. Denis-Bacelar, A. M. Fenwick, A. Ferreira, K. Finocchiaro, D. Fioroni, F.
Tran-Gia, J.
Robinson, A. P.
Bobin, C.
Calvert, Nicholas
Collins, S.
Denis-Bacelar, A. M.
Fenwick, A.
Ferreira, K.
Finocchiaro, D.
Fioroni, F.
Citations
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Abstract
Aim/Introduction: In nuclear medicine imaging,
commissioning and quality control are typically
performed based on hollow containers manually filled
with radionuclide solutions. Most associated sources of
uncertainty (e.g., filling volume, activity concentration)
can be overcome by sealed, long-lived surrogate sources
containing a radionuclide of comparable energies and
emission probabilities, traceable to a primary standard.
This study presents the results of a quantitative SPECT/
CT imaging comparison exercise performed within the
MRTDosimetry project to assess the applicability of Ba-133
sources as a surrogate for I-131 and to determine a crosscalibration
factor. Materials and Methods: Cylinders of four different dimensions (active volumes of diameters 7.5, 15,
30, and 60 mm and 38 mm height, resulting in volumes of
1.68, 6.72, 26.9 and 107.4 cm3) and two different caps (one
for complete closure, one with filling hole) were fabricated
with a stereolithography 3D printing system (Formlabs
Form 2, Tough resin). Optimal source placement in 216-mm
Jaszczak cylinder was ensured by a laser-cut attachment
baseplate designed based on simulations of spilled-out
counts (Gaussian convolution with 20-mm FWHM). Solid
Ba-133 surrogate sources were produced at two metrology
institutions: CEA (activity concentration [206.2±5.8] kBq.
mL−1) and CMI ([99.8±1.6] kBq.mL−1), with leakage and
contamination tests according to ISO9978. The comparison
exercise included eight SPECT/CT systems (3×Siemens,
5×GE). Each site had to perform three measurements with
different sources attached in a water-filled Jaszczak cylinder:
1) Ba-133 CEA sources, 2) Ba-133 CMI sources, 3) identical
containers filled with liquid I-131. Parameters: High-energy
collimator, 2×60 projections of 30s, Ba-133: 356.0keV [5%-
15%-10% scatter-main-scatter], I-131: 364.5keV [6%-20%-
6%], low-dose CT, OSEM with standard corrections. A CTbased
VOI analysis was carried out to compare differences
in pseudo-ICF (image calibration factor including partialvolume
related errors: counts in VOI per activity and
scan duration). A regression analysis was performed to
determine a cross-calibration factor. Results: Iodine-131
pseudo-ICFs were higher than Ba-133 pseudo-ICFs for all
reconstructions and systems. Equivalent setups (camera and
reconstruction) yielded comparable pseudo-ICFs (average
relative error 5.6% between three equivalent GE setups).
The regression analysis resulted in a cross-calibration factor
of 0.70±0.02. This value is in agreement with the ratio
0.764±0.005 of the emission probabilities (62.05±0.19)%
(Ba-133) and (81.2±0.5)% (I-131) [1]. Conclusion: Although
this international comparison exercise was challenging
due to varying transport regulations between countries, we could show that traceable solid Ba-133 sources can be
used as surrogate for liquid I-131, thus potentially reducing
inherent problems with on-site activity measurement and
phantom preparation.
Authors
Tran-Gia, J.
Robinson, A. P.
Bobin, C.
Calvert, Nicholas
Collins, S.
Denis-Bacelar, A. M.
Fenwick, A.
Ferreira, K.
Finocchiaro, D.
Fioroni, F.
Gianopoulou, K.
Grassi, E.
Heetun, W.
Jewitt, S. J.
Kotzasarlidou, M.
Ljungberg, M.
Lourenco, V.
McGowan, D. R.
Scuffham, J.
Gleisner, K. S.
Solc, J.
Thiam, C.
Tipping, Jill
Wevrett, J.
Lassmann, M.
Robinson, A. P.
Bobin, C.
Calvert, Nicholas
Collins, S.
Denis-Bacelar, A. M.
Fenwick, A.
Ferreira, K.
Finocchiaro, D.
Fioroni, F.
Gianopoulou, K.
Grassi, E.
Heetun, W.
Jewitt, S. J.
Kotzasarlidou, M.
Ljungberg, M.
Lourenco, V.
McGowan, D. R.
Scuffham, J.
Gleisner, K. S.
Solc, J.
Thiam, C.
Tipping, Jill
Wevrett, J.
Lassmann, M.
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Tran-Gia J, Robinson AP, Bobin C, Calvert N, Collins S, Denis-Bacelar AM, et al. An international quantitative SPECT/CT imaging exercise for assessment of Ba-133 as surrogate for I-131. European Journal of Nuclear Medicine and Molecular Imaging. 2020;47(SUPPL 1):S448-S9