135 research outputs found
Impact of the dosimetry approach on the resulting 90Y radioembolization planned absorbed doses based on 99mTc-MAA SPEC T-CT: is there agreement between dosimetry methods?
Background: Prior radioembolization, a simulation using 99mTc-macroaggregated
albumin as 90Y-microspheres surrogate is performed. Gamma scintigraphy images
(planar, SPECT, or SPECT-CT) are acquired to evaluate intrahepatic 90Y-microspheres
distribution and detect possible extrahepatic and lung shunting. These images may
be used for pre-treatment dosimetry evaluation to calculate the 90Y activity that
would get an optimal tumor response while sparing healthy tissues.
Several dosimetry methods are available, but there is still no consensus on the best
methodology to calculate absorbed doses. The goal of this study was to
retrospectively evaluate the impact of using different dosimetry approaches on the
resulting 90Y-radioembolization pre-treatment absorbed dose evaluation based on 99mTc-MAA images.
Methods: Absorbed doses within volumes of interest resulting from partition model
(PM) and 3D voxel dosimetry methods (3D-VDM) (dose-point kernel convolution and
local deposition method) were evaluated. Additionally, a new âMulti-tumor Partition
Modelâ (MTPM) was developed. The differences among dosimetry approaches were
evaluated in terms of mean absorbed dose and dose volume histograms within the
volumes of interest.
Results: Differences in mean absorbed dose among dosimetry methods are higher
in tumor volumes than in non-tumoral ones. The differences between MTPM and
both 3D-VDM were substantially lower than those observed between PM and any
3D-VDM. A poor correlation and concordance were found between PM and the
other studied dosimetry approaches.
DVH obtained from either 3D-VDM are pretty similar in both healthy liver and
individual tumors. Although no relevant global differences, in terms of absorbed
dose in Gy, between both 3D-VDM were found, important voxel-by-voxel differences
have been observed. Conclusions: Significant differences among the studied dosimetry approaches for 90Y-radioembolization treatments exist. Differences do not yield a substantial impact
in treatment planning for healthy tissue but they do for tumoral liver.
An individual segmentation and evaluation of the tumors is essential. In patients with
multiple tumors, the application of PM is not optimal and the 3D-VDM or the new
MTPM are suggested instead. If a 3D-VDM method is not available, MTPM is the best
option. Furthermore, both 3D-VDM approaches may be indistinctly used
Proton dripline studies at ISOLDE: Ar and C
In this contribution examples of the application of new technologies to disentangle the mechanism of -delayed multiparticle emission are given. In particular the mechanism of 2p-emission from Ar has been resolved and proved to be sequential, a preview of C-decay data is discussed
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