Purpose: Transarterial 90Y
microspheres radioembolization is emerging as a multidisciplinary promising
therapeutic modality for primary and metastatic cancer in the liver. Actually
two different type of microspheres are used, whose main characteristic is the
different density of activity (activity per microsphere). In this paper the
effect due to the possible different distribution of the microspheres in a
target is presented and discussed from a macrodosimetric point of view.
Material and methods: A 100 g virtual soft-tissue target region has been
builded. The administered activity was chosen to have a target average absorbed
dose of 100 Gy and the number of 90Y microspheres needed was calculated for two
different activity-per-microsphere values (2500) Bq/microsphere and 50
Bq/microsphere, respectively). The spheres were randomly distributed in the
target and the Dose Volume Histograms were obtained for both. The cells
surviving fractions (SF) for four different values of the radiobiological parameter
α were calculated from the Linear - Quadratic model.
Results: The DVH obtained
are very similar and the SF is almost equal for both the activity-per-
microsphere values. Conclusions: This macrodosimetric approach shows no
radiobiological difference between the glass and resin microspheres. Thus the
different number of microspheres seems to have no effect when the number of
spheres is big enough that the distance between the spheres in the target can
be considered small compared to the range of the β-particles of 90Y.Read More...
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