title: Influence of voxel S factors on three-dimensional internal dosimetry calculations.
abstract: Internal dosimetry is a fundamental instrument for the personalization of nuclear medicine therapies, to maximize the therapeutic effect while minimizing the radiation burden to other organs. Three-dimensional (3D) dosimetry can quantify the impact of heterogeneous radiopharmaceutical distributions in organs, lesions and tissues. We analysed the influence of radionuclide voxel S factors in 3D dosimetry of111In,177Lu and90Y, the most used radionuclides in Peptide Receptor Radionuclide Therapy (PRRT). Calculations were carried out for kidneys on a workstation equipped with a software for 3D dosimetry (Imalytics STRATOS, Philips AG), adopting a computational anthropomorphic phantom and, retrospectively, the SPECT-CT image series of a clinical case of PRRT. Two sets of voxel S factors were adopted: the pre-loaded Philips kernels, calculated by direct Monte Carlo simulation, and the ones calculated through a previously proposed analytical approach. Philips111In kernel did not account for mono-energetic Auger or Conversion electrons. Results indicate a difference of about -32% in voxel S factors for111In in 4.42mm voxel size and around -35% in 4.80mm voxel size, particularly self-dose values; this lead to significant shift in dose histograms and average doses. For177Lu and90Y, differences are about 2% and 12% for 4.42mm voxels and about -8% and 9% for 4.80mm voxels, respectively, attributable to the different calculation methods of the voxel S factors; this does not lead to significant discrepancies between the two dose histograms. Consequently, voxel S factors must account accurately for all radiations emitted by the nuclide.
authors.affiliation: Biomedical Research Group, School of Engineering, Cardiff University, Cardiff, UK.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Berenato
authors.affiliation: Section of Radiological Sciences, Department of Biomedical and Dental Sciences and Morpho-functional Imaging, University of Messina, Italy. Electronic address: eamato@unime.it.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Amato
authors.affiliation: Philips GmbH Innovative Technologies, Aachen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Section of Radiological Sciences, Department of Biomedical and Dental Sciences and Morpho-functional Imaging, University of Messina, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Baldari
mesh_terms: D055592:Biophysical Phenomena; D003198:Computer Simulation; D006801:Humans; D021621:Imaging, Three-Dimensional; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D057285:Precision Medicine; D011874:Radiometry / Q000706:statistics & numerical data; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data*; D018000:Receptors, Peptide / Q000378:metabolism / Q000528:radiation effects; D000072098:Single Photon Emission Computed Tomography Computed Tomography; D012984:Software
chemical_list: D019275:Radiopharmaceuticals; D018000:Receptors, Peptide
keywords: Internal dosimetry; Radionuclide therapy; voxel S factor