title: Calculation of tumour and normal tissue biological effective dose in90Y liver radioembolization with different dosimetric methods.
abstract: OBJECTIVE
  Radioembolization with90Y microspheres is an effective treatment for unresectable liver tumours. Two types of microspheres are available: resin (SIR-Spheres®) and glass (Theraspheres®). The aim of this study is to compare biological effective dose (BED) values obtained with three different dosimetric methods.
  
  
  METHODS
  29 HCC patients were included in this study: 15 were treated with resin(mean injected activity 1.5GBq, range 0.8-2.7GBq) and 14 with glass microspheres (2.6GBq, range 1.3-4.1GBq). Average doses to tumours and normal liver tissues were calculated with AAPM, multi-compartmental MIRD and Voxel-based methods and consequently the BED values were obtained. Planar images were used for the AAPM method:99mTc-MAA SPECT-CT attenuation and scatter corrected images (resin) and99m Tc-MAA SPECT attenuation corrected (glass) were employed for the other two methods.
  
  
  RESULTS
  Regardless of type of microspheres, both for tumours and normal liver tissues, no significant statistical differences were found between MIRD and Voxel for both doses and BED values. Conversely AAPM gave discordant results with respect to the other two methods (Mann-Whitney p-values⩽0.01). For resin spheres the calculated tumour-to-normal tissue ratios on planar images were on average 14 times greater than those obtained on SPECT-CT images, while they were 4 times greater on glass. A linear correlation was observed between MIRD and Voxel BEDs.
  
  
  CONCLUSIONS
  The AAPM method appears to be less precise for absorbed dose and BED estimation, while MIRD and voxel based dosimetry are more confident each other.
authors.affiliation: S.C. Fisica Sanitaria, A.O.U. Città della Salute e della Scienza, Corso Bramante 88/90, 10126 Turin, Italy. Electronic address: egallio@cittadellasalute.to.it.
authors.forename: Elena
authors.initials: E
authors.lastname: Gallio
authors.affiliation: S.C. Fisica Sanitaria, A.O. Ordine Mauriziano, via Ferdinando Magellano 1, 10128 Turin, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Richetta
authors.affiliation: S.C. Medicina Nucleare U, A.O.U. Città della Salute e della Scienza, Corso Bramante 88/90, 10126 Turin, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Finessi
authors.affiliation: S.C. Fisica Sanitaria, A.O. Ordine Mauriziano, via Ferdinando Magellano 1, 10128 Turin, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Stasi
authors.affiliation: S.C. Medicina Nucleare, A.O. Ordine Mauriziano, via Ferdinando Magellano 1, 10128 Turin, Italy.
authors.forename: Riccardo Emanuele
authors.initials: RE
authors.lastname: Pellerito
authors.affiliation: S.C. Medicina Nucleare U, A.O.U. Città della Salute e della Scienza, Corso Bramante 88/90, 10126 Turin, Italy.
authors.forename: Gianni
authors.initials: G
authors.lastname: Bisi
authors.affiliation: S.C. Fisica Sanitaria, A.O.U. Città della Salute e della Scienza, Corso Bramante 88/90, 10126 Turin, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ropolo
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000532:radiotherapy*; D004621:Embolization, Therapeutic; D006801:Humans; D008099:Liver / Q000166:cytology / Q000473:pathology / Q000528:radiation effects*; D008113:Liver Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008863:Microspheres; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D012062:Relative Biological Effectiveness; D015021:Yttrium Radioisotopes / Q000737:chemistry / Q000627:therapeutic use*
chemical_list: D015021:Yttrium Radioisotopes
keywords: BED; Dosimetry; Microspheres; Yttrium-90