title: Image-guided personalized predictive dosimetry by artery-specific SPECT/CT partition modeling for safe and effective 90Y radioembolization.
abstract: Compliance with radiobiologic principles of radionuclide internal dosimetry is fundamental to the success of (90)Y radioembolization. The artery-specific SPECT/CT partition model is an image-guided personalized predictive dosimetric technique developed by our institution, integrating catheter-directed CT hepatic angiography (CTHA), (99m)Tc-macroaggregated albumin SPECT/CT, and partition modeling for unified dosimetry. Catheter-directed CTHA accurately delineates planning target volumes. SPECT/CT tomographically evaluates (99m)Tc-macroaggregated albumin hepatic biodistribution. The partition model is validated for (90)Y resin microspheres based on MIRD macrodosimetry.
  
  
  METHODS
  This was a retrospective analysis of our early clinical outcomes for inoperable hepatocellular carcinoma. Mapping hepatic angiography was performed according to standard technique with the addition of catheter-directed CTHA. (99m)Tc-MAA planar scintigraphy was used for liver-to-lung shunt estimation, and SPECT/CT was used for liver dosimetry. Artery-specific SPECT/CT partition modeling was planned by experienced nuclear medicine physicians.
  
  
  RESULTS
  From January to May 2011, 20 arterial territories were treated in 10 hepatocellular carcinoma patients. Median follow-up was 21 wk (95% confidence interval [CI], 12-50 wk). When analyzed strictly as brachytherapy, (90)Y radioembolization planned by predictive dosimetry achieved index tumor regression in 8 of 8 patients, with a median size decrease of 58% (95% CI, 40%-72%). Tumor thrombosis regressed or remained stable in 3 of 4 patients with baseline involvement. The best α-fetoprotein reduction ranged from 32% to 95%. Clinical success was achieved in 7 of 8 patients, including 2 by sublesional dosimetry, in 1 of whom there was radioembolization lobectomy intent. Median predicted mean radiation absorbed doses were 106 Gy (95% CI, 105-146 Gy) to tumor, 27 Gy (95% CI, 22-33 Gy) to nontumorous liver, and 2 Gy (95% CI, 1.3-7.3 Gy) to lungs. Across all patients, tumor, nontumorous liver, and lungs received predicted ≥91 Gy, ≤51 Gy, and ≤16 Gy, respectively, via at least 1 target arterial territory. No patients developed significant toxicities within 3 mo after radioembolization. The median time to best imaging response was 76 d (95% CI, 55-114 d). Median time to progression and overall survival were not reached. SPECT/CT-derived mean tumor-to-normal liver ratios varied widely across all planning target volumes (median, 5.4; 95% CI, 4.1-6.7), even within the same patient.
  
  
  CONCLUSIONS
  Image-guided personalized predictive dosimetry by artery-specific SPECT/CT partition modeling achieves high clinical success rates for safe and effective (90)Y radioembolization.
authors.affiliation: Department of Nuclear Medicine and PET, Singapore General Hospital, Singapore. yung.h.kao@gmail.com
authors.forename: Yung Hsiang
authors.initials: YH
authors.lastname: Kao
authors.forename: Andrew Eik
authors.initials: AE
authors.lastname: Hock Tan
authors.forename: Mark Christiaan
authors.initials: MC
authors.lastname: Burgmans
authors.forename: Farah Gillian
authors.initials: FG
authors.lastname: Irani
authors.forename: Li Ser
authors.initials: LS
authors.lastname: Khoo
authors.forename: Richard Hoau
authors.initials: RH
authors.lastname: Gong Lo
authors.forename: Kiang Hiong
authors.initials: KH
authors.lastname: Tay
authors.forename: Bien Soo
authors.initials: BS
authors.lastname: Tan
authors.forename: Pierce Kah
authors.initials: PK
authors.lastname: Hoe Chow
authors.forename: David Chee
authors.initials: DC
authors.lastname: Eng Ng
authors.forename: Anthony Soon
authors.initials: AS
authors.lastname: Whatt Goh
mesh_terms: D000368:Aged; D001158:Arteries / Q000000981:diagnostic imaging*; D006528:Carcinoma, Hepatocellular / Q000098:blood supply / Q000000981:diagnostic imaging / Q000628:therapy; D004621:Embolization, Therapeutic / Q000009:adverse effects* / Q000379:methods*; D006801:Humans; D008113:Liver Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging / Q000628:therapy; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D064847:Multimodal Imaging; D009928:Organ Specificity; D049268:Positron-Emission Tomography; D057285:Precision Medicine / Q000379:methods*; D011874:Radiometry; D012189:Retrospective Studies; D012449:Safety; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D015021:Yttrium Radioisotopes