title: Comparison of positron emission tomography and bremsstrahlung imaging to detect particle distribution in patients undergoing yttrium-90 radioembolization for large hepatocellular carcinomas or associated portal vein thrombosis.
abstract: OBJECTIVE
  To compare positron emission tomography/computed tomography (PET/CT) imaging with bremsstrahlung single photon emission computed tomography (SPECT) in patients after yttrium-90 ((90)Y) microsphere radioembolization to assess particle uptake.
  
  
  METHODS
  This prospective study comprised patients with large (> 5 cm) hepatocellular carcinoma (HCC) or tumor-associated portal vein thrombus (PVT), or both. After radioembolization for HCC, patients underwent bremsstrahlung SPECT/CT and time-of-flight PET/CT imaging of (90)Y without additional tracer administration. Follow-up imaging and toxicity was analyzed. Imaging analyses of PET/CT and bremsstrahlung SPECT/CT were independently performed.
  
  
  RESULTS
  There were 13 patients enrolled in the study, including 7 with PVT. Median tumor diameter was 7 cm. PET/CT demonstrated precise localization of (90)Y particles in the liver, with specific patterns of uptake in large tumors. In cases of PVT, PET/CT showed activity within the PVT. When correlated to short-term follow-up imaging, areas of necrosis correlated with regions of uptake seen on PET/CT. Compared with bremsstrahlung imaging, PET/CT demonstrated at least comparable spatial resolution with less scatter. Quantitative uptake in nontreated regions of interest showed significantly reduced scatter with PET/CT versus SPECT/CT (1% vs 14%, P < .001).
  
  
  CONCLUSIONS
  Evaluation of (90)Y particle uptake with PET/CT potentially demonstrates high spatial resolution and low scatter compared with bremsstrahlung SPECT/CT. Confirmation of particles within PVT on PET/CT correlates with response on follow-up imaging and may account for the efficacy of radioembolization in patients with PVT.
authors.affiliation: Section of Interventional Radiology, University of Washington, Seattle, WA 98119, USA. spadia@uw.edu
authors.forename: Siddharth A
authors.initials: SA
authors.lastname: Padia
authors.forename: Adam
authors.initials: A
authors.lastname: Alessio
authors.forename: Sharon W
authors.initials: SW
authors.lastname: Kwan
authors.forename: David H
authors.initials: DH
authors.lastname: Lewis
authors.forename: Sandeep
authors.initials: S
authors.lastname: Vaidya
authors.forename: Satoshi
authors.initials: S
authors.lastname: Minoshima
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism / Q000532:radiotherapy*; D004621:Embolization, Therapeutic / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D011169:Portal Vein / Q000000981:diagnostic imaging / Q000378:metabolism / Q000528:radiation effects*; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011446:Prospective Studies; D019275:Radiopharmaceuticals / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D047368:Tumor Burden; D020246:Venous Thrombosis / Q000000981:diagnostic imaging / Q000209:etiology / Q000378:metabolism / Q000532:radiotherapy*; D015021:Yttrium Radioisotopes / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes
keywords: (90)Y; HCC; PET; PVT; ROI; SPECT; hepatocellular carcinoma; portal vein thrombus; positron emission tomography; region of interest; single photon emission computed tomography; yttrium-90