title: Feasibility and reproducibility of BOLD and TOLD measurements in the liver with oxygen and carbogen gas challenge in healthy volunteers and patients with hepatocellular carcinoma.
abstract: OBJECTIVE
  To quantify baseline relaxation rates R2* and R1 in the abdomen, their changes after respiratory challenges, and their reproducibility in healthy volunteers and patients with hepatocellular carcinoma (HCC) at 1.5T and 3.0T.
  
  
  METHODS
  R2* measurements were acquired in the liver in 8 volunteers and 27 patients with 34 HCCs using multiecho T2* at baseline and after respiratory challenges with 100% oxygen (O2 ) and carbogen (CB = 95%O2 /5%CO2 ). R1 was measured at 1.5T in one volunteer and 21 patients with 23 HCCs. Test-retest coefficient of variation (CV) was assessed in 10 subjects. Intra- and interobserver variability of R2* and R1 measurements was assessed in 12 and 10 patients, respectively. Parameters for HCC, liver, and muscle were compared between baseline and after gas challenges.
  
  
  RESULTS
  We observed that R2* and R1 imaging of HCCs with O2 and CB is feasible and reproducible (test-retest CV R2*<15%/R1 <5%; intra- and interobserver intraclass correlation coefficient R2*>0.88/R1 >0.7 and CV R2*<7%/R1 <3% at 1.5T). R2* measurements were observed to be less reproducible at 3.0T (CV<35%). There was a statistically significant decrease in R2* values in HCC before and after O2 (P = 0.02) and increase in R1 after O2 (P = 0.004). CB had no significant effect (P R2* = 0.47/R1  = 0.278).
  
  
  CONCLUSIONS
  R2* measurements in HCC and liver parenchyma are more reproducible at 1.5T than at 3.0T, and with O2 than with CB challenge. We observed a decrease in R2* and an increase in R1 of HCCs from baseline in response to O2 challenge, as expected with increased tissue and blood oxygenation.
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Octavia
authors.initials: O
authors.lastname: Bane
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.|Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Besa
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Siemens Healthcare, New York, NY, USA.
authors.forename: Niels
authors.initials: N
authors.lastname: Oesingmann
authors.affiliation: Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Hongfa
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Fiel
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.|Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
authors.forename: Bachir
authors.initials: B
authors.lastname: Taouli
mesh_terms: D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000737:chemistry*; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000473:pathology; D005240:Feasibility Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000000981:diagnostic imaging; D015588:Observer Variation; D010100:Oxygen / Q000737:chemistry*; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen
keywords: R1; R2*; hepatocellular carcinoma; liver