title: SPIO-labeled Yttrium Microspheres for MR Imaging Quantification of Transcatheter Intrahepatic Delivery in a Rodent Model.
abstract: OBJECTIVE
  To investigate the qualitative and quantitative impacts of labeling yttrium microspheres with increasing amounts of superparamagnetic iron oxide (SPIO) material for magnetic resonance (MR) imaging in phantom and rodent models.
  
  
  METHODS
  Animal model studies were approved by the institutional Animal Care and Use Committee. The r2* relaxivity for each of four microsphere SPIO compositions was determined from 32 phantoms constructed with agarose gel and in eight concentrations from each of the four compositions. Intrahepatic transcatheter infusion procedures were performed in rats by using each of the four compositions before MR imaging to visualize distributions within the liver. For quantitative studies, doses of 5, 10, 15, or 20 mg 2% SPIO-labeled yttrium microspheres were infused into 24 rats (six rats per group). MR imaging R2* measurements were used to quantify the dose delivered to each liver. Pearson correlation, analysis of variance, and intraclass correlation analyses were performed to compare MR imaging measurements in phantoms and animal models.
  
  
  RESULTS
  Increased r2* relaxivity was observed with incremental increases of SPIO microsphere content. R2* measurements of the 2% SPIO-labeled yttrium microsphere concentration were well correlated with known phantom concentrations (R(2) = 1.00, P < .001) over a broader linear range than observed for the other three compositions. Microspheres were heterogeneously distributed within each liver; increasing microsphere SPIO content produced marked signal voids. R2*-based measurements of 2% SPIO-labeled yttrium microsphere delivery were well correlated with infused dose (intraclass correlation coefficient, 0.98; P < .001).
  
  
  CONCLUSIONS
  MR imaging R2* measurements of yttrium microspheres labeled with 2% SPIO can quantitatively depict in vivo intrahepatic biodistribution in a rat model.
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Weiguo
authors: W
authors: Li
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Zhuoli
authors: Z
authors: Zhang
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Andrew C
authors: AC
authors: Gordon
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Jeane
authors: J
authors: Chen
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Jodi
authors: J
authors: Nicolai
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Robert J
authors: RJ
authors: Lewandowski
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Reed A
authors: RA
authors: Omary
authors: From the Department of Radiology, Northwestern University, 737 N Michigan Ave, 16th Floor, Chicago, IL 60611 (W.L., Z.Z., A.C.G., J.C., J.N., R.J.L., A.C.L.); and Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn (R.A.O.).
authors: Andrew C
authors: AC
authors: Larson
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000493:pharmacokinetics; D003911:Dextrans / Q000493:pharmacokinetics*; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D008863:Microspheres; D023421:Models, Animal; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley; D055425:Respiratory-Gated Imaging Techniques; D015019:Yttrium / Q000493:pharmacokinetics*
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D015019:Yttrium; C065507:ferumoxides