title: In vitro evaluation of a novel fiducial marker for computed tomography and magnetic resonance imaging of soft tissues in small animals.
abstract: OBJECTIVE
  To construct and optimize a fiducial marker suitable for both CT and MRI.
  
  
  METHODS
  Fiducial markers containing serial dilutions of iopamidol mixed with water.
  
  
  METHODS
  IV tubing sets were infused with serial dilutions (0% to 100%; increments of 10%) of iopamidol. Tubing ends were sealed; additional seals were added to create an equilateral triangle. A reference point was created by placing a crimp in 1 side. Markers were fixed to a gelatin soft tissue-attenuating phantom and evaluated by use of CT and MRI. For CT, simple linear regression analysis was used to assess the relationship between the percentage of marker contrast medium and quantitative variables, including marker attenuation, attenuation changes in the phantom, and beam-hardening artifact length. A subjective grading scheme for artifact creation on CT images and marker visibility on MRI images was used. Measurements were obtained by investigators who were unaware of the contents of each marker.
  
  
  RESULTS
  Percentage of contrast medium in each marker was strongly correlated with marker attenuation (r(2) = 0.96), artifact length (r(2) = 0.765), and mean attenuation changes within the phantom (r(2) = 0.826) for CT. Subjective CT scores indicated that concentrations of contrast medium > 50% resulted in excessive artifacts. Markers with concentrations of iopamidol > 50% had poor subjective MRI visibility scores. No artifacts were seen on MRI.
  
  
  CONCLUSIONS
  A marker containing a 10% solution of iodinated contrast medium mixed with water provided ideal contrast for both CT and MRI.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.
authors.forename: Jesse L
authors.initials: JL
authors.lastname: Terry
authors.forename: Milan
authors.initials: M
authors.lastname: Milovancev
authors.forename: Sarah
authors.initials: S
authors.lastname: Nemanic
mesh_terms: D000818:Animals; D016477:Artifacts; D003287:Contrast Media / Q000008:administration & dosage; D057918:Fiducial Markers / Q000662:veterinary*; D066298:In Vitro Techniques; D007479:Iopamidol / Q000008:administration & dosage; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000592:standards / Q000662:veterinary*; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards / Q000662:veterinary*
chemical_list: D003287:Contrast Media; D007479:Iopamidol