title: Evaluation of accuracy in activity calculations for the conjugate view method from Monte Carlo simulated scintillation camera images using experimental data in an anthropomorphic phantom.
abstract: Activity determination from scintillation camera images using the conjugate view method may be inaccurate because of variation in scattered radiation from adjacent organs and activity from overlapping tissues. The aim of this study was to simulate patient scintillation camera images and from these evaluate the accuracy of 2 correction methods. The contribution from overlapping tissue activity was also calculated for some organs.
  
  
  METHODS
  Biokinetic data for (99m)Tc-sestamibi obtained in rats was used as input to simulate scintillation camera images with a voxel-based computer phantom using the Monte Carlo method. The organ activity was calculated using the conjugate view method with either the effective attenuation coefficient method or scatter correction using the triple-energy window (TEW) method combined with attenuation correction with a transmission factor image. Images were simulated with activity in organs one by one to evaluate the accuracy of the 2 correction methods and to evaluate the activity contribution from activity in adjacent or overlapping tissues. To allow comparison with the clinical situation, the total activity distribution from the animal study was used to simulate scintillation camera images at different points in time and the calculated activity was compared with both the input data and some patient data from the literature.
  
  
  RESULTS
  The combination of scatter and attenuation correction gave the most accurate calculated activity, +/-10% of the true activity from the images with activity in one organ at a time. In the images similar to the clinical situation, the kidney activity was overestimated up to a factor of 34, mainly because of excretion of activity through the intestines.
  
  
  CONCLUSIONS
  The scatter correction using the TEW method in combination with attenuation correction with the measured transmission factor resulted in the most accurate activity determination of the methods used. This study also shows that organ activity data calculated from scintillation camera images may be overestimated by >90% because of activity in overlapping tissues.
authors.affiliation: Department of Medical Radiation Physics, Clinical Sciences Lund, Lund University, Lund, Sweden. Lena_M.Jonsson@med.lu.se
authors.forename: Lena
authors.initials: L
authors.lastname: Jönsson
authors.forename: Michael
authors.initials: M
authors.lastname: Ljungberg
authors.forename: Sven-Erik
authors.initials: SE
authors.lastname: Strand
mesh_terms: D000818:Animals; D016477:Artifacts; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007700:Kinetics; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D009010:Monte Carlo Method; D009928:Organ Specificity; D019047:Phantoms, Imaging; D011877:Radionuclide Imaging / Q000295:instrumentation / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi