Assessment of the sources of error affecting the quantitative accuracy of SPECT imaging in small animals

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Small animal SPECT imaging systems have multiple potential applications in biomedical research. Whereas SPECT data are commonly interpreted qualitatively in a clinical setting, the ability to accurately quantify measurements will increase the utility of the SPECT data for laboratory measurements involving small animals. In this work, we assess the effect of photon attenuation, scatter and partial volume errors on the quantitative accuracy of small animal SPECT measurements, first with Monte Carlo simulation and then confirmed with experimental measurements. The simulations modeled the imaging geometry of a commercially available small animal SPECT system. We simulated the imaging of a radioactive source ... continued below

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Joint Graduate Group in Bioengineering, University of California, San Francisco and University of California, Berkeley; Department of Radiology, University of California; Gullberg, Grant T; Hwang, Andrew B.; Franc, Benjamin L.; Gullberg, Grant T. et al. February 15, 2008.

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Description

Small animal SPECT imaging systems have multiple potential applications in biomedical research. Whereas SPECT data are commonly interpreted qualitatively in a clinical setting, the ability to accurately quantify measurements will increase the utility of the SPECT data for laboratory measurements involving small animals. In this work, we assess the effect of photon attenuation, scatter and partial volume errors on the quantitative accuracy of small animal SPECT measurements, first with Monte Carlo simulation and then confirmed with experimental measurements. The simulations modeled the imaging geometry of a commercially available small animal SPECT system. We simulated the imaging of a radioactive source within a cylinder of water, and reconstructed the projection data using iterative reconstruction algorithms. The size of the source and the size of the surrounding cylinder were varied to evaluate the effects of photon attenuation and scatter on quantitative accuracy. We found that photon attenuation can reduce the measured concentration of radioactivity in a volume of interest in the center of a rat-sized cylinder of water by up to 50percent when imaging with iodine-125, and up to 25percent when imaging with technetium-99m. When imaging with iodine-125, the scatter-to-primary ratio can reach up to approximately 30percent, and can cause overestimation of the radioactivity concentration when reconstructing data with attenuation correction. We varied the size of the source to evaluate partial volume errors, which we found to be a strong function of the size of the volume of interest and the spatial resolution. These errors can result in large (>50percent) changes in the measured amount of radioactivity. The simulation results were compared with and found to agree with experimental measurements. The inclusion of attenuation correction in the reconstruction algorithm improved quantitative accuracy. We also found that an improvement of the spatial resolution through the use of resolution recovery techniques (i.e. modeling the finite collimator spatial resolution in iterative reconstruction algorithms) can significantly reduce the partial volume errors.

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  • Journal Name: Physics in Medicine and Biology; Journal Volume: 53; Related Information: Journal Publication Date: 4/9/2008

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  • Report No.: LBNL-379E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 934672
  • Archival Resource Key: ark:/67531/metadc896124

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  • February 15, 2008

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  • Sept. 27, 2016, 1:39 a.m.

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  • Sept. 30, 2016, 6:17 p.m.

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Joint Graduate Group in Bioengineering, University of California, San Francisco and University of California, Berkeley; Department of Radiology, University of California; Gullberg, Grant T; Hwang, Andrew B.; Franc, Benjamin L.; Gullberg, Grant T. et al. Assessment of the sources of error affecting the quantitative accuracy of SPECT imaging in small animals, article, February 15, 2008; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc896124/: accessed August 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.