title: Technical Note: Fully-automated analysis of Jaszczak phantom measurements as part of routine SPECT quality control.
abstract: OBJECTIVE
  Inspection and quantitative validation of tomographic imaging properties of SPECT systems, i.e., spatial resolution, contrast, and inhomogeneity must be performed in regular intervals. Typically, the modular Jaszczak phantom is used for that purpose, as it offers the possibility to investigate all three system properties with a single measurement. The interpretation of the measurement is performed visually, thus, being insensitive to subtle changes in system performance. To overcome this limitation, a fully-automated software for the objective analysis of Jaszczak phantom measurements is proposed here.
  
  
  METHODS
  The software was developed as an ImageJ plugin and offers a number of sequential evaluation steps: automatic determination of the type of Jaszczak phantom, calculation of sector and sphere contrast, detection of ring artifacts using either the Hough transform, followed by a threshold-based decision criterion, or Student's t-test. Monte Carlo simulations were used to estimate the detectability limits for ring artifacts.
  
  
  RESULTS
  The software successfully calculated sector and sphere contrasts and reliably determined ring artifacts present in the homogeneity part of the Jaszczak phantom, based on automatic identification of the phantom type.
  
  
  CONCLUSIONS
  Given the quantitative nature of the produced output, results from one imaging system can easily be compared to another in an objective way. The advantage of the software is clearly that the information provided is objective and does not rely on the experience level of the user.
authors.affiliation: Division of Nuclear Medicine, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Austria.
authors.forename: Albert
authors.initials: A
authors.lastname: Hirtl
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.
authors.forename: Helmar
authors.initials: H
authors.lastname: Bergmann
authors.affiliation: Department of Radiation Oncology & Christian Doppler Laboratory for Medical Radiation Physics for Radiation Oncology, Medical University of Vienna, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Knäusl
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Beyer
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Figl
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.
authors.forename: Johann
authors.initials: J
authors.lastname: Hummel
mesh_terms: D006801:Humans; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011786:Quality Control; D012984:Software; D015899:Tomography, Emission-Computed, Single-Photon
keywords: Jaszczak phantom; SPECT; quality assurance