title: Generation of realistic HMPAO SPECT images using a subresolution sandwich phantom.
abstract: Traditional interpretation of rCBF SPECT data is of a qualitative nature and is dependent on the observer's understanding of the normal distribution of the tracer. The use of a normal database in quantitative regional analysis facilitates the detection of functional abnormality in individual and group studies by accounting for inter-subject variability. The ability to simulate realistic images would allow various important areas related to the use of normal databases to be studied. These include the optimisation of the detection of abnormal blood flow and the portability of normal databases between gamma camera systems. To investigate this further we have constructed a hardware phantom and scanned various configurations of radioactive brain patterns and simulated skull configurations.
  
  
  METHODS
  A subresolution sandwich phantom was constructed with a simulated skull which was assembled using a high-resolution segmented MR scan printed with a (99m)TcO₄ - mixture and scanned using a double-headed gamma camera with parallel-hole collimators. Various different grey-to-white matter (GM:WM) ratios and aluminium simulated skull configurations were used. A single difference measure between the phantom data and a control database mean image was used for optimisation. The realism of phantom data was assessed using statistical parametric mapping (SPM) and ROI analysis.
  
  
  RESULTS
  Optimisation was achieved with a range of WM:GM ratios from 1.9 to 2.4:1 with various simulated skull configurations.
  
  
  CONCLUSIONS
  The ability to simulate realistic HMPAO SPECT scans has been demonstrated using a subresolution sandwich phantom. Further work, involving scanning the optimised phantom on different gamma camera systems and comparison with camera-specific normal databases should further refine the phantom configuration.
authors.affiliation: Department of Medical Physics and Bioengineering, University Hospitals Bristol, UK. Electronic address: robin.holmes@nhs.net.
authors.forename: Robin B
authors.initials: RB
authors.lastname: Holmes
authors.affiliation: Nuclear Medicine Physics Group, University Hospital Southampton, UK.
authors.forename: Sandra M A
authors.initials: SMA
authors.lastname: Hoffman
authors.affiliation: Department of Nuclear Medicine, University Hospital Southampton, UK.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Kemp
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime
keywords: Brain mapping/methods; Brain/physiology; Calibration; Computer-assisted; Data interpretation; Emission-computed; Feasibility studies; Image processing; Single-photon; Statistical; Tomography