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SPECT QC (Monthly (Jaszczak Phantom (Used for validating scanner geometry,…

- - - - The phantom should be placed on the headrest of the imaging table
      - The transaxial images of the phantom is reconstructed with minimum smoothing
      - Single pixel thick slices through the uniform section of the phantom can be used to evaluate uniformity
      - Thicker slices through the resolution elements can be used to determine tomographic resolution
      - As there is high counts present in such an acquisition, it is often necessary to acquire a high-count uniformity correction map (~ 100 Mcts or more) in order to provide adequate uniformity correction for this study.
      - Recommended Frequency : Semi-anually
  - - - Knowing the FOV and applying specific matrix size allows you to quantify the actual size of the pixel
      - To verity this value, the following procedure is recommmended
        
        a. Take a large enough piece of cardboard, draw two 10cm lines at right angles to each
        
        b. Place the drops of Tc - 99m at each end of both lines and a third one where the lines intersect forming the right angle
        
        c. Place cardboard on surface of FOV so that it lines up with the camera's X and Y axis
        
        d. Apply a count profuile at each end point of the two lines and at the piint where they intersect
        
        e. Count the amount of pixels between the peak of the two points for X and Y. These measurements define the amount of pixels in 10cm
  - - - Tape film centred to side of acrylic plate, with film edge carefully aligned to edge of plate
      - Lower table to body scan position
      - For systems which tilt the gantry or table in vertical plane: Align plate with long axis of table, parallel to vertical plane. Fix in position with tape extending from table edge to table edge across top of plate
      - For tables tilting in horizontal plane: Place plate flat on tabletop with plate edge aligned to table long axis, tape into position
      - Move tabletop into gantry opening: centre plate to alignment light
      - Expose the film at inner light location using narrowest slice setting at ~ 50 to 100 mAs, 120 to 140 kVp
      - Tilt gantry to one extreme from operators console: record angle indicated on gantry and operator's console, repeat exposure.
      - Measure gantry clearance from closest point on gantry to table midline
      - Tilt to opposite extreme, record indicated angles, repeat exposure and clearance measurement
- - - - Correction for non-uniformity is normally done by the process of normalisation, a simple mathematical procedure
      - The mean number of counts pen pixel is calculated for the high-count flood image. The edge of the flood image is not used in this calculation to avoid the possibility of dividing by a small number on zero
      - A set of correction factors is generated by dividing the mean counts pen pixel by the number of counts in each individual pixel
      - A renormalisation is accomplished by multiplying the raw data in each projection by the correction matrix
      - High count images for flood correction can be acquired with Co-57 disk sources or Tc-99m liquid-filled flood phantoms
  - - - Distance from the cource has no effect on the AOR acquisition
      - If multiple point sources are required then usually a FOV is applied
      - Number of stops is not that important, however 32 projections is recommended
      - Usually 1 milliCurie of Tc - 99m is considered an adequate amount of activity
      - Apply 128 matrix and collect between 5 to 20k counts per projection. This usually only takes less than 5 seconds a stop
      - From this analysis, the x-axis offset should be less than 0.5 pixel and requires no correction. However, if 1 or more pixels then a correction is applied. Any offsets of greater than 3 pixel requires a service call
- - - - Extrinsic
        
        Co-57 sheet source or a uniform filled flood phantom Tcm 99 is used with about 200 MBq for small FOV and 400 for large FOV
        
        Mount a low energy parallel hole collimator on the detector head and turn the head to face vertically upward
        
        Centre the manufacturer's default PHA window on the photopeak
        
        Acquire an image on the display device with hard copy, at a present count of 2x10^6 for a small FOV or 5x10^6 for large FOV
        
        Record all imaging parameters including the present count and the count time and the time of day corresponding to the midpoint of the count.
        
        Remove the source and source mounting or flood phantom.
      - Intrinsic
        
        Point source is located at a distance at least 5 times the max detector dimension and immediately followed by peaking of the detector
        
        Remove the collimator from detector head and align the detector head and source mounting as well as position the lead mask centrally on the crystal housing
        
        Mount the source in the source mounting
        
        Known activity (10 to 40 MBq) of Tcm 99 is determined by measurement in dose calibrator and the exact time that corresponds to the activity determination is recorded