There are a lot of factors to consider when checking for the performance of the gamma camera. These factors are summarized and listed below.

SPATIAL RESOLUTION

• Intrinsic spatial resolution defines the ability of the uncollimated scintillation camera to determine accurately the original location of the gamma camera ray on an X-Y plane.


• Causes of Intrinsic Spatial Resolution Degradation:
  a. statistical variations in the distribution of light photons between the PM
  tubes of successive identical scintillation events.
  b. increased crystal thickness because of greater spreading of light before
  reaching the PM tubes, which increases the uncertainty of the location of scintillation event.
  c. reduction in gamma energy because of a greater relative statistical
  variation in the number of light photons produced by scintillation event.


• Improvement results in more efficient and more numerous, smaller PM tubes which are more efficiently coupled to the crystal.

MULTIPLE – WINDOW SPATIAL REGISTRATION

• Determines the positional deviations in the image at different energies and is determined by measuring the spatial registration of the images from each of the camera’s windows and calculating the deviation between these images from the collimated point source.

SYSTEM SPATIAL RESOLUTION

• Characterizes the ability of the collimated camera system to determine accurately the originals location of gamma ray on an X – Y plane.

ENERGY RESOLUTION

• Characterizes the ability of the uncollimated scintillation camera to accurately identify photopeak events and discriminate against scattered events.

SPATIAL LINEARITY

• characterizes the amount of positional distortion caused by the camera with respect to incident gamma events entering the detector.


• Image non linearity results from the fact that PM tubes collect light more efficiently from sources that occur over their centers than from sources nearer their periphery.


• Additional nonlinearity also arises from the differences in sensitivity among PM tubes, non uniformities in light pipes.

FLOOD FIELD UNIFORMITY

• Characterizes the variability of observed count density with homogenous flux.
  
  DIFFERENTIAL UNIFORMITY
  Measures the maximum rate of change over a specified distance.
  INTEGRAL UNIFORMITY
  Measures maximum deviation across the field.

COUNT RATE PERFORMANCE

• Characterizes the ability of scintillation camera to function accurately at count rates that approach the maximum rate of camera operation

SENSITIVITY

• Characterizes the ability of the collimated scintillation camera to detect incident gamma rays efficiently.

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