Precision measurements of the reconstructed image resolution for different PET and PET/CT scanners with the NEMA phantom.


Precision measurements of the reconstructed image resolution for different PET and PET/CT scanners with the NEMA phantom.

Mix, M.; Weber, W. A.; van den Hoff, J.

Objectives:

For multicenter PET studies robust techniques are required to measure the reconstructed image resolution of different PET systems. The aim of this study was to determine the reconstructed image resolution (RIR) using a NEMA phantom as a function of count statistics and image contrast.

Methods:

Measurements with the NEMA whole-body (WB) phantom at 7 scanner systems at different signal-to-noise levels and different target to background (T/BG) ratios were analyzed. Images were reconstructed iteratively using the default scanner WB reconstruction protocol. For each sphere, the image data were transformed to spherical coordinates relative to the center of the respective sphere yielding radial profiles. The RIR was then determined by fitting the convolution of a Gaussian point spread function with the object function (sphere+wall+BG) to these profiles.

Results:

With the presented procedure the RIR can be determined easily with a high statistical accuracy (average accuracy in 593 spheres 2.8+/-0.1%). For all scanners the RIR was distinctly lower than the scanner resolution according to NEMA. Image resolution was independent from counting statistic but deteriorated with decreasing target to BG (T/BG) ratios. The average resolution degradation in relation to the background free case was ~30% for a 6:1 T/BG ratio, over 50% for 3:1 and ~80% for 1.5:1. The degradation of RIR with decreasing contrast differed between the studied scanners.

Conclusions:

The presented algorithm is a robust approach for precise measuring reconstructed image resolution (RIR). The marked contrast ratio dependence of the RIR should be considered for quantitative PET studies in a multicenter setting.

  • Lecture (Conference)
    SNM 56th Annual Meeting, 13.-17.06.2009, Toronto, Canada

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Publ.-Id: 12203