Evaluation of noise equivalent count parameters as indicators of adult whole-body FDG-PET image quality

Objectives

The aim of this study was to assess variation of qualitative and quantitative PET/CT image quality parameters with acquisition time, injection activity and body mass for a representative group of adults undergoing whole-body PET/CT imaging.

Methods

PET scan data from sixty patients were reconstructed with a scan time of 1, 2 and 3 min/bed position. These images were visually scored and three quantitative parameters were calculated: noise equivalent counts per axial length (NEC_patient), noise equivalent count density (NEC_density) and liver signal to noise ratio (liver SNR). The ability of the three quantitative parameters to discriminate qualitative image quality was assessed using ROC analysis.

Results

The quantitative parameters were shown to discriminate images of good/excellent quality from those of poorer image quality with a high degree of accuracy (ROC area >0.9); further, NEC_patient had significantly higher discrimination than either NEC_density or liver SNR (ROC area = 0.97).

Conclusions

NEC_patient, NEC_density and liver SNR all have high discrimination for qualitatively assessed PET image quality. NEC_patient in particular is an effective objective indicator of patient image quality, which will help to assess and standardise scan protocols for purposes such as multi-centre research trials.