A CLINICAL-EVALUATION OF THE QUANTITATIVE ACCURACY OF SIMULTANEOUS EMISSION TRANSMISSION SCANNING IN WHOLE-BODY POSITRON-EMISSION-TOMOGRAPHY/

We present a clinical evaluation of the quantitative bias which is int roduced during simultaneous emission/transmission (SET) acquisition fo r the application of whole-body positron emission tomography (PET) wit h fluorine-18 2-fluoro-2-deoxy-D-glucose. The quantitative accuracy of the SET technique was assessed by means of a clinical study involving 28 patients and a realistic phantom experiment. In the clinical study , SET overestimated the activity concentration in the tumours by a fac tor of approximately 1.10, but in the phantom study, where the tumours were smaller, the bias was found to increase to a value of 1.39. The bias in the soft tissue regions of the patient studies varied between 1.03 and 1.36, and close agreement was observed with the corresponding phantom results. The extent of the bias increased as the local activi ty concentration decreased and we attribute the effect to scattered ph otons from the transmission source which are detected in the emission window during SET.