Measurement of standard uptake value in dual-head coincidence system

The standard uptake value (SUV) is an important semi-quantitative parameter in positron emission tomography (PET). But SUV is not available in dual-head coincidence imaging system (DHC) which is widely used in clinical practice. This study was designed to develop a method for measuring SUV in DHC system, and then compared SUV in DHC and SUV in PET.

Firstly, the calibration factor (CF) for converting the voxel count rate to radioactivity concentration was determined by a phantom study in DHC. Then the method for calculating SUV in DHC was formulated. Finally, SUV in DHC and SUV in PET were compared through another phantom study. The phantoms used in the comparing study were cylindrical and consisted of several hot lesions.

The CF varied with the detected single count rate in a biquadratic polynomial; the lesion's radioactivity concentration was got based on the CF and the voxel count rate. From the lesion's radioactivity concentration, the lesion's SUV in DHC was obtained. The comparison study showed that SUV in PET was higher than SUV in DHC. The SUV in both DHC and PET increased with increasing sizes of lesions and were related with the reconstruction algorithm.

SUV in DHC images could be obtained in our method; the value in DHC images was lower than that in PET image; and many factors, such as system performance, lesion's size, and reconstruction algorithm could influence the SUV accuracy in both DHC and PET.