Implementation of quadratic dose protocol for 18F-FDG whole-body PET imaging using a BGO-based PET/CT scanner, GE Discovery ST

The ability of quadratic dose protocol to maintain a good quality image for an overweight and obese patient is well reported. However, a practical approach to the implementation of this protocol in whole-body imaging in Malaysia is currently lacking. Hence, the aim of this study is to derive the quadratic dose formula that suits our PET system. Whole-body PET imaging protocol was performed using NEMA 2012/IEC 2008 phantom. Two dose protocols were adhered, namely linear and quadratic dose protocol. A PET Discovery ST, which is BGO-based PET system was used in this study. This study was guided by technical guidelines published by Koopman et al. Finally, a comparative analysis between the effective dose yielded by linear and quadratic dose protocols was performed. Implementation of quadratic dose protocol using our PET system lengthen the scanning time to 226 s, as compared to 150 s currently used in the linear dose protocol. Meanwhile, the findings revealed that the quadratic dose protocol led to a greater effective dose for the body weight of 62 kg and above. These findings were observed in all the five groups of patient studied. In conclusion, a successful trial of the quadratic dose protocol on our PET system has been established. Despite the long acquisition time and greater effective dose, implementation of quadratic dose protocol is necessary for better quantification of the image, as well as ensuring constant image quality across all patients, especially overweight and obese patients.