Can body volume be determined by PET?

Purpose: To avoid dependence on body weight, the standardised uptake value (SUV) in positron emission tomography ( PET) can instead be normalised to the lean body mass (LBM), which can be determined from body volume and mass. This study was designed to answer the following questions: Firstly, can the total body volume in principle be determined using PET? Secondly, is the precision of this measurement comparable to that achieved using an established standard method. Methods: Ten patients were examined during oncological whole-body PET examinations. The whole-body volume of the patients was determined from the transmission scan in PET. Air displacement plethysmography with BOD POD was used for comparison as the standard method of volume determination. Results: In all patients, the whole-body volumes could be determined using PET and the standard method. Bland and Altman [23] analysis for agreement between the volumes determined by the two methods ( presentation of differences vs means) revealed a very small difference of - 0.14 l. With a mean patient volume of 71.81 +/- 15.93 l, the relative systematic error is only < 0.1%. On this basis, equality of the volume values determined by the two methods can be assumed. Conclusion: PET can be used as a supplementary method for experimental determination of whole-body volume and total body fat in tumour patients. The fat content can be used to calculate the LBM and to determine body weight-independent SUVs (SUVLBM).