Measurement uncertainty of lesion and reference mediastinum standardized uptake value in lung cancer

To assess standardized uptake value (SUV) measurement uncertainty (MU) of lung cancer lesions with uptake greater than mediastinum but less than or equal to the liver and that of the mediastinum blood pool, and to compare lesion SUV with mediastinum SUV by assessing MU of their ratio.

Dynamic PET data involving 10 frames were retrospectively analyzed in 10 patients, yielding maximal SUV of 25 lesions (Lesion-SUVmax), 10 mediastinum SUV, either maximal or mean (Med-SUVmax, Med-SUVmean), 25 Rmax ratios (=Lesion-SUVmax/Med-SUVmax), and 25 Rmean ratios (=Lesion-SUVmax/Med-SUVmean). A mean coefficient of variation was calculated for each parameter, leading to relative measurement uncertainty (MUr), respectively.

MU of Rmax was found to involve both Lesion-SUVmax and Med-SUVmax MU: MUr=33.3-23.3-21.9%, respectively (95% confidence level). No significant difference in MUr was found between Med-SUVmax and Med-SUVmean and between Rmax and Rmean.

Comparison between target lesion SUV and reference mediastinum SUV must take into account SUV MU of both. Therefore, no MU reduction can be expected from using the lesion/mediastinum SUVmax ratio instead of Lesion-SUVmax. Moreover, no MU reduction can be expected from using the mean mediastinum SUV instead of the maximal one.