TY - JOUR T1 - Failure to account for density variation during respiration can significantly affect PET quantitation in the lung. JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1770 LP - 1770 VL - 56 IS - supplement 3 AU - Beverley Holman AU - Vesna Cuplov AU - Lynn Millner AU - Brian Hutton AU - Ashley Groves AU - Kris Thielemans Y1 - 2015/05/01 UR - http://jnm.snmjournals.org/content/56/supplement_3/1770.abstract N2 - 1770 Objectives PET quantitation in the lung is affected by local density changes due to respiration and hence needs accurate attenuation maps (AM) for attenuation correction (AC) and tissue fraction correction (TFC). However, respiration often causes pulmonary density mismatch between the AM and actual attenuation during the PET acquisition. Motivated by findings in analysis of kinetic lung data using FDG and FMISO, we explored the effect of density errors on derived kinetic parameters.Methods Clinically determined time activity curves (TACs) for all organs within the thorax were used to produce FDG and FMISO XCAT PET/CT noise-free dynamic simulations. Lung voxel values were varied according to expected density changes. Respiratory averaged dynamic PET data were simulated including effects of attenuation and scatter, where matched AM were used for simulation. These data were reconstructed with FBP using ‘snap shot’ CT’s at expiration, mid-cycle or inspiration. ROIs were drawn on the whole lung away from artefacts and boundaries. Influx rate constants (k­i) from a 2 tissue compartment model and the Patlak-Rutland technique were compared.Results Visualisation of the lung TACs clearly displayed differences between true and measured curves with error depending on global activity distribution at the time of measurement, which is different for the 2 tracers. When applying AC and TFC, the error range for k­i was 10-166% for FMISO as opposed to 1-11% for FDG. In all cases, the Patlak technique was less sensitive to errors with an average of 53% increase in accuracy compared to the compartment model case. The results found are consistent with our findings in the clinical kinetic lung studies.Conclusions Respiratory associated density errors in the AM affect quantitation throughout the lung, not just regions near boundaries. The extent of this error is dependent on the activity distribution in the thorax and hence on the tracer and time of acquisition. Consequently there is a significant impact on estimated kinetic parameters throughout the lung.Research Support This work is supported by funding from GSK, Fibrosis DPU, GlaxoSmithKline R&D and EPSRC. This project is supported by researchers at the National Institute for Health Research, University College London Hospitals Biomedical Research Centre. ER -