Comparison of dual-energy CT with positron emission tomography for lung perfusion imaging in patients with non-small cell lung cancer

Objective. Functional lung avoidance (FLA) radiotherapy treatment aims to spare lung regions identified as functional from imaging. Perfusion contributes to lung function and can be measured from the determination of pulmonary blood volume (PBV). An advantageous alternative to the current determination of PBV from positron emission tomography (PET) maybe from dual energyCT(DECT), due to shorter examination time and widespread availability. This study aims to determine the correlation between PBV determined from DECT and PET in the context of FLA radiotherapy. Approach. DECT and PET acquisitions at baseline of patients enrolled in the HI-FIVE clinical trial (ID: NCT03569072) were reviewed. Determination of PBV from PET imaging (PBVPET), from DECT imaging generated from a commercial software (Syngo.via, Siemens Healthineers, Forchheim, Germany) withits lowest (PBVsyngoR=1) and highest (PBVsyngoR=10) smoothing level parameter value (R), and from a two-material decomposition (TMD) method (PBVTMDL) with variable median filter kernel size (L) were compared. Deformable image registration between DECTimages and the CT component of the PET/CT was applied to PBV maps before resampling to the PET resolution. The Spearman correlation coefficient (r(s)) between PBV determinations was calculated voxel-wise in lung subvolumes. Main results. Of this cohort of 19 patients, 17 had a DECT acquisition at baseline. PBV maps determined from the commercial software and the TMD method were very strongly correlated [r(s)(PBVsyngoR=1 PBVTMDL=1)= 0.94 +/- 0.01 and rs( PBVsyngoR=10 PBVTMDL=9)= 0.94 +/- 0.02]. PBVPET was strongly correlatedwith PBVTMDL [rs( PBVPET, PBVTMDL=28)= 0.67 +/- 0.11]. Perfusion patterns differed along the posterior-anterior direction [rs(PBVPET, PBVTMDL=28)= 0.77 +/- 0.13/0.57 +/- 0.16 in the anterior/posterior region]. Significance. A strong correlation betweenDECTandPETdetermination ofPBVwas observed. Streak and smoothing effects inDECTand gravitational artefacts andmisregistrationinPETreduced the correlation posteriorly.