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Radiology. 2020 Mar 24:192013. doi: 10.1148/radiol.2020192013. [Epub ahead of print]

Diffusion-weighted Imaging Voxelwise-matched Analyses of Lung Cancer at 3.0-T PET/MRI: Reverse Phase Encoding Approach for Echo-planar Imaging Distortion Correction.

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From the Dept of Biophysics and Nuclear Medicine-Molecular Imaging, Hôpitaux Universitaires Paris-Saclay, Assistance Publique-Hôpitaux de Paris, CHU Bicêtre, 94270, Le Kremlin-Bicêtre, France (F.L.B., E.D.); Université Paris-Saclay, School of Medicine, Le Kremlin-Bicêtre, France (F.L.B., O.M., A.S., S.B., S.M., F.P., D. Montani, D. Mitiliian, E.F., V.L., E.D.), Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, 91401, France (F.L.B., C.C., V.L., E.D.); Applications and Workflow, GE Healthcare, Buc, France (B.F.); Laboratoire de Mathématiques d'Orsay, Université Paris-Saclay CNRS, 91405 Orsay, France (S.F.); Dept of Thoracic and Vascular Surgery and Heart-Lung Transplantation, Hôpital Marie Lannelongue, 92350 Le Plessis Robinson, France (O.M., S.M., D. Mitilian, E.F.); Dept of Respiratory and Intensive Care Medicine, Pulmonary Hypertension National Referral Center, Hôpitaux Universitaires Paris-Saclay, Assistance Publique-Hôpitaux de Paris, CHU Bicêtre, 94270, Le Kremlin-Bicêtre, France (A.S., X.M., S.B., F.P., D. Montani); Inserm UMR_S999 Pulmonary Hypertension: Pathophysiology and Novel Therapies, Hôpital Marie Lannelongue, 92350 Le Plessis Robinson, France (A.S., D. Montani); Service Hospitalier Frédéric Joliot (SHFJ), CEA/Université Paris-Saclay, Orsay, France (É.B., A.C., F.B., V.L.); Dept of Pathology, Hôpital Marie Lannelongue, 92350 Le Plessis Robinson, France (M.R.G.B.); NeuroSpin, CEA Saclay, Université Paris-Saclay, Gif-sur-Yvette, France and Parietal, INRIA, Palaiseau, 91120, France (H.C.).


Background PET/MRI has drawn increasing interest in thoracic oncology due to the simultaneous acquisition of PET and MRI data. Geometric distortions related to diffusion-weighted imaging (DWI) limit the evaluation of voxelwise multimodal analyses. Purpose To assess the effectiveness of reverse phase encoding in correcting DWI geometric distortion for multimodal PET/MRI voxelwise lung tumor analyses. Materials and Methods In this prospective study, reverse phase encoding method was implemented with 3.0-T PET/MRI to correct geometric distortions related to DWI. The method was validated in dedicated phantom and then applied to 12 consecutive patients (mean age, 66 years ± 13 [standard deviation]; 10 men) suspected of having lung cancer who underwent fluorodeoxyglucose PET/MRI between October 2018 and April 2019. The effects on DWI-related image matching and apparent diffusion coefficient (ADC) regional map computation were assessed. Consequences on multimodal PET/MRI voxelwise lung tumor analyses were evaluated. Spearman correlation coefficients (rs) between the standardized uptake value (SUV) and ADC data corrected for distortion were computed from optimal realigned DWI PET data, along with bootstrap confidence intervals. Results Phantom results showed that in highly distorted areas, correcting the distortion significantly reduced the mean error against the ground truth (-25% ± 10.6 to -18.4% ± 12.6; P < .001) and the number of voxels with more than 20% error (from 85.3% to 31.4%). In the 12 patients, the coregistration of multimodal PET/MRI tumor data was improved by using the reverse phase encoding method (0.4%-44%). In all tumors, voxelwise correlations (rs) between ADC and SUV revealed null or weak monotonic relationships (mean rs of 0.016 ± 0.24 with none above 0.5). Conclusion Reverse phase encoding is a simple-to-implement method for improved diffusion-weighted multimodal PET/MRI voxelwise-matched analyses in lung cancer.


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