Regional detection of edema following segmental LPS challenge using functional MR imaging

Background: Segmental LPS challenge is used in studies which examine inflammation induced edema in the lung. Currently, bronchoalveolar lavage (BAL) is used to quantify the LPS-induced amount of inflammation. Objectives: MRI is investigated to quantify regional edema following endobronchial LPS challenge using a scoring system and a quantitative method. Methods: In 23 healthy smokers segments 4 or 5 of the right lung were challenged with LPS and of the left lung with saline as control. BAL was performed prior to challenge and 24h after. Seven days before and prior the BAL 24h post LPS challenge the volunteers underwent a lung MRI scan. Edema was quantified on the TIRM images (score) and T1 maps (volume over threshold [VOT]) before contrast agent (CA) administration. Results: The percentage of neutrophilic cells was higher in LPS challenged segments (58.5%) compared to baseline (0.75%;p<0.0001) and saline treated segments (1.5 %;p<0.0001). Median [min; max] TIRM score and VOT showed a significantly higher amount of edema (3[1;4] and 7.3[0.2;36.6]mL) in LPS challenged segments compared to baseline (0[0;1];p<0.0001 and 0.0[0.0; 1.8]mL;p<0.0001) and saline treated segments (0[0;2];p<0.0001 and 1.1[0.0;10.5]mL;p=0.001). Median CA washout time was not significantly different between the corresponding segments before challenge (1.01[0.9;1.12]h vs 0.97[0.8;1.11]h, p=0.29) and remained stable in the LPS challenged (1.08[0.93;1.18]h;p=0.47) and saline treated segments (0.88[0.68;1.07]h;p=0.21). CA washout time was different in LPS challenged segments compared to saline treated segments (p=0.003) at 24h. Conclusion: Proton lung MRI can detect regional edema after segmental LPS challenge in healthy smokers.