Abstract
ObjectivesThe purpose of our study was to assess proton density (PD) and T2 relaxation time of usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) and to evaluate their utility in differentiating the two patterns. Furthermore, we aim to investigate whether these two parameters could help differentiate active-inflammatory and stable-fibrotic lesions in NSIP.Methods32 patients (mean age: 69 years; M:F, 1:1) with pathologically proven disease (UIP:NSIP, 1:1), underwent thoracic thin-section multislice CT scan and 1.5T MRI. A total of 437 regions-of-interest (ROIs) were classified at CT as advanced, moderate or mild alterations. Based on multi-echo single-shot TSE sequence acquired at five echo times, with breath-holding at end-expiration and ECG-triggering, entire lung T2 and PD maps were generated from each subject. The T2 relaxation time and the respective signal intensity were quantified by performing a ROI measurement on the T2 and PD maps in the corresponding CT selected areas of the lung.ResultsUIP and NSIP regional patterns could not be differentiated by T2 relaxation times or PD values alone. Overall, a strong positive correlation was found between T2 relaxation and PD in NSIP, r = 0.64, p<0.001; however, this correlation was weak in UIP, r = 0.20, p = 0.01. T2 relaxation showed significant statistical difference between active-inflammatory and stable-fibrotic NSIP regions at all levels, p<0.05, while for the analysis of ventral lesions PD proved no statistical difference, p>0.05.ConclusionsT2 relaxation times and PD values may provide helpful quantitative information for differentiating NSIP from UIP pattern. These parameters have the potential to differentiate active-inflammatory and stable-fibrotic lesions in NSIP.
Highlights
Interstitial lung diseases comprise a group of diffuse parenchymal pulmonary diseases that are classified together due to their similar clinical, radiologic, physiologic, and/or pathologic manifestations [1]
usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) regional patterns could not be differentiated by T2 relaxation times or proton density (PD) values alone
A strong positive correlation was found between T2 relaxation and PD in stable NSIP, r = 0.64, p
Summary
Interstitial lung diseases comprise a group of diffuse parenchymal pulmonary diseases that are classified together due to their similar clinical, radiologic, physiologic, and/or pathologic manifestations [1]. The new ATS/ERS/JRS/ALAT guidelines for idiopathic pulmonary fibrosis provide criteria to define the usual interstitial pneumonia (UIP) pattern, possible UIP pattern, and patterns inconsistent with UIP on HRCT [2]. The radiological patterns of UIP and some NSIP may share criteria for possible UIP pattern. With the exception that patients displaying NSIP pattern are more commonly female and generally have a younger mean age than those exhibiting UIP pattern [6], there is substantial overlap in the clinical and physiologic features between the two forms, both presenting insidious onset of dyspnea, dry cough and a restrictive ventilatory defect [7]
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