Signal enhancement ratio imaging of the lung parenchyma with ultra‐fast steady‐state free precession MRI at 1.5T

Background Lung perfusion MRI after i.v. gadolinium (Gd) contrast administration is commonly based on spoiled gradient‐echo acquisitions, such as volume‐interpolated breath‐hold examinations (VIBE), suffering from low signal‐to‐noise in the parenchyma. Purpose To investigate the lung signal enhancement ratio (SER) with ultra‐fast steady‐state free precession (ufSSFP) after Gd‐administration. Study Type Retrospective. Subjects Ten subjects with healthy lungs; nine patients with pulmonary diseases (chronic obstructive pulmonary disease [COPD], lung cancer, pulmonary fibrosis, lung contusion). Field Strength/Sequence VIBE and ufSSFP imaging of the chest was performed at 1.5T before and 3 minutes after i.v. gadobenate dimeglumine. Assessment A workflow including deformable image registration and median filtering was used to compute 3D SER maps. SER was analyzed in the lung, blood pool, liver, muscles, and fat. The artifacts were assessed by a radiologist. In the COPD patients, ufSSFP‐SER was compared to 99mTc‐MAA‐SPECT/CT by visual scoring of lung enhancement deficits. Statistical Tests Mean signal, standard deviation (SD), intersubject SD, and coefficient of variation (CV) were calculated for SER. Statistical significance of differences in signal and artifacts were determined using Wilcoxon signed‐rank paired test. Intermodality agreement between ufSSFP‐SER and SPECT/CT was calculated by Cohen's kappa (κq). Results In healthy lungs, ufSSFP‐SER (99% ± 23%, mean ± pooled intrasubject SD, CV = 23%) was significantly higher (P