The effect of the pulmonary flow change on the signal intensity of the oxygen-enhanced lung MRI

Abstract

PURPOSE: We investigated the effect of changes in pulmonary blood flow on the signal intensity (SI) of the oxygen-enhanced lung magnetic resonance imaging (MRI).MATERIALS AND METHODS: Increased pulmonary flow was produced by intravenous infusion of sildenafil (0.2 mg/kg) in 9 New Zealand white rabbits. Decreased pulmonary flow was produced by a single subcutaneous injection of monocrotaline (60 mg/kg). MRI consisted of a velocity-encoded cine MRI for pulmonary blood flow and an oxygen-enhanced MRI. Oxygen-enhanced MRI data were acquired while animals received mechanical ventilation alternately with room air or 100% oxygen. We performed MRI at baseline and during sildenafil infusion or after monocrotaline injection. Arterial blood gas analysis was performed during room air and 100% oxygen ventilation. We compared baseline data to those during sildenafil infusion and after monocrotaline injection for changes of pulmonary blood flow, percentage change of partial pressure of arterial oxygen (PaO2), and SI enhancement ratio of oxygen-enhanced lung MRI. The Wilcoxon signed rank test was used for statistical analysis.RESULTS: Our results at baseline and sildenafil infusion status or monocrotaline injection status were as follows: mean pulmonary blood flow (ml/min), 415.4 ± 115.0, 488.0 ± 124.5, and 357.3 ± 90.9, respectively; percentage change of PaO2 (%), 279.1 ± 49.1, 254.6 ± 38.8, and 245.7 ± 26.8, respectively; and SI enhancement ratio on MRI (%), 23.8 ± 11.4, 24.0 ± 7.9, and 22.7 ± 10.3, respectively. There was a significant difference in pulmonary blood flow between baseline and sildenafil infusion status (p = 0.005) and between baseline and monocrotaline injection status (p = 0.017). However, there were no significant differences between the percent change of PaO2 or SI enhancement ratio between baseline and sildenafil infusion status (p = 0.081 and p = 0.953, respectively) or between baseline and monocrotaline injection status (p = 0.076 and p = 0.374, respectively).CONCLUSION: There was little effect of pulmonary blood flow alteration on the signal intensity enhancement ratio of the oxygen-enhanced MRI.