Role of pulmonary perfusion magnetic resonance imaging for the diagnosis of pulmonary hypertension:A review

Among five types of pulmonary hypertension,chronic thromboembolic pulmonary hypertension(CTEPH)is the only curable form,but prompt and accurate diagnosis can be challenging.Computed tomography and nuclear medicine-based techniques are standard imaging modalities to non-invasively diagnose CTEPH,however these are limited by radiation exposure,subjective qualitative bias,and lack of cardiac functional assessment.This review aims to assess the methodology,diagnostic accuracy of pulmonary perfusion imaging in the current literature and discuss its advantages,limitations and future research scope.

Pulmonary Perfusion Asymmetry in Patients after Repair of Tetralogy of Fallot: A 4D Flow MRI-Based Study

Background:Repaired Tetralogy of Fallot(rTOF)patients may have residual lesions such as main(MPA)and branch pulmonary artery stenosis(BPAS).While MPA stenosis is well studied,few data are available on BPAS in rTOF.We aimed to describe pulmonary perfusion in a large paediatric cohort of rTOF and its impact on right ventricular and outflow-tract hemodynamics using 4D flow CMR.Methods:130 consecutive patients(mean age at CMR 14.3±4.6 years)were retrospectively reviewed.96 patients had transannular patch without valve preservation while 34 patients had conserved annulus or valved conduit.A pulmonary blood flow ratio(right pulmonary artery(RPA)/left pulmonary artery(LPA))between 0.75 and 1.56 was considered normal.Results:Asymmetric pulmonary perfusion was present in 59/130 patients(45%),with 54/59(91%)having left lung hypoperfusion(blood flow ratio>1.56).RPA/LPA perfusion ratio in the whole cohort was independently associated with the LPA Z-score(−0.053,p=0.007),the RPA regurgitant fraction(RF)(0.013,p=0.011)and previous LPA stenting(0.648,p=0.004).Decreasing LPA%perfusion(and conversely increasing RPA%perfusion)was significantly associated with higher MPA diameter Z-score(−0.06,p=0.007).On multivariate analysis,MPA Z-score was independently associated with pulmonary RF(0.48,p<0.001)and with right ventricular indexed volumes(coefficient 3.6,p=0.023).In patients with transannular patch repair,asymmetric pulmonary flow was an independent predictor of right ventricular ejection fraction(RVEF)(−3.66,p=0.04).Conclusions:Pulmonary perfusion asymmetry is frequent in rTOF and is associated with abnormal right ventricular and outflow-tract hemodynamics,including MPA dilatation and decreased RVEF in patients after transannular patch.

A perfusion mode of pulmonary artery during cardiopulmonary bypass

Objective Lung injury occurred during cardiopulmonary bypass as a result of both ischemic reperfusion injury and systemic inflammatory response is critical for patients’recovery. This study was designed to establish a convenient and appropriate mode for pulmonary arteryperfusion and evaluate its effects on the

Pulmonary functional MRI: an animal model study of oxygen-enhanced ventilation combined with Gd-DTPA-enhanced perfusion

Background The assessment of regional pulmonary ventilation and perfusion is essential for the evaluation of a variety of lung disorders. Pulmonary ventilation MRI using inhaled oxygen as a contrast medium can be obtained with a clinical MR scanner, without additional equipment, and has been demonstrated to be a feasible means of assessing ventilation in animal models and some clinical patients. However, few studies have reported on MR ventilation-perfusion imaging. In this study, we evaluated the usefulness of oxygen-enhanced ventilation in combination with first-pass Gd-DTPA-enhanced perfusion MRI in a canine model of pulmonary embolism and airway obstruction.Methods Peripheral pulmonary embolisms were produced in eight dogs by intravenous injection of gelfoam strips at the pulmonary segmental arterial level, and airway obstructions were created in five of the dogs by inserting a self-designed balloon catheter into a secondary bronchus. Oxygen-enhanced MR ventilation images were produced by subtracting images from before and after inhalation of pure oxygen. Pulmonary perfusion MR images were acquired with a dynamic three-dimensional fast gradient-echo sequence. MR ventilation and perfusion images were read and contrasted with results from general examinations of pathological anatomy, ventilation-perfusion scintigraphy, and pulmonary angiography. Results Regions identified as having airway obstructions matched using both MR ventilation and perfusion imaging, but regions of pulmonary embolisms were mismatched. The area of airway obstruction defects was smaller using MR ventilation imagery than that using ventilation scintigraphy. Abnormal perfusion regions due to pulmonary embolisms were divided into defective regions and reduced regions based on the time course of signal intensity changes. In the diagnosis of pulmonary embolisms with the technique of ventilation and perfusion MRI, sensitivity and specificity were 75.0% and 98.1%, respectively, and the diagnostic results of this MRI technique were in agreement with the results of ventilation-perfusion scintigraphy and pulmonary angiography (K: 0.899, 0.743).Conclusions Oxygen-enhanced ventilation in combination with pulmonary perfusion MRI can be used to diagnose abnormalities of airways and blood vessels in the lungs, and can provide regional functional information with high spatial and temporal resolution. This method possesses great potential value for clinical applications. F