Feasibility of combining MR perfusion, angiography, and 3He ventilation imaging for evaluation of lung function in a porcine model1

Abstract

Rationale and Objective-To assess the feasibility of combining magnetic resonance (MR) perfusion, angiography, and 3 He ventilation imaging for the evaluation of lung function in a porcine model. Materials and Methods-Fourteen consecutive porcine models with externally delivered pulmonary emboli and/or airway occlusions were examined with MR perfusion, angiography, and 3 He ventilation imaging. Ultrafast gradient-echo sequences were used for 3D perfusion and angiographic imaging, in conjunction with the use of contrast-agent injections. 2D multiplesection 3 He imaging was performed subsequently via the inhalation of hyperpolarized 3 He gas. The diagnostic accuracy of MR angiography for detecting pulmonary emboli was determined by two reviewers. The diagnostic confidence for different combinations of MR techniques was rated on the basis of a 5-point grading scale (5 = definite). Results-The sensitivity, specificity, and accuracy of MR angiography for detecting pulmonary emboli were approximately 85.7%, 90.5%, and 88.1%, respectively. The interobserver agreement was very strong (k = 0.82). There was a clear tendency for confidence to increase when first perfusion and then ventilation imaging were added to the angiographic image (Wilcoxon signed ranks test, P = 0.03). Conclusion-The combination of the three methods of MR perfusion, angiography, and 3 H ventilation imaging may provide complementary information on abnormal lung anatomy and function. KeywordsAngiography; pulmonary embolism; lung perfusion; lung ventilation; magnetic resonance Contrast-enhanced magnetic resonance pulmonary angiography (MRPA) and MR pulmonary perfusion (MRPP) are emerging imaging techniques for idenfiying pulmonary arterial structure (1-8). Subsecond temporal resolution and submillimeter spatial resolution can be achieved with state-of-the-art clinical magnetic resonance imaging(MRI) systems. Ultrashort repetition time/echo time (TR/ TE) gradient-echo sequences can be applied to obtain volumetric lung imaging within a single breath-hold. The short TE of such sequences is particularly important because of a very short T2* in lung tissue (9-12). This technical advantage was reflected in two pulmonary artery applications: simultaneous assessment of lung perfusion and flow in the major pulmonary vasculature, and MRPA with relatively high spatial resolution by means of Address correspondence to: J.Z. e-mail: zhengj@mir.wustl.edu. first-pass MR data acquisition during the arterial phase of contrast enhancement (13-15). The latter technique has shown a high signal-to-noise ratio (SNR), and permits the visualization of pulmonary arteries beyond the subsegmental branches. On the other hand, assessment of regional lung ventilation with hyperpolarized noble gas has emerged as an imaging technique for evaluating lung diseases, including tumors, emphysema, bronchiectasis, cystic fibrosis, and asthma (16)(17)(18)(19)(20)(21)(22)(23). A promising MR technique for visualizing the air spaces of the lung is the use of 3 He gas as a contrast agent...

A method for quantitative analysis of regional lung ventilation using deformable image registration of CT and hybrid hyperpolarized gas/1H MRI

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