Improvement of multislice oxygen-enhanced MRI of the lung by fully automatic non-rigid image registration

Dynamic contrast-enhanced MRI versus 18F-FDG PET/CT: Which is better in differentiation between malignant and benign solitary pulmonary nodules?

Objective

To prospectively compare the discriminative capacity of dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) with that of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in the differentiation of malignant and benign solitary pulmonary nodules (SPNs).

Methods

Forty-nine patients with SPNs were included in this prospective study. Thirty-two of the patients had malignant SPNs, while the other 17 had benign SPNs. All these patients underwent DCE-MRI and ¹⁸F-FDG PET/CT examinations. The quantitative MRI pharmacokinetic parameters, including the trans-endothelial transfer constant (K^trans), redistribution rate constant (K_ep), and fractional volume (V_e), were calculated using the Extended-Tofts Linear two-compartment model. The ¹⁸F-FDG PET/CT parameter, maximum standardized uptake value (SUV_max), was also measured. Spearman's correlations were calculated between the MRI pharmacokinetic parameters and the SUV_max of each SPN. These parameters were statistically compared between the malignant and benign nodules. Receiver operating characteristic (ROC) analyses were used to compare the diagnostic capability between the DCE-MRI and ¹⁸F-FDG PET/CT indexes.

Results

Positive correlations were found between K^trans and SUV_max, and between K_ep and SUV_max (P<0.05). There were significant differences between the malignant and benign nodules in terms of the K^trans, K_ep and SUV_max values (P<0.05). The areas under the ROC curve (AUC) of K^trans, K_ep and SUV_max between the malignant and benign nodules were 0.909, 0.838 and 0.759, respectively. The sensitivity and specificity in differentiating malignant from benign SPNs were 90.6% and 82.4% for K^trans; 87.5% and 76.5% for K_ep; and 75.0% and 70.6% for SUV_max, respectively. The sensitivity and specificity of K^trans and K_ep were higher than those of SUV_max, but there was no significant difference between them (P>0.05).

Conclusions

DCE-MRI can be used to differentiate between benign and malignant SPNs and has the advantage of being radiation free.

Ventilation and perfusion magnetic resonance imaging of the lung

A close interaction between the respiratory pump, pulmonary parenchyma and blood circulation is essential for a normal lung function. Many pulmonary diseases present, especially in their initial phase, a variable regional impairment of ventilation and perfusion. In the last decades various techniques have been established to measure the lung function. Besides the global pulmonary function tests (PFTs) imaging techniques gained increasing importance to detect local variations in lung function, especially for ventilation and perfusion assessment. Imaging modalities allow for a deeper regional insight into pathophysiological processes and enable improved planning of invasive procedures. In contrast to computed tomography (CT) and the nuclear medicine techniques, magnetic resonance imaging (MRI), as a radiation free imaging modality gained increasing importance since the early 1990 for the assessment of pulmonary function. The major inherent problems of lung tissue, namely the low proton density and the pulmonary and cardiac motion, were overcome in the last years by a constant progress in MR technology. Some MR techniques are still under development, a process which is driven by scientific questions regarding the physiology and pathophysiology of pulmonary diseases, as well as by the need for fast and robust clinically applicable imaging techniques as safe therapy monitoring tools. MRI can be considered a promising ionizing-free alternative to techniques like CT or nuclear medicine techniques for the evaluation of lung function. The goal of this article is to provide an overview on selected MRI techniques for the assessment of pulmonary ventilation and perfusion.