Estimation of pulmonary motion in healthy subjects and patients with intrathoracic tumors using 3D-dynamic MRI: initial results

Abstract

Objective: To estimate a new technique for quantifying regional lung motion using 3D-MRI in healthy volunteers and to apply the technique in patients with intra- or extrapulmonary tumors.

Materials and methods: Intraparenchymal lung motion during a whole breathing cycle was quantified in 30 healthy volunteers using 3D-dynamic MRI (FLASH [fast low angle shot] 3D, TRICKS [time-resolved interpolated contrast kinetics]). Qualitative and quantitative vector color maps and cumulative histograms were performed using an introduced semiautomatic algorithm. An analysis of lung motion was performed and correlated with an established 2D-MRI technique for verification. As a proof of concept, the technique was applied in five patients with non-small cell lung cancer (NSCLC) and 5 patients with malignant pleural mesothelioma (MPM).

Results: The correlation between intraparenchymal lung motion of the basal lung parts and the 2D-MRI technique was significant (r = 0.89, p < 0.05). Also, the vector color maps quantitatively illustrated regional lung motion in all healthy volunteers. No differences were observed between both hemithoraces, which was verified by cumulative histograms. The patients with NSCLC showed a local lack of lung motion in the area of the tumor. In the patients with MPM, there was global diminished motion of the tumor bearing hemithorax, which improved significantly after chemotherapy (CHT) (assessed by the 2D- and 3D-techniques) (p < 0.01). Using global spirometry, an improvement could also be shown (vital capacity 2.9 +/- 0.5 versus 3.4 L +/- 0.6, FEV1 0.9 +/- 0.2 versus 1.4 +/- 0.2 L) after CHT, but this improvement was not significant.

Conclusion: A 3D-dynamic MRI is able to quantify intraparenchymal lung motion. Local and global parenchymal pathologies can be precisely located and might be a new tool used to quantify even slight changes in lung motion (e.g. in therapy monitoring, follow-up studies or even benign lung diseases).

Keywords: Biomechanics; Dynamic MRI; Intraparenchymal lung motion; Pleural mesothelioma; Tumor.

Fig. 1

Motion information of healthy subject covering whole breathing cycle. A. Color map shows absolute strength of motion (maximum extension from end-inspiration to end-expiration). Upon comparison, it can clearly be seen that most substantial symmetric intraparenchymal motion is in lower parts of lung. B. Cumulative motion histogram shows relative motion of lung to its maximum.

Fig. 2

Mean cumulative relative motion histogram calculated over 30 healthy volunteers. Dotted lines indicate corresponding standard deviations.

Fig. 3

MRI depiction of parenchymal lung motion. A. Patient with solitary non-small cell lung cancer in upper right lung. B. Using simple vector field representation for one time frame of breathing cycle, limited lung motion in right upper lung can hardly be seen. C. Using color map representation of breathing cycle, from maximum expiration to maximum inspiration, limited asymmetric lung motion can clearly be seen. In this patient, overall lung motion was limited because of limited lung function.

Fig. 4

Patient with malignant pleural mesothelioma in left hemithorax before (left) and after (right) chemotherapy. Substantial restriction of left-sided intrapulmonary motion can be observed. After therapy, lung motion increased slightly and in good correlation with improved lung function.

Fig. 5

Cumulative relative motion histogram for patient with malignant pleural mesothelioma (from Fig. 4). Following therapy, slight increase of overall lung motion, especially left side, can be observed.