[MRI study of the arterial ligament and the left pulmonary artery in the preoperative staging of left upper lobe bronchial cancers].

Purpose: To demonstrate that the ligamentum arteriosum is visible by precisely-oriented MRI. To demonstrate the predictive value of the ligament involvement for left upper lobe cancer surgery.

Material And Methods: Fifteen controls, age-matched with bronchial cancer patients, were studied to establish how the ligamentum arteriosum could best be visualized on MRI. Visibility was optimal on RASE T1-weighted sequences on the frontal and sagittal oblique planes (aorto-pulmonary window). Acquisitions were performed with a body coil, 7 mm slices, 480 mm Fov, on a Magnetom Expert, 1T Siemens machine. Forty five patients with left upper lobe cancer underwent MRI investigation after CT had shown mediastinal proximity of the left pulmonary artery and the tumor. They underwent surgery with manual localization of the ligament at the beginning of the procedure. Findings and operative decisions were compared with those of MRI, establishing its predictive value. MRI defined the tumor-ligament and tumor first centimeters of the left pulmonary artery (LPA) relationships.

Results: MRI ligamentum visibility was about 87%. Ligament non-involvement on MRI (n = 23) was confirmed at surgery in all cases (100% concordance). Involvement suggested on MRI was confirmed in 18 cases and surgery was impossible or unsatisfactory. There were four false-positives with successful surgery (8% false positives).

Conclusion: When CT shows left lobe cancers extending in the mediastinum towards the LPA, precisely-oriented MRI assesses surgical difficulty and resectability by demonstration involvement of the ligamentum and the first two centimeters of the LPA.