MR tomography of lung metastases with rapid gradient echo sequences. Initial results in diagnostic applications

Rapid gradient echo sequences enable MR imaging (MRI) of pulmonary metastases with acquisition times of less than 1 s per slice. By optimization of this technique, density, T1- and T2-weighted images can be obtained (FLASH: TR 6.5 ms, TE2 = 3 ms, alpha = 10 degrees; T1w-Turbo-FLASH: TI 200 ms, TR 6.5 ms, TE2 = 3 ms, alpha = 10 degrees; T2w-Turbo-FLASH: TE1 = 50 ms, TR = 6.5 ms, TE2 = 3.5 ms; alpha = 10 degrees). In a prospective study 25 patients in whom pulmonary metastases were suspected were examined with three techniques in all three anatomical planes prior to surgery. All lung metastases revealed a high signal intensity on the FLASH as well as the T2w-Turbo-FLASH images, whereas vascular structures revealed a low signal intensity on the T2-weighted Turbo-FLASH images. Analysis regarding detection and correct number of lung metastases per patient with MRI compared with the histology revealed (n = 25): sensitivity of 82%, specificity 67%, positive predictive value of 95% and negative predictive value of 33%. While MRI does not currently have any diagnostic advantages over CT, the excellent differentiation of parenchymal lesions and vascular structures without the use of contrast medium and the variability of imaging planes are significant methodological advantages.