The Radiologic Diagnostic Oncology Group [98] compared CT and MRI in 170 patients with NSCLC, 90% of whom went on to thoracotomy. There was no significant difference between the sensitivity of the two modalities (63% and 56% respectively) or the specificity (84% and 80%) for distinguishing between T3–4 and T1–2 tumours, except when receiver operating characteristic analysis was performed on the statistics. These showed that MRI is better than CT at diagnosing mediastinal invasion. MRI is particularly useful in determining invasion of the myocardium or tumour extension into the left atrium via the pulmonary veins [76].