Diagnostic accuracy of MRI compared to CCT in patients with brain metastases

In patients with extracranial neoplasms, the occurrence and number of brain metastases (BM) are critical for further diagnostic approaches and therapeutic strategies and the patient's prognosis. Although widely accepted, there is surprisingly little evidence in the literature that MRI is superior to CCT. Therefore, in patients with solitary BM according to diagnostic contrast-enhanced computed tomography (CCT), we investigated, what additional information could be gained by contrast-enhanced magnetic resonance imaging (MRI).

Among 55 patients with solitary BM according to CCT, 17 had multiple BM on MRI (31%) and 38 had solitary BM in both. Based on a presumed binomial distribution of our data, we calculated a rate of at least 19% of patients with solitary BM on CCT, in which MRI would show multiple lesions (p = 0.05). The two main characteristics for BM missed by CCT were the smaller diameter, which averages 2 cm less than in BM identified with both modalities, and a preferential frontotemporal location.

MRI is indeed superior to CCT in the diagnosis of BM the essential reasons besides detection of smaller lesions being a better soft tissue contrast, significantly stronger enhancement with paramagnetic contrast agents, the lack of bone artifacts, fewer partial volume effects, and direct imaging in three different planes. Therefore, MRI is indispensable in the diagnostic workup of patients with BM for choosing the optimum therapeutic approach, especially with regard to the decision whether to operate or to primarily irradiate the patient's metastases.