Magnetic resonance imaging of solitary brain metastases: main findings of nonmorphological sequences

Purpose

This study was done to investigate the usefulness of diffusion-weighted (DWI), perfusion-weighted (PWI) and proton magnetic resonance (MR) spectroscopy imaging in characterising solitary brain metastases.

Materials and methods

Fifty-nine solitary brain metastases were evaluated with conventional and nonmorphological MR imaging: DWI, PWI and MR spectroscopy. We evaluated size, signal intensity and contrast enhancement and calculated apparent diffusion coefficient (ADC), relative cerebral blood volume (rCBV), percentage of signal intensity recovery (PSR) and maximum values of N-acetylaspartate (NAA), choline (Cho), creatine (Cr), lipids (Lip), NAA/Cr and Cho/Cr. The nonmorphological parameters were compared with those from the literature for brain lesions that frequently enter the differential diagnosis with metastases.

Results

Signal intensity and contrast enhancement patterns were variable. There was a wide range of ADC values: min:max 0.59×10^?3:1.88×10^?3. Compared with normal white matter, rCBV was higher in lesions (3.30±1.59) and lower in perilesional oedema (0.42±0.15). Mean and minimum PSR were 57% and 48%, respectively; lip and Cho were elevated and NAA reduced.

Conclusions

Conventional MR findings of solitary metastases are heterogeneous, and some values of nonmorphological sequences are similar to those of other brain lesions. PWI seems to be the nonmorphological MR technique that may best contribute to the diagnosis of brain metastases.