Stereotactic radiation therapy is an important and common method of treating brain metastases in patients with malignant disease. Today, however, there are no methods available to determine the metastasis' radiation sensitivity in advance and treatment responses can only be seen by changing of the size of the metastasis on conventional X-ray examinations, computed tomography (CT) and magnetic resonance imaging (MRI). Changes in the size of the metastases is something that is often seen weeks / months after treatment is completed. At Lund University Hospital, a new imaging technique, diffusional variance decomposition (DIVIDE), has now been developed. With this technique, the scatter in isotropic and anisotropic diffusion can be measured for each measuring point, which provides significantly more information about the properties of the tissue compared to current methods.

Inclusion Criteria:

1. Patients prescribed stereotactic radiation therapy to the brain, where MRI imaging is included in the treatment preparations.
2. Cohesive remaining solid tumor component of ≥10mm.
3. Age ≥18 years.
4. World Health Organisation (WHO) performance status 0-1.

Exclusion Criteria:

1. Inability to decide for oneself on participation in the study.

2. Inability to understand the Swedish language.

3. Metastases close to the base of the skull.

4. Contraindications to conducting an MRI examination.

5. Contraindications to obtaining contrast media during MRI examination.

6. Expected survival less than 6 months.

7. Previous radiation treatment to the same site in the brain, i.e. current treatment is a rope radiation.

   -