Hi and welcome,
I'm going to assume you are hoping to understand this part of your brain MRI report because you haven't asked a question, unfortunately though there isn't anything i can tell you that isn't very basic....
What this is basically saying is quite vague in itself, you should find some more specific information about the hyperintensities mentioned within the report.....pretty much all i can give you is that your brain MRI has found something that isn't normally found and it is coming up as one large irregular shaped spot-splodge-blob of unmentioned sizing, the area is showing up brighter than normal white matter should be in a few different techniques that are used in getting the images.
When something shows up using different techniques it's usually suggestive of it being an abnormality and not an unmeaningful unidentified bright object from a system error. The thing to keep in mind though is the word 'large' could mean anything, the only thought i have is that it's size is most likely greater than 3mm and that's about all i can tell you....
Why did you have an MRI?
Hope it helps a little.....JJ