dynamodb - scan items by value inside array

I'm doing a table scan. This table has an array as one of its fields, the "apps" field (apps is not a key of any kind). I want to select all rows, whose apps array contains a certain value "MyApp". I tried something of that kind, but my syntax is incorrect:

    ComparisonOperator = "#apps CONTAINS :v",
    ExpressionAttributeNames = {
        '#apps': 'apps'
    },
    ExpressionAttributeValues = {
        ":v": "MyApp"
    }

Thanks.