Use context var for custom docker image repo

Build Environment
1

Hi I have a context env vars for AWS access, and a custom docker image in our AWS ECR. The circleci config.yml file looks like this:

    docker:
      - image: accountid.dkr.ecr.us-east-2.amazonaws.com/image:tag
        aws_auth:
          aws_access_key_id: $AWS_ACCESS_KEY_ID
          aws_secret_access_key: $AWS_SECRET_ACCESS_KEY

This works, but I would like to hide the image registry domain, but this does not work:

    docker:
      - image: $MY_AWS_ECR_URI/my_image:tag
        aws_auth:
          aws_access_key_id: $AWS_ACCESS_KEY_ID
          aws_secret_access_key: $AWS_SECRET_ACCESS_KEY

Is there a way to achieve this?