Is a stereotactic/ thin-slice MRI of the brain absolutely necessary to determine eligibility for hippocampal sparing whole brain radiation therapy?

The small size of the hippocampal dentate gyrus (3-4cc) can render it difficult to delineate and conformally avoid if both the brain MRI and the treatment-planning CT simulation are not obtained with thin-slice axial images (not exceeding 1.5mm on the MRI, not exceeding 2.5mm on the treatment-planni...