Several tests are performed to determine the precise extent of lymphoma before starting treatment. This staging work-up usually includes a CT scan of the chest, abdomen and pelvis, a gallium scan, a bone marrow biopsy and a spinal tap to see if there are lymphoma cells floating in the spinal fluid surrounding the brain and spinal cord. If there are symptoms or other evidence suggesting involvement of the bones, stomach or other specific areas, tests such as x-rays may be done.