Treatment planning of paraspinal tumors with CT-myelography

Background and Aim: Artifacts due to metal implants are an important proble m in diagnostic radiology and radiotherapy planning in tumors such as chord oma of the spine. A strict differentiation between target and radiosensitiv e structures e.g. spinal cord is absolutely essential for high-dose radioth erapy. Up to now CT and MRI techniques have provided onlylimited image qual ity in such situations. We introduce an approach to facilitate segmentation by using the technique of CT-myelography for radiation treatment. Patient and Method: A 48-year-old woman with multiple inoperable relapses o f a chordoma in the Lumbar spine and extensive metal instrumentation in thi s area was given to radiotherapy using IMRT-technique (intensity modulated) . MRI- and CT-planning images did not allow differentiation between myelon, cauda equina, dural sac and tumor. In this situation we performed a CT-mye lography with the patient in treatment position. Results: CT-myelographic images enabled precise differentiation between mye lon, cauda equina and intraspinal tumor. A substantial improvement of the s egmentation of the spinal cord was obtained. There was no compression of th e dural sac along the spine. This information provided the basis for a prec ise radiotherapy planning in IMRT-technique. Conclusion: In situations where CT- and MRI-techniques are not able to gene rate precise images which allow differentiation between tumor, myelon and c auda equina because of metal artifacts, CT-myelography is a promising techn ique which may help the diagnostic radiologist and radiation oncologist in planning radiotherapy.