[Radiotherapy planning for paraspinal tumors with CT-myelography].
OBJECTIVE
Artifacts due to metal implants are an important problem in diagnostic radiology and radiotherapy planning in tumors such as chordoma of the spine. A strict differentiation between target and radiosensitive structures e.g. spinal cord is absolutely essential for high-dose radiotherapy. Up to now CT and MRI techniques have provided only limited image quality in such situations. We introduce an approach to facilitate segmentation by using the technique of CT-myelography for radiation treatment.


METHODS
A 48-year-old woman with multiple inoperable relapses of a chordoma in the lumbar spine and extensive metal instrumentation in this 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-myelography with the patient in treatment position.


RESULTS
CT-myelographic images enabled precise differentiation between myelon, cauda equina and intraspinal tumor. A substantial improvement of the segmentation of the spinal cord was obtained. There was no compression of the dural sac along the spine. This information provided the basis for a precise radiotherapy planning in IMRT-technique.


CONCLUSIONS
In situations where CT- and MRI-techniques are not able to generate precise images which allow differentiation between tumor, myelon and cauda equina because of metal artifacts, CT-myelography is a promising technique which may help the diagnostic radiologist and radiation oncologist in planning radiotherapy.
Plathow
C
C
Abteilung Strahlentherapie, Deutsches Krebsforschungszentrum Heidelberg. c.plathow@dkfz-heidelberg.de
Thilmann
C
C
Delorme
S
S
Stippich
C
C
Wannenmacher
M
M
Debus
J
J
D006801:Humans; D009192:Myelography / Q000379:methods; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed