The role of CT myelography in sparing the spinal cord during definitive radiotherapy in vertebral hemangioma

Abstract

IntroductionThe spinal cord is poorly visualized on CT images but is well visualized in MRI images. However, implants used for spinal stabilization can produce artifacts on the MRI images which can interfere with identification of the cord. CT myelography in conjunction with CT simulation helps to clearly delineate the cord.Materials and methods CT simulation was done in a patient with vertebral hemangioma. Pre‐ and post myelography images were obtained. Two plans were generated on pre and post myelography CT images using Eclipse™ treatment planning system (TPS) version 10.0, Varian Medical Systems, USA. The prescribed total dose to PTV was 40 Gy in 20 fractions.ResultsThe cord was poorly visualized in the premyelogram CT images. The titanium implants used for spinal cord stabilization produced artifacts in the MRI images. Figure 1 Post myelogram, the contrast lit up the spinal cord.There was an overlap of 0.75 cc volume of the spinal cord with the PTV in the premyelogram images. This volume was reduced to 0 cc in the post myelogram images. There was an overlap of 5.4 cc volume of the PRV of spinal cord with the PTV in the premyelogram images which was reduced to 1 cc in the post myelogram images. The overlap region between the PTV and spinal cord received around 71% of the prescribed dose in premyelogram CT could be reduced to 0% in the post myelogram CT. The mean dose received by the overlap PRV spinal cord and PTV could be increased from 70% in the premyelogram to 92% in the post myelogram plans.Conclusion CT myelogram in conjunction with CT simulation is particularly useful in cases where the tumor margin is very close to the cord and spinal implants are causing distortion of magnetic resonance images.

Spinal Cord Delineation Based on Computed Tomography Myelogram Versus T2 Magnetic Resonance Imaging in Spinal Stereotactic Body Radiation Therapy

“…The administered contrast fills the CSF space around the spinal cord, resulting in good contrast between the spinal cord and CSF so that the spinal cord contours can be delineated. Sudha et al 29 assessed the role of CT myelography in sparing the spinal cord during definitive radiation therapy in vertebral hemangioma. They found that CT myelogram was useful in cases where the tumor margin is in close relation to the spinal cord and in cases of spinal implants that result in MRI distortions.…”

“…A potential imaging method for overcoming this issue is the use of 3-dimensional T2-weighted sequences with small isotropic voxels, such as T2 SPACE. 29 , 30 Our group is currently pursuing a study to compare standard T2-weighted MRI versus T2 Space MRI sequences for spinal cord definition to determine whether this modality may aid in reducing uncertainty at the spinal cord-CSF interface. Differences may also be related to parameters of the CT myelogram, for example, the smoothing algorithm used in the reconstruction based on either a soft tissue versus a bone reconstruction kernel.…”

CT-Myelografie: klinische Indikationen und Bildgebungsbefunde

“…Schließlich spielt die CT-Myelografie eine wichtige Rolle bei der Behandlung maligner oder metastasierter Erkrankungen der Wirbelsäule, indem sie die leptomeningeale Beteiligung von Neoplasmen des zentralen Nervensystems oder metastasierten Erkrankungen dar-stellt und bei der Planung der Strahlentherapie hilft. Sie ist insbesondere dann sehr nützlich, wenn die MRT eingeschränkt einsetzbar oder kontraindiziert ist [8][9][10].…”

CT Myelography: Clinical Indications and Imaging Findings

“…Last, CT myelography plays an important role in management of spine malignancy or metastatic disease by depicting leptomeningeal involvement of central nervous system neoplasm or metastatic disease and helping plan radiation therapy, especially when MRI is limited or contraindicated (8)(9)(10).…”