CT vs MRI In The Workup Of Spinal Diseases

 

Avi Avner, BSc BVSc CVR MRCVS DVDI

 

The overall diagnostic sensitivity of MRI is superior to CT, and as such MR can be used to image the vast majority of spinal disorders, with few exceptions (e.g. spinal trauma).

 

Routine survey radiographs are always recommended before proceeding with advanced imaging because the area of interest may be more specifically localized, thus reducing scanning time, and severe spinal/ osseous lesions, such as hemivertebrae or discospondylitis, may be identified without the need of advanced imaging studies.

 

In general CT is better suited for imaging of bone and mineralized foci or fragments. CT exam may be quicker and therefore require shorter anesthesia. Subsequently is the examination of choice in cases of spinal trauma.

 

MR provides superior contrast resolution and is better suited for imaging of soft tissues, such as the spinal cord, nerve roots, and intervertebral discs. Images can be acquired in multiple planes whereas CT images can only be acquired in one plane (transverse). Although CT images can be reformatted into any plane desirable, the image detail is slightly reduced on reformatted as compared with acquired images.

 

Myelography is still often used in conjunction with CT of the spine in order to compensate for the poor contrast resolution and soft tissue differentiation. This procedure (Myelo-CT) is invasive and may be associated with increased morbidity. Whereas MRI of the spine does not require such invasive procedure due to its ability to alter tissue contrast by applying different acquisition sequences

 

 

cervical MRI: Sag T1W
Fig 1: Cervical MRI; Sagittal T1W post IV contrast (Gd) showing multiple intra-parenchymal enhancing masses. Provisional diagnosis was lymphoma.  

 

 

 

cervical MRI: Sag T2W
Fig 2: Cervical MRI: Sagittal T2W showing multiple hypointense dehydrated discs and associated protrusions leading to mild impingement onto the spinal cord.  

 

 

 

 Thoracic MRI: Sag T2W

  myelogram T2W 

Fig 3&4: Thoracic MRI: Sagittal T2W (Fig 3) showing focal dorsally positioned tear drop shape hyperintense distension of the subarachnod space leading to moderate cord compression and CSF distension of the central canal (caudally to the lesion). A myelogram like picture (strong T2W features)  constructed without injection of contrast, clearly depict the focal subrachnoid cyst-like distension.