Imaging of the Spine: A Medical and Physical Perspective - Spinal Imaging and Image Analysis - page 6

Fig. 3 Post-surgical follow up of spinal fixation procedure on a radiograph. Frontal and lateral
view radiographic follow up series of spinal fixation, in a 25 year old male with history of cervical
spine fracture. The patient is status-post multilevel cervical vertebral corpectomy, with anterior and
posterior instrumented fusion from C3 to C6, and with integrated vertebral body strut spacer
placement. Follow-up radiographic series allow for assessment of spinal alignment, as well as for
inspection for hardware fracture and loosening

whereby the beam photons pass through numerous anatomic structures on their way
to the detector plate, many internal structures will be superimposed on one another
in the radiograph. Again, deconvolution of these objects into individually identi-

fiable structures may necessitate alternative modalities of visualization such as cross
sectional imaging. Radiographs, which are incomplete data sets, typically allow for
a limited number of inferences to be drawn. Multiple orthogonal perspective views
of a body structure may be taken as part of a radiographic series, increasing the
information content regarding a particular structure, decreasing the level of data
degeneracy and so increasing the diagnostic usefulness.
From a clinical medical perspective, radiographs commonly find use as general

screening examinations for the spine, as well as for postsurgical follow-up of spinal
procedures, as in Fig. 3 . Relative drawbacks for radiographic imaging include lower
sensitivity for certain classes of subtle pathology such as subtle fractures, low
contrast in soft tissues, and patient radiation exposure.

3 Computed Tomography

Computed tomography (CT) is a sophisticated scanning technique for creating cross
sectional volumetric X-ray images of body anatomy, which are, in effect, maps of
tissue density. As previously described, the beam creates X-rays which penetrate