The history and physical exam may help physicians decide which imaging modalities are indicated. Radiography can be used to evaluate bony abnormalities (fractures, osteophytes), ligamentous changes (ossification), and degenerative joints (Waldman 2006a). Pain physicians oftentimes work with radiologists to decide which views are necessary to adequately evaluate structures. While radiography provides a decent initial workup of bony structural abnormalities, this study modality (unless modified) is unable to provide an assessment of underlying soft tissue or vascular abnormalities.
Computerized tomography (CT) (Waldman 2006b) scan utilizes X-rays to provide a more comprehensive radiographic image. Unlike radiography, CTs provide highly detailed, sequential images of the scanned area. These images can be viewed in a number of different dimensions: axial, sagittal, and frontal, with three-dimensional reconstructions available. CT scans provide an assessment of bony and joint abnormalities, readily detecting fractures, subluxations, cystic bone lesions, and assessing bone mineral density. Additionally, CT scans produce images of soft tissue pathology.
Magnetic resonance imaging (MRI) (Waldman et al. 2006c) captures absorption and emission energies of molecules in the body to reproduce images of the scanned area. MRI provides excellent soft tissue contrast resolution. Spinous abnormalities like degenerative disk disease, joint disease, fractures, and neoplasms are readily discernable using MRI images. While tendons and ligaments prove hard to evaluate on CT, MRI is able to evaluate these soft tissue structures for sprains, tears, and inflammation. Gadolinium contrast further enhances MRI by enabling the detection of vascular abnormalities and epidural scarring.
When CT and MRI images prove insufficient or when MRI is contraindicated (pacemakers, ferromagnetic aneurysm clips), CT myelography may be a useful alternative. Myelography consists of instilling dye into the subarachnoid space while radiographic images are taken in the anteroposterior, lateral, and oblique planes. Based on defects within the dye column, one can determine areas of neural compression. With CT imaging in conjunction with myelography, a physician can see interactions of bony structures and neural elements. However, unlike CT and MRI, CT myelography poses the additional risks associated with invasively injecting dye into the subarachnoid space.
Ultrasonography avoids effects associated with ionizing radiation and also provides real-time assessment of soft tissue structures. Nerves and blood vessels within soft tissue structures, muscles, tendons, and many internal organs can be assessed with ultrasound techniques. Ultrasound, however, does not provide the resolution capacity with CT or MRI for imaging soft tissue structure, nor does ultrasound penetrate through bone well or provide a good assessment of anatomically deep structures like the spinal cord.
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