Progress in sinonasal imaging.

Imaging of sinonasal structures has evolved from standard radiographs to the much more complicated and informative techniques used today. The plain radiograph was useful when the surgical techniques practiced were primarily aimed at the maxillary and frontal sinuses. With a better understanding of the mucociliary clearance of the nasal cavity and the paranasal sinuses, the surgical technique was shifted to the ethmoid sinuses and became more focal, thus needing a better understanding and display of the intricate morphology of the nasal cavity and paranasal sinuses. Polytomography was a step above plain radiographs and was first used in the display of the regional anatomy for the development of functional endoscopic sinus surgery. Polytomography was quickly replaced by computed tomography, as this imaging technique provides a much more detailed view of the sinonasal architecture than does polytomography. Magnetic resonance imaging has also shown usefulness in imaging this morphological area, as it provides better soft tissue resolution, but it does not allow good visualization of bony structures. Newer computer systems with software capable of reconstructing the digitized information into a 3-dimensional display further enhance our understanding of the regional morphology and afford an improved means of correlating the imaging and endoscopic information. Furthermore, stereotactic navigation systems allow surgeons the ability to visualize the endoscope-instrument tip position, as instruments are actively being used during surgery, on the computed tomographic and/or magnetic resonance images. There is a persistent trend toward reducing the size of the imaging equipment to render it more mobile (computed tomography) and adapt it for operating room use.