Norm of Tomography of Paranasal Sinuses
Negative for foreign body, fracture, tumor, or anatomic anomalies.
Usage of Tomography of Paranasal Sinuses
Adjunct to conventional radiography for clients with suspected fracture (status post trauma), bony tumor invasion of the paranasal sinus area, or foreign-body introduction into the paranasal sinus area; evaluation of the extent and location of sinus disease; detection of anatomic abnormalities before surgery. Improves planning and safety of paranasal sinus surgery by providing a map of the area.
Description of Tomography of Paranasal Sinuses
Computed tomography (CT) of the paranasal sinuses is a radiographic scan that reconstructs an image of the paranasal sinus area based on differing densities and composition of the tissues. A detector records the intensity of the x-rays from multiple angles as they are transmitted through the paranasal sinus area. A computer then reconstructs the differing intensities into pixels, which appear in different shades for different tissues and represent “slices” across the plane of the area. This test may provide additional information that standard radiography cannot because it can portray boundaries between tissues that are normally indistinguishable by traditional radiography. In particular, CT provides a sensitive display of the deep air passages and posterior ethmoid and sphenoid sinuses, which are difficult to reach by nasal endoscopy. By providing the landmarks necessary to recognize hazardous anatomy and pathologic conditions, tomography of the paranasal sinuses can increase the safety and efficacy of paranasal sinus surgery. This procedure also offers the advantage of superior visibility of the ethmoid sinus over plain films of the paranasal sinuses. See also Computed tomography of the body for a further description of the types of CT technology available.
Professional Considerations of Tomography of Paranasal Sinuses
Consent form NOT required.
Clients who are unable to lie motionless.
During pregnancy, risks of cumulative radiation exposure to the fetus from this and other previous or future imaging studies must be weighed against the benefits of the procedure. Although formal limits for client exposure are relative to this risk:benefit comparison, the United States Nuclear Regulatory Commission requires that the cumulative dose equivalent to an embryo/ fetus from occupational exposure not exceed 0.5 rem (5 mSv). Radiation dosage to the fetus is proportional to the distance of the anatomy studied from the abdomen and decreases as pregnancy progresses. For pregnant clients, consult the radiologist/ radiology department to obtain estimated fetal radiation exposure from this procedure.
- Remove radiopaque objects such as jewelry, eyeglasses, or hairpins from the head area.
- The client is positioned supine, with the head secured in a hyperextended position on a headrest (coronal imaging); or prone, resting on chin with the head hyperextended (axial imaging) on a motorized handling table.
- The client must lie motionless as the table slowly advances through the circular opening of the scanner. The CT scanner sends a narrow beam of x-rays across the area to be imaged in a linear fashion.
- Imaging in both axial and coronal planes is completed.
- Replace radiopaque objects that were removed before the scan.
Client and Family Teaching
- It is necessary to lie motionless during the scan. Because this can be a frightening test, it should be carefully described before the client enters the CT room.
Factors That Affect Results
- Radiopaque objects left in place obscure visualization.
- Increase in size of the maxillary sinus is normal in aging but often not found in aging in persons with cystic fibrosis.
- Further testing may include magnetic resonance imaging (MRI), which is more sensitive than CT for identification of neoplasm. MRI is replacing CT of the paranasal sinuses as the study of choice for oropharyngeal and paranasal sinus lesions.
- Anatomic anomalies, such as paradoxical middle turbinates, are common findings in persons with chronic sinusitis.