Nasal endoscopy: an adjunct to patient selection for preoperative low-dose CT examination in chronic rhinosinusitis.

Abstract

The growing awareness of increased X-ray exposure to the public has led to the propagation of several methods for reducing the radiation dose during CT examination. Low-dose CT protocols do not, however, have an established role in pre-operative evaluation. The aim of this article was to assess the usefulness of nasal endoscopy in the selection of patients under pre-operative care for low-dose CT examination. A cadaver head was used to discover institutional minimum acceptable CT image quality and scanning settings. Then, 134 adult patients with chronic rhinosinusitis (CRS) were enrolled into the study and divided randomly into standard dose (120 kVp, 100 mAs) or low-dose CT groups (120 kVp, 45 mAs). Subjective assessment of the diagnostic image quality of the surgically relevant anatomical structures was compared using a five-point scale (from excellent to unacceptable) by a radiologist and sinus surgeon independently. Pathologic states of the nose were quantified according to the Lund-Kennedy endoscopic system (LKES) and Lildholdt's scale. Image quality was similar in low-dose and standard dose groups in patients without polyps. The quality of 13% of scans from patients with polyps from the low-dose group and 4% from the standard dose group was in the range from moderate to poor. The quality of scans obtained with low milliamperes second (mAs) values worsened in patients with polyps in the middle meatus, but the difference was particularly pronounced compared with standard dose among subjects with Lildholdt's score above 2 (p < 0.001). Correlation with LKES revealed that changes other than polyps (i.e. discharge, oedema, scaring or crusting) in the nasal cavity alone do not affect the image quality. Interobserver agreement in both groups was very high. Low-dose scanning should be promoted as the screening imaging method of choice in patients with suspected CRS. Furthermore, low mAs value examination can be performed pre-operatively without fear of significant image quality deterioration in uncomplicated CRS patients without polyps, or with minor changes in nasal endoscopy. Standard dose CT, which provides a better identification of bony landmarks, minimizes diagnostic errors and risk to patients, so it might be considered in those with polyps below the middle turbinate.