CT radiation dose for computer-assisted endoscopic sinus surgery: dose survey and determination of dose-reduction limits

BACKGROUND AND PURPOSE: Computer-assisted navigation is increasingly used in functional endoscopic sinus surgery (FESS) to prevent injury to vital structures, necessitating preparative CT and, thus, radiation exposure. The purpose of our study was to investigate currently used radiation doses for CT in computer-assisted navigation in sinus surgery (CAS-CT) and to assess minimal doses required. MATERIALS AND METHODS: A questionnaire inquiring about dose parameters used for CAS-CT was sent to 30 radiologic institutions. The feasibility of low-dose registration was tested with a phantom. The influence of CAS-CT dose on technical accuracy and on the practical performance of 5 ear, nose, and throat (ENT) surgeons was evaluated with cadaver heads. RESULTS: The questionnaire response rate was 63%. Variation between minimal and maximal dose used for CAS-CT was 18-fold. Phantom registration was possible with doses as low as 1.1 mGy. No dose dependence on technical accuracy was found. ENT surgeons were able to identify anatomic landmarks on scans with a dose as low as 3.1 mGy. CONCLUSIONS: The vast dose difference between institutions mirrors different attitudes toward image quality and radiation-protection issues rather than being technically founded, and many patients undergo CAS-CT at higher doses than necessary. The only limit for dose reduction in CT for computer-assisted endoscopic sinus surgery is the ENT surgeon's ability to cope with impaired image quality, whereas there is no technically justified lower dose limit. We recommend, generally, doses used for the typical diagnostic low-dose sinus CT (120 kV/20-50 mAs). When no diagnostic image quality is needed, even a reduction down to a third is possible.

Comparison of periapical radiography and limited cone-beam tomography in posterior maxillary teeth referred for apical surgery

This study compared periapical (PA) radiography and cone-beam tomography (CBT) for preoperative diagnosis in posterior maxillary teeth of consecutive patients referred for possible apical surgery. Images were concurrently analyzed by an oral radiologist and an endodontist to reach consensus in interpretation of the radiographic findings. The final material included 37 premolars and 37 molars with a total of 156 roots. CBT showed significantly more lesions (34%, p < 0.001) than PA radiography. Detecting lesions with PA radiography alone was most difficult in second molars or in roots in close proximity to the maxillary sinus floor. Additional findings were seen significantly more frequently in CBT compared with PA radiography including expansion of lesions into the maxillary sinus (p < 0.001), sinus membrane thickening (p < 0.001), and missed canals (p < 0.05). The present study highlights the advantages of using CBT for preoperative treatment planning in maxillary posterior teeth with apical pathology.

Evaluation of healing criteria for success after periapical surgery

INTRODUCTION: In periapical surgery, the absence of standardization between different studies makes it difficult to compare the outcomes. OBJECTIVE: To compare the healing classification of different authors and evaluate the prognostic criteria of periapical surgery at 12 months. MATERIAL AND METHODS: 278 patients (101 men and 177 women) with a mean age of 38.1 years (range 11 to 77) treated with periapical surgery using the ultrasound technique and a 2.6x magnifying glass, and silver amalgam as root-end filling material were included in the study. Evolution was analyzed using the clinical criteria of Mikkonen et al., 1983; radiographic criteria of Rud et al., 1972; the overall combined clinical and radiographic criteria of von Arx and Kurt, 1999; and the Friedman (2005) concept of functional tooth at 12 months of surgery. RESULTS: After 12 months, 87.2% clinical success was obtained according to the Mikkonen et al., 1983 criteria; 73.9% complete radiographic healing using Rud et al. criteria; 62.1% overall success, following the clinical and radiographic parameters of von Arx and Kurt, and 91.9% of teeth were functional. The von Arx and Kurt criteria was found to be the most reliable. CONCLUSION: Overall evolution according to von Arx and Kurt agreed most closely with the other scales.