Radiation dose reduction in computer assisted navigation for functional endoscopic sinus surgery--cadaver head experiments and clinical implementation

Sinus floor elevation or referral for further diagnosis and therapy: A comparison of maxillary sinus assessment by ENT specialists and dentists using cone beam computed tomography

OBJECTIVES

To compare ear, nose, and throat (ENT) specialists and dentists assessing health or pathology of maxillary sinuses using cone beam computed tomography (CBCT).

MATERIAL AND METHODS

Two ENT specialists and two oral surgeons assessed 100 CBCT datasets of healthy patients referred for dental implant placement in the posterior maxilla and decided on the possibility of sinus floor elevation or the necessity for further diagnostic examinations based solely on radiographic findings. Inter-rater agreements within the same specialty were calculated with Cohen's kappa and overall agreements with Fleiss kappa, and factors influencing the decisions taken were evaluated using regression analyses.

RESULTS

The correlation between all four raters was generally fair to moderate. The intra-specialty comparison showed a lower correlation between dentists than between ENT specialists. Absence of membrane thickening and total or subtotal sinus opacification showed the highest predictive value for a consensus in favor of sinus floor elevation and ENT referral, respectively. Flat membrane thickening with an irregular surface morphology was associated with disagreement between the examiners. Dome-shaped membrane thickenings were often considered as to be referred by dentists but not by ENTs.

CONCLUSION

The assessment of maxillary sinuses using CBCT imaging exhibited unsatisfactory agreement between ENT specialists and oral surgeons. Referral guidelines based on accidental CBCT findings that aim to diagnose relevant sinus pathologies early and avoid unnecessary diagnostics and/or therapies are needed, and an initial proposal for such recommendations is provided. Further research on correct interpretation of sinus findings and a validation of the present recommendations are required.

Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT

BACKGROUND AND PURPOSE

Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues.

MATERIALS AND METHODS

Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36.69 mGy) and a subsequent series of low-dose protocols (LDPs I-4: CT dose index volume = 4.18, 2.64, 0.99, and 0.53 mGy) with filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR)-50, ASIR-100, and model-based iterative reconstruction. The Dunn Multiple Comparison Test was used to compare each combination of protocols (α = .05).

RESULTS

Compared with the reference dose protocol with FBP, the following statistically significant differences in contrast-to-noise ratios were shown (all, P ≤ .012) for the following: 1) optic nerve: LDP-I with FBP; LDP-II with FBP and ASIR-50; LDP-III with FBP, ASIR-50, and ASIR-100; and LDP-IV with FBP, ASIR-50, and ASIR-100; and 2) inferior rectus muscle: LDP-II with FBP, LDP-III with FBP and ASIR-50, and LDP-IV with FBP, ASIR-50, and ASIR-100. Model-based iterative reconstruction showed the best contrast-to-noise ratio in all images and provided similar subjective scores for LDP-II. ASIR-50 had no remarkable effect, and ASIR-100, a small effect on subjective scores.

CONCLUSIONS

Compared with a reference dose protocol with FBP, model-based iterative reconstruction may show similar diagnostic visibility of orbital soft tissues at a CT dose index volume of 2.64 mGy. Low-dose technology and iterative reconstruction technology may redefine current reference dose levels in maxillofacial CT.

A Clinical and Radiological Approach to the Management of Benign Mesenchymal Sinonasal Tumors

PURPOSE

Benign mesenchymal sinonasal neoplasms (BMSN) are rare and histologically heterogeneous. Differential diagnosis, appropriate management, and outcome are still a matter of debate. The aim of this study is to provide evidence for further refinement of assessment and treatment in the future.

PROCEDURES

We retrospectively reviewed data on 93 patients with neuroradiologically verified BMSN treated at our university reference center during the past 22 years.

RESULTS

The most frequent BMSN recorded in our cohort was osteoma of the frontal sinus. Only one-third of the patients affected were symptomatic at initial presentation. The 2 other common fibro-osseous tumor entities, fibrous dysplasia and ossifying fibroma, were confirmed in 12 and 6 patients, respectively. Patients with soft tissue tumor entities such as hemangioma, glomangiopericytoma, angiofibroma, and hamartoma were all symptomatic and underwent surgical resection.

CONCLUSION

Understanding and recognizing the spectrum of appearances of benign mesenchymal sinonasal tumors will improve patient assessment and clinical management. The pathognomonic neuroradiological signs of a particular tumor entity should be actively sought as the neuroradiological features may be the diagnostic clues. Computed tomography and magnetic resonance imaging play complementary roles in identifying the morphological details and locoregional staging of benign mesenchymal sinonasal tumors.

Universal sinus computed tomography protocol for diagnostic imaging and intraoperative navigation

Background:

Sinus computed tomography (CT) is performed for the diagnosis of paranasal sinus disease and to assess response to medical therapy. In addition, sinus CT is used for intraoperative imaging guidance. Multiple CTs increase cost and radiation exposure.

Objective:

To determine potential cost savings and radiation dose reduction that result from the use of a single universal sinus CT protocol for diagnostic imaging and intraoperative navigation.

Materials and Methods:

For sinus CT at the authors' institution, a single imaging protocol was begun and deemed acceptable by neuroradiologists and surgeons for diagnostic imaging and intraoperative guidance. The electronic medical record was queried over a 4-year period to determine the number of sinus CTs performed, dose-length products, referring providers' specialties, percentage of CTs used for intraoperative navigation, and the elapsed time between CT and surgery.

Results:

A total of 6187 sinus CTs were performed by using a 64-detector scanner during the study period (2759 women and 3428 men; 53.6 ± 16.7 years [mean ± SD]), and 596 endoscopic sinus surgery cases used imaging guidance, for which all the CTs were deemed technically adequate. The mean dose-length product for the CTs was 338.4 ± 31.9 mGy-cm (mean ± SD). Of the 3702 sinus CTs ordered by nonotolaryngology providers, 167 surgeries with intraoperative navigation (4.5%) were performed. A higher percentage of CT referrals from sinus surgeons (23.9%) and other otolaryngology providers (11.4%) was used for imaging guidance (p < 0.0001). The time interval between sinus CT and surgery was greatest for nonotolaryngology providers (63.1 days, p < 0.01). Based on Medicare reimbursement, the total estimated saving was $147,628.

Conclusions:

Adopting a single universal sinus CT protocol for diagnostic imaging and intraoperative navigation can be an effective means of decreasing cost and radiation exposure. However, successful implementation must take into account multiple practice-based considerations.

Radiation dose reduction in paranasal sinus CT using model-based iterative reconstruction

BACKGROUND AND PURPOSE

CT performed with Veo model-based iterative reconstruction has shown the potential for radiation-dose reduction. This study sought to determine whether Veo could reduce noise and improve the image quality of low-dose sinus CT.

MATERIALS AND METHODS

Twenty patients consented to participate and underwent low- and standard-dose sinus CT on the same day. Standard-dose CT was created with filtered back-projection (120 kV[peak], 210 mA, 0.4-second rotation, and 0.531 pitch). For low-dose CT, mA was decreased to 20 (the remaining parameters were unchanged), and images were generated with filtered back-projection and Veo. Standard- and low-dose datasets were reconstructed by using bone and soft-tissue algorithms, while the low-dose Veo reconstruction only had a standard kernel. Two blinded neuroradiologists independently evaluated the image quality of multiple osseous and soft-tissue craniofacial structures. Image noise was measured by using multiple regions of interest.

RESULTS

Eight women and 12 men (mean age, 63.3 years) participated. Volume CT dose indices were 2.9 mGy (low dose) and 31.6 mGy (standard dose), and mean dose-length products were 37.4 mGy-cm (low dose) and 406.1 mGy-cm (standard dose). Of all the imaging series, low-dose Veo demonstrated the least noise (P < .001). Compared with filtered back-projection low-dose CT using soft-tissue and bone algorithms, Veo had the best soft-tissue image quality but the poorest bone image quality (P < .001).

CONCLUSIONS

Veo significantly reduces noise in low-dose sinus CT. Although this reduction improves soft-tissue evaluation, thin bone becomes less distinct.