Diagnostic value of cone-beam CT in histologically confirmed otosclerosis

Effect of Matrix Size and Acquisition Mode on Image Quality and Radiation Dose of Ultra-High-Resolution CT of the Temporal Bone: An Anatomical Study

Purpose: To compare image quality and radiation exposure between super- and ultra-high-resolution helical and super-high-resolution volumetric CT of the temporal bone. Methods: Six cadaveric temporal bone specimens were used to evaluate key temporal bone structures using the following CT reconstruction and acquisition modes: helical and single-volume acquisition modes in super-high resolution (0.25-mm slice thickness, 10242 matrix), and helical mode in ultra-high resolution (0.25-mm slice thickness, 20482 matrix). Two observers performed 5 previously described preoperative measurements, measured noise and signal-to-noise ratios for air, and noise for bone, and rated the visualization of 5 anatomical structures on a 4-point scale, for each reconstruction mode. Radiation dose exposure was recorded for each examination. Results: There was no significant difference between any of the quantitative or qualitative measurements in any of the reconstruction and acquisition modes. There was a slight increase in noise and a decrease in signal-to-noise ratio in the air using the single-volume mode (115 ± 13.1 HU and 8.37 ± 0.91, respectively) compared to the helicoidal super-high-resolution (92.4 ± 11.8 HU and 10.8 ± 1.26, respectively) and helicoidal ultra-high-resolution (91.1 ± 10.7 HU and 10.9 ± 1.39, respectively) modes (P < .002). The volumic CT dose index was 50.9 mGy with helical acquisition and 29.8 mGy with single-volume acquisition mode (P < .0001). Conclusion: The single-volume super-high-resolution acquisition mode allows a reduction in radiation dose exposure without compromising image quality compared to helical scanning, but with a slightly lower signal-to-noise ratio in air with the single-volume mode, while there was no difference in image quality between the helical super- and ultra-high-resolution modes.

Comparative study of the sensitivity of ultra-high-resolution CT and high-resolution CT in the diagnosis of isolated fenestral otosclerosis

PURPOSE

To compare the diagnostic sensitivity of ultra-high-resolution computed tomography (U-HRCT) and HRCT in isolated fenestral otosclerosis (IFO).

METHODS

A retrospective analysis was conducted on 85 patients (85 ears) diagnosed with IFO between October 2020 and November 2022. U-HRCT (0.1 mm thickness) was performed for 20 ears, HRCT (0.67 mm thickness) for 45 ears, and both for 20 ears. The images were evaluated by general radiologists and neuroradiologists who were blinded to the diagnosis and surgical information. The diagnostic sensitivity of U-HRCT and HRCT for detecting IFO was compared between the two groups.

RESULTS

Excellent inter-observer agreement existed between the two neuroradiologists (Cohen's κ coefficient 0.806, 95% CI 0.692-0.920), with good agreement between the general radiologists (Cohen's κ coefficient 0.680, 95% CI 0.417-0.943). U-HRCT had a sensitivity of 100% (40/40 ears) for neuroradiologists and 87.5% (35/40 ears) for general radiologists, significantly higher than HRCT (89.2% [58/65 ears] for neuroradiologists; 41.5% [27/65 ears] for general radiologists) (p = 0.042, p' < 0.000). General radiologists' sensitivity with HRCT was significantly lower compared to neuroradiologists (p < 0.000), but no significant difference was observed when general radiologists switched to U-HRCT (p = 0.152). Among the 20 ears that underwent both examinations, U-HRCT detected lesions smaller than 1 mm in 5 ears, whereas HRCT's sensitivity for neuroradiologists was 40% (2/5 ears), significantly lower than for lesions larger than 1 mm (93.3%, 14/15 ears, p = 0.032).

CONCLUSION

U-HRCT exhibits higher sensitivity than HRCT in diagnosing IFO, suggesting its potential as a screening tool for suspected otosclerosis patients.

CRITICAL RELEVANCE STATEMENT

Ultra-high-resolution computed tomography has the potential to become a screening tool in patients with suspected otosclerosis and to bridge the diagnostic accuracy gap between general radiologists and neuroradiologists.

KEY POINTS

• U-HRCT exhibits higher sensitivity than HRCT in the diagnosis of IFO. • U-HRCT has a significant advantage in the detection of less than 1 mm IFO. • U-HRCT has the potential to be used for screening of patients with suspected otosclerosis.

Missed Radiological Diagnosis of Otosclerosis in High-Resolution Computed Tomography of the Temporal Bone-Retrospective Analysis of Imaging, Radiological Reports, and Request Forms

Objectives: Several studies reported low detection rates of otosclerosis in high-resolution computed tomography (HRCT), especially when the scans were reviewed by non-specialized general radiologists. In the present study, we conducted a retrospective review of the detection of otosclerosis in HRCT by general radiologists and the impact of inadequately filled radiological request forms on the detection rate. Methods: Retrospective analysis of hospital records, HRCT reports, and radiological referral notes of 40 patients who underwent stapedotomy surgery for otosclerosis. HRCT imaging data sets were retrospectively reviewed by a blinded experienced neuroradiologist, whose reading served as the gold standard. Results: General radiologists reading HRCT scans had an overall detection rate of otosclerosis of 36.1% in this cohort (13 of 36 available HRCT reports). The neuroradiologist had a much higher detection rate of 82.5% (33 of 40 cases). Interobserver agreement between the general radiologists and the subspecialist neuroradiologist was poor (Cohen’s kappa κ = 0.26). General radiologists missed the diagnosis in 15 of the 33 CT-positive scans, corresponding to a missed diagnosis rate of 45.4%. There was a highly significant association between a missed diagnosis and the lack of an explicitly mentioned clinical suspicion of otosclerosis in the request forms (Pearson’s chi-squared test, p < 0.005). Conclusion: The diagnosis of otosclerosis is frequently missed by radiologists on HRCT scans of the temporal bone in a clinical setting. Possible reasons include a relative lack of experience of general radiologists with temporal bone imaging as well as the failure of clinicians to unambiguously communicate their suspicion of otosclerosis.

Feasibility of CBCT in Diagnosing Otosclerosis by Measuring CBCT Bone Density: A Preliminary Study

The aim of this study was to measure cone beam computed tomography (CBCT) derived bone density of 6 anatomic points around the otic capsule in preoperative assessment of patients with clinically suspected otosclerosis, and to compare these densities with control group. CBCT images of 21 patients (34 ears, the otosclerosis group) with surgically confirmed otosclerosis and 26 patients (52 normal ears, the control group) were evaluated in this prospective study. Six regions of interest (ROI) were set manually around the otic capsule with the slice thickness of 0.3 mm. The mean CBCT bone density these regions were measured and compared in the case and control groups. In the case group, the mean CBCT bone density at the fissula ante fenestram (FAF) was significantly lower than the control group. Moreover, at the 4 points of the other ROIs (3-6) CBCT bone densities were significantly lower in the case group compared to the control group (p < 0.01). In this group, among 13 bilateral otosclerosis, 22 ears had conductive hearing loss (CHL), 4 ears had mixed hearing loss (MHL) and among 8 unilateral otosclerosis, 5 ears had CHL, 3 ears had MHL. Our study showed the mean CBCT bone density of ROIs 1 and 6 were correlated with the average air-bone gap in the bilateral and unilateral otosclerosis group, respectively. Quantitative evaluation of CBCT with a slice thickness of 0.3 mm can be used as a suitable tool for diagnosis and follow-up of otosclerosis in temporal bone.

Role of Radiologic Imaging in Otosclerosis

Purpose of Review

To review the role of imaging in otosclerosis with an emphasis on pre- and post-operative imaging evaluation.

Recent Findings

Pre-operative CT imaging can help define the extent of bone involvement in otosclerosis and may help avoid surgical complications due to variant anatomy or unsuspected alternative causes of conductive hearing loss. In patients with recurrent hearing loss after surgery, CT imaging can clarify prosthesis position and re-assess anatomy.

Summary

CT imaging complements otologic exam and audiometry findings in patients with suspected otosclerosis, for pre-operative planning, and post-operative assessment for patients with recurrent symptoms.

Whether cochlea involvement on CT in otosclerosis patients impacts the effect of stapedotomy

BACKGROUND

The success rate of stapedotomy in otosclerosis patients with cochlea involvement was unknown.

AIMS/OBJECTIVES

To determine the difference of surgical outcomes and symptomatology in otosclerosis patients with or without cochlea involvement on CT.

MATERIAL AND METHODS

79 otosclerosis patients were included and grouped by HRCT, including cochlear-involved otosclerosis (C-group) or non-cochlear-involved otosclerosis (NC-group, control group). Patients were defined as NC-group in the presence of normal or solely fenestral involvement, or C-group if the hypodensities involve other parts of the labyrinthine bone Patients in the control group were collected at a 2:1 ratio to the C-group with similar follow-up times. Detailed complaints and surgical outcomes were compared between these groups.

RESULTS

Chief complaints were similar in the C-group and NC-group. Although postoperative AC, BC, and ABG decreased significantly in both groups, the success rate was significantly higher in C-group regarding the postoperative ABG ≤10 dB. Furthermore, diffuse lesions may indicate a more severe disease and a poorer prognosis.

CONCLUSIONS AND SIGNIFICANCE

Stapedotomy was effective for clinical otosclerosis. The surgical outcome was inferior favorable for cochlea involvement patients, especially for cases with widely involvement. There was no difference in chief complaints among patients with different CT degree of otosclerosis.

Stapes visualization by ultra-high resolution CT in cadaveric heads: A preliminary study

PURPOSE

This study aimed to assess stapes visualization using an ultra-high resolution computed tomography (U-HRCT).

METHOD

Sixty ears from 30 cadaveric human heads were scanned by both U-HRCT and 128-section multislice CT (MSCT) with clinical parameters. Image quality of the stapes head, anterior and posterior crura, footplate, incudostapedial joint and stapedial muscle within the pyramidal eminence was scored using a 3-point Likert scale. Linear measurements of the stapes configuration were performed on U-HRCT.

RESULTS

The interobserver agreement for image qualitative score on U-HRCT was good to excellent (interobserver agreement coefficients 0.65-0.86). With the exception of the stapes head, U-HRCT achieved significantly higher qualitative scores than MSCT across all anatomical structures (Ps < 0.05). The total height of the stapes was measured to be 3.48 ± 0.33 mm. The height and width of the obturator foramen were 1.77 ± 0.28 mm and 2.19 ± 0.33 mm, respectively. The widths of the anterior and posterior crura were 0.20 ± 0.06 mm and 0.22 ± 0.06 mm, respectively. The thickness of the footplate was 0.22 ± 0.06 mm, and the angle of the incudostapedial joint was 95.91 ± 10.69°.

CONCLUSIONS

U-HRCT is capable of delineating fine structures of the stapes and provides linear data on dimensions of the stapes, which could be helpful for detecting stapes disease and making individualized surgical plans in the clinical setting.

Novel Radiologic Approaches for Cholesteatoma Detection: Implications for Endoscopic Ear Surgery

Technological advancement in computed tomography (CT) and MRI has improved cholesteatoma detection rates considerably in the past decade. Accurately predicting disease location and extension is essential for staging, planning, and preoperative counseling, in particular in the newer approach of endoscopic ear surgery. Improved sensitivity and specificity of these radiological methods may allow the surgeon to confidently monitor patients, therefore avoiding unnecessary surgery. This article outlines recent advances in CT and MRI technology and advantages and disadvantages of the newer techniques. Emphasis on improving the feedback loop between the radiologist and surgeon will increase the accuracy of these new technologies.

Imaging Studies in Otosclerosis: An Up-to-date Comprehensive Review

Introduction  Otosclerosis is a primary osteodystrophy of the otic capsule, frequently responsible for acquired hearing loss in adults. Although the diagnostic value of imaging investigations in otosclerosis is debatable, they might still be employed with different goals within the context of the disease.

Objectives  The present paper aims to review the most recent literature on the use of imaging studies in otosclerosis for the most varied purposes, from routine application and differential diagnosis to prognostic prediction and investigation of surgical failure.

Data Synthesis  The diagnosis of otosclerosis is usually clinical, but computed tomography (CT) is paramount in particular cases for the differential diagnosis. The routine use, however, is not supported by strong evidence. Even so, there is growing evidence of the role of this method in surgical planning and prediction of postoperative prognosis. In specific scenarios, for example when superior semicircular canal dehiscence (SSCD) syndrome is suspected or in surgical failure, CT is crucial indeed. Magnetic resonance imaging (MRI), however, has limited – although important – indications in the management of individuals with otosclerosis, especially in the evaluation of postoperative complications and in the follow-up of medical treatment in active ostosclerosis.

Conclusion  Imaging studies have a broad range of well-established indications in otosclerosis. Besides, although the routine use of CT remains controversial, the most recent papers have shed light into new potential benefits of imaging prior to surgery.

Audiometric Results of Stapedotomy Surgery for Otoscelorsis: Influence of the Radiological Stage

BACKGROUND

The objective of this study was to identify a correlation between the radiological stage of otosclerosis and the pre- and postoperative audiometric results of patients who underwent a stapedotomy.

METHODS

Ninety-three patients with radiologically and surgically confirmed otosclerosis who underwent stapedotomy surgery and CT scanning within 18 months before the operation were included. The CT scans were interpreted by an otologist and a specialised radiologist to determine their radiological stage according to the classification of Veillon and Fraysse. The patients received a pre- and postoperative audiogram in the short and long term.

RESULTS

The preoperative bone conduction thresholds were higher in patients who presented with an advanced radiological stage of otosclerosis: 32.7 dB ± 12.4 compared with those who presented with a less advanced radiological stage: 24.3 dB ± 10.0. The preoperative air conduction thresholds were higher in patients who presented with an impairment of the round window: 58.1 dB ± 13.5 compared with those who presented with no impairment of the round window: 48.7 dB ± 14.5. The postoperative improvement in the air-bone gap was significantly higher for the localised foci: 16.9 dB ± 8.6 versus 11.0 dB ± 9.2, but only in the short term.

CONCLUSION

There was a clinical radiological correlation with the preoperative results: In BC, there was a correlation with the radiological stage of Veillon and in AC, there was a correlation with impairment of the round window. The link between the radiological stage of otosclerosis and the postoperative audiometric results is less obvious. In the short term, the audiometric improvements in the air-bone gap were greater in patients in the early stages according to the Veillon classification, but this result was not sustained in the long-term.

Diagnostic Protocol for Detecting Otosclerosis on High-Resolution Temporal Bone CT

OBJECTIVES

To present a systematic checklist to improve diagnosing otosclerosis (OS) on high-resolution computed tomography (HRCT) of the temporal bones and review this protocol's efficacy in diagnosing OS on HRCT.

METHODS

A retrospective case series was performed at a University Referral Hospital in urban Chicago, Illinois. High-resolution computed tomographies of the temporal bone were reviewed including 17 ears in the test group with surgically confirmed OS and 21 ears in the control group surgically confirmed to not have OS. Preoperative HRCTs were evaluated by a single neuroradiologist using a systematic protocol created to assist in diagnosing OS. This looked for radiolucency at the fissula ante fenestram and pericochlear region, and new bone formation around the oval and round windows.

RESULTS

The radiologist accurately diagnosed OS in all 17 test group ears and ruled out OS in all 21 control group ears using the protocol. All 17 test ears were read to have lucency at the fissula ante fenestram, 9 (53.0%) to have new bone formation, and 8 (47.1%) to have cochlear lucency. The radiologist was more confident in diagnosing OS when cochlear lucency was present with the fissula ante fenestram lucency.

CONCLUSIONS

This HRCT checklist is a highly accurate tool for evaluating the presence of OS when images are reviewed in the systematic fashion described. Imaging prior to surgery aids in counseling patients, preparing surgically, and excluding other pathologies.

High-Resolution Computed Tomography of the Inner Ear: Effect of Otosclerosis on Cochlear Aqueduct Dimensions

OBJECTIVES

The cochlear aqueduct is a bony duct connecting the scala tympani with the subarachnoid space. Given the pathophysiology of otosclerosis, including bone resorption and new bone deposition, we hypothesize that the cochlear aqueduct in otosclerotic ears is narrowed.

METHODS

A retrospective review of patients with otosclerosis who have undergone high-resolution computed tomography (HRCT) of the temporal bone was completed. The control cohort included 20 patients with the diagnosis of noise-induced hearing loss, without the diagnosis of otosclerosis. Uniform measurements of cochlear aqueduct dimensions were performed using the axial plane.

RESULTS

The otosclerosis cohort included 25 males and 52 females with mean age of 52.2 ± 17.6 years. The control group included 10 males and 10 females with mean age of 64.0 ± 18.5 years. The mean cochlear aqueduct length, width mid canal, aperture base, aperture widest diameter, and funnel diameter in millimeters were 12.19 ± 1.66, 0.68 ± 0.28, 4.21 ± 1.67, 3.23 ± 1.47, and 2.70 ± 1.05 in the ears with otosclerotic foci and 11.57 ± 1.66, 0.69 ± 0.29, 2.56 ± 1.59, 2.77 ± 1.67, and 2.58 ± 1.03 in control group, respectively. Statistical difference was seen in length of cochlear aqueduct, aperture base, and aperture widest diameters (P = .017, <.001, .007).

CONCLUSIONS

The length of the cochlear aqueduct and the funnel width are statistically longer in the otosclerotic population compared to control. The width of the cochlear aqueduct is not statistically different.

Retrospective Review of Otic Capsule Contour and Thickness in Patients with Otosclerosis and Individuals with Normal Hearing on CT

BACKGROUND AND PURPOSE

Otosclerosis is commonly identified on CT as a focus of hypodensity in the otic capsule anterior to the oval window. However, otosclerosis can have a sclerotic phase approximating the density of normal bone, making diagnosis challenging. This study assesses differences in otic capsule contour and thickness anterolateral to the anterior margin of the oval window in patients with otosclerosis compared with individuals with normal hearing.

MATERIALS AND METHODS

Axial CT of 104 ears with clinically diagnosed otosclerosis and 108 consecutive ears of audiometrically normal individuals were retrospectively reviewed. Two radiologists independently evaluated the pattern of otosclerosis, otic capsule contour, and bone thickness on standardized axial images at the level of the oval window and cochleariform process. Measurements were made from the posterolateral margin of the cochlea to the apex of the otic capsule convex contour just anterolateral to the anterior margin of the oval window. In the absence of a convex contour, the sulcus between the oval window and the cochleariform process was identified, and measurement to the depth of the sulcus was used. Receiver operating characteristic analysis determined the best cutoff value of otic capsule thickness.

RESULTS

Mean otic capsule thickness (2 SDs) was 3.08 (0.93) mm and 1.82 (0.31) mm in patients with otosclerosis and individuals with normal hearing, respectively (P < .001), with excellent interobserver agreement. Otic capsule thickness of >2.3 mm had 96.2% sensitivity, 100% specificity, 100% positive predictive value, and 96.4% negative predictive value for otosclerosis. A bulging/convex contour of the otic capsule had 68.3% sensitivity, 98.1% specificity, 97.3% positive predictive value, and 76.3% negative predictive value.

CONCLUSIONS

Patients with otosclerosis have significantly thicker bone abutting the oval window than individuals with normal hearing.

[Techniques and progress in the imaging of the ear]

Ear and temporal bone imaging is essential for the diagnostic and preoperative management of middle ear lesions. The scanner is the exam of choice to analyze the walls and the contents of the middle ear. MRI is used to characterize the opacities of the middle ear and to evaluate possible neurological complications. Modern imaging techniques allow intraoperative guidance in otological surgery. Hearing implants are not always a contraindication to MRI but require precautions according to the type of implant.

Additive value of "otosclerosis-weighted" images for the CT diagnosis of fenestral otosclerosis

Background Otosclerotic foci are usually seen as minute low-density lesions and this may be attributed to relatively low sensitivity on visual assessment using computed tomography (CT). Otosclerotic foci can be detected by using the accurate region of interest (ROI) setting, while small ROI settings by less-experienced radiologists may result in false negative findings. Purpose To evaluate the diagnostic ability of our proposed method ("otosclerosis-weighted" imaging [OWI]), which is based on reversing the density, compared with conventional CT (CCT) imaging alone. Material and Methods Temporal bone CTs of consecutive patients with otosclerosis were analyzed. Gender- and age-matched control participants were also included. All CT images were obtained using a 64-detector row scanner. OWI was obtained by extracting the temporal bone region using the threshold technique and reversing the density (black to white). Four independent radiologists took part in two reading sessions. In the first session, the observers read only CCT imaging. In the second session, they read OWI along with the CCT imaging. Sensitivity was assessed for the four readers. Results Thirty temporal bones of 25 patients with otosclerosis (3 men, 22 women; mean age, 53.9 ± 9.0 years) and 30 temporal bones of 30 control participants (4 men, 26 women; mean age, 44.0 ± 16.2 years) were included. For all observers, reading with a combination of the two methods was associated with a higher sensitivity (63.3-80.0%) than with conventional CT images alone (30.0-60.0%; P < 0.05, each). Conclusion Application of our proposed method based on threshold value may help detect foci of fenestral otosclerosis.

A Systematic Review of the Diagnostic Value of CT Imaging in Diagnosing Otosclerosis

OBJECTIVE

To evaluate the diagnostic value of computed tomography (CT) in detecting otosclerosis in patients with conductive hearing loss and a clinical suspicion of otosclerosis.

DATA SOURCES

PubMed, Embase, and the Cochrane Library.

STUDY SELECTION

A systematic search was conducted. Studies reporting original study data were included.

DATA EXTRACTION

Relevance and risk of bias of the selected articles were assessed. Studies with low relevance, high risk of bias, or both were excluded. Prevalences, sensitivities, specificities, and post-test probabilities were extracted from the included articles.

DATA SYNTHESIS

Seven studies characterized by a moderate to high relevance and moderate to low risk of bias were included for data extraction. The prevalence of otosclerosis was high (up to 100%) in the majority of the included studies. In those studies with a high prevalence of disease, both positive and negative post-test probabilities were (relatively) high: 99% and between 51% and 67% respectively. In one study with a low prevalence of disease (9%), both positive and negative post-test probabilities were low (23% and 3% respectively). Overall, reported sensitivities ranged between 60% and 95%.

CONCLUSION

Preoperative CT has little to add in establishing otosclerosis and may not be necessary to confirm the diagnosis. We would recommend reserving CT for those patients with suspected additional abnormalities, for specific preoperative planning, or out of legal necessity.

[The potential of cone beam computed tomography of the temporal bones in the patients presenting with otosclerosis]

The objective of the present study was to analyze the potential of cone beam computed tomography of the temporal bones in the patients presenting with otosclerosis for the detection of surgically significant specific structural features of the labyrinth wall of the tympanic cavity. More than 400 tomograms of the temporal bones were obtained with the use of a cone beam tomographwere available for the investigation during the period from 2012 till 2016. The study was carried out in several steps, viz. the search for the optimal (for the given instrument) position of the patient, the experimental stage, the retrospective analysis of the tomograms and the comparison of the temporal bones of different types (pneumatic, mixed, and sclerotic) in individual patients, the comparison of the results of cone beam computed tomography (CBCT) with the intraoperative observations, and the modification of the algorithm for the analysis of temporal bone cone beam tomograms. The study included a total of 16 patients (15 women at the age from 32 to 56 years and one managed 58 years) presenting with the clinical diagnosis of otosclerosis. The results of the study were used to elaborate the algorithm for the analysis of cone beam tomograms of the temporal bones to be performed inthe stage by stage manner including the qualitative analysis of tomograms, evaluation of their quantitative parameters and additional characteristics to be taken into consideration when planning the surgical interventions on the labyrinth wall and the tympanic cavity as a preparation for the stapedoplastic treatment. The results of CBCT obtained in the present study were compared with the surgical observations. The diagnostic sensitivity and specificity of the method were estimated to be 100% and 83% respectively. It is concluded that cone beam computed tomography can be employed as a component of the diagnostic algorithm prior to the planning of surgical interventions onthe medial wall of the tympanic cavity and the assessment of dynamics of the clinical course of middle ear diseases.