Evaluation of the internal auditory canal with virtual endoscopy

Detection of hypoplasia of bony cochlear nerve canal by the opening threshold of virtual endoscopy: a pilot study

BACKGROUND

Dimensions of the bony cochlear nerve canal (BCNC) have been proposed as a potential diagnostic standard for BCNC hypoplasia, but the standard remains inconsistent. Some studies have revealed that computed tomography virtual endoscopy (CTVE) with variation of reconstruction threshold is good at identifying labyrinthine fistulas or semi-circular canal dehiscence.

PURPOSE

To examine diagnostic accuracy of VE in the evaluation of BCNC hypoplasia on basis of opening threshold.

MATERIAL AND METHODS

Twenty ears diagnosed with BCNC hypoplasia were included in this study. One hundred ears served as controls. The opening thresholds were measured by two reviewers. Intraclass correlation coefficients (ICC) were reported. The width of BCNC was obtained on transverse CT images. Association between the width of BCNC and opening threshold was assessed by using Spearman correlation coefficients. ROC curves were applied to assess the best cut-off value of opening threshold.

RESULTS

The opening threshold of BCNC was significantly higher in diseased ears (926 ± 308 Hounsfield units [HU]) than that in control ears (287 ± 72 HU). Inter-observer agreement was very good. The mean width of BCNC for diseased ears and control ears were 0.83 ± 0.36 mm and 2.21 ± 0.35 mm, respectively. Significant negative linear correlation was found between opening thresholds and width of BCNC (Spearman coefficient, -0.768; P < 0.001). The area under the ROC curve was 0.981. The cut-off opening thresholds of 408 for differentiation between the two groups provided the best combination of sensitivity (85%) and specificity (94%).

CONCLUSION

The VE with opening threshold may be an effective optional tool for prediction of hypoplasia of BCNC.

Detection of hypoplasia of bony cochlear nerve canal by virtual endoscopy: a pilot study

BACKGROUND

Dimensions of the bony cochlear nerve canal (BCNC) have been proposed as a potential diagnostic standard for hypoplasia of BCNC, but the standard remains inconsistent. We have previously found that a helix-like shape appears in normal BCNCs at VE images, whereas, the sign does not appear in some hypoplastic BCNCs.

PURPOSE

To retrospectively examine the feasibility of computed tomographic (CT) virtual endoscopy (VE) in the evaluation of hypoplasia of BCNC on the basis of absence of a helix-like shape.

MATERIAL AND METHODS

Twenty ears in 14 consecutive patients (mean age 5.5 years, range 1-15 years, 6 boys, 8 girls) diagnosed with hypoplasia of BCNC were included in this work. One hundred ears in 50 gender- and age-matched individuals (mean age 6.6 years, range 1-15 years, 29 boys, 21 girls) without inner ear disease and internal auditory canal (IAC) malformations served as controls. The presence or absence of a helix-like shape was evaluated by two independent reviewers. The value of VE for the diagnosis of hypoplasia of BCNC was assessed with clinical results and routine radiologic evaluation as the reference standard. Inter-observer agreement was calculated. Sensitivity, specificity, and accuracy were selected to test the diagnostic ability of the VE.

RESULTS

Absence of a helix-like shape was found in the cochlear area of 17 of 20 ears in patients with hypoplasia of BCNC but in none of the control subjects. Inter-observer agreement was substantial (к = 0.773). The diagnostic rates of absence of a helix-like shape for hypoplasia of BCNC in terms of sensitivity, specificity, and accuracy were 85%, 100%, and 98%, respectively. There were significant differences between the two groups with respect to VE findings for absence of a helix-like shape (P < 0.001).

CONCLUSION

The absence of a helix-like shape at VE images may be used as a potentially useful sign in the diagnosis of hypoplasia of BCNC.

Reconstruction and exploration of virtual middle-ear models derived from micro-CT datasets

BACKGROUND

Middle-ear anatomy is integrally linked to both its normal function and its response to disease processes. Micro-CT imaging provides an opportunity to capture high-resolution anatomical data in a relatively quick and non-destructive manner. However, to optimally extract functionally relevant details, an intuitive means of reconstructing and interacting with these data is needed.

MATERIALS AND METHODS

A micro-CT scanner was used to obtain high-resolution scans of freshly explanted human temporal bones. An advanced volume renderer was adapted to enable real-time reconstruction, display, and manipulation of these volumetric datasets. A custom-designed user interface provided for semi-automated threshold segmentation. A 6-degrees-of-freedom navigation device was designed and fabricated to enable exploration of the 3D space in a manner intuitive to those comfortable with the use of a surgical microscope. Standard haptic devices were also incorporated to assist in navigation and exploration.

RESULTS

Our visualization workstation could be adapted to allow for the effective exploration of middle-ear micro-CT datasets. Functionally significant anatomical details could be recognized and objective data could be extracted.

CONCLUSIONS

We have developed an intuitive, rapid, and effective means of exploring otological micro-CT datasets. This system may provide a foundation for additional work based on middle-ear anatomical data.

Detection of superior semicircular canal dehiscence by virtual endoscopy: a pilot study

OBJECTIVE

To examine the threshold of virtual endoscopy in the confirmation of superior semicircular canal dehiscence (SSCD).

STUDY DESIGN

Retrospective case series.

SUBJECTS

Three definite SSCD subjects, two possible SSCD subjects, and five control subjects.

METHODS

High-resolution temporal bone computed tomography and virtual endoscopy were performed in all subjects. Main outcome measures were to evaluate both intrajudge and interjudge reliability and to compare the closed threshold of diseased side with the contralateral side, both ears of patients with those of the control group.

RESULTS

The interjudge reliability between two observers was 0.934 and 0.926 (P < 0.001). The intrajudge reliability for two reviews were 0.916 and 0.902 (P < 0.001). The affected ear thresholds significantly differed from those of both unaffected ears and normal controls (P < 0.001 for both comparisons). Thresholds of unaffected ears and normal controls did not differ (P > 0.05).

CONCLUSION

Virtual endoscopy with critical evaluation of the consistent closed threshold provides an additional role in SSCD diagnosis.

Management of obstructing pulmonary broncholithiasis with three-dimensional imaging and holmium laser lithotripsy

Major airway obstruction due to broncholithiasis produces significant morbidity, and management is difficult. Many of the patients are elderly and are not good candidates for surgical removal. Bronchoscopic removal may be limited due to anatomic considerations, skill of the bronchoscopist, and exposure of the patient to additional procedural risks. Preprocedural planning with three-dimensional (3D) multidetector CT (MDCT) imaging enhances the bronchoscopist's knowledge of the relationships of the target lesions with critical structures, and improves the efficiency of the application of specific endobronchial therapies. Here we report our experience treating obstructing broncholithiasis in two patients utilizing pretreatment planning with 3D MDCT imaging, followed by bronchoscopically delivered holmium laser fragmentation of the stones.