Multidetector row CT demonstration of inner and middle ear structures

Radiological requirements for surgical planning in cochlear implant candidates

Objective:

This study is concerned with clarification of radiological findings that should be addressed and reported in patients listed for cochlear implant (CI) operation. These findings may force a surgeon to consider modifications of the surgical approach by a CI surgeon.

Materials and Methods:

The study was performed from January 2015 to January 2016. It included 50 patients with severe-to-profound sensorineural hearing loss who fulfilled the criteria for CI. Patients underwent CI surgery in the Department of Otolaryngology. All patients underwent preoperative computed tomography (CT) and magnetic resonance imaging (MRI) assessment in the Department of Diagnostic Radiology. Combined examination of the CT and MRI by the radiologist and the surgeon was advocated.

Results:

Many anatomical variants were observed regarding the pattern of mastoid pneumatization, position of middle cranial fossa dura, sigmoid sinus position jugular bulb position, and the size and position of the mastoid segment of facial nerve canal. Labyrinthitis ossificans was seen in 3 patients (6%), otospongiosis in 1 patient (2%), and dilated vestibular aqueduct and endolymphatic sac in 9 patients (18%).

Conclusion:

Cochlear implantation is a major treatment modality in patients with severe-to-profound sensorineural hearing loss. Radiological evaluation is integral in surgery planning.

Accuracy of individualized 3D modeling of ossicles using high-resolution computed tomography imaging data

Background

The present study aimed to investigate the visibility of small ossicle parts/landmarks on high-resolution computed tomography (HRCT)/3D reconstruction (3D) to investigate what improvements in scanning resolution are needed before accurate 3D printing of patient-specific ossicles is possible.

Methods

A total of 24 patients with sudden deafness sought consultation at the Department of Otorhinolaryngology Head and Neck Surgery at the Sixth Medical Center of People's Liberation Army General Hospital between October 2013 and June 2014 were enrolled in the study. All participants underwent a 256-slice spiral HRCT temporal bone axial scan, yielding a Digital Imaging and Communications in Medicine documents series. These documents were then inputted into Mimics 16.0 interactive medical image processing software for data conversion and the creation of 3D segmentation and visualizations of the ossicles. Finally, the 3D images were compared using multiplanar reformation (MPR) and 3D volume-rendering (VR) reconstructed images of ossicles to verify their consistency. These were then compared with the normal ossicle structure to evaluate the accuracy of the restoration.

Results

The findings indicated that the morphology of the ossicles from the converted Mimics 16.0 data achieved a display rate of ≥90% when used to display 7 landmarks (the caput mallei, collum mallei, processus lateralis mallei, manubrium mallei, corpus incudis, crus longum incudis, and crus breve incudis). This demonstrates excellent matching with the images of ossicles obtained from MPR and 3D VR reconstruction. Kappa consistency testing found that the κ-value was higher than 0.75. When displaying the lenticular process, caput stapedis, crus anterius stapedis, and crus posterius stapedis landmarks. The display rate was around 60%, which shows good matching with the ossicles' images obtained from MPR and 3D VR reconstruction, with a κ-value >0.4. However, the display rate of the stapes footplate was only 25%, showing greater differences with the images obtained from MPR (76.4%) and 3D VR reconstruction (52.8%), with a κ-value <0.4.

Conclusions

The accuracy of the visualization of the malleus and incus after restoration via Mimics 16.0 software, based on temporal bone HRCT data, was high, and the degree of restoration was good. However, the accuracy and degree of restoration of the stapes footplate require further improvement.

Improved image quality of temporal bone CT with an ultrahigh-resolution CT scanner: clinical pilot studies

Purpose

Ultrahigh-resolution CT (UHRCT) with slice collimation of 0.25 mm × 160 and matrix size of 1024 × 1024 has become clinically available. We compared the image quality of temporal bone CT (TBCT) between UHRCT and conventional multidetector CT (MDCT).

Materials and methods

We retrospectively enrolled 20 patients who underwent TBCT by MDCT (matrix size, 512 × 512) and subsequently by UHRCT (matrix size, 1024 × 1024). Two independent reviewers subjectively graded delineation of normal stapes, oval window, facial nerve canal, incudostapedial joint, and tympanic tegmen. We also quantified image noise in the cerebellar hemisphere. Between MDCT and UHRCT, we compared mean subjective grades using the Wilcoxon signed-rank test and the image noise using paired t test.

Results

Grades were significantly higher with UHRCT than with MDCT for all the anatomies (P < 0.001), whereas noise was significantly higher with UHRCT than with MDCT (P = 0.002).

Conclusion

For TBCT, UHRCT shows better delineation of the fine anatomical structures compared with MDCT.

High resolution multi detector computed tomography of temporal bone: our experience in a tertiary care service hospital

High resolution multi detector computed tomography (HRMDCT) is an excellent tool for evaluation of a variety of congenital and acquired conditions affecting the temporal bones. We describe our experience of HRMDCT of temporal bones of 145 patients in a tertiary care and teaching hospital of Armed Forces Medical Services of India over a period of three and half years. Hearing loss was the most frequent indication for HRMDCT and congenital bilateral profound sensorineural hearing loss for evaluation prior to possible cochlear implant formed the single largest group (62, 42%) among all indications for HRMDCT of temporal bones. Major vestibule-cochlear and semicircular canal anomalies were noted in 11 such cases. Seven patients of microtia were studied and all had positive CT scan findings. All patients of vertigo had normal HRCT study. Extent of temporal bone injuries and inflammatory conditions were clearly delineated in all cases. Thinner collimations allowing image reconstructions in planes of anatomical interest with near isotropic resolution has been a major advantage of HRMDCT of temporal bones.

Comparison of 128-section single-shot technique with conventional spiral multisection CT for imaging of the temporal bone

BACKGROUND AND PURPOSE

Computed tomography is an essential modality for imaging of the temporal bone. Newest generation scanners allow the coverage of large examination volumes with a single gantry rotation. The objective of this study was to compare a 128-section SST (1 single rotation of the x-ray tube) with conventional spiral MSCT (ultra-high-resolution mode) for imaging of the temporal bone.

MATERIALS AND METHODS

Fifty-four temporal bones in 27 patients were scanned with both a conventional MSCT and 128-section SST. After blinding and randomization of both examinations, 2 observers assessed the visualization of 38 anatomic structures (eg, various segments of the facial nerve canal, mallear ligaments) by using multiplanar reconstructions in the axial and coronal planes. The differences in evaluation scores obtained for the 2 techniques were analyzed by using a Wilcoxon signed rank test, with a P value of < .05 considered significant. For both methods, imaging time and radiation exposure were noted.

RESULTS

Overall visualization of anatomic structures did not differ significantly between the 2 techniques (P > .05). When we compared the anatomic structures separately, there was better visualization of the lateral mallear ligament with MSCT, whereas the cochlear septa were ranked higher with SST (P < .05). Imaging time and average DLP for MSCT were 12.3 seconds and 306 mGy cm, respectively; for SST, values they were 1 second and 64 mGy cm, respectively (ie, a dose reduction of 79%).

CONCLUSIONS

For imaging of the temporal bone with adequate diagnostic quality, 128-section SST can be used. The main advantages over MSCT are the dramatic reductions of imaging time and radiation exposure, which are particularly important when scanning uncooperative patients or children.

Optical coherence tomography of the oval window niche

OBJECTIVE

Optical coherence tomography was used to study the stapes footplate, both in cadaveric temporal bones and during middle-ear surgery.

MATERIALS AND METHODS

Optical coherence tomography was conducted on five temporal bone preparations (from two children and three adults) and in eight patients during middle-ear surgery. A specially equipped operating microscope with integrated spectral domain optical coherence tomography apparatus was used for standard middle-ear surgical procedures.

RESULTS

This optical coherence tomography investigation enabled in vivo visualisation and documentation of the annular ligament, the different layers of the footplate and the inner-ear structures, both in non-fixed and fixed stapes footplates. In cases of otosclerosis and tympanosclerosis, an inhomogeneous and irregularly thickened footplate was found, in contrast to the appearance of non-fixed footplates. In both fixed and non-fixed footplates, there was a lack of visualisation of the border between the footplate and the otic capsule.

CONCLUSIONS

Investigation of the relatively new technology of optical coherence tomography indicated that this imaging modality may assist the ear surgeon to assess the oval window niche intra-operatively.

Role of 3D CT in the Evaluation of the Temporal Bone

In recent years, three-dimensional (3D) multiplanar reformatted images from conventional cross-sectional computed tomographic (CT) data have been increasingly used to better demonstrate the anatomy and pathologic conditions of various organ systems. Three-dimensional volume-rendered (VR) CT images can aid in understanding the temporal bone, a region of complex anatomy containing multiple small structures within a relatively compact area, which makes evaluation of this region difficult. These images can be rotated in space and dissected in any plane, allowing assessment of the morphologic features of individual structures, including the small ossicles of the middle ear and the intricate components of the inner ear. The use of submillimeter two-dimensional reconstruction from CT data in addition to 3D reformation allows depiction of microanatomic structures such as the osseous spiral lamina and hamulus. Furthermore, 3D VR CT images can be used to evaluate various conditions of the temporal bone, including congenital malformations, vascular anomalies, inflammatory or neoplastic conditions, and trauma. The additional information provided by 3D reformatted images allows a better understanding of temporal bone anatomy and improves the ability to evaluate related disease, thereby helping to optimize surgical planning.