Position of TORP on the Stapes Footplate Assessed With Cone Beam Computed Tomography

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.

Virtual Quality Control in Middle Ear Surgery: Is Image-guided Tympanoscopy a Valuable Tool for Depicting Borderline Situations?

HYPOTHESIS

Before modern imaging was introduced, revision surgery was the only way to evaluate possible reasons for inadequate improvement in hearing after ossicular replacement during reconstructive middle ear surgery.

BACKGROUND

The aim of this study was to evaluate freely navigable virtual tympanoscopy using different computed tomographic modalities. We compared cone-beam computed tomography (CBCT), flat panel computed tomography (FPCT), and conventional computed tomography in helical mode (CTH), volume mode (CTV), and ultra high resolution mode (CTD).

METHODS

Four temporal bone specimens were reconstructed with partial or total ossicular replacement prostheses. The best functional results for prosthetic coupling were achieved under the control of laser Doppler vibrometry (LDV). Afterward, a progressive step-by-step decoupling of the prostheses was carried out. Different prosthesis positions were evaluated by LDV as well as different computed tomographic modalities with 3D reconstruction of each dataset.

RESULTS

Anatomical structures were better depicted and the best position and coupling of inserted prostheses were achieved using CBCT. All imaging techniques could be used to control the position of middle ear prostheses, but CBCT provided the highest resolution and the best image quality in both 2D and 3D reformations and in 3D-animated video representation.

CONCLUSION

Compared with several other imaging modalities, CBCT was best at depicting miscellaneous coupling problems. Noninvasive detection of coupling problems caused by minimal loss of contact between prostheses and middle ear ossicles will influence the clinical outcome. This early detection will help to determine whether revision surgery is needed.

Volume-rendered computed tomography images of the surgical field for endolymphatic sac surgery

PURPOSE

Identification of the endolymphatic sac has failed occasionally. Postoperative complications have also rarely been reported. Given a safer and more reliable surgery, preoperative anatomical assessments are valuable, however, the vestibular aqueduct has seldom been seen with multi-planar reconstruction (MPR) computed tomography (CT) images yet. Our study aimed to determine the significance and utility of volume-rendered (VR) CT images of the surgical field for identifying the vestibular aqueduct, compared with MPR CT images.

SUBJECTS AND METHODS

14 patients with Meniere's disease who underwent endolymphatic sac surgery between 2008 and 2011. Location and size of the vestibular aqueduct were assessed using VR and MPR CT images, independently.

RESULTS

Accuracy of identifying the location differed significantly between VR and MPR CT images (rate of total correct evaluations: 100% by VR CT images vs 75% by MPR CT images, p = 0.02). Size was correctly identified in cases with a small endolymphatic sac using VR CT images (rate of total correct evaluations for size of the vestibular aqueduct: 100% by VR CT vs 57% by MPR CT, p = 0.046). VR CT images also demonstrated clearly the relationship between the endolymphatic sac and high jugular bulb. In two cases, the endolymphatic sac was identified by VR images, not by MPR images.

CONCLUSION

Accurate information about the location and size of vestibular aqueduct can allow sac surgeons to identify a tiny endolymphatic sac more easily and certainly, and also aids surgical trainees to learn sac surgery safely.

The benefit of trans-attic endoscopic control of ossicular prosthesis after cholesteatoma surgery

OBJECTIVE

To show the efficiency of using transmastoid atticotomy (TMA) endoscopy on the outcome of ossiculoplasty in patients with cholesteatoma. TMA is often performed as part of the surgical management of patients with middle ear cholesteatoma extending to the epitympanum. TMA can also be used as an access for endoscopic view to confirm the right alignment and stability of the ossicular prosthesis because the reconstruction of the tympanic membrane will obscure the visualization of the prosthesis.

METHODS

A retrospective study was done at a tertiary referral institute, including 133 ears with cholesteatoma that underwent canal wall-up tympanomastoidectomy (CWU) with ossicular reconstruction using titanium prosthesis between August 2013 and August 2015. Post packing of the ear canal and position, stability, and axis of the prosthesis were checked using endoscope positioned in the attic through TMA. A postoperative pure-tone average air-bone gap (ABG) of 20 dB or less was considered as a successful hearing result. Results are compared with historical control groups.

RESULTS

Of the 133 ears, 88 patients underwent reconstruction with partial ossicular replacement prosthesis (PORP), whereas the rest (45 patients) had total ossicular replacement prosthesis (TORP). A postoperative ABG ≤ 20 dB was obtained in 77.4% of all the patients (79.5% for PORP; 73.3% for TORP).

CONCLUSION

Endoscopic assessment of the ossicular prosthesis via the attic, after repositioning of the tympanomeatal flap and packing the ear canal, decreases the risk of immediate ossiculoplasty failure and improves the functional outcome after ossicular chain reconstruction in cholesteatoma surgery.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2754-2759, 2019.

The gray scale value of ear tissues undergoing volume-rendering high-resolution cone-beam computed tomography

OBJECTIVE

When the thresholds for VR reconstruction from multi-slice CT images are changed, problems develop when assessing pathologies in the absence of standardized thresholds. The advantages of CBCT include lower radiation exposure compared with other techniques and better visualization of small ear structures. However, a disadvantage is that the scanner provides unstandardized gray scale values, thus not CT numbers (Hounsfield units, HU).

METHODS

We analyzed 88 sets of volume data obtained from temporal bones. The gray scale values were measured in aerated areas (two sites), along the ossicular chain (four sites) and in a bone area (one site) in the external and middle ears, and in soft tissue areas (five sites) and bone areas (two sites) in the inner ear.

RESULTS

The standard male and female gray scale values were 2448-2970 and 2585-3091 for the aerated areas, 3248-4945 and 3359-5223 for the ossicular chains, 3368-4109 and 3371-4147 for soft tissues, and 4790-5776 and 5044-5959 for bone, respectively. Sex significantly affected the values (p<0.05). Significant differences between aerated areas and ossicular chains, and between soft tissues and bone, were evident (all p<0.0001).

CONCLUSION

Volume-rendering (VR) images obtained by cone-beam computed tomography (CBCT) can be standardized simply by using fixed thresholds.

Experimental Simulation of Clinical Borderline Situations in Temporal Bone Specimens After Ossiculoplasty

OBJECTIVES

One reason for insufficient hearing improvement with a distinct air-bone gap after ossiculoplasty with implantation of partial or total ossicular replacement prostheses can be the dislocation or minimal shifting of the prosthesis. The aim of this study was the simulation of common clinical borderline situations with minimal shifting of the prosthesis in temporal bone specimens after ossiculoplasty. It was furthermore the goal to identify these specific situations through imaging by cone beam computed tomography (cbCT) and direct visual inspection using the operation microscope. Additionally, the functional status was evaluated using laser-Doppler vibrometry (LDV).

DESIGN

We used a total of four temporal bone specimens for this study. A reconstruction with a partial ossicular replacement prostheses was performed in three specimens and with a total ossicular replacement prostheses in one specimen, with good initial acoustic properties. Subsequently, one specific type of prosthesis failure was simulated in each specimen, respectively, by minimally shifting, tilting, or bending the prostheses from their initial positions. These changes were introduced step-by-step until a borderline situation just short of complete acoustic decoupling was reached. Each step was examined using both LDV and cbCT and observed through the operation microscope.

RESULTS

LDV was able to quantify the mechanic function of the ossicular chain after most of the manipulation steps by demonstrating the effect of any shifting of the prosthesis on the middle ear transfer function. However, in some situations, the middle ear transfer function was better with a visually more advanced failure of the prosthesis. In addition, cbCT showed most of the steps with excellent resolution and was able to delineate changes in soft tissue (e.g., cartilage covering).

CONCLUSION

cbCT seems to be a promising imaging technique for middle ear problems. As cbCT and LDV exhibited slightly different advantages and disadvantages regarding the demonstration of borderline situations, the combination of both techniques allowed for a more precise evaluation of middle ear reconstructions. Knowledge of the specific characteristics of these methods and their possible combination might help otologists and otosurgeons to refine indications for revision surgery and improve their personal patient counseling.

The use of cone-beam computed tomography to determine cochlear implant electrode position in human temporal bones

OBJECTIVE

To assess the utility of cone-beam computed tomography (CBCT) imaging in the estimation of cochlear implant (CI) electrode position in implanted temporal bones.

STUDY DESIGN

Eight fresh frozen temporal bones were mounted and oriented as for standard surgery and were implanted with Cochlear Slim-Straight (SS) or Contour Advance electrode arrays by 2 CI surgeons. The bones were then imaged using an Accuitomo F170 CBCT scanner (isometric 250 μm voxel size) and were then processed for histologic sectioning (500 μm sections).

MAIN OUTCOME MEASURES

The CBCT images and the histologic micrographs (providing the "gold standard") were examined independently by several observers who assessed the scalar position (tympani or vestibuli) of each electrode in each temporal bone specimen.

RESULTS

Examination of the histologic micrographs confirmed that all electrodes were positioned within the scala tympani in all 8 bones. Similar judgments were made by the observers rating the CBCT images, except that one of the 2 observers estimated some of the apical electrodes to be located in the scala vestibuli in two of the bones implanted with the SS electrode.

CONCLUSION

Cone-beam CT imaging is able to provide a good indication of the scalar position of implanted electrodes, although estimation may be slightly less reliable for apical electrodes and for straight electrode designs. Additional advantages of using CBCT for this purpose are shorter acquisition time and reduction of radiation dose as compared with conventional CT.

Prediction of the attachment site of sinonasal inverted papillomas by preoperative imaging

OBJECTIVE

Accurate preoperative identification of the attachment site is the key to the successful surgical management of sinonasal inverted papillomas (IPs). This study investigated the value of preoperative imaging to identify the attachment sites of IPs.

METHODS

We analyzed I 0 consecutive patients with pathologically proven IPs. Two radiologists predicted the attachment sites of IPs from computed tomography (CT), 3.0 Tesla magnetic resonance imaging (3.0T MRI), 1.5T MRI, and CT plus 3.0T MRI. The actual tumor attachment sites were confirmed via pathological examination of specimens and compared with the predicted sites.

RESULTS

Computed tomography showed the highest sensitivity (P < .0001), although both MRI formats showed greater specificity (P < .0001). The sensitivity of MRI plus CT was equal to that of CT and better than that of MRI (P < .0001), whereas its specificity was better than that of CT (P < .0001) and comparable to that of MRI. Prediction using 3.0T MRI appeared slightly superior to that using 1.5T MRI in terms of sensitivity and specificity, although the differences were not significant.

CONCLUSION

Computed tomography and MRI had different features for prediction of sinonasal IP attachment sites. Preoperative CT plus MRI provided more useful information than CT or MRI alone.

Air-bone gap in ears with a well-repaired tympanic membrane after Type III and Type IV tympanoplasty

OBJECTIVE

To investigate the air-bone conduction hearing gap (A-B gap) after Type III and Type IV stapes columella tympanoplasty in ears with mobile stapes and a well repaired tympanic membrane (TM).

METHODS

Those patients who underwent tympanoplasty in our hospital between 2003 and 2009 and satisfied the following criteria were eligible: (1) good stapes mobility, confirmed intraoperatively; (2) postoperative TM and/or computed tomography (CT) findings that showed a well-aerated tympanic cavity without TM perforation, otorrhea, or middle ear effusion; and (3) measurable air and bone conduction hearing thresholds 1 year postoperatively at all test frequencies (250 Hz, 500 Hz, 1 kHz, 2 kHz, and 4 kHz).

RESULTS

Hearing results were better after Type III tympanoplasty than after Type IV tympanoplasty. After Type III (n=70) and Type IV (n=24) tympanoplasty, the respective mean A-B gaps were 16.4 ± 7.2 dB and 20.1 ± 5.6 dB, respectively. The mean A-B gap was significantly smaller after Type III tympanoplasty than after Type IV tympanoplasty (p<0.05). Regardless of the type of tympanoplasty, the postoperative A-B gap was greatest at 4 kHz.

CONCLUSION

The mean A-B gap was smaller after Type III tympanoplasty than after Type IV tympanoplasty. The magnitude of the A-B gap was greatest at 4 kHz in both procedures.