Ulrich Ecke, MDKopfklinik Frankfurt GmbH, GermanyEmail: dr.ecke@hno -doktor.dePhone: 0049/69/50775817Website: www.kopfklinik-frankfurt.de

Volume Computed Tomography (VT) Prior Temporal Bone Procedures

Objectives:

Learn that the MiniCATTM (Xoran Tech.) is a flat panel system using scan protocols optimized for sinus and temporal bone imaging. These protocols were designed to reduce radiation dosage, while still maintaining the highest level of image quality possible. Be able to evaluate the vulnerable toloplogy of the middle ear and temporal bone (e.g. facial nerve) prior surgical approach.

Methods:

Retrospective review of 25 patients, who underwent VT the middle ear and temporal bone prior surgical interventions. VT has been performed over a 12-month period using MiniCATTM (Xoran Tech.). Preoperative, computer-enabled triplanar review of reformatted 0.4-mm images was performed in all cases.

Results:

Specific parameters to be assessed, included the evaluation of overall image quality, possible image artifacts, and ability to identify the course of the facial nerve within the tympanic and mastoid segment. Reliable correlation have been made to intraoperative findings during surgery while approaching vulnerable structures within the temporal bone (e.g. posterior wall of the tympanum).

Conclusion:

Volume computed tomography prior temporal bone procedures may have an important role in preoperative evaluation of vulnerable topography of the middle ear and the temporal bone, e.g. facial nerve, ossicles, semicircular canals and bony limitations of the lateral skull base.

Volume Computed Tomography Prior Temporal Bone ProceduresUlrich Ecke, MD; Josef Lindenberger, PhD, MD; Juergen Wilhelm, MD,

Kopfklinik Frankfurt GmbH; Frankfurt am Main, Germany

Retrospective study

(May 2008 – September 2009); 25 patients:12 males, 13 females; max. 68 years of age, min. 21 years of age, mean 42,5 years of age.

Cone-beam CT scanner MiniCAT TM (Xoran Tech.) :

Flat panel based Volume CTLimited footprint: 1.17 x 1.19 x 1.83 mFollows ALARA principleMains voltage 220-240 VVoxel Size 0.2 mm minimumWorkstation: Intel-based PCCompability: DICOM 3.0

Point-of-care imaging of the temporal bones. Specifically designed for imaging tasks that are critically dependent on spatial resolution.Compact size, timesaving by only one rotation required.

Effective dose estimates:

The effective dose of the temporal bone set is decreased to standard dosimetry on a multi -slice unit. This value is representing approx. 25% of the standard dosage

Versatile images of temporal bones for digital manipulation withcurved real-time multi-planar reconstructions. VT is a new technology that offers high-quality low-radiation

imaging of the temporal bone.

VT prior temporal bone procedures may have an important role in preoperative evaluation of vulnerable topography of the middle ear and the temporal bone, e.g. facial nerve, ossicles, semicircular canals and bony limitations of the lateral skull base.

The introduction of volume computed tomography (VT) has open up new opportunities in management of disease of the middle ear and the temporal bone1.

The availability of a limited footprint in-office VT scanner (Fig.1) provides out patient imaging with reduced waiting time and improved patient satisfaction. MiniCAT TM (Xoran Tech.) has demonstrated the advantages of VT in evaluating the complex anatomical structures of the paranasal sinuses as well as the anterior skull base2.

Furthermore, its application for evaluation of the vulnerable topology of the middle ear and petrous bone opens up additional opportunities for significant patient care and patient satisfaction benefit.

The contribution of VT for a detailed and accurate information in assessing the various anatomical structures of the middle ear and the temporal bone (e.g. facial nerve) is worthwhile to be investigated.

INTRODUCTION METHODS AND MATERIALS

1. CT Scan Severity Correlates with Improvement in Quality of Life Outcome after Endoscopic Sinus Surgery in Patients with Chronic Rhinosinusitisand Asthma, Poster at 2008 ARS Annual Meeting by Patricia Maeso et al, Augusta, GA.

2. Comparison of Cone Beam CT for Paranasal Sinus Imaging, Poster at the 2008 ARS Annual Meeting by Boris Karanfilov et al, Dublin.OH

3. Multi-slice spiral computed tomography of the skull base. B a um U, Tomandl B, Lell M et al (2001) In: Marincek et al Multislice CT: a practical guide. Springer, pp 65-75.

CONCLUSIONS

RESULTS

REFERENCES

Figure 2. Recurrent cholesteatoma (right), Sample of axial, coronal and sagittal slices are displayed at once; a 3D-picture allows a more spatially understanding of the individual anatomical situation.

Figure 1. Flat panel volume tomograph MiniCAT TM Xoran Tech.

ABSTRACT

CONTACT

Specific parameters to be assessed included the effective dose estimates, evaluation of overall image quality, possible image artifacts and the ability to identify the vulnerable topology (landmarks) of the middle ear and temporal bone.

Effective dose estimates: Imaging protocol effective dose estimates for temporal bone 0.13 mSv. Comparison to other modalities: skull X-ray 0.07 mSv, chest X-ray.

Overall image quality:High-quality images provide significant information about small anatomic structures (Fig. 2,3), critical to assessing morphology (Fig. 4 and 5) and pathological processes (Fig.6 and 7).

Possibillity of image artifacts:Head movement leads to pictures out of focus. No artefacts by metal bodies (e.g. ossicle prothesis) (Fig. 8 and 9)

Identification of anatomical landmarks:VT is sensitive and accurate in assessing bony landmarks within the middle ear and temporal bone but less specific in distinction between neoplasm and retrotympanic inspissated secretions, mucosal disease and inflammation.

Figure 3. Recurrent cholesteatoma (right),. Course of the facial nerve visible by using oblique tool technique.

Figure 7. Chronic mastoiditis of the left temporal one. Sample of axial, coronal and saggital slices are displayed at once; a 3D-picture allows a more spatially understanding of the individual anatomical situation.

Figure 8. Displaced ceramic ossicle (right).

Figure 4. Soft tissue tumor of the right outer ear canal. Sample of axial, coronal and saggital slices are displayed at once; a 3D-picture allows a more spatially under-standing of the individual anatomical situation.

Figure 5. Soft tissue tumor of the right outer ear canal .Sample of an axial view.

Computed tomography (CT) and magnetic resonance (MR) imaging play complimentary roles in the assessment of temporal bone pathology. Computed tomography is more sensitive and accurate in assessing the osseous parts of the petrous bone whereas MR allows accurate distinction between neoplasm and inspissated secretions, vascular malformation and inflammation3.

Figure 6. Chronic Mastoiditis (right), Sample of an axial view.

Figure 9. Displaced ceramic ossicle prothesis (right). Position of the prothesis visible by oblique tool technique.Sample of an axial view.