0. Influence of Image Quality on Semi-Automatic 3D Reconstructions of the Lateral Skull Base for Cochlear Implantation
Frank Heckel1,2, Stephan Zidowitz1, Thomas Neumuth2, Mary Tittmann3, Markus Pirlich3, Mathias Hofer3
1 Fraunhofer Institute for Medical Image Computing MEVIS, Bremen, Germany
2 Innovation Center Computer Assisted Surgery, Leipzig, Germany
3 Leipzig University Hospital, Department of ENT-Surgery, Leipzig, Germany

1. Introduction Complex Ear Anatomy Ossicles Ossicels = Gehörknöchelchen
Semicircular canals = Bogengänge
Cochlea = Hörschnecke
Tympanic cavity = Paukenhöhle
Corda tympani = „Zugennerv“
Facial nerve
Corda tympani
Round window

2. Introduction
Real Situs

3. Introduction
Image Data and 3D Reconstruction

4. Is the quality of the CT images sufficient for surgery planning?
Introduction
Research Questions
Is the quality of the CT images sufficient for surgery planning?
Does bad image quality influence the quality of semi-automatic 3D reconstructions (accuracy and reproducibility)?

5. Material and Methods Study: Segmentation Quality*
CT data from 12 patients
Acquired at University Hospital Leipzig
Resolution: 0.19 x 0.19 x 0.19mm – x x 0.393mm
Reference segmentation for each structure in each image by an experienced ENT surgeon in cooperation with an experienced neuroradiologist
Each image was processed by 2-4 physicians
Segmentation quality was measured by Jaccard index
Average = measure for accuracy
Maximum difference = measure for reproducibility
We used only a subset of the data of the study by Prilich et al.
* Pirlich et al., European Archives of Oto-Rhino-Laryngology, 2016, available online 09/16

6. Material and Methods Wizard-Based Semi-Automatic 3D Reconstruction*
* Franz et al., BVM 2014

7. Material and Methods Study: Image Quality
Annotation of each image by an experienced ENT surgeon

8. Results
Image Quality

9. Results
Accuracy
Ossicels = Gehörknöchelchen
Semicircular canals = Bogengänge
Cochlea = Hörschnecke
Tympanic cavity = Paukenhöhle
Corda tympani = „Zugennerv“
AC = acoustic canal, OS = ossicles, TC = tympanic cavity, NF = facial nerve, NC = chorda tympani, RW = round window, CO = cochlea, vestibule, inner ear canal, SC = semicircular canal

10. Results Reproducibility
Ossicels = Gehörknöchelchen
Semicircular canals = Bogengänge
Cochlea = Hörschnecke
Tympanic cavity = Paukenhöhle
Corda tympani = „Zugennerv“
AC = acoustic canal, OS = ossicles, TC = tympanic cavity, NF = facial nerve, NC = chorda tympani, RW = round window, CO = cochlea, vestibule, inner ear canal, SC = semicircular canal

11. Conclusion Image quality is not always sufficient (resolution and SNR)
Even though the data has been acquired at a University Hospital
Suboptimal image quality seems to (negatively) influence reconstruction quality (accuracy and reproducibility) – at least for some structures
Limitations of the study:
Small number of CT images from only one site
Jaccard index as only indicator for reconstruction quality
Image quality has only been rated by one ENT surgeon
Low reproducibility of absolute grading studies

12. Thank You