Synergistic EEG and machine learning enhanced low-dose PET for objective diagnostics of speech comprehension in cochlear implant users

• Applicants: Professor Dr. Georg Berding; Professor Dr. Andreas Büchner; Privatdozent Dr. Florian Büther; Professor Dr. Jörg Lücke; Professorin Dr. Pascale Sandmann
• Subject Area: Biomedical Systems Technology ; Otolaryngology, Phoniatrics and Audiology ; Medical Physics, Biomedical Technology ; Nuclear Medicine, Radiotherapy, Radiobiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 471410050

The proposed funding will be used to achieve fundamental methodological improvements in functional studies of the auditory system with PET/EEG (positron emission tomography / electroencephalography) and explanations for variable speech understanding performance after cochlear implantation. To improve O-15 water PET activation studies of the auditory system, the minimum amount of radioactivity that can be used without compromising diagnostic performance will be determined. For this purpose, a program will be used which generates data sets with reduced number of coincidences based on measured PET studies - simulating studies with lower amounts of radioactivity. The high sensitivity of modern PET devices suggests that studies with significantly lower amounts of activity than has been usual so far are possible. In addition, the low-count studies will be denoised at the sinogram level using machine learning techniques. This will involve statistical modeling of the data without extensive well-controlled data for training (evidence lower bound as learning objective, ELBO) and will be combined with deep neural networks (DNN). The PET data (with/without reduction or denoising) will be analyzed using statistical parametric mapping (SPM) and the results compared. Furthermore, for validation purposes, data with and without reduction or denoising will be generated based on a simulated brain phantom (XCAT) and the respective results will be compared. In addition to providing evidence for a significantly reducible radiation exposure, the planned study will demonstrate the reliable imageability of the central auditory pathway in the brainstem/thalamus with modern high-resolution PET devices. For automated anatomical delineation, a volume of interest (VOI) template of auditory regions in brainstem and thalamus (e.g. inferior colliculus) will be generated based on histomorphometric and MRI data. The multimodal approach will objectively measure central processing of speech with high spatial (PET) and temporal resolution (EEG). Specifically, late auditory evoked potentials (N400) will be measured under stimulation with a sentence discrimination task and spatially assigned in the context of regions activated during speech processing (in PET). This should allow a better understanding of the resource allocation and strategies of speech processing in CI users with different speech comprehension performance. As a major factor in the speech comprehension of CI users, the influence of background noise on speech intelligibility and cortical activation during speech processing will be investigated. Through all this, objective procedures for the evaluation and optimization of auditory rehabilitation after cochlear implantation will be developed. Evidence of the reducibility of radiation exposure should encourage the use of PET in other settings.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Thomas Lenarz; Professor Dr. Tobias Ludwig Ross