Objective: We are presenting follow-up results on our previous study for 3D volumetric measurements of SN hyper-echogenicities, to differentiate PD patients from healthy controls (HC). Additionally, and for the first time, we show detailed information about the 3D positional distribution of hyper-echogenicities via co-localization with MRI.

Background: Transcranial sonography (TCS) has become an additional tool to diagnose movement disorders like Parkinson`s disease (PD). In PD patients, hyper-echogenicities have been detected at the area of the substantia nigra (SN). So far, 2D measurements of these 3D structures are used for diagnosis.

Methods: 3D-TCS as well as MRI was performed for 20 PD patients and 24 healthy controls (HC). 3D datasets were segmented manually, concerning ipsi-lateral hyper-echogenicities and the midbrain. Extracted features for differentiation were i) the maximum 2D area (“2.5D”), and ii) the 3D volume of all slices of 5.5mm length along the 3D axial direction. TCS and MRI were aligned semi-automatically in 3D, via an image-based registration algorithm and comparison of voxel grey-level intensities. Additionally, a novel group-MRI-atlas was generated for our cohort. It was then possible to fuse all individual 3D-TCS scans into a volumetric TCS-atlas for the first time. The fusion was based on a concatenation of the multi-modal transformations of TCS-to-MRI and MRI-to-atlas.

Results: A cut-off was detected for the bi-lateral 2.5D and the 3D features in order to classify between PD and HC via a ROC-analysis.  Our results were able to achieve a sensitivity of 85.7% and a specifity of 88%. All TCS volumes could be registered into the multi modal group atlas. First group-based volumetric localization results regarding the TCS hyper-echogenicities were gained.

Conclusions: Our results demonstrate a good classification of HC versus PD patients with the help of the 2.5D as well as the 3D features. Our aim is to generate a fully automated segmentation, which could help in clinical practice.

Interestingly, hyper-echogenicities in PD patients are located in the area of the Nucleus parabrachialis pigmentosus cranially. Caudally, they are rather located in the pars compacta of the SN. Especially hyper-echogenicities in the area of the nigrosome seem to underline a certain importance of those structures in the degeneration process in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/volume-analysis-and-localization-of-midbrain-hyperechogenecities-via-tcs-and-mri/