2023-02, Vergne, Céline, Féry, Corentin, Quirin, Thomas, Nicolas, Hugo, Madec, Morgan, Hemm-Ode, Simone, Pascal, Joris

2021-11, Park, Sung Hea, Altermatt, Sven, Widmer Beierlein, Sandra, Blechschmidt, Anja, Reymond, Claire, Degen, Markus, Rickert, Eliane, Wyss, Sandra, Kuntner, Katrin Petra, Hemm-Ode, Simone

2020-07-06, Mozaffarzadeh, Moein, Minonzio, Claudio, de Jong, Nico, Verweij, Martin, Hemm-Ode, Simone, Daeichin, Verya

Phase aberration in transcranial ultrasound imaging (TUI) caused by the human skull leads to an inaccurate image reconstruction. In this article, we present a novel method for estimating the speed of sound and an adaptive beamforming technique for phase aberration correction in a flat polyvinylchloride (PVC) slab as a model for the human skull. First, the speed of sound of the PVC slab is found by extracting the overlapping quasi-longitudinal wave velocities of symmetrical Lamb waves in the frequency-wavenumber domain. Then, the thickness of the plate is determined by the echoes from its front and back side. Next, an adaptive beamforming method is developed, utilizing the measured sound speed map of the imaging medium. Finally, to minimize reverberation artifacts caused by strong scatterers (i.e., needles), a dual probe setup is proposed. In this setup, we image the medium from two opposite directions, and the final image can be the minimum intensity projection of the inherently co-registered images of the opposed probes. Our results confirm that the Lamb wave method estimates the longitudinal speed of the slab with an error of 3.5% and is independent of its shear wave speed. Benefiting from the acquired sound speed map, our adaptive beamformer reduces (in real time) a mislocation error of 3.1, caused by an 8 mm slab, to 0.1 mm. Finally, the dual probe configuration shows 7 dB improvement in removing reverberation artifacts of the needle, at the cost of only 2.4-dB contrast loss. The proposed image formation method can be used, e.g., to monitor deep brain stimulation procedures and localization of the electrode(s) deep inside the brain from two temporal bones on the sides of the human skull.

2019-05-07, Hemm-Ode, Simone, Degen, Markus, Shah, Ashesh, Parrillo, Fabrizio, Karlin, Stefan, Altermatt, Sven, Blechschmidt, Anja, Bucheli, Sandra, Kuntner, Katrin Petra, Widmer Beierlein, Sandra, Reymond, Claire, Müller, Christine, Grumbinaite, Indre

2023, Vergne, Céline, Morgan, Madec, Guzmann, Raphael, Pascal, Joris, Hemm-Ode, Simone

2021-02, Mozaffarzadeh, Moein, Minonzio, Claudio, De jong, Nico, Verweij, Martin, Hemm-Ode, Simone, Renaud, Guillaume, Daeichin, Verya

In the above article [1] , we mentioned that the superposition of the different symmetric (S) modes in the frequency wavenumber (f-k) domain results in a high-intensity region where its slope corresponds to the longitudinal wave speed in the slab. However, we have recently understood that this high intensity region belongs to the propagation of a wave called lateral wave or head wave [2] – [5] . It is generated if the longitudinal sound speed of the aberrator (i.e., the PVC slab) is larger than that of water and if the incident wavefront is curved. When the incidence angle at the interface between water and PVC is near the critical angle, the refracted wave in PVC reradiates a small part of its energy into the fluid (i.e., the head wave). As discussed in [4] , if the thickness of the waveguide is larger than the wavelength, the first arriving signal is the head wave. This is also the case in our study [1] where the ultrasound wavelength of a compressional wave in PVC was close to 1 mm, and a PVC slab with a thickness of 8 mm was used.

2020-04-25, Vogel, Dorian, Shah, Ashesh, Hemm-Ode, Simone

Deep brain stimulation (DBS) therapy requires extensive patient-specific planning prior to implantation to achieve optimal clinical outcomes. Collective analysis of patient’s brain images is promising in order to provide more systematic planning assistance. In this paper the design of a normalization pipeline using a group specific multi-modality iterative template creation process is presented. The focus was to compare the performance of a selection of freely available registration tools and select the best combination. The workflow was applied on 19 DBS patients with T1 and WAIR modality images available. Non-linear registrations were computed with ANTS, FNIRT and DRAMMS, using several settings from the literature. Registration accuracy was measured using single-expert labels of thalamic and subthalamic structures and their agreement across the group. The best performance was provided by ANTS using the High Variance settings published elsewhere. Neither FNIRT nor DRAMMS reached the level of performance of ANTS. The resulting normalized definition of anatomical structures were used to propose an atlas of the diencephalon region defining 58 structures using data from 19 patients.

2023, Vergne, Céline, Nicolas, Hugo, Madec, Morgan, Hemm-Ode, Simone, Guzman, Raphael, Pascal, Joris

On-chip magnetometers are already integrated within long-term implants such as cardiac implantable electronic devices. They are also good candidates to be integrated within the next generations of brain stimulation electrodes to provide their position and orientation. In all cases, long-term implants are expected to be at least certified as MRI conditional. We investigated the resilience to the exposure to 3 T and 7 T of an anisotropic magnetoresistive sensor integrating a set/reset function. The sensitivity, non-linearity, and offset of a batch of 63 identical sensors were not affected by the exposure. These preliminary results provide new insights on the usability of magnetoresistive sensors for biomedical applications requiring MRI conditionality.

2020-11-30, Vogel, Dorian, Wardell, Karin, Coste, Jérôme, Lemaire, Jean-Jaques, Hemm-Ode, Simone, Jarm, Tomaz, Cvetkoska, Aleksandra, Mahnič-Kalamiza, Samo, Miklavcic, Damijan

Abstract : Electrical stimulation of the deep parts of the brain is the standard answer for patients subject to drug-refractory movement disorders. Collective analysis of data collected during surgeries are crucial in order to provide more systematic planning assistance and understanding the physiological mechanisms of action. To that end, the process of normalizing anatomies captured with Magnetic Resonance imaging across patients is a key component. In this work, we present the optimization of a workflow designed to create group-specific anatomical templates: a group template is refined iteratively using the results of successive non-linear image registrations with refinement steps in the in the basal-ganglia area. All non-linear registrations were executed using the Advanced Normalization Tools (ANTs) and the quality of the nor-malization was measured using spacial overlap of anatomical structures manually delineated during the planning of the surgery. The parameters of the workflow evaluated were: the use of multiple modalities sequentially or together during each registration to the template, the number of iterations in the template creation and the fine settings of the non-linear registration tool. Using the T1 and white matter attenuated inverse recovery modalities (WAIR) together produced the best results, especially in the center of the brain. The optimal numbers of iterations of the template creation were higher than those from the literature and our previous works. Finally, the setting of the non-linear registration tool that improved results the most was the activation of the registration with the native voxel sizes of images, as opposed to down-sampled version of the images. The normalization process was optimized over our previous study and allowed to obtain the best possible anatomical nor-malization of this specific group of patient. It will be used to summarize and analyze peri-operative measurements during test stimulation. The aim is that the conclusions obtained from this analysis will be useful for assistance during the planning of new surgeries.

2020-01-30, Shah, Ashesh, Vogel, Dorian, Pison, Daniela, Schkommodau, Erik, Hemm-Ode, Simone