Multi-locus transcranial magnetic stimulation system for electronically targeted brain stimulation

Background: Transcranial magnetic stimulation (TMS) allows non-invasive stimulation of the cortex. In multi-locus TMS (mTMS), the stimulating electric field (E-field) is controlled electronically without coil movement by adjusting currents in the coils of a transducer. Objective: To develop an mTMS system that allows adjusting the location and orientation of the E-field maximum within a cortical region. Methods: We designed and manufactured a planar 5-coil mTMS transducer to allow controlling the maximum of the induced E-field within a cortical region approximately 30 mm in diameter. We developed electronics with a design consisting of independently controlled H-bridge circuits to drive up to six TMS coils. To control the hardware, we programmed software that runs on a field-programmable gate array and a computer. To induce the desired E-field in the cortex, we developed an optimization method to calculate the currents needed in the coils. We characterized the mTMS system and conducted a proof-of-concept motor-mapping experiment on a healthy volunteer. In the motor mapping, we kept the transducer placement fixed while electronically shifting the E-field maximum on the precentral gyrus and measuring electromyography from the contralateral hand. Results: The transducer consists of an oval coil, two figure-of-eight coils, and two four-leaf-clover coils stacked on top of each other. The technical characterization indicated that the mTMS system performs as designed. The measured motor evoked potential amplitudes varied consistently as a function of the location of the E-field maximum. Conclusion: The developed mTMS system enables electronically targeted brain stimulation within a cortical region. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer reviewe

Kastuvuustutkimuksia: Peruskäsitteistä ja kuitumaisista nanorakenteista sovelluksiin

Water is among the most vital substances on earth. Despite being an everyday element, prominently interesting phenomena occur when water is in contact with a surface. Superhydrophobic surfaces are ones that do not wet. In the extreme, they repel water to such a large degree that water does not stick to even nearly horizontal planes. Nowadays, many researchers pursue the magnificent examples set by nature, such as the extraordinary water repellency of a lotus leaf. Even though the basis of the study of wetting dates back to the 1800s, many elementary concepts remain unexplored. This thesis combines fundamental notions of wetting to experimental material science and demonstrates applications based on these materials, ranging from memory devices and sensors to pellets, which facilitate environmental clean-up. Publication I studies the fundamental concepts of surface wetting characterization and introduces a quantitative method for measuring the receding contact angle using the sessile-drop method. Theory and experiments together with calculations evaluate the validity of the developed model, and good agreement between theory and experiments is found. Furthermore, a novel definition for superhydrophobicity is proposed. Publication II introduces a growth model for the synthesis of silicone nanofilaments, which are one-dimensional nanostructures used to create superhydrophobic surfaces. In contrast to the previous studies, the present model explains the break of symmetry occurring in the initial phase of the growth, which has so far been implicitly assumed. Publication III demonstrates a hierarchically rough surface, which exhibits bi-stable superhydrophobic wetting states under water. A rapid local wetting transition occurs simply by locally applying pressure or suction onto the surface. Theoretical considerations explain the phenomena and a simple display demonstrates the concept. Publications IV and V introduce nanocellulose aerogels coated by atomic layer deposition with inorganic thin films. These materials are further employed as a resistive/capacitive humidity sensor and for oil spill cleanup from a water surface. The porosity and high surface area of the structures together with the wetting properties of the inorganic coating account for the observed properties. In addition, the study evaluates different drying methods for the nanocellulose aerogels based on the aggregation of the fibrils. Combining basic principles of wetting and superhydrophobicity to novel materials, as shown in this study, can lead to applications from myriad fields of technology. The concepts and applications demonstrated hopefully inspire future research towards many wetting-based applications.Vesi on arkipäiväinen, mutta elintärkeä aine. Veden kastelemilla pinnoilla tapahtuu erittäin mielenkiintoisia ilmiöitä. Superhydrofoobiset pinnat ovat sellaisia, joilta pisarat vierivät pois vaikka pinta olisi lähes vaakasuorassa. Nykyään monet tutkijat pyrkivät jäljittelemään luonnossa esiintyviä ilmiöitä ja rakenteita, kuten esimerkiksi lootuskukan lehden äärimmäistä vedenhylkimiskykyä. Vaikka pintojen kastuvuustutkimuksen perusta luotiin jo 1800-luvun alussa, monia perustavanlaatuisia käsitteitä on edelleen tutkimatta. Tämä työ yhdistää teoreettisia konsepteja kokeelliseen materiaalitieteeseen ja esittelee näille uusille materiaaleille sovelluksia digitaalisista muisteista öljyntorjuntapelletteihin. Julkaisu I tutkii pintojen kastuvuuden peruskäsitteitä ja esittää kvantitatiivisen kokeellisen menetelmän, jolla voidaan mitata pinnan vetäytyvän kontaktikulman arvo käyttämällä ns. pisaramenetelmää. Vastaavuus teorettisen konseptin, laskennallisten mallin sekä kokeiden välillä todennetaan. Lisäksi työssä ehdotetaan uutta määritelmää superhydrofoobisuudelle. Julkaisu II esittelee kasvumallin, joka selittää kuinka silikoninanofilamentit, jotka ovat superhydrofoobisia kuitumaisia nanorakenteita, kasvavat pinnoille. Aiemmissa malleissa ei olla pystytty täysin kuvaamaan kuinka tetragonaalisista lähtöaineista muodostuu yksiulotteisia rakenteita. Ehdotettu malli pyrkii kattamaan juuri tämän symmetrian rikkoutumisen. Julkaisu III käsittelee hierarkkista pintaa, jolla esiintyy kaksi superhydrofoobista kastumistilaa, kun se asetetaan veden alle. Paikalliset painemuutokset aiheuttavat nopean ja paikallisen muutoksen tilasta toiseen. Teoria ja kokeet osoittavat, että molemmat tilat ovat pitkäikäisiä ja konseptia havainnollistetaan käyttämällä pintaa yksinkertaisena näyttölaitteena. Julkaisut IV ja V kuvailevat nanoselluloosa-aerogeelejä, jotka on pinnoitettu epäorgaanisilla aineilla käyttäen atomikerroskasvatusmenetelmää, ja joiden avulla voidaan luoda sekä resistiivinen/ kapasitiivinen kosteusanturi että pelletti, jota voidaan käyttää öljylauttojen imeyttämiseen suoraan veden pinnalta. Aerogeelien suuri huokoisuus ja suuri pinta-ala mahdollistavat esitellyt ominaisuudet. Lisäksi työssä vertaillaan erilaisia nanoselluloosa-aerogeelien kuivausmenetelmiä kuitumaisen verkostorakenteen säätämiseksi. Kastuvuusilmiöiden peruskäsitteiden yhdistäminen materiaalitieteeseen, kuten tässä työssä on tehty, voi johtaa mielenkiintoisiin sovelluksiin monella tekniikan alalla. Esitellyt konseptit ja sovellukset toivottavasti inspiroivat jatkotukimuksia, joissa yhdistellään kastuvuusilmiöitä sovelluksiin

Optical spectroscopic characterization of human meniscus biomechanical properties

This study investigates the capacity of optical spectroscopy in the visible (VIS) and near-infrared (NIR) spectral ranges for estimating the biomechanical properties of human meniscus. Seventy-two samples obtained from the anterior, central, and posterior locations of the medial and lateral menisci of 12 human cadaver joints were used. The samples were subjected to mechanical indentation, then traditional biomechanical parameters (equilibrium and dynamic moduli) were calculated. In addition, strain-dependent fibril network modulus and permeability strain-dependency coefficient were determined via finite-element modeling. Subsequently, absorption spectra were acquired from each location in the VIS (400 to 750 nm) and NIR (750 to 1100 nm) spectral ranges. Partial least squares regression, combined with spectral preprocessing and transformation, was then used to investigate the relationship between the biomechanical properties and spectral response. The NIR spectral region was observed to be optimal for model development (83.0% Le R2 ≤ 90.8%).e. The NIR spectral region was observed to be optimal for model development (83.0%≤R2≤90.8%). The percentage error of the models are: Eeq (7.1%), E (9.6%), E (8.4%), and M (8.9%). Thus, we conclude that optical spectroscopy in the NIR range is a potential method for rapid and nondestructive evaluation of human meniscus functional integrity and health in real time during arthroscopic surgery

Ultrasound assessment of human meniscus

Abstract The aim of the present study was to evaluate the applicability of ultrasound imaging to quantitative assessment of human meniscus in vitro. Meniscus samples (n = 26) were harvested from 13 knee joints of non-arthritic human cadavers. Subsequently, three locations (anterior, center and posterior) from each meniscus were imaged with two ultrasound transducers (frequencies 9 and 40 MHz), and quantitative ultrasound parameters were determined. Furthermore, partial-least-squares regression analysis was applied for ultrasound signal to determine the relations between ultrasound scattering and meniscus integrity. Significant correlations between measured and predicted meniscus compositions and mechanical properties were obtained (R² = 0.38–0.69, p < 0.05). The relationship between conventional ultrasound parameters and integrity of the meniscus was weaker. To conclude, ultrasound imaging exhibited a potential for evaluation of meniscus integrity. Higher ultrasound frequency combined with multivariate analysis of ultrasound backscattering was found to be the most sensitive for evaluation of meniscus integrity

A multi-channel TMS system enabling accurate stimulus orientation control during concurrent ultra-high-field MRI for preclinical applications

Data and code used in the design and validation of the tools described in the study at DOI: 10.1101/2023.08.10.55240

Hierarchical Structures of Hydrogen-Bonded Liquid-Crystalline Side-Chain Diblock Copolymers in Nanoparticles

Here we show that it is possible to control the overall morphology as well as hierarchical microstructure of lamellae-forming block copolymers within nanoparticles by altering side-chain content and processing temperature. We used cholesteryl hemisuccinate (CholHS) as hydrogen-bonded side chains and poly­(styrene)-<i>block</i>-poly­(4-vinylpyridine) (PS–P4VP) as backbone to produce submicrometer particles with the aerosol method. With CholHS-to-P4VP repeat unit ratio of 0.25 and 0.50, we obtained onion-like particles with either single CholHS layers sandwiched between P4VP rich lamellae or smectic P4VP­(CholHS) layers perpendicular to the polymer domain interfaces. When the fraction of CholHS was increased to 0.75, the onion-like structure broke down due to increased splay deformation energy of the liquid crystalline P4VP­(CholHS) domains. The onion-like structure could be re-established, however, when the particles were produced at a higher temperature which made the CholHS molecules partially soluble into the PS phase. Because of the reversible nature of the hydrogen bonds, it was possible to selectively remove the CholHS side chains from the particles

Interior photon counting computed tomography for quantification of coronary artery calcium:pre-clinical phantom study

Abstract Computed tomography (CT) is the reference method for cardiac imaging, but concerns have been raised regarding the radiation dose of CT examinations. Recently, photon counting detectors (PCDs) and interior tomography, in which the radiation beam is limited to the organ-of-interest, have been suggested for patient dose reduction. In this study, we investigated interior PCD-CT (iPCD-CT) for non-enhanced quantification of coronary artery calcium (CAC) using an anthropomorphic torso phantom and ex vivo coronary artery samples. We reconstructed the iPCD-CT measurements with filtered back projection (FBP), iterative total variation (TV) regularization, padded FBP, and adaptively detruncated FBP and adaptively detruncated TV. We compared the organ doses between conventional CT and iPCD-CT geometries, assessed the truncation and cupping artifacts with iPCD-CT, and evaluated the CAC quantification performance of iPCD-CT. With approximately the same effective dose between conventional CT geometry (0.30 mSv) and interior PCD-CT with 10.2 cm field-of-view (0.27 mSv), the organ dose of the heart was increased by 52.3% with interior PCD-CT when compared to CT. Conversely, the organ doses to peripheral and radiosensitive organs, such as the stomach (55.0% reduction), were often reduced with interior PCD-CT. FBP and TV did not sufficiently reduce the truncation artifact, whereas padded FBP and adaptively detruncated FBP and TV yielded satisfactory truncation artifact reduction. Notably, the adaptive detruncation algorithm reduced truncation artifacts effectively when it was combined with reconstruction detrending. With this approach, the CAC quantification accuracy was good, and the coronary artery disease grade reclassification rate was particularly low (5.6%). Thus, our results confirm that CAC quantification can be performed with the interior CT geometry, that the artifacts are effectively reduced with suitable interior reconstruction methods, and that interior tomography provides efficient patient dose reduction