Coil Holder Research Articles

Lessons learned from an fMRI-guided rTMS study on performance in a numerical Stroop task.

The Stroop task is a well-established tool to investigate the influence of competing visual categories on decision making. Neuroimaging as well as rTMS studies have demonstrated the involvement of parietal structures, particularly the intraparietal sulcus (IPS), in this task. Given its reliability, the numerical Stroop task was used to compare the effects of different TMS targeting approaches by Sack and colleagues (Sack AT 2009), who elegantly demonstrated the superiority of individualized fMRI targeting. We performed the present study to test whether fMRI-guided rTMS effects on numerical Stroop task performance could still be observed while using more advanced techniques that have emerged in the last decade (e.g., electrical sham, robotic coil holder system, etc.). To do so we used a traditional reaction time analysis and we performed, post-hoc, a more advanced comprehensive drift diffusion modeling approach. Fifteen participants performed the numerical Stroop task while active or sham 10 Hz rTMS was applied over the region of the right intraparietal sulcus (IPS) showing the strongest functional activation in the Incongruent > Congruent contrast. This target was determined based on individualized fMRI data collected during a separate session. Contrary to our assumption, the classical reaction time analysis did not show any superiority of active rTMS over sham, probably due to confounds such as potential cumulative rTMS effects, and the effect of practice. However, the modeling approach revealed a robust effect of rTMS on the drift rate variable, suggesting differential processing of congruent and incongruent properties in perceptual decision-making, and more generally, illustrating that more advanced computational analysis of performance can elucidate the effects of rTMS on the brain where simpler methods may not.

Design of coil holder for the improved maneuvering in concurrent TMS-MRI

BackgroundConcurrent transcranial magnetic stimulation (TMS) and magnetic resonance imaging (MRI) is time-consuming because of the limited space in the MRI bore and the sophisticated placement and orientation of the TMS coil to elicit the desired brain activities and behaviors. ObjectiveWe developed a TMS coil holder capable of quick adjustment of the TMS coil position and orientation. The holder can also hold an MRI receiver coil array. MethodsA holder with one controlling knob, two omni-direction rotation joints, and two in-plane rotation joints was developed. ResultsDifferent TMS coil positions and orientations can be arranged and fixed in seconds. The holder can also accommodate two TMS coils to allow for multi-coil TMS-MRI. ConclusionOur development significantly improves the workflow of the concurrent TMS-MRI in new neuroscience studies and clinical applications.

Quality assurance and temporal stability of a 1.5 T MRI scanner for MR-guided Photon and Particle Therapy

PurposeTo describe performance measurements, adaptations and time stability over 20 months of a diagnostic MR scanner for integration into MR-guided photon and particle radiotherapy. Material and methodsFor realization of MR-guided photon and particle therapy (MRgRT/MRgPT), a 1.5 T MR scanner was installed at the Heidelberg Ion Beam Therapy Center. To integrate MRI into the treatment process, a flat tabletop and dedicated coil holders for flex coils were used, which prevent deformation of the patient external contour and allow for the use of immobilization tools for reproducible positioning. The signal-to-noise ratio (SNR) was compared for the diagnostic and therapy-specific setup using the flat couch top and flexible coils for the a) head & neck and b) abdominal region as well as for different bandwidths and clinical pulse sequences. Additionally, a quality assurance (QA) protocol with monthly measurements of the ACR phantom and measurement of geometric distortions for a large field-of-view (FOV) was implemented to assess the imaging quality parameters of the device over the course of 20 months. ResultsThe SNR measurements showed a decreased SNR for the RT-specific as compared to the diagnostic setup of (a) 26% to 34% and (b) 11% to 33%. No significant bandwidth dependency for this ratio was found. The longitudinal assessment of the image quality parameters with the ACR and distortion phantom confirmed the long-term stability of the MRI device. ConclusionA diagnostic MRI was commissioned for use in MR-guided particle therapy. Using a radiotherapy specific setup, a high geometric accuracy and signal homogeneity was obtained after some adaptions and the measured parameters were shown to be stable over a period of 20 months.

A hybrid flow energy harvester using combined piezoelectric and electromagnetic transductions for pipeline network monitoring

An energy harvester that employs both electromagnetic and piezoelectric effects to convert fluid flow energy in the pipeline into electrical energy for powering wireless sensor nodes (WSNs) of the pipeline condition monitoring system has been developed. The devised hybrid energy harvester comprised a unimorph circular piezoelectric plate fixed in a T-joint, three stacked magnets attached at the middle of the piezoelectric plate, and an adjustable coil holder holding a wound coil. Experimental results of the developed prototype depict that it can produce a maximum load RMS voltage of 3.36 V with the piezoelectric part at 27 kΩ of optimal load resistance and 286 mV from the electromagnetic part at 335 Ω of optimum load resistance. Moreover, at 2.9 kPa flow pressure amplitude and 11.08 l/s flow rate, a maximum load power of 418 µW from the piezoelectric portion and 244 µW with the electromagnetic portion is produced. Upon integrating the harvester with a rectifier circuit, an open circuit DC voltage of 9.4 and 3.32 V are generated with piezoelectric and electromagnetic parts, respectively. Furthermore, under the same fluid flow condition, the piezoelectric part produces 404 µW DC power at 92 kΩ of optimum load resistance, while the electromagnetic portion produces 163 µW DC power at 10 kΩ of optimum load resistance. The developed harvester is also utilized to recharge a 4.8 V power bank from 1.11 to 4.2 V in 210 min. Moreover, it is also integrated with a pipeline condition monitoring system to power a WSN, a controller, and relevant circuitry.

Clinical Practice Guidelines for the Therapeutic Use of Repetitive Transcranial Magnetic Stimulation in Neuropsychiatric Disorders.

Clinical Practice Guidelines for the Therapeutic Use of Repetitive Transcranial Magnetic Stimulation in Neuropsychiatric Disorders.

Estimation of stress and deformation on steel coil holder fixtures using finite element analysis

Abstract For engineering components, fixtures are essential elements for holding proper design and provide safety of the work-space. Any failure results are occurs in chain type hindrance of manufacturing process and system delivery causes delay in production time. In this present works, a steel coil holder has been selected for alignment of fixtures with coil capacity of 40tons. The components are shell slide, support channel, connecting plate, channel connector, pipe elements, and final assembly of top cylinder. Finite element analysis (FEA) was chosen to optimization of design factors and material of the plate SAILMA550 with allowable stress (250 MPa). A physical parameters are load-withstands and deformation of the plate were examined. Results show that optimization of initial stress has found 1443.5 MPa and final stress component falls to 253.85 MPa. The higher load deflection of initial design was obtained 4.8489 mm and lower deflection of the plate is reached to 4.5833 mm. However, the initial setting results shows heavy stress on the components (shell slide, support channel & pipe element) it leads more sufficient allowable stress performed on steel coil holder within their limits.

CT-based attenuation correction of whole-body radiotherapy treatment positioning devices in PET/MRI hybrid imaging

Objective.To implement computed tomography (CT)-based attenuation maps of radiotherapy (RT) positioning hardware and radiofrequency (RF) coils to enable hybrid positron emission tomography/magnetic resonance imaging (PET/MRI)-based RT treatment planning. Materials and Methods. The RT positioning hardware consisted of a flat RT table overlay, coil holders for abdominal scans, coil holders for head and neck scans and an MRI compatible hip and leg immobilization device. CT images of each hardware element were acquired on a CT scanner. Based on the CT images, attenuation maps of the devices were created. Validation measurements were performed on a PET/MR scanner using a 68Ge phantom (48 MBq, 10 min scan time). Scans with each device in treatment position were performed. Then, reference scans containing only the phantom were taken. The scans were reconstructed online (at the PET/MRI scanner) and offline (via e7tools on a PC) using identical reconstruction parameters. Average reconstructed activity concentrations of the device and reference scans were compared. Results. The device attenuation maps were successfully implemented. The RT positioning devices caused an average decrease of reconstructed PET activity concentration in the range between −8.3 ± 2.1% (mean ± SD) (head and neck coil holder with coils) to −1.0 ± 0.5% (abdominal coil holder). With attenuation correction taking into account RT hardware, these values were reduced to −2.0 ± 1.2% and −0.6 ± 0.5%, respectively. The results of the offline and online reconstructions were nearly identical, with a difference of up to 0.2%. Conclusion. The decrease in reconstructed activity concentration caused by the RT positioning devices is clinically relevant and can successfully be corrected using CT-based attenuation maps. Both the offline and online reconstruction methods are viable options.

Subject-Specific, Non-Invasive Helmet-Restraint RF Coil for Awake, Non-Human Primate MR Imaging

The purpose of this study was to develop a non-invasive restraint helmet integrated with an radio frequency (RF) coil for awake-behaving non-human primate MR imaging. To prevent image-corrupting motion, the head needs to be immobilized, which is currently achieved via invasive surgical headpost implants. In this work, an RF coil holder was integrated into the design of a subject-specific helmet to place the coil in closest distance to the head for improved signal-to-noise ratio (SNR). Additive manufacturing was used to print the helmet based upon computed tomography images of the subject. A single channel transmit/receive loop coil was designed using electromagnetic simulations loaded with a voxel-based monkey head model. The Rhesus macaque used in this study underwent behavioral training based on positive reinforcement before engaging in MR imaging. Imaging was performed using the helmet coil, which was successful in immobilizing the macaque head in an awake, unanesthetized subject. Results showed improved SNR by approximately 30% compared to a loop coil used with an implanted head post, and minimal motion artifact in structural imaging. The non-invasive helmet coil eliminates the need for permanently implanting monkeys with a headpost, provides the necessary head immobilization, and allows the use of more subjects for neuroimaging studies.

17. Evaluation of MR and PET compatibility of dedicated radiotherapy positioning devices – a preliminary study

Purpose The aim of this preliminary study was to assess the compatibility of dedicated positioning devices developed for MR/PET imaging integration into radiotherapy planning. Methods The X-Tend Flat Table Top and specifically designed radiofrequency coil holders were tested on an integrated Biograph mMR MR/PET scanner (Siemens Healthcare). Magnetic field homogeneity and MR image quality in terms of artifacts and signal-to-noise ratio (SNR), with and without the radiotherapy positioning devices, were evaluated by means of a field sequence with 0.1 ppm/line and a clinical T2-weighted sequence, respectively. Acquisitions of a cylindrical (diameter 16 cm) doped (NiSO4) water phantom were performed by using a flexible 8-channel radiofrequency coil. SNR was estimated through the subtraction method. Since glass fiber table top and radiofrequency coil holders can attenuate PET signal, introducing potential quantification errors, PET photon attenuation was tested by the use of a cylindrical uniform phantom filled with 18-F and a sealed 68-Ge phantom. Also, a CT scan of the equipment was performed to calculate the transmission factor at 511 keV. Results The use of the dedicated radiotherapy positioning devices did not affect appreciably magnetic field homogeneity, and did not yield evident artifacts in T2-weighted images. When using the radiotherapy devices, SNR showed a reduction of less than 5% with respect to standard MR acquisitions. The average transmission factor of the radiotherapy table was computed to be around 90% from both CT scan and PET photon attenuation. Conclusions Based on our preliminary results, the dedicated radiotherapy positioning devices seem to be MR and PET compatible. Effect of radiotherapy devices on MR geometrical distortion and image uniformity, also for non-conventional quantitative diffusion-weighted imaging (a useful and sensitive tool for oncologic applications), are under evaluation. Further investigation is needed to assess the effect of radiotherapy table attenuation on PET contrast of lesions.

Technical Note: Adapting a GE SIGNA PET/MR scanner for radiotherapy.

Simultaneous collection of PET and MR data for radiotherapy purposes are useful for, for example, target definition and dose escalations. However, a prerequisite for using PET/MR in the radiotherapy workflow is the ability to image the patient in treatment position. The aim of this work was to adapt a GE SIGNA PET/MR scanner to image patients for radiotherapy treatment planning and evaluate the impact on signal-to-noise (SNR) of the MR images, and the accuracy of the PET attenuation correction. A flat tabletop and a coil holder were developed to image patients in the treatment position, avoid patient contour deformation, and facilitate attenuation correction of flex coils. Attenuation corrections for the developed hardware and an anterior array flex coil were also measured and implemented to the PET/MR system to minimize PET quantitation errors. The reduction of SNR in the MR images due to the added distance between the coils and the patient was evaluated using a large homogenous saline-doped water phantom, and the activity quantitation errors in PET imaging were evaluated with and without the developed attenuation corrections. We showed that the activity quantitation errors in PET imaging were within ±5% when correcting for attenuation of the flat tabletop, coil holder, and flex coil. The SNR of the MRI images were reduced to 74% using the tabletop, and 66% using the tabletop and coil holders. We present a tabletop and coil holder for an anterior array coil to be used with a GE SIGNA PET/MR scanner, for scanning patients in the radiotherapy work flow. Implementing attenuation correction of the added hardware from the radiotherapy setup leads to acceptable PET image quantitation. The drop in SNR in MR images may require adjustment of the imaging protocols.

Electromagnetic based acoustic energy harvester for low power wireless autonomous sensor applications

PurposeThe purpose of this paper is to develop a novel electromagnetic-based acoustic energy harvester (EH) for the application of wireless autonomous sensors.Design/methodology/approachThe developed acoustic EH comprises a Helmholtz resonator (HR), a suspension system that consists of a flexible membrane and a permanent magnet, a couple of coils and a coil holder. Furthermore, the HR, used in the harvester, is designed for a specific resonant frequency based on simulation carried out in COMSOL Multiphysics®.FindingsThe developed harvester is tested both in lab under harmonic sound pressure levels (SPLs) and in real environment under random SPLs. In lab, when exposed to 100 dB SPL, the harvester generated a peak power of 212 µW. Furthermore, in real environment in vicinity of electric generator, the harvester produced an output voltage of about 110 mV collectively from its both coils.Originality/valueIn this paper, a novel geometric configuration for electromagnetic-based acoustic EH is proposed. In the developed harvester, two coils are placed in it to achieve enhanced electrical output from it for the first time.

SU‐F‐J‐143: Initial Assessment of Image Quality of An Integrated MR‐Linac System with ACR Phantom

Purpose/Objective(s):To assess the image quality of an integrated MR‐Linac system and compare with other MRI systems that are primarily used for diagnostic purposes.Materials/Methods:An ACR MRI quality control (QC) phantom was used to evaluate the image quality of a fully integrated 1.5T MRI‐Linac system recently installed at our institution. This system has a new split magnet design which gives the magnetic field strength of 1.5T. All images were acquired with a set of phased‐array surface coils which are designed to have minimal attention of radiation beam. The anterior coil rests on a coil holder which keeps the anterior coil's position consistent for QA purposes. The posterior coil is imbedded in the patient couch. Multiple sets of T1, T2/PD images were acquired using the protocols as prescribed by the ACR on three different dates, ranging 3 months apart.Results:The geometric distortion are within 0.5 mm in the axial scans and within 1mm in the saggital (z‐direction) scans. Slice thickness accuracy, image uniformity, ghosting ratio, high contrast detectability are comparable to other 1.5T diagnostic MRI scanners. The low‐contrast object detectability are lower comparatively, which is a result of using the body array coil. Additionally, the beam's‐eye‐view images (oblique coronal and saggital images) have minimal geometric distortion at all linac gantry angles tested. No observable changes or drift in image quality is found from images acquired 3 month apart.Conclusion:Despite the use of a body array surface coil, the image quality is comparable to that of an 1.5T MRI scanner and is of sufficient quality to pass the ACR MRI accreditation program. The geometric distortion of the MRI system of the integrated MR‐Linac is within 1mm for an object size similar to the ACR phantom, sufficient for radiation therapy treatment purpose.The authors received corporate sponsored research grants from Elekta which is the vendor for the MR‐Linac evaluated in this study.

Whole-body hybrid imaging concept for the integration of PET/MR into radiation therapy treatment planning

Modern radiation therapy (RT) treatment planning is based on multimodality imaging. With the recent availability of whole-body PET/MR hybrid imaging new opportunities arise to improve target volume delineation in RT treatment planning. This, however, requires dedicated RT equipment for reproducible patient positioning on the PET/MR system, which has to be compatible with MR and PET imaging.A prototype flat RT table overlay, radiofrequency (RF) coil holders for head imaging, and RF body bridges for body imaging were developed and tested towards PET/MR system integration. Attenuation correction (AC) of all individual RT components was performed by generating 3D CT-based template models. A custom-built program for μ-map generation assembles all AC templates depending on the presence and position of each RT component. All RT devices were evaluated in phantom experiments with regards to MR and PET imaging compatibility, attenuation correction, PET quantification, and position accuracy. The entire RT setup was then evaluated in a first PET/MR patient study on five patients at different body regions.All tested devices are PET/MR compatible and do not produce visible artifacts or disturb image quality. The RT components showed a repositioning accuracy of better than 2 mm. Photon attenuation of −11.8% in the top part of the phantom was observable, which was reduced to −1.7% with AC using the μ-map generator. Active lesions of 3 subjects were evaluated in terms of SUVmean and an underestimation of −10.0% and −2.4% was calculated without and with AC of the RF body bridges, respectively. The new dedicated RT equipment for hybrid PET/MR imaging enables acquisitions in all body regions. It is compatible with PET/MR imaging and all hardware components can be corrected in hardware AC by using the suggested μ-map generator. These developments provide the technical and methodological basis for integration of PET/MR hybrid imaging into RT planning.

Non-contact method for directing electrotaxis.

We present a method to induce electric fields and drive electrotaxis (galvanotaxis) without the need for electrodes to be in contact with the media containing the cell cultures. We report experimental results using a modification of the transmembrane assay, demonstrating the hindrance of migration of breast cancer cells (SCP2) when an induced a.c. electric field is present in the appropriate direction (i.e. in the direction of migration). Of significance is that migration of these cells is hindered at electric field strengths many orders of magnitude (5 to 6) below those previously reported for d.c. electrotaxis, and even in the presence of a chemokine (SDF-1α) or a growth factor (EGF). Induced a.c. electric fields applied in the direction of migration are also shown to hinder motility of non-transformed human mammary epithelial cells (MCF10A) in the presence of the growth factor EGF. In addition, we also show how our method can be applied to other cell migration assays (scratch assay), and by changing the coil design and holder, that it is also compatible with commercially available multi-well culture plates.

Energy Harvesting and Regeneration from the Vibration of Suspension System

Two conceptual designs of energy regenerative suspension have been developed using commercial computer aided design (CAD) software. The designs are based on the available conventional suspension. They consist of basic magnet and coil for electrical energy regeneration and additional components for magnet support and coil winding circular holder. The selection of the design is based on weighted matrix which consists of reliability, cost, time consumption and weight. The score of the matrix is formulated based on relative weighted factor among the selections. All designs are fabricated using selected and available materials. The actual cost, time consumption and weight of the suspensions are compared with the theoretical weighted scores. Standard processes of cuttings, fittings and welding are performed in fabrication. Suitable magnet design is attached on the suspensions. The other moving part of the suspensions is attached by coil and coil holder. The suspensions are tested with various strokes and frequencies for feasibility studies and energy regeneration capability using suspension test rig. The evaluation of the suspensions is performed based on actual experimental results of voltage and power regenerated.

Design of wideband vibration-based electromagnetic generator by means of dual-resonator

This paper describes the design of a wideband electromagnetic energy harvester that utilizes a novel dual-resonator method to improve the operational frequency range of the vibration-based generator. The device consists of two separate resonator systems (coil and magnet), which each comply with their respective resonance frequencies. This is because both resonators are designed in such a way that both magnet and coil components will oscillate at an additive phase angle, and hence create greater relative motion between the two dominating resonance frequencies, which realizes the wideband generator. Each resonator system consists of a distinctive cantilever beam, one attached with four magnets and steel keepers, the other attached with a copper coil and stainless steel holder as the free end mass. Both cantilevers are clamped and fitted to a common base that is subjected to a vibration source. Basic analytical models are derived and a numerical model is implemented in MATLAB-Simulink. Electromagnetic, structural modal and static mechanical analysis for the design of the prototype are completed using ANSYS finite element tools. For a 0.8ms−2 acceleration, the open-loop voltage obtained from the experiment shows a good correlation with those from the simulation. Peak induced voltage is measured to be 259.5Vrms as compared to 240.9Vrms from the simulator at 21.3Hz, which implies an error range of 7.7%. The results also indicate that there is a maximum of 58.22% improvement in the induced voltage within the intermediate region which occurs at the intersection point between the output response plots of two single resonator generators.

Stimulus Intensity for Hand Held and Robotic Transcranial Magnetic Stimulation

BackgroundTranscranial Magnetic Stimulation (TMS) is based on a changing magnetic field inducing an electric field in the brain. Conventionally, the TMS coil is mounted to a static holder and the subject is asked to avoid head motion. Additionally, head resting frames have been used. In contrast, our robotized TMS system employs active motion compensation (MC) to maintain the correct coil position. Objective/hypothesisWe study the effect of patient motion on TMS. In particular, we compare different coil positioning techniques with respect to the induced electric field. MethodsWe recorded head motion for six subjects in three scenarios: (a) avoiding head motion, (b) using a head rest, and (c) moving the head freely. Subsequently, the motion traces were replayed using a second robot to move a sensor to measure the electric field in the target region. These head movements were combined with 2 types of coil positioning: (1) using a coil holder and (2) using robotized TMS with MC. ResultsAfter 30 min the induced electric field was reduced by 32.0% and 19.7% for scenarios (1a) and (1b), respectively. For scenarios (2a)–(2c) it was reduced by only 4.9%, 1.4% and 2.0%, respectively, which is a significant improvement (P < 0.05). Furthermore, the orientation of the induced field changed by 5.5°, 7.6°, 0.4°, 0.2°, 0.2° for scenarios (1a)–(2c). ConclusionWhile none of the scenarios required rigid head fixation, using a simple holder to position a coil during TMS can lead to substantial deviations in the induced electric field. In contrast, robotic motion compensation results in clinically acceptable positioning throughout treatment.

Thermal-noise-limited underground interferometer CLIO

We report on the current status of CLIO (Cryogenic Laser Interferometer Observatory), which is a prototype interferometer for LCGT (large scale cryogenic gravitational-wave telescope). LCGT is a Japanese next-generation interferometric gravitational-wave detector featuring the use of cryogenic mirrors and a quiet underground site. The main purpose of CLIO is to demonstrate a reduction of the mirror thermal noise by cooling the sapphire mirrors. CLIO is located in an underground site of the Kamioka mine, 1000 m deep from the mountain top, to verify its advantages. After a few years of commissioning work, we have achieved a thermal-noise-limited sensitivity at room temperature. One of the main results of noise hunting was the elimination of thermal noise caused by a conductive coil holder coupled with a pendulum through magnets.

Gadolinium-containing phosphatidylserine liposomes for molecular imaging of atherosclerosis

Exteriorized phosphatidylserine (PS) residues in apoptotic cells trigger rapid phagocytosis by macrophage scavenger receptor pathways. Mimicking apoptosis with liposomes containing PS may represent an attractive approach for molecular imaging of atherosclerosis. We investigated the utility of paramagnetic gadolinium liposomes enriched with PS (Gd-PS) in imaging atherosclerotic plaque. Gd-PS-containing Gd-conjugated lipids, fluorescent rhodamine, and PS were prepared and characterized. Cellular uptake in RAW macrophages (fluorescent uptake of rhodamine) was studied on a fluorescence plate reader, while Gd-PS-induced alteration in T1 relaxivity was evaluated using a 1.5 T MRI scanner. RAW cells demonstrate PS-dependent uptake of across a range of concentrations (2, 6, 12, and 20%) in comparison to control liposomes with no PS (0%). In vivo performance of Gd-PS was evaluated in the ApoE(-/-) mouse model by collection of serial T1 weighted gradient echo MR images using an 11.7 T MRI system and revealed rapid and significant enhancement of the aortic wall that was seen for at least 4 h after injection. Gd-PS-enriched liposomes enhance atherosclerotic plaque and colocalize with macrophages in experimental atherosclerosis.

A rotatable flat coil for static solid-state nuclear magnetic resonance spectroscopy

A holder allowing rotation of a flat coil relative to the static magnetic field (B0) of a nuclear magnetic resonance (NMR) spectrometer over the range of orientations from parallel to perpendicular has been built and incorporated into a two-channel wide line static solid-state NMR probe. Radiofrequency induction by the coil is perpendicular to B0 for all rotational angles. Such a coil holder provides ready access to an additional directional variable for experiments exploiting sample orientation such as those using planar-supported oriented phospholipid bilayers. Rotation of the flat coil is demonstrated using P31 NMR of oriented phospholipid and peptide bilayers sandwiched between pairs of mica substrates.