A database of multi-channel intramuscular electromyogram ...

topics

Fourteen male equipped-bodied volunteers aged between 25 and fifty seven years (suggest 39 years) participated within the study. All topics have been right-exceeded and neurologically intact. The recordings were divided into two protocols and two subjects had been included in both protocols, therefore the last database contains sixteen info, eight for each protocol. all of the subjects signed the recommended consent, and the analyze become approved by using the Regional moral review Board in Lund, Sweden (Dnr 2017-297).

Intramuscular EMG recordings

The intramuscular EMG indicators have been recorded using the Quattrocento (OT Bioelettronica, Torino, Italia) biomedical amplifier device. The system comprises a four hundred channel amplifier, digitalization unit and preamplifiers with 5x benefit for interfacing electrodes with the amplifier. All iEMG indicators had been amplified 150 instances and sampled with 16-bit amplitude decision at 10240 Hz. A hardware excessive-pass filter at 10 Hz and a low-move filter at 4400 Hz had been used all the way through recordings. The intramuscular electrodes used in this look at had been paired exceptional-wire electrodes from Chalgren, Gilroy, u . s . a .. every wire is 200 mm long and zero.051 mm in diameter, made of stainless-steel with nylon insulation for better visibility. each pair of wires ends with a 2 mm naked wire (the insulation is offset to avoid short circuits). The positioning of the first-class-wire electrodes changed into performed with the aid of a boss profess ional in medical neurophysiology using the guidelines from Anatomical e-book for the electromyographer: the limbs and trunk27. The localization of the inserted wires was accomplished by checking the circulate of the guiding cannula whereas performing unique hand manoeuvre detailed for the focused muscle. The second investigate of the sign fine was done with the cannula nonetheless inserted through showing iEMG signal in actual-time while performing the hand manoeuvre. The last verify of the signal changed into after the removing of cannula. Upon validation that the fine-wires were internal the focused muscle, the wire leads and the preamplifier had been taped to the lessen arm to ensure low noise size. in addition, to investigate the suitable position of the electrodes a boss professional in musculoskeletal radiology performed an ultrasound examination in two topics (topics 13 and 14), one per every recording protocol. The goal of ultrasound examination became to confirm that the needle tip turned into located in the centered muscle after which the needle turned into retracted. The DICOM and JPEG photos of the needle positions inside the targeted muscle tissues are supplied with the rest of the recorded records. it should be noted that the ultrasound desktop used for this study (EPIQ 7, Phillips, The Netherlands, with linear transducer L18-5 engaged on 9 MHz) changed into not in a position to discover the exceptional-wire ends because of their small dimension, so the position identification become executed the use of the needle tip.

during this analyze we defined two size protocols, each targeting certain muscular tissues which correspond to 2 different degrees of forearm amputation, therefore mimicking skills person situations of myoelectric prosthesis manage. the first protocol, called brief residual limb (SRL) protocol centered the following muscle tissues: flexor carpi radialis (FCR) – liable for wrist flexion, extensor carpi radialis longus (ECR) – responsible for wrist extension, pronator teres (PT) – responsible for forearm pronation, flexor digitorum profundus (FDP) – chargeable for flexion of fingers D2-D5, extensor digitorum communis (EDC) – chargeable for extension of fingers D2-D5, and abductor pollicis longus (APL) – responsible for thumb abduction. The 2d protocol, known as lengthy residual limb (LRL) focused the following muscle tissues: flexor digitorum profundus (FDP), extensor digitorum communis (EDC), abductor pollicis longus (APL), flexor pollicis longus (FPL) – answerable fo r thumb flexion, extensor pollicis longus (EPL) – chargeable for thumb extension, and extensor indicis proprius (EIP) – chargeable for index finger (D2) extension. The splitting into two protocols, each and every focusing on one of the eventualities (SRL or LRL) encountered in amputees also decreased the possibility of failed measurements as a result of, for instance a area experiencing vasovagal syncope (fainting) or a excessive stage of ache or pain. The twelve subjects had six pairs of exceptional-wires inserted inspite of the protocol, while two topics had been recorded with 9 electrodes that have been later additionally divided into two subsets (SRL and LRL).

Isometric force recording

Synchronously with the iEMG signal recording, hand forces have been assessed the use of a custom-made force measurement equipment. The leading reason behind using the force/torque measurement machine changed into to acquire records of individual joint torques all over the execution of predefined movements. The rationale for opting for an isometric setup changed into to simulate muscle behaviour in a forearm amputee and to restrict muscle displacement that could influence mechanical balance of the inserted pleasant-wire electrodes. The device changed into designed with the intention to constrain the joints in the wrist and hand in a neutral posture approximately within the core of the latitude of action of the individual joints. additionally, this biomechanically beneficial position enabled the generation of surprisingly tremendous forces for both flexion and extension of particular person joints. during the size, the machine was firmly positioned on the table with rubber patches p reventing the device from slipping or accidental lifting. The area's forearm became supported by means of an adjustable bracket, and also, the subject changed into urged to remain firmly seated all through the measurement session to steer clear of compensatory movements. The force sensors' outputs have been conditioned to an output of 0–5 V, with the voltage proportional to the exerted force in the range ± one hundred N. The sensors were manufacturing facility calibrated by the company as a way to have lower than 1% full scale error. The linearity error was additionally validated after integrating force gauge sensors into the machine. This changed into completed to assess have an effect on of the semi-inflexible aluminium frame on the measured drive. The ensuing transfer feature between readings of the reference force gauge and the sensor of the instrumented platform became enormously linear all through the operating range (R2 = 0.9999, RMSE = 0.010 42 V (0. forty one N)). The analog alerts from the drive sensors were digitalized the use of NI-USB 6218 (country wide gadgets, Austin, Texas, u . s .) A/D with 16-bit amplitude resolution and sampling frequency of 200 Hz. A customized-made LabView (country wide instruments, Austin, Texas, usa) software recorded force alerts in a _.tdms file. at the onset of recording, the NI-USB 6218 card generated pulses that had been routed to Quattrocento auxiliary input with a purpose to synchronize the force and EMG facts. The synchronization pulses had 5 V amplitude, 200 ms width and zero.5 Hz frequency and had been additionally recorded with the NI card analog input to ensure synchronization within the case of any variety of delay involving the output of the NI device.

The precise description of the measurement gadget and its error validation can also be found in our old booklet28.

Recording protocol

As brought up earlier than, two measurement protocols have been designed for this look at, with the handiest change being the option of centered muscle tissues. consequently, anyway the recorded muscular tissues, the protocol become the equal in both situations. originally of the recording session the discipline changed into counseled about the entire elements including possible dangers after which he signed the advised consent. within the subsequent stage, the isometric drive size device was configured to healthy the area's hand. This changed into adopted by way of a familiarization period (lasting about 30 minutes) all the way through which the discipline bought familiar with the mandatory hand movements, utility and cues. Upon finishing the familiarization period, the neurophysiologist placed the electrodes. If a subject skilled high level of ache or nausea the size became paused and the continuation become evaluated by way of the neurophysiologist. Two of the volunteers fa inted all the way through the electrode insertion manner and did not participate in the recordings. moreover, one discipline experienced excessive pain from the electrode positioned in pronator teres muscle which had to be removed. nonetheless, during this case, the recording changed into carried out with the different 5 electrodes. however sometimes experiencing ache or nausea, different topics had the entire electrodes in targeted muscle tissues. After securing all wires and preamplifiers with the adhesion tape, the subject turned into advised to vicinity his hand in the force measurement gadget and sit comfortably (see Fig. 1).

Fig. 1

Experimental setup. (a) targeted muscular tissues for the brief residual limb (SRL) and lengthy residual limb (LRL) protocols. higher rows of both protocols show manoeuvres previous needle insertion and the insertion facets. backside rows show places of targeted muscular tissues (T), ulna (U) and radius (R) in the forearm pass sections at the needles insertion facets. Modified from Perotto et al.27. Courtesy of Charles C Thomas writer, Ltd., Springfield, Illinois. (b) signal size chain displaying two separate techniques for acquisition of EMG and joint forces. The hardware synchronization was implemented as a digital line betw een the NI card and the Quattrocento machine. (c) dimension setup: force/torque size apparatus, preamplifiers, visual cue and measurement movement handle, Quattrocento amplifier and OT BioLab utility for true-time monitoring of the iEMG signals. (d) Screenshot of the LabVIEW GUI during the sine-tracking assignment. (e) exceptional-wire electrode guidance. (f) position of the hand within the drive size equipment.

The complete measurement protocol changed into controlled and guided instantly (devoid of the need of a manual protocol control or an instructor) with the aid of the custom-made utility developed in LabVIEW. earlier than every project, a short written description become offered on the monitor, followed by using the onset indicator comprising a huge green easy indicator (visible cue) and a beeping sound (auditory cue). This "go cue" changed into handiest crucial for maximal voluntary contraction (MVC) and grasping tiers of the dimension as the relaxation of the protocol ranges were focusing on sine tracking. throughout the measurement, chosen forces have been introduced to the topics, e.g. whereas performing index finger stream, handiest the index finger force changed into shown. during any circulate, a manual override of a offered cue became viable upon discipline's request, e.g. decreasing/expanding visual cue force. because the whole manner turned into computerized, codes for particular person tiers had been generated and recorded alongside the force signals. The automated protocol executed experimental substages in the same order as offered in desk 1. all the way through the measurements, a medical neurophysiologist turned into gazing the iEMG signals in actual-time.

desk 1 The list of different actions and their codes within the database information. The identical desk can be discovered within each and every database entry (telephone ".actions"). during this table x could be 0 or 1, where 1 denotes duration1.1 of the movement cue and 0 rest length inside the protocol substage.

The gadget setup for the primary actions' protocol (Single DoF initiatives) blanketed a MVC of individual joints (codes x.1 and x.2 for x in [1,8]) and a torque tracking task (code x.3 for x in [1,8]). For the MVC project, the topics were instructed to operate one effective contraction the use of handiest the designated joints. The onset and duration (5 s) were guided via the onscreen indicator and a beeping sound. These periods are labelled within the recorded files with increments of 0.01 on the bottom stream codes. for example, code 3.eleven denotes exact MVC contraction cue of the ring finger whereas 3.10 is rest/preparation length in the ring finger MVC sub stage. The MVC test turned into performed to investigate maximal joint force/torque (used in cue verify as the reference) and to listing muscle contraction with the maximal number of active fibres. within the tracking projects, the subject changed into requested to provide force/torque that matched the cue offered on t he display. Sinusoidal waveforms had been supplied as visual cues to estimate gradual drive increase. The motive at the back of the sinusoidal monitoring task became to give iEMG facts and drive records for proportional control of a hand prosthesis. The repetition frequency became set to 0.1 Hz to enable a gradual and controllable drive boost. apart from the basic actions (individual fingers and wrist flexion-extension, abduction-adduction and pronation-supination) a set of single joint 2DoF (code x.1 for x in [9,10]), multi-joint 2DoF (code x.1 for x in [11,14]) and synergistic (code x.1 for x in [15,22]) hand and wrist movements were blanketed in the protocol. each single and multi-joint 2DoF movements were in keeping with trajectory tracking cues. in the case of single joint actions, the subject became monitoring a 2nd trajectory (circle) on the screen, the place the circle radius changed into calculated because the lesser of two values from the corresponding single DoF sub tie rs. for example, for thumb joystick sub stage (9.1) the circle radius turned into calculated the usage of the smaller of the two amplitudes used for sub tiers 5.three and 6.three. The synergistic movements were defined as 4 repetitions of movements with self-chosen drive and timings governed by way of each a visible and an audio cue. The subjects had been advised to execute the synergistic multi-joint movements synchronously () other than both movements that covered the observe "adopted" within the circulate description (see actions 18 and 22 in table 1). In these two instances, the topics had been prompt to first comprehensive the first circulate (i.e. for stage 18: pronation) after which birth the 2d stream (i.e. for stage 18: palmar draw close). To make it clear, we protected this clarification within the textual content. The labeli ng of synergistic circulation cues turned into performed in a similar fashion to the labeling of the circulation cue implemented for single DoF MVC sub tiers. as an instance, three-digit pinch move cue was labeled with 0.01 increment on the bottom movement code leading to 20.11, whereas the leisure between repetitions become labeled with 20.10. The chosen movements were foreseen as the most commonplace gestures and grasps that a user will frequently operate with a hand prosthesis29,30,31. The recording lasted for 30 minutes. A mock-up video (iEMG_movements.mp4) demonstrating the hand gestures in free-movement situations is supplied inside the equal repository because the recorded records.

statistics pre-processing

The iEMG records recorded with OT BioLab turned into imported to Matlab (MathWorks, Natick, Massachusetts, u . s . a .). The 2nd statistics file (_.tdms) containing force dimension, synchronization indicators, monitoring cue, the stage label, channel labels and time stamps recorded with the NI-6218 and LabVIEW utility become also imported in Matlab. the 1st step of the facts processing was to eradicate 50 Hz noise and its harmonics from the iEMG information. however iEMG turned into recorded with an amplifier with 50 Hz suppression circuitry, the recorded records nevertheless contained some suggested spectral add-ons at 50 Hz and some of the harmonics. To reduce the noise, a filter financial institution comprising slender notch filters centred at 50 Hz and harmonic values up to 5 kHz with 2 Hz width become developed. The applied filter changed into custom-made for each and every recording to reduce spectral distortion. To conserve synchronization between channels, zero part filters (Matlab command: filtfilt) had been used. The subsequent step in the statistics processing changed into to realize synchronization pulses in each information. This was achieved by numerically differentiating the 1D synchronization signal (Matlab command: diff) to stress pulse edges. the usage of the differentiated signal, the detection of the primary pulse leading edge and the closing pulse trailing facet in each files was performed. As a verify-up, the count number of all synchronization pulses was in comparison to investigate that each information include the identical records. To put together the facts for the joint database, an interpolation of the force statistics gathered the usage of LabVIEW turned into executed to accommodate the Quattrocento iEMG statistics sampling price (Matlab command: interp1).

anyway uncooked statistics, motor unit motion potentials (MUAPs) detected and sorted from the recorded iEMG are provided as metadata. MUAP sorting changed into performed using an algorithm based on prior work by using the authors32, which assigns MUAPs to the most an identical waveform template in a collection. To investigate similarity between the MUAPs and each waveform template, the MUAPs had been first aligned to the template the usage of the lag that maximizes the cross-correlation between them, and then here two criteria h ave been evaluated: a) correlation coefficient between the MUAP and waveform template improved than 0.9; b) mean square change between the MUAP and the waveform template smaller than half of the power of the waveform template. The spike sorting algorithm become carried out three times, wherein all motor unit action potentials (initially detected by means of a threshold) have been processed in chronological order. within the first generation, if the present MUAP turned into akin to any template already in the set, that template changed into updated to account for the brand new MUAP; otherwise, a brand new template became created. in the 2d iteration, all detected MUAP have been re-processed, and present templates were updated, however no new templates were created. in the final new release, MUAPs had been in comparison with each and every template and labelled as belonging to their surest fit, offered the above criteria have been met, in any other case the MUAP changed into labelled as unknown. at the end of the primary two iterations, the templates that had under 5% of MUAPs with appreciate to the whole variety of MUAPs were discarded.

as the database is basically recoded for the goal of deriving and checking out of distinct handle algorithms for prosthetic fingers, an iEMG signal feature changed into also calculated the use of raw indicators. To provide alerts for the benchmarking of novel algorithms, envelopes of the recorded iEMG signals were extracted and supplied as metadata. the basis suggest square (RMS), as one of the most common EMG sign elements, changed into selected to signify the signal envelope. within the metadata associated with the leading iEMG database, the RMS turned into calculated using 250 ms broad window which changed into shifted in steps of one sample. The sliding window become centred over the existing sample, leading to zero part shift between the uncooked sign and its envelope. it's going to be stated that this processing does not satisfy the condition of causality this is existing in precise-time purposes where the value of the current signal feature may be calculated the use of si mplest previous samples. then again, the zero-phase shifted envelope is supplied with the statistics as a measure of an "most fulfilling" sign feature, and it can be transposed into a practical envelope by moving the entire signal by using half of the window dimension (125 ms which equals 1280 samples). The envelope alerts were now not normalized.