QtracW Threshold Tracking Software
Introduction to QtracW Threshold Tracking Software
QtracW Threshold Tracking Software is a flexible, stimulus-response data acquisition program with averaging, threshold-tracking and latency-tracking facilities, originally written for studies of human nerves in vivo, but also used for microneurography, muscle excitability testing and cortical excitability testing with transcranial magnetic stimulation.
It is most appropriate for experiments in which the excitability or response of the preparation varies slowly with time, either due to programmed changes in the stimulus or to an externally initiated treatment, and the data of primary interest are the changes in selected parameters (threshold, amplitude, latency, etc.) of the response with time. All or selected raw response waveforms can also be recorded, enabling the time course of additional response parameters to be calculated after the recording is finished. QTrac (which became QtracW when adapted for Windows) comprises separate stimulation and plotting programs, QTracS and QTracP, both written in Visual Basic 6.0, which have the same mode of operation and share many of the same facilities.
The Digitimer DS5 Bipolar Constant Current Stimulator was specifically designed to work with QtracW software for human studies of nerve/muscle excitability. The major components of a human nerve excitability setup include a PC running QtracW software, a nerve stimulator (e.g. Digitimer DS5), an isolated EMG amplifier (e.g. Digitimer D440-2) and a compatible DAQ interface. We also strongly recommend the Digitimer Humbug Noise Eliminator or D400-2/D400-4 to remove mains interference, as many QtracW systems are mobile and used in electrically noisy hospital environments. For animal-based studies, our DS4 Biphasic Stimulator is a suitable alternative to the DS5 and compatible with QtracW.
For those unfamiliar with the application of QtracW software in studies of nerve excitability, we recommend the recent article by Prof. Matthew Kiernan and colleagues (Kiernan et al. 2020), which provides guidelines for the measurement of axonal excitability and provides a state of the art review of axonal excitability research.
Compatible DAQ Hardware
National Instruments DAQ interfaces are recommended for use with QtracW software (see below). Please consult the QtracW users manual for the latest details on specific models.
Obtaining QtracW
The most recent version of QtracW software can be freely downloaded from here. After 50 days evaluation QtracW will only function through use of a USB hardware dongle/key which is provided once a licence has been purchased from Digitimer. All new licences are activated for a minimum of 3 years.
Installation Instructions
All the necessary files and installation instructions are available from here.
QtracW Training
A series of highly successful nerve excitability workshops have been held between 2009 and 2023. Further workshops may be organised in the future if there is adequate demand. Please contact us if you are interested in attending a workshop and we can put you in touch with the organisers if any are planned.
Purchasing QtracW
New QtracW users need to purchase a 3 year licence pack from Digitimer, with non-commercial academic and clinical users receiving a 50% discount from the full list price of £4,000.
This initial pack consists of one QtracSP dongle (stimulation and analysis/plotting) and two QtracP (analysis/plotting only) dongles. Once a user becomes a registered QtracW licensee, further dongles can be purchased individually with variable lifetimes (one to five years) and capabilities (either QtracP or QtracSP).
Additional USB Dongles and Licence Extensions for Existing Users
Registered users can purchase additional dongles or extend the lifetime of an existing dongle by paying the appropriate licence fee. Existing QtracW users can also transfer licence time from a dongle to their computer using a new “dongle internalisation” feature. Please contact Digitimer for further details.
Hardware & Software Requirements
QtracW can be used with PCs running Windows 10. (QtracW may also be used on a Mac, if Parallels is used to install Windows and a Windows keyboard is added.)
QtracS currently supports the following data acquisition cards/units:
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PCI: PCI-6221M (National Instruments) (All Qtrac functions)
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PCMCIA: DAQCard-6062E (National Instruments) (Digital o/p not supported)
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USB: USB-6221, USB-6251 (NI) (All Qtrac functions)
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USB-6341 (National Instruments) (All Qtrac functions)
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Micro-1401 (Cambridge Electronic Design) (Digital o/p not supported)
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Power-1401 (Cambridge Electronic Design) (Digital o/p not supported)
Motor Unit Number Estimation (MUNE) – MScanFit
Compound muscle action potential (CMAP) scans are detailed stimulus-response curves which provide information about motor unit properties in neuromuscular disorders. Available from the QtracW download page, MScanFit is a freeware program which is described in the paper ‘Estimating motor unit numbers from a CMAP scan’ (Bostock, 2015). The program works by generating a motor unit model to account for a detailed stimulus-response curve or CMAP scan obtained using QtracW protocols. Full details of the assumptions, the generation of a preliminary model, and the method of refining the model to improve the fit to the recorded CMAP scan can be found in that paper.
QTMS Cortical Excitability Protocols for Solo TMS Operators
QtracW is increasingly being used for microneurography, muscle excitability testing and cortical excitability testing with transcranial magnetic stimulation. Although control of magnetic stimulators has been possible for several years under standard QtracS protocols, Prof. Hugh Bostock and his colleagues at QTMS Science Ltd. have recently launched a new QTMSG recording suite specifically aimed at TMS users, allowing a solo operator to run QtracW TMS protocols and obtain standardized recordings automatically. Please see our QTMS product page for further details.
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D501 Isolated Temperature Monitor
The NEW Digitimer D501 Isolated Temperature Monitor is specifically intended for use with QtracW software for monitoring human body temperature during muscle and axonal excitability measurements. A USB Type B cable provides PC communication and power. The D501 has a large backlit LCD screen allowing temperature to be monitored visually while a protocol is in progress.
Data obtained from in vivo physiological studies are highly temperature dependent, and because a QtracW protocol can take 10-15 minutes to complete any changes in body temperature will be reflected in the results. By recording skin temperature alongside excitability measurements, temperature changes can be controlled for, or at least checked for significant shifts during a recording.
The ability to continuously record temperature alongside excitability data also means that research studies specifically intended to examine the effect of cooling or heating are more easily accomplished.
Designed for Safe Use in Human Research Studies
The D501 is supplied with a USB cable and a compact, 5mm diameter, cable-mounted flat thermistor (D501-PROBE), which is easily attached to the skin, either using micropore tape or by placing it under a self-adhesive stimulating electrode. Please note that while the D501 has been designed to provide medical device compliant levels of isolation, it is not a certified medical device and is marketed specifically for human research applications.
Although the D501 has been specifically developed for use with QtracW software, we expect it to have wider uses, where there is a requirement to monitor the temperature of a subject or animal in a safe, electrically isolated manner.
D501 Compatible Temperature Monitoring Features Added to QtracW Software
Nerve excitability measurements, particularly components of the recovery cycle are highly temperature-dependent (1), and as it is not particularly easy to accurately control nerve temperature (2), a reliable method of temperature monitoring is advised. This allows users to compare recordings across experimental groups of subjects with a point of reference in respect of temperature. Temperature correction factors may also be employed to compensate for inter-operator variations (3).
In combination with our new D501 Temperature Monitor, users of the QtracS program are now able to measure and display instantaneous temperature with each stimulus and record this temperature alongside other data. QtracP has also been updated to provide automatic addition of protocol-specific temperatures as EXTRA VARIABLES for every component of a TRNDNF recording. Note that this new software requires use of the lastest versions of QtracS (2024-07-15) and QtracP (2024-07-15). These are available from the QtracW Dropbox folder.
Here is a recording made in conjunction with the D501 Temperature Monitor, kindly provided by Prof. Martin Koltzenburg (University College London), of two TRONDNF protocols, one cool, one after warming:
The temperature is plotted against elapsed time by V..@, and the temperature at a specific time by Temp at the bottom of the second data box on the right. Clicking on ‘MEM/Create MEM file’ compares the two recordings, e.g.:
By default, the latest of the two repeats is used for the MEM file, which has the temperatures of the different protocols added as EXTRA VARIABLES, as shown. To confine analysis to the first TROND recording, you can now simply limit the display to the first with e.g. in this case DE20, then:
N.B. The times at which the temperatures were recorded are given with the relevant waveform data, e.g. in this case: RECOVERY CYCLE DATA (7.5-11.1m)
References
1. Kiernan MC, Cikurel K, Bostock H. (2001) Effects of temperature on the excitability properties of human motor axons. Brain 124, 816-825. [link]
2. Kovalchuk MO, Franssen H, Scheijmans FEV, van Schelven LJ, van den Berg, LH, Sleutjes BTHM. (2019) Warming nerves for excitability testing. Muscle Nerve 60, 279-285. [link]
3. Tomlinson S, Burke D, Hanna M, Koltzenburg M & Bostock H. (2010). In vivo assessment of HCN channel current (I(h)) in human motor axons. Muscle Nerve 41, 247-56. [link]