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Project Overview
The Real-Time eXperiment Interface (RTXI) is a collaborative open-source
software development project aimed at producing a real-time Linux based
software system for hard real-time data acquisition and control
applications in biological research.
The ability of experimentalists to perturb biological systems has
traditionally been limited to rigid pre-programmed protocols or more
flexible, but reflex constrained, operator-controlled protocols. In
contrast, real-time control allows the researcher to dynamically probe a
biological system with parameter perturbations that are calculated
functions of instantaneous system measurements, thereby providing the
ability to address diverse unanswered questions that are not amenable to
traditional approaches. Real-time control applications are abundant
throughout biological research, including, for example, dynamic probing of
ion-channel function, control of cardiac arrhythmia dynamics, and control
of deep-brain stimulation patterns.
Unfortunately, for a number of technical reasons, real-time control is not
possible with standard computer operating systems and software.
Furthermore, commercial real-time systems are costly and often tailored
for industrial applications. To circumvent these limitations, we have developed
RTXI, a fast and highly versatile real-time biological experimentation system
which is based on Real-Time Linux, is open source and free, can be used with
an extensive range of experimentation hardware, and can be run on Linux or
Windows computers (when temporarily booted into Linux using an RTXI
LiveCD).
For more details about the RTXI system, please
click here.
Screen Shots
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A screenshot of RTXI controlling a single-cell cardiac ventricular
myocyte (from a guinea pig) experiment. The system is acquiring and
plotting the membrane potential signal in the oscilloscope screen. The
control block labeled "12 stim" allows the experimentalist to control
the experiment. This particular experiment is performing control of
alternations of action-potential duration. Such control requires real-time
analysis of the action-potential morphology, which is fed into a feedback
equation that governs the stimulus timing. The analysis and feedback are
performed in sub-millisecond resolution.
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A screenshot of RTXI controlling
an isolated guinea-pig ventricular myocyte patch-clamp experiment. The system is acquiring and plotting the membrane potential signal in the oscilloscope
screen. The GUI control block labeled
"12 stim" is the interface for a plugin that
allows the experimentalist to control the
experiment. This particular
experiment is performing control of alternations of action-potential duration in a
single patch-clamped cell. Such control
requires real-time analysis of the actionpotential morphology, which is fed into a
set of feedback equations that govern the
stimulus timing. The analysis and feedback are performed in sub-millisecond
resolution.
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A screenshot of RTXI controlling a multi-channel (6 in this example)
cardiac tissue experiment. The system is acquiring and plotting the voltages measured from 6 spatially dispersed glass microelectrodes in the oscilloscope screens. The GUI block labeled "11 Alternan Control" is used to
control the experiment, which aims to
quantify and control (both in real time)
action-potential duration dynamics. The
lower-right graph with red/blue points is
designed for rapid visualization of spatiotemporal action-potential duration dynamics. This experiment was run at
a real-time frequency of 10kHz, and
showed the ability of RTXI both to operate at rapid rates and to provide the
user with a rich GUI and data display, thereby enabling better experiment monitoring. (Figure courtesy of R.
Gilmour.)
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Acknowledgements
Current support:
- This project is supported by the National Institutes of Health,
National Center for Research Resources (R01RR020115; PI: David J.
Christini, co-PIs: John A White and Robert
J. Butera).
Prior support:
RTXI is the result of merging three open-source real-time experiment
control systems, each of which was developed under support from the National Science Foundation:
- RTLab: Real-Time Linux Lab is
a general-purpose control system used primarily for tissue-level excitable system experiments
(NSF grant DBI-0096596; PI: David J. Christini).
- RTLDC:
Realtime Linux Dynamic Controller is an open-source implementation of
the dynamic clamp, which is a methodology that integrates the
real-time simulation of ion-channel kinetics (or entire models of
excitable cells, such as neurons) with intracellular
electrophysiological experiments (NSF grant BES-0085177; PI: John A. White).
- MRCI: Model
Reference Current Injection system is also an open-source
dynamic-clamp system (NSF grant DBI-9987074; PI: Robert Butera).
Additionally, we would like to thank members of the open-source
software community. Dozens of people have offered tons of
advice, suggestions, and/or source code to aid us in the development
of this software.
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