Eqtype
Specifies the PDE system to solve. The following values are supported:
Monodomain
: solve the monodomain equation.
BidomainRoth
: solve the bidomain equations using the Roth formulation.CellModel
Specifies the cell model to use. Available cell models are
Projection
Specifies the Galerkin projection type to use. Only Continuous
has been
extensively tested.
TimeIntegrationMethod
Specifies the time integration scheme to use for advancing the
PDE system. This must be an IMEX scheme. Suitable choices are: IMEXOrder1
,
IMEXOrder2
, IMEXOrder3
, IMEXdirk_3_4_3
. The cell model state variables are time
advanced using Forward Euler for the ion concentrations, and Rush-Larsen for the cell
model gating variables.
DiffusionAdvancement
Specifies whether the diffusion is handled implicitly
or explicitly in the time integration scheme. The current code only supports
Implicit
integration of the diffusion term. The cell model is always integrated
explicitly.
The following parameters can be specified in the PARAMETERS
section of the session file.
Example values are taken from [11].
Chi
sets the surface-to-volume ratio (Units: mm−1).Cm
sets the specific membrane capacitance (Units: μFmm−2).Substeps
sets the number of substeps taken in time integrating the cell model for
each PDE timestep.d_min
, d_max
, o_min
, o_max
specifies a bijective map to assign conductivity values σ to
intensity values μ when using the IsotropicConductivity
function. The intensity map
is first thresholded to the range [dmin,dmax] and then the conductivity is calculated
as
σ = (1 − μ) + omin |
The following functions can be specified inside the CONDITIONS
section of the session file. If
both are specified, the effect is multiplicative. Example values are taken from [11].
IsotropicConductivity
specifies the conductivity σ of the tissue. The variable name to use is intensity
since the conductivity may be derived
from late-Gadolinium enhanced MRA imaging. Example specifications are
where scarmap.con
is a Nektar++ field file containing a variable intensity
describing
the conductivity across the domain.
AnisotropicConductivity
specifies the conductivity σ of the tissue.
CellHistoryPoints
writes all cell model states over time at fixed points. Can be used
along with the HistoryPoints
filter to record all variables at specific points during a
simulation.
OutputFile
specifies the filename to write history data to.
OutputFrequency
specifies the number of steps between successive outputs.
Points
lists coordinates at which history data is to be recorded.CheckpointCellModel
checkpoints the cell model. Can be used along with the
Checkpoint
filter to record complete simulation state and regular intervals.
OutputFile
(optional) specifies the base filename to use. If not specified, the
session name is used. Checkpoint files are suffixed with the process ID and
the extension ‘.chk‘.
OutputFrequency
specifies the number of timesteps between checkpoints.Electrogram
Computes virtual unipolar electrograms at a prescribed set of points.
OutputFile
(optional) specifies the base filename to use. If not specified, the
session name is used. The extension ‘.ecg‘ is appended if not already specified.
OutputFrequency
specifies the number of resolution of the electrogram data.
Points
specifies a list of coordinates at which electrograms are desired. They
must not lie within the domain.Benchmark
Records spatially distributed event times for activation and repolarisation
(recovert) during a simulation, for undertaking benchmark test problems.
ThresholdValue
specifies the value above which tissue is considered to be
depolarised and below which is considered repolarised.
InitialValue
specifies the initial value of the activation or repolarisation
time map.
OutputFile
specifies the base filename of activation and repolarisation maps
output from the filter. This name is appended with the index of the event
and the suffix ‘.fld‘.
StartTime
(optional) specifies the simulation time at which to start detecting
events.
Electrophysiological propagaion is initiated through the stimulus current Iion. The STIMULI
section describes one or more regions of stimulus and the time-dependent protocol with which
they are applied.
A number of stimulus types are available
StimulusRect
stimulates a cuboid-shaped region of the domain, specified by two
coordinates (x1,y1,z1) and (x2,y2,z2). An additional parameter specifies the
"smoothness" of the boundaries of the region; higher values produce a sharper boundary.
Finally, the maximum strength of the stimulus current is specified in μA∕mm3
StimulusCirc
stimulates a spherical region of the domain, as specified by a centre and
radius. The smoothness and strength parameters are also specified as for ‘StimulusRect‘.
A protocol specifies the time-dependent function indicating the strength of the stimulus and
one such PROTOCOL
section should be included within each STIMULUS
. This can be expressed as
one of:
ProtocolSingle
a single stimulus is applied at a given start time and for a given
duration
ProtocolS1
a train of pulses of fixed duration applied at a given start time and with a
given cycle length.
ProtocolS1S2
same as ‘ProtocolS1‘ except with an additional single pulse applied at a
different cycle length at the end of the train of S1 pulses.