Scanners
The MRI scanner that is used during acquisition puts various constraints on the MR sequences that can be used. These constraints include safety considerations, such as tissue heating, and hardware constraints, such as maximum gradient strength and slew rate. Currently, MRIBuilder only considers the latter.
To define a sequence appropriate for a specific scanner, a user would define a new Scanner
with the appropriate B0
, maximum variables.gradient_strength
, and maximum variables.slew_rate
. This scanner would then be passed on to the sequence optimisation.
For ease of use, the gradient_strength
and slew_rate
of many scanners have already been pre-defined. These are listed below.
Scanners API
MRIBuilder.Scanners
— ModuleDefine general Scanner
type and methods as well as some concrete scanners.
MRIBuilder.Scanners.Default_Scanner
— ConstantA default 1.5T scanner.
Matches the one used in pulseq
(https://github.com/pulseq/pulseq/blob/master/matlab/%2Bmr/opts.m).
MRIBuilder.Scanners.Siemens_Connectom
— ConstantSiemens 3T Connectom MRI scanner (fan22_MappingHumanConnectome).
MRIBuilder.Scanners.Siemens_Connectom_v2
— ConstantSiemens 3T Connectom 2.0 MRI scanner (huang21_ConnectomeDevelopingnextgeneration)
MRIBuilder.Scanners.Siemens_Prisma
— ConstantSiemens MAGNETOM 3T Prisma MRI scanner (https://www.siemens-healthineers.com/en-uk/magnetic-resonance-imaging/3t-mri-scanner/magnetom-prisma).
MRIBuilder.Scanners.Siemens_Terra
— ConstantSiemens MAGNETOM 7T Terra MRI scanner (https://www.siemens-healthineers.com/en-uk/magnetic-resonance-imaging/7t-mri-scanner/magnetom-terra)
MRIBuilder.Scanners.Scanner
— TypeScanner(;B0=3., gradient=Inf, slew_rate=Inf, units=:kHz)
Properties of an MRI scanner relevant for the MR signal simulations.
B0
: magnetic field strength (in Tesla)gradient_strength
: maximum gradient strength long each axis.slew_rate
: maximum rate of change in the gradient strength
By default gradient
and slew_rate
are expected to be provided in units of, respectively, kHz/um and kHz/um/ms. However, if the keyword units=:Tesla
is set, the gradient
and slew_rate
should be provided in units of, respectively, mT/m and T/m/s.
MRIBuilder.Scanners.B0
— MethodB0(scanner)
B0(sequence)
Returns the magnetic field strength of the scanner in Tesla.
MRIBuilder.Scanners.gradient_strength
— Functiongradient_strength(scanner[, units])
Returns the maximum magnetic field gradient of the scanner in kHz/um. By setting units
to :Tesla, the gradient strength can be returned in mT/m instead.
MRIBuilder.Scanners.slew_rate
— Functionslew_rate(scanner[, units])
Returns the maximum magnetic field slew rate of the scanner in kHz/um/ms. By setting units
to :Tesla, the slew rate can be returned in T/m/s instead.