from typing import Union
from pypulseq.convert import convert
class Opts:
"""
System limits of an MR scanner.
Note: Default values can be overwritten by creating an Opts object and
calling `set_as_default`.
Attributes
----------
adc_dead_time : float, default=0
Dead time for ADC readout pulses.
adc_raster_time : float, default=100e-9
Raster time for ADC readout pulses.
block_duration_raster : float, default=10e-6
Raster time for block durations.
gamma : float, default=42.576e6
Gyromagnetic ratio. Default gamma is specified for Hydrogen.
grad_raster_time : float, default=10e-6
Raster time for gradient waveforms.
grad_unit : str, default='Hz/m'
Unit of maximum gradient amplitude. Must be one of 'Hz/m', 'mT/m' or 'rad/ms/mm'.
max_grad : float, default=40 mT/m
Maximum gradient amplitude.
max_slew : float, default=170 T/m/s
Maximum slew rate.
rf_dead_time : float, default=0
Dead time for radio-frequency pulses.
rf_raster_time : float, default=1e-6
Raster time for radio-frequency pulses.
rf_ringdown_time : float, default=0
Ringdown time for radio-frequency pulses.
adc_samples_limit : int, default=0
Maximum number of samples for a single ADC object. If 0, no limit is set.
adc_samples_divisor : int, default=4
Samples of ADC must be divisible by 'adc_samples_divisor'.
rise_time : float, default=0
Rise time for gradients.
slew_unit : str, default='Hz/m/s'
Unit of maximum slew rate. Must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s' or 'rad/ms/mm/ms'.
B0 : float, default=1.5
Main magnetic field strength (in tesla)
Raises
------
ValueError
If invalid `grad_unit` is passed. Must be one of 'Hz/m', 'mT/m' or 'rad/ms/mm'.
If invalid `slew_unit` is passed. Must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s' or 'rad/ms/mm/ms'.
"""
def __init__(
self,
adc_dead_time: Union[float, None] = None,
adc_raster_time: Union[float, None] = None,
block_duration_raster: Union[float, None] = None,
gamma: Union[float, None] = None,
grad_raster_time: Union[float, None] = None,
grad_unit: str = 'Hz/m',
max_grad: Union[float, None] = None,
max_slew: Union[float, None] = None,
rf_dead_time: Union[float, None] = None,
rf_raster_time: Union[float, None] = None,
rf_ringdown_time: Union[float, None] = None,
adc_samples_limit: Union[int, None] = None,
adc_samples_divisor: Union[int, None] = None,
rise_time: Union[float, None] = None,
slew_unit: str = 'Hz/m/s',
B0: Union[float, None] = None,
):
valid_grad_units = ['Hz/m', 'mT/m', 'rad/ms/mm']
valid_slew_units = ['Hz/m/s', 'mT/m/ms', 'T/m/s', 'rad/ms/mm/ms']
if grad_unit not in valid_grad_units:
raise ValueError(
f"Invalid gradient unit. Must be one of 'Hz/m', 'mT/m' or 'rad/ms/mm'. Passed: {grad_unit}"
)
if slew_unit not in valid_slew_units:
raise ValueError(
f"Invalid slew rate unit. Must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s' or 'rad/ms/mm/ms'. "
f'Passed: {slew_unit}'
)
if gamma is None:
gamma = Opts.default.gamma
if max_grad is not None:
max_grad = convert(from_value=max_grad, from_unit=grad_unit, to_unit='Hz/m', gamma=abs(gamma))
else:
max_grad = Opts.default.max_grad
if max_slew is not None:
max_slew = convert(from_value=max_slew, from_unit=slew_unit, to_unit='Hz/m', gamma=abs(gamma))
else:
max_slew = Opts.default.max_slew
if rise_time is not None:
max_slew = max_grad / rise_time
if adc_dead_time is None:
adc_dead_time = Opts.default.adc_dead_time
if adc_raster_time is None:
adc_raster_time = Opts.default.adc_raster_time
if block_duration_raster is None:
block_duration_raster = Opts.default.block_duration_raster
if rf_dead_time is None:
rf_dead_time = Opts.default.rf_dead_time
if rf_raster_time is None:
rf_raster_time = Opts.default.rf_raster_time
if grad_raster_time is None:
grad_raster_time = Opts.default.grad_raster_time
if rf_ringdown_time is None:
rf_ringdown_time = Opts.default.rf_ringdown_time
if adc_samples_limit is None:
adc_samples_limit = Opts.default.adc_samples_limit
if adc_samples_divisor is None:
adc_samples_divisor = Opts.default.adc_samples_divisor
if B0 is None:
B0 = Opts.default.B0
self.max_grad = max_grad
self.max_slew = max_slew
self.rise_time = rise_time
self.rf_dead_time = rf_dead_time
self.rf_ringdown_time = rf_ringdown_time
self.adc_dead_time = adc_dead_time
self.adc_raster_time = adc_raster_time
self.rf_raster_time = rf_raster_time
self.grad_raster_time = grad_raster_time
self.block_duration_raster = block_duration_raster
self.adc_samples_limit = adc_samples_limit
self.adc_samples_divisor = adc_samples_divisor
self.gamma = gamma
self.B0 = B0
[docs]
def set_as_default(self):
Opts.default = self
@classmethod
def reset_default(cls):
cls.default = Opts(
max_grad=convert(from_value=40, from_unit='mT/m'),
max_slew=convert(from_value=170, from_unit='T/m/s'),
rf_dead_time=0,
rf_ringdown_time=0,
adc_dead_time=0,
adc_raster_time=100e-9,
rf_raster_time=1e-6,
grad_raster_time=10e-6,
block_duration_raster=10e-6,
adc_samples_limit=0,
adc_samples_divisor=4,
gamma=42576000,
B0=1.5,
)
def __str__(self) -> str:
"""
Print a string representation of the system limits objects.
"""
variables = vars(self)
s = [f'{key}: {value}' for key, value in variables.items()]
s = '\n'.join(s)
s = 'System limits:\n' + s
return s
Opts.reset_default()
