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convert.py
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Thu, May 9, 04:34

convert.py
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from typing import Iterable, Union
import numpy as np
def convert(from_value: Union[float, Iterable], from_unit: str, to_unit: str = str(),
gamma: float = 42.576e6) -> Union[float, Iterable]:
""""
Converts gradient amplitude or slew rate from unit `from_unit` to unit `to_unit` with gyromagnetic ratio `gamma`.
Parameters
----------
from_value : float
Gradient amplitude or slew rate to convert from.
from_unit : str
Unit of gradient amplitude or slew rate to convert from.
to_unit : str, optional, default=''
Unit of gradient amplitude or slew rate to convert to.
gamma : float, optional, default=42.576e6
Gyromagnetic ratio. Default is 42.576e6, for Hydrogen.
Returns
-------
out : float
Converted gradient amplitude or slew rate.
Raises
------
ValueError
If an invalid `from_unit` is passed. Must be one of 'Hz/m', 'mT/m', or 'rad/ms/mm'.
If an invalid `to_unit` is passed. Must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s', 'rad/ms/mm/ms'.
"""
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']
valid_units = valid_grad_units + valid_slew_units
if from_unit not in valid_units:
raise ValueError("Invalid from_unit. Must be one of 'Hz/m', 'mT/m', or 'rad/ms/mm' for gradients;"
"or must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s', 'rad/ms/mm/ms' for slew rate.")
if to_unit != '' and to_unit not in valid_units:
raise ValueError("Invalid to_unit. Must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s', 'rad/ms/mm/ms' for gradients;"
"or must be one of 'Hz/m/s', 'mT/m/ms', 'T/m/s', 'rad/ms/mm/ms' for slew rate..")
if to_unit == '':
if from_unit in valid_grad_units:
to_unit = valid_grad_units[0]
elif from_unit in valid_slew_units:
to_unit = valid_slew_units[0]
# Convert to standard units
# Grad units
if from_unit == 'Hz/m':
standard = from_value
elif from_unit == 'mT/m':
standard = from_value * 1e-3 * gamma
elif from_unit == 'rad/ms/mm':
standard = from_value * 1e6 / (2 * np.pi)
# Slew units
elif from_unit == 'Hz/m/s':
standard = from_value
elif from_unit == 'mT/m/ms' or from_unit == 'T/m/s':
standard = from_value * gamma
elif from_unit == 'rad/ms/mm/ms':
standard = from_value * 1e9 / (2 * np.pi)
# Convert from standard units
# Grad units
if to_unit == 'Hz/m':
out = standard
elif to_unit == 'mT/m':
out = 1e3 * standard / gamma
elif to_unit == 'rad/ms/mm':
out = standard * 2 * np.pi * 1e-6
# Slew units
elif to_unit == 'Hz/m/s':
out = standard
elif to_unit == 'mT/m/ms' or to_unit == 'T/m/s':
out = standard / gamma
elif to_unit == 'rad/ms/mm/ms':
out = standard * 2 * np.pi * 1e-9
return out

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