calc_rf_center.py
7542b39630c1feature-gammamri

calc_rf_center.py
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			from types import SimpleNamespace
			from typing import Tuple

			import numpy as np


			def calc_rf_center(rf: SimpleNamespace) -> Tuple[float, float]:
			"""
			Calculate the time point of the effective rotation calculated as the peak of the radio-frequency amplitude for the
			shaped pulses and the center of the pulse for the block pulses. Zero padding in the radio-frequency pulse is
			considered as a part of the shape. Delay field of the radio-frequency object is not taken into account.

			Parameters
			----------
			rf : SimpleNamespace
			Radio-frequency pulse event.

			Returns
			-------
			time_center : float
			Time point of the center of the radio-frequency pulse.
			id_center : float
			Corresponding position of `time_center` in the radio-frequency pulse's envelope.
			"""
			eps = np.finfo(float).eps
			for first, x in enumerate(rf.signal):
			if abs(x) > eps:
			break

			for last, x in enumerate(rf.signal[::-1]):
			if abs(x) > eps:
			break

			# Detect the excitation peak: we traverse over in-place reverse of rf.signal; we want index from the ending
			last = len(rf.signal) - last - 1
			rf_min = min(abs(rf.signal[first:last + 1]))
			rf_max = max(abs(rf.signal[first:last + 1]))
			id_center = np.argmax(abs(rf.signal[first:last + 1]))
			if rf_max - rf_min <= eps:
			id_center = round((last - first + 1) / 2) - 1

			time_center = rf.t[first + id_center]

			return time_center, id_center