Page MenuHomec4science
Files F84236766

add_gradients.py
No OneTemporary
Actions

File Metadata

Created
Sat, Sep 21, 13:26

add_gradients.py
View Options

import numpy as np
from pypulseq.opts import Opts
from pypulseq.calc_duration import calc_duration
from pypulseq.make_arbitrary_grad import make_arbitrary_grad
from pypulseq.points_to_waveform import points_to_waveform
def add_gradients(grads, system=Opts(), max_grad=0, max_slew=0):
max_grad = max_grad if max_grad > 0 else system.max_grad
max_slew = max_slew if max_slew > 0 else system.max_slew
if len(grads) < 2:
raise Exception()
# First gradient defines channel
channel = grads[0].channel
# Find out the general delay of all gradients and other statistics
delays, firsts, lasts, durs = [], [], [], []
for ii in range(len(grads)):
delays.append(grads[ii].delay)
firsts.append(grads[ii].first)
lasts.append(grads[ii].last)
durs.append(calc_duration(grads[ii]))
common_delay = min(delays)
total_duration = max(durs)
waveforms = dict()
max_length = 0
for ii in range(len(grads)):
g = grads[ii]
if g.type == 'grad':
waveforms[ii] = g.waveform
elif g.type == 'trap':
if g.flat_time > 0: # Triangle or trapezoid
times = [g.delay - common_delay,
g.delay - common_delay + g.rise_time,
g.delay - common_delay + g.rise_time + g.flat_time,
g.delay - common_delay + g.rise_time + g.flat_time + g.fall_time]
amplitudes = [0, g.amplitude, g.amplitude, 0]
else:
times = [g.delay - common_delay,
g.delay - common_delay + g.rise_time,
g.delay - common_delay + g.rise_time + g.flat_time]
amplitudes = [0, g.amplitude, 0]
waveforms[ii] = points_to_waveform(times=times, amplitudes=amplitudes,
grad_raster_time=system.grad_raster_time)
else:
raise ValueError('Unknown gradient type')
if g.delay - common_delay > 0:
t_delay = list(range(0, g.delay - common_delay - system.grad_raster_time, system.grad_raster_time))
waveforms[ii] = waveforms[ii].insert(0, t_delay)
num_points = len(waveforms[ii])
max_length = num_points if num_points > max_length else max_length
w = np.zeros((max_length, 1))
for ii in range(len(grads)):
wt = np.zeros((max_length, 1))
wt[0:len(waveforms[ii])] = waveforms[ii]
w += wt
grad = make_arbitrary_grad(channel, w, system, max_slew=max_slew, max_grad=max_grad, delay=common_delay)
grad.first = np.sum(firsts[np.where(delays == common_delay)])
grad.last = np.sum(lasts[np.where(durs == total_duration)])
return grad

Event Timeline

c4science · Help