Pulseq interpreter for OCRA -- upon testing, will be merged into the OCRA repository
Current OCRA software uses hand-written machine code to function -- this limits ease of use. PulSeq is an open-source library widely used in MR pulse design, available in MATLAB and Python. The library primarily functions by generating a .seq file, which scanners interpret. pulseq_assembler.py is an assembler that takes a .seq file and assembles OCRA machine code and data to the specifications of the file.
PSAssembler is an object that initializes with timing and system specifications.
After initializing, run PSAssembler.assemble("[filepath]") to return a list of:
[tx_data, [gx_data, gy_data, gz_data], command_bytes, output_dict] with data in either bytes format or numpy.ndarray
You can pass these to existing OCRA servers, such as MaRCoS
rf_center (int): RF center (local oscillator frequency) in Hz.
rf_amp_max (int): Default 5e+3 -- System RF amplitude max in Hz.
grad_max (int): Default 1e+6 -- System gradient max in Hz/m.
clk_t (float): Default 7e-3 -- System clock period in us.
tx_t (float): Default 1.001 -- Transmit raster period in us.
grad_t (float): Default 10.003 -- Gradient raster period in us.
pulseq_t_match (bool): Default False -- If PulSeq file transmit and gradient raster times match OCRA transmit and raster times.
ps_tx_t (float): Default 1 -- PulSeq transmit raster period in us. Used only if pulseq_t_match is False.
ps_grad_t (float): Default 10 -- PulSeq gradient raster period in us. Used only if pulseq_t_match is False.
tx_warmup (float): Default 0 -- Padding delay at the beginning of RF to give TR warmup in us. PADDING WILL CHANGE TIMING.
grad_pad (int): Default 0 -- Padding zero samples at the end of gradients to prevent maintained gradient levels. PADDING WILL DISTORT GRADIENTS TO KEEP LENGTH
adc_pad (int): Default 0 -- Padding samples in ADC to account for junk in system buffer. PADDING WILL CHANGE TIMING.
addresses_per_grad_sample (int): Default 1 -- Memory offset step per gradient readout, to account for different DAC boards.
rf_delay_preload (bool): Default False -- If True, turn on TX_GATE whenever a block contains RF
fix_grad_length (bool): Default True -- If True, fix the length of the gradient and distort when padded instead of extending.