tools.estimate_epi_phase#
- bartorch.tools.estimate_epi_phase()#
Odd/even phase of an EPI readout, fitted to a three-line navigator.
The navigator is three blip-nulled readouts of alternating polarity. In hybrid space (the centred inverse transform along the readout), the phase of \(\sum_c m_c b_c^*\), with \(m\) the mean of the two forward lines and \(b\) the reversed line, is unwrapped and fitted with a polynomial by least squares weighted by the modulus of that sum, ignoring samples below a tenth of its peak.
- Parameters:
navigator_lines (list of torch.Tensor) – Three
(coils, samples)lines of polarity+ - +, the reversed line already flipped into forward readout order.polynomial_order (int, default=1) – Polynomial order; one is a constant and a linear term, the phase of a constant offset and a gradient or ADC delay.
- Returns:
Float64 coefficients, lowest order first, on the navigator’s device, in a coordinate running from -1 to 1 across the readout. They are the correction
correct_lines()applies to a reversed line: the negative of the phase that line carries. The constant is defined modulo \(2\pi\).- Return type:
torch.Tensor
- Raises:
ValueError – If fewer than three lines are given, or the order is negative.
