Sampling (ADC)#

Module containing the implementation of sampling blocks

Classes:

`ADC`(system_specs, name, adc_timing, ...)	ADC-specific extension to the SequenceBaseBlock, serves as base class for all ADC implementations.
`SymmetricADC`(system_specs, num_samples[, ...])	ADC with instantaneous encoding events at k-space positions.
`GridSamplingADC`(system_specs, duration[, ...])	Defines an oversampling adc-block on system adc_raster_time

class ADC(system_specs, name, adc_timing, adc_center, frequency_offset, phase_offset)[source]#

Bases: SequenceBaseBlock

ADC-specific extension to the SequenceBaseBlock, serves as base class for all ADC implementations.

Parameters:

system_specs (SystemSpec) – System Limits specification object
name (str) –
adc_timing (Quantity) – Quantity array of dimension time, containing all sampling event timings.
adc_center (Quantity) – Time point defining the center of the ADC object
phase_offset (Quantity) – Phase-offset for all adc-samples, added when computing the adc-phase.
frequency_offset (Quantity) – Frequency offset for all adc-samples, converted to an additional phase offset per sample

Attributes:

`adc_timing`	Timing of ADC-sampling events.
`adc_center`	Time defining the center of the adc-events.
`frequency_offset`	Frequency offset for all adc-samples, converted to an additional phase offset per sample and added when computing the adc-phase property.
`phase_offset`	Phase-offset for all adc-samples, added when computing the adc-phase property.
`adc_phase`	Returns the phase \(\phi_s\) at each adc sample \(s\) in radians given the phase offset \(\phi_0\) and frequency offset \(\delta f\) according to the formular:
`tmin`	Calculates the smallest time occuring in all contained definitions.
`tmax`	Calculates the largest time occuring in all contained definitions.

Methods:

`validate`(system_specs)	Should raise a ValueError if subclass logic is not met by definition :type system_specs: `SystemSpec` :param system_specs: :return:
`shift`(time_shift)	Adds the time-shift to all adc definition points and the adc-center
`flip`([time_flip])	Flips block around specified time point
`snap_to_raster`(system_specs)	rtype: `None`

adc_timing: Quantity#: Timing of ADC-sampling events. Exact definition of the meaning of that sampling time is delegated to subclass implementation. Quantity[ms]

adc_center: Quantity#: Time defining the center of the adc-events. Meant to synchronize the ADC block with echo times. Quantity[ms]

frequency_offset: Quantity#: Frequency offset for all adc-samples, converted to an additional phase offset per sample and added when computing the adc-phase property. Quantity[Hz]

phase_offset: Quantity#: Phase-offset for all adc-samples, added when computing the adc-phase property. Quantity[rad]

property adc_phase: Quantity#: Returns the phase \(\phi_s\) at each adc sample \(s\) in radians given the phase offset \(\phi_0\) and frequency offset \(\delta f\) according to the formular:

\[\phi_s = \phi_0 + 2 * \pi * \delta f\]

property tmin: Quantity#: Calculates the smallest time occuring in all contained definitions. :return: Quantity[time]

property tmax: Quantity#: Calculates the largest time occuring in all contained definitions. :return: Quantity[time]

validate(system_specs)[source]#

Should raise a ValueError if subclass logic is not met by definition :type system_specs: SystemSpec :param system_specs: :return:

Parameters:: system_specs (SystemSpec) –

shift(time_shift)[source]#

Adds the time-shift to all adc definition points and the adc-center

Return type:: None
Parameters:: time_shift (Quantity) –

flip(time_flip=None)[source]#

Flips block around specified time point

Parameters:: time_flip (Quantity | None) –

snap_to_raster(system_specs)[source]#

Return type:: None
Parameters:: system_specs (SystemSpec) –

name: str#

class SymmetricADC(system_specs, num_samples, dwell=None, duration=None, delay=None, frequency_offset=<Quantity(0.0, 'hertz')>, phase_offset=<Quantity(0.0, 'radian')>, name='adc')[source]#

Bases: ADC

ADC with instantaneous encoding events at k-space positions.

Defines an ADC with sampling events uniformly distributed over the given duration. The central time point is allways contained as sampling event.

Note

For even number of samples the left border of the dwell time interval is defined as sampling events. For odd number of samples, the events are symmetric around center time.

Parameters:

num_samples (int) – number of sampling events over duration
system_specs (SystemSpec) – cmrseq.SystemSpec object
dwell (Optional[Quantity]) – Quantity[time] Interval length associated with 1 sampling event. Corresponds to kspace extend in readout-direction (1/FOV_kx).
duration (Optional[Quantity]) – Quantity[time] Total sampling duration corresponding to (1 / Delta kx). Usually is the same as flat_duration of accompanying trapezoidal gradient.
delay (Optional[Quantity]) – Quantity[time] Leading time without sampling events
frequency_offset (Quantity) – Adds a linearly increasing phase over the ADC duration, used for e.g. RF-spoiling or in-plane FOV shift.
phase_offset (Quantity) – Adds a constant phase offset to the adc, e.g. in RF spoiling
name (str) –

Attributes:

`tmin`	Returns the time of the first sampling event.
`tmax`	Returns the time of the last sampling event.

Methods:

from_centered_valid(system_specs, ...[, ...])

Creates an ADC block with valid duration (dwell time on raster) where the stated duration

property tmin: Quantity#

Returns the time of the first sampling event. Behavior varies for odd/even number of samples:

odd: Returns the time of the first sampling event minus half a dwell time on
gradient raster time.

even: Returns the time of the first sampling event

In both cases this corresponds to the start of the plateau of a readout gradient

property tmax: Quantity#

Returns the time of the last sampling event. Behavior varies for odd/even number of samples:

odd: Returns the time of the last sampling event plus half a dwell time.

even: Returns the time of the last sampling event plus a full dwell time.

In both cases this corresponds to the end of the plateau of a readout gradient

classmethod from_centered_valid(system_specs, num_samples, duration, delay=None, frequency_offset=<Quantity(0.0, 'hertz')>, phase_offset=<Quantity(0.0, 'radian')>, name='adc')[source]#

Creates an ADC block with valid duration (dwell time on raster) where the stated duration: is the upper bound (altered by at max num_samples * adc_raster_time). The difference in

duration is padded around at the start and end of the block to maintain the center.

Guarantees to have a sample at the exact half duration of the ADC block.

Parameters:

num_samples (int) – number of sampling events over duration
system_specs (SystemSpec) – cmrseq.SystemSpec object
duration (Quantity) – target duration that is modified such that the resulting dwell time is on the adc raster
delay (Optional[Quantity]) – Quantity[time] Leading time without sampling events
frequency_offset (Quantity) – Adds a linearly increasing phase over the ADC duration, used for e.g. RF-spoiling or in-plane FOV shift.
phase_offset (Quantity) – Adds a constant phase offset to the adc, e.g. in RF spoiling

Return type:

SymmetricADC

class GridSamplingADC(system_specs, duration, delay=<Quantity(0, 'millisecond')>, frequency_offset=<Quantity(0.0, 'hertz')>, phase_offset=<Quantity(0.0, 'radian')>, name='adc')[source]#

Bases: ADC

Defines an oversampling adc-block on system adc_raster_time

Attributes:

`tmin`	Calculates the smallest time occuring in all contained definitions.
`tmax`	Calculates the largest time occuring in all contained definitions.

Parameters:

system_specs (SystemSpec) –
duration (Quantity) –
delay (Quantity) –
frequency_offset (Quantity) –
phase_offset (Quantity) –
name (str) –

property tmin: Quantity#: Calculates the smallest time occuring in all contained definitions. :return: Quantity[time]

property tmax: Quantity#: Calculates the largest time occuring in all contained definitions. :return: Quantity[time]

This module contains definition of a simple delay building block

Classes:

Delay(system_specs, duration[, delay, name])

Defines a gradient with zero magnitude and given duration

class Delay(system_specs, duration, delay=<Quantity(0.0, 'millisecond')>, name='delay')[source]#

Defines a gradient with zero magnitude and given duration

Parameters:

system_specs (SystemSpec) –
duration (Quantity) –
delay (Quantity) –
name (str) –