Time Reversal Reconstruction

The TimeReversal class provides functionality for time reversal reconstruction in photoacoustic imaging. It handles the reconstruction of initial pressure distributions from recorded sensor data.

Tip

Migration from Legacy Time Reversal

Previous versions used sensor.time_reversal_boundary_data directly with kspaceFirstOrder2D/3D. This approach is now deprecated. Instead, use the new TimeReversal class:

# Old approach (deprecated)
sensor.time_reversal_boundary_data = sensor_data
p0_recon = kspaceFirstOrder2D(kgrid, source, sensor, medium, simulation_options, execution_options)

# New approach
sensor.recorded_pressure = sensor_data  # Store recorded data
tr = TimeReversal(kgrid, medium, sensor)
p0_recon = tr(kspaceFirstOrder2D, simulation_options, execution_options)

Class Documentation

class TimeReversal[source]

Bases: object

Time reversal reconstruction for photoacoustic imaging.

This class handles time reversal reconstruction of initial pressure distribution from sensor data. It supports both 2D and 3D simulations and automatically applies compensation for half-plane recording.

Parameters:

  • kgrid – Computational grid for the simulation

  • medium – Medium properties for wave propagation

  • sensor – Sensor object containing the sensor mask

  • compensation_factor – Factor to compensate for half-plane recording (default: 2.0)

Raises:

ValueError – If inputs are invalid for time reversal

Note

Future versions may support: - GPU acceleration via use_gpu parameter - Differentiable operations via differentiable parameter - Custom boundary conditions via boundary_condition parameter - Elastic wave propagation via elastic parameter

__init__(kgrid, medium, sensor, compensation_factor=2.0)[source]

Initialize time reversal reconstruction.

Parameters:

  • kgrid (kWaveGrid) – Computational grid for the simulation

  • medium (kWaveMedium) – Medium properties for wave propagation

  • sensor (kSensor) – Sensor object containing the sensor mask

  • compensation_factor (float) – Factor to compensate for half-plane recording (default: 2.0)

Raises:

ValueError – If inputs are invalid for time reversal

Return type:

None

Key Features

  • Automatic compensation for half-plane recording

  • Support for both 2D and 3D reconstructions

  • Input validation and error checking

  • Clean interface separating data recording from reconstruction

Example Usage

Here’s a complete example showing forward simulation and time reversal reconstruction:

import numpy as np
from kwave import *

# Setup grid and medium
kgrid = kWaveGrid([64, 64], [0.1e-3, 0.1e-3])
medium = kWaveMedium(sound_speed=1500)
kgrid.makeTime(medium.sound_speed)

# Create initial pressure
source = kSource()
source.p0 = np.zeros(kgrid.N)
source.p0[32, 32] = 1

# Setup sensor
sensor = kSensor()
sensor.mask = np.zeros(kgrid.N)
sensor.mask[0, :] = 1  # Line sensor

# Forward simulation
sensor_data = kspaceFirstOrder2D(kgrid, source, sensor, medium,
                   simulation_options, execution_options)
sensor.recorded_pressure = sensor_data["p"].T

# Time reversal reconstruction
tr = TimeReversal(kgrid, medium, sensor)
p0_recon = tr(kspaceFirstOrder2D, simulation_options, execution_options)

Notes

  • The compensation factor (default=2.0) accounts for energy loss when recording over a half-plane

  • The time array must be explicitly defined (not ‘auto’) for time reversal

  • The sensor mask must have at least one active point

  • The sensor mask shape must match the grid dimensions