Stradwin can be used to acquire data from a mechanically-swept 3D probe. The motor can be driven through a Phytron GLD stepper motor controller, and the raw RF data acquired through a Gage Compuscope digitizing card. Alternatively, you can use an Ultrasonix Sonix with a 3D convex probe, and the porta driver.
This configuration dialog box controls how the motor in a mechanically swept 3D probe is driven during acquisition.
To record data using a 3D probe, you need to specify the required range and number of frames in each recorded volume using the first two sliders, and also the number of volumes using the third slider. There are then various options controlling exactly how the volumes are acquired. Multiple volumes can be recorded either by moving the transducer forwards and backwards over the volume using the "Alternating sweeps" option, or by moving in the same direction for each sweep and returning to the start between each volume (the "Repeated sweeps" option). The "Data acquisition mode" options control how data is transferred to the PC, which can potentially be done after each frame, after each volume, or after multiple volumes. This should be set according to the acquisition speed required, since there is a time delay while the data is transferred. Finally, the five buttons at the bottom of the window allow direct control over the transducer position within the probe.
When recording volumes, the "Video rate" control in the Record task page should be set to either "Full speed" or "Buffered". In full speed mode, Stradwin will record the number of volumes specified in the probe controls dialog and then stop recording. Buffered mode records continuously in the same way as for a 2D probe except that it will store only whole volumes: the last n volumes are stored, where n is the number of volumes specified in the probe controls dialog. In both cases the motor will be stationary in the central position until the record button is pressed. This allows the probe to be centred easily on the scanning target in live mode.
The "Use positions" control in the Record task page should always be set to "Yes". If there is a position sensor available, Stradwin will record positions taking into account both the sensor and the transducer location inside the probe. It is therefore not necessary to hold the probe stationary while each volume is recorded. Each individual volume will be treated as a separate sweep in a multisweep data set. Without a position sensor, positions will be recorded using only the transducer location within the probe. Multiple volumes are then assumed to be overlaid and the probe must be held stationary during recording for the positions to be valid. In this case, any reslice view is derived from frames in the last volume only.
Stradwin has facilities for calculating strain data using a mechanically-swept 3D probe. This can be done in two ways. To record inter-volume strain data, the motor control options should be set to "Repeated sweeps" and "Volume at once". Also, set the "Video rate" in the record task page to "Buffered" and "Display" in the RF Display dialog to "Strain". When you start recording, Stradwin will display (in real-time) only the central strain image from each volume pair while recording whole volumes. The probe must be held stationary while recording each volume and the pressure adjusted slightly in the short pause between volumes while the data is transferred to the PC. When there is at least one pair of volumes in the record buffer providing good strain data, the recording can be stopped and the "Export volumes" option in the File menu used to save this pair of volumes.
Alternatively, to record inter-frame strain data in a mechanically controlled sweep, set the motor control options to "Repeated sweeps" and "Multiple frames". Set the video rate to "Full speed" and again set "Display" to "Strain". While recording, you should continually vary the probe contact pressure, as in 2D strain imaging. The motor will advance gradually through the sweep and Stradwin will acquire multiple images (set by the "Volumes" slider in the probe motor controls) at each motor step. Only the best strain image from each step will be displayed (in real-time). Recording will stop automatically once acquisition is complete and the "Export volumes" option can be used to extract the pair of frames giving the best strain image at each location.