Record

Select the record task page using the task menu, or use the tabs at the top of the task pages to make the same selection.

Recording using a pre-prepared template

If you have a template for the recording you wish to make, you should first load it using the template task page.

If you have an appropriate template loaded, you should now be able to start recording. Use the 'Live' button on the toolbar to see the current image in the B-scan image window and its position in the 3D window. The second button on the toolbar (a red circle) starts and stops the recording.

It is convenient to have the image and 3D windows displaying live information while you record. This enables you to see the position of the probe in relation to the active volume of the position sensor. Running the live display reduces the speed at which the computer can record data. If you find that you are not getting a fast enough recording frame rate displayed on the toolbar, you can throttle the rate at which the computer updates the live display. This is achieved using the 'Live display rate' selector. The default setting of this selector is 'Full speed'. If you are running Stradwin on a slower computer, you may wish to set it to one of the lower frequencies provided.

Gated recording

Among the options offered by the 'Video rate' selector is 'Gated' mode. This mode is the default, and it affects more than just the rate at which images are acquired. In 'Gated' mode a recording is made as follows.

  1. Press the record button .
    2. This will not start the recording immediately.
  2. Move the ultrasound probe to the place where you want to begin the scan and hold the probe still, in contact with the object being scanned. When the system detects that you are holding the probe still, the system will make a rising beep noise and recording will begin.
  3. Move the probe slowly and steadily over the volume to be scanned.
  4. When you have finished scanning, hold the probe still again. The system will detect that you are holding the probe still, make a falling beep noise and stop recording data.
  5. If you wish to accept the recorded data, click on the record button
    6. to leave recording mode.
  6. If you want to delete the recorded data and try again, click on the erase button and repeat the recording from step (2) above.

If you move the probe too fast or unsteadily during the scan , the system will abort the recording, delete the data and make a 'dush' noise. You will then need to repeat the scan from stage (2) above. This feature can be used to scrub a scan that you are not happy with by sweeping the probe rapidly away at the end rather than holding it still.

In 'Gated' mode, B-scans are recorded not at a constant frame rate, but when the probe has moved by the amount set on the 'Gating threshold' slider. To be precise, B-scans are acquired from the video source as quickly as possible, but discarded if the motion of all four corners of the B-scan is within the gating threshold. On the other hand, if one or more of the corners has moved by the gating threshold since the last recorded B-scan, then the frame is recorded. Motion gated acquisition can be used to acquire regularly sampled volumes, even when the freehand scanning motion is not smooth.

The 'Gating threshold' slider also affects the threshold that determines how still the probe has to be for recording to begin and end. Furthermore, it influences the amount of movement that is considered excessive and triggers the data to be deleted as described above. Generally, you will need to set this threshold slightly higher for probes with larger depth settings, and for more noisy position sensors (for example, magnetic rather than optical devices).

Recordings in 'Gated' mode can be made with or without the live display in the B-scan and 3D windows. If you record with the live display off, you will probably be able to get a faster maximum acquisition rate.

'Multiple gated' recording mode is the same as 'Gated' except that it can be used to record multiple sweeps.

Setting up for recording without a template

To record 3D ultrasound data, you need a source of ultrasound images and a position sensor. The fourth and sixth lines of the record task page tell you whether or not images and positions are available, and which sources you are currently using for them. If you wish to change these selections or check the detailed settings, use the buttons underneath each line. These will open the configuration dialogs for the image source and the position source.

To record 3D ultrasound, you should set the 'Positions required' selector to 'Yes'. If this is set to 'No', only images will be recorded.

Using the 'Video rate' selector, you can choose to record at the maximum available frame rate or to limit the recording rate to 5, 10, 15, 20 or 25 Hz. You can also record individual frames using the 'Single shot' option, or record indefinitely to a first-in-first-out buffer using the 'Buffered option' (the most recent 1000 frames are preserved in the buffer, or a user-selectable number of volumes if recording with a mechanically swept 3D probe). The default recording option is 'Gated', which is described in the previous section.

Select the 'Doppler' button if you intend to record colour Doppler data. If you wish to record only greyscale data, do not select this feature. Stradwin stores each image pixel as one byte. If you have selected 'Doppler', then each B-scan is stored as 128 levels of grey, and 64 levels each of red and blue. If you have not selected 'Doppler', then each B-scan is stored as 256 levels of grey. See the image source dialog for more details about the way the Doppler image is encoded, including how to fine tune the encoding algorithm.

Select the 'RF' button if you intend to record RF data: this button has an effect only if you are recording RF on a Terason or Sonix ultrasound machine, or when using a Gage CompuScope. Note that, even if you are recording RF signals, de-selecting this option will cause the data to be recorded as B-scans. See the RF display dialog for more information.

For B-scan data recorded with a position sensor, slight errors in the position sensor readings can be corrected during recording. See the probe pressure correction task for further details.