Figure 1.
The configuration of the active reflector tracking system.
Left: the imaging probe fires a serious of ultrasound beams scanning the image region. The center plane of the image region is the mid-plane. Middle: When an ultrasound beam intersects the active echo element, an electrical pulse is received by the electronics. Right: The received pulse triggers the electronics, a driving pulse is sent to the element to fire an active echo pulse.
Figure 2.
B-mode Pattern injection with a linear array.
This picture illustrates how a single virtual pixel is injected to the B-mode image from an active echo element.
Figure 3.
a) The block diagram of the AUSPIS. b) The pulser and logic unit board. c) One of the prototype catheters; it has an active echo element very close to the tip.
Figure 4.
The system received and transmitted signals.
a) The signal received by the active echo element (black), the output of the trigger unit (green), the output of the active echo driving pulse (red). b) A RF line received by the imaging probe with and without enabling the active echo system. The active echo adds a ringing tail after the original signal.
Figure 5.
The active echo image in water tank.
The catheter used in this experiment has an AE element integrated about 5 mm away from the tip. a)∼d) The B-mode image of the catheter in water tank. a, b) the in-plane configuration, c, d) the off-plane configuration. The active echo is enabled in b) and d). e) The B mode image of the catheter with the active echo signal. f) The active echo signal extracted from the B mode image using the template filtering method. The color code represents the convolution value between the signal and template.
Figure 6.
The trigger count versus the offset between the active element and the mid-plane.
In this experiment the catheter is fixed in a water tank and perpendicular to the image plane. The probe is mounted on a translation stage, which moves perpendicular to the mid-plane. The error bar represents the standard deviation over 10 measurements, each time the translation stage moves from −9 mm to 9 mm, stops at the same sample positions and takes the trigger count reading.
Figure 7.
The local ultrasound amplitude measurement for mid-plane detection.
a, b) the amplitude of the signal received by the active echo element verses the position of the probe. The depth of the US transmission beam focus is close to the catheter to probe distance, so the two plots are showing the signal distribution near the focus. a) The results with catheter perpendicular to the image plane (off-plane) b) catheter parallel to the image plane (in-plane). The error bar represents the standard deviation over 10 measurements, each time the translation stage moves from −9 mm to 9 mm, stops at the same sample positions and takes the signal amplitude reading.
Figure 8.
The trigger count versus ultrasound system settings.
Catheter is perpendicular to the image plane. Ultrasound beams are focused to the catheter insertion depth.
Figure 9.
The trigger count versus ultrasound system settings.
Catheter is perpendicular to the image plane. Ultrasound pulses are not focused.
Figure 10.
The trigger count versus ultrasound system settings.
Catheter is parallel to the image plane. Ultrasound beams are focused to the catheter insertion depth.
Figure 11.
The trigger count versus ultrasound system settings.
Catheter is parallel to the image plane. Ultrasound beams are not focused.
Figure 12.
Large depth and impedance mismatching condition test result.
Left: the active echo spot under 8.5 cm deep chicken breast tissue. Right: the active echo spot below a 1 inch thick aluminum plate.
Figure 13.
The B-mode and M-mode image of active echo spot using different imaging methods.
The echo spot blinking can be clearly seen as a “dashed line” in the M-mode image. The blinking frequency is about 2 Hz.
Table 1.
The SNR and CNR under different ultrasound imaging mode.
Figure 14.
The active echo spot with different driving voltage.
The left images are the active echo spot and the reference frame at 58 V driven voltage. In the right images, the driven voltage is reduced to 20 V. The echo intensity is dimmer on the right image; a lower SNR and CNR is expected.
Table 2.
The SNR and CNR with different driving pulse voltage.
Figure 15.
The B mode image of arbitrary pattern injection.
The experiment is in a water tank with Sonix CEP machine and L12-5 linear probe. Left image is the reference without turning on the AUSPIS. On the right image, a virtual “JHU” pattern is injected to the image.
Figure 16.
Mid-plane indication using the pattern injection method.
The top column shows when the catheter moves closer to the mid-pane, the number of injected virtual bar increases. More bars means higher trigger count, thus indicating the catheter is closer to the mid-plane. The bottom picture shows an M-mode image acquired during the catheter moving in process.
Figure 17.
In vivo B-mode images extracted from the 3D volumetric data.
The imaging array scans perpendicularly to the image plane with a step size of 0.5 mm. a–b) B mode images with the catheter in-plane. c–d) B mode images with the catheter perpendicular to the image plane. a) & c) Reference images with active element turned off. b) & d) images with the active echo spot.
Figure 18.
Degree of freedom (DOF) comparison between AUSPIS and beam steering method.
a) Beam steering method requires the image plane to intersect the catheter line (the green line in figure a), the probe DOF is 4. b) The AUSPIS requires the image plane to intersect the AE element point (the green dot in figure b), the probe DOF is 5.