# Real-Time Volumetric Ultrasound Research Platform with 1024 Parallel Transmit and Receive Channels
## 3 Results
### Signal Processing and Imaging Pipeline
After volumetric reconstruction of 1 \(\times\) 1, 3 \(\times\) 3, 5 \(\times\) 5, 7 \(\times\) 7, 9 \(\times\) 9, 11 \(\times\) 11, 13 \(\times\) 13 and 15 \(\times\) 15 transmit-receive events, with a plane wave increment of 1\({}^{\circ}\) per angle  
Figure 13: Real-time volumetric imaging user interface “USPilot” with device parameterization, volumetric rendering and orthogonal slice display. step and coherence receive beamforming, the analysis was performed in the XZ and YZ imaging planes (Figure 14). As can be seen in Figure 14, the FWHM (\(-6\) dB width of the PSF) is reduced with an increasing number of plane wave angles, especially in the case of the Vermon \(32\,\times\,32\) transducer, while it remains almost constant in the case of the custom AMPHORA \(26\,\times\,39\) transducer. This can be explained by the different element sizes, leading to a much smaller element opening angle in the case of the AMPHORA transducer. Consequently, angular compounding is much less efficient when it comes to the improvement of the PSF in this case. For the Vermon probe, having comparable aperture sizes in both directions, the PSF ranges between \(1800\,\upmu\)m and \(1400\,\upmu\)m for the \(1\,\times\,1\) to \(15\,\times\,15\) angles, respectively, independently of the orientation. While the effects of the orientation is very limited on the FWHM, the inactive rows introduce a higher clutter background level around the wire target (Figure 15). On the other hand, the PSFs strongly differ for the AMPHORA probe, with approximately \(900\,\upmu\)m and \(1290\,\upmu\)m, respectively, for the YZ and XZ direction, with little influence of the number of angles as expected by the rectangular shape of the aperture and the limited element opening angle. To characterize the possible dynamic range and contrast of the imaging pipeline, we performed In Vivo measurements of the human bladder with both transducers with an imaging depth of \(90\) mm. To acquire enough bladder volume, we used \(13\,\times\,13\) volumetric plane wave compounding with an angle increment of \(4^{\circ}\), resulting in an opening angle of \(48^{\circ}\) for the  
Figure 14: Full-width half maximum of the PSF evaluated for both transducers in both directions as a function of the number of compounding angles. Figure 15: Point spread function of the Vermon \(32\,\times\,32\) element transducer in the XZ and YZ imaging plane after volumetric reconstruction using volumetric plane wave compounding with \(9,25,121\) and \(225\) angles. Vermon probe (Figure 16). Our custom large footprint transducer was used with the same amount of measurements using only an angle increment of 1\({}^{\circ}\), resulting in an opening angle of 12\({}^{\circ}\). The transducer compensates for this limitation in the maximum beam steering angle with its large footprint in parts (Figure 17). Figure 16: Volumetric imaging of an In Vivo human bladder using the Vermon 32 \(\times\) 32 matrix array: orthogonal XZ, YZ plane (**a**); volume rendering of the full volume at different angles (**b**). Figure 17: Volumetric imaging of an In Vivo human bladder using our 26 \(\times\) 39 matrix array: orthogonal XZ, YZ plane (**a**); volume rendering of the full volume at different angles (**b**). In order to assess the dynamic range of the imaging, we analyzed the contrast of the echo-free volume inside the bladder (Figures 16 and 17, red circle) in relation to a subvolume of the tissue before the bladder (Figures 16 and 17, green circle). Using the Vermon 32 \(\times\) 32 probe and sign coherence beamforming, we achieved a contrast of up to 49.1 dB while our custom large footprint 26 \(\times\) 39 element transducer yielded a contrast of up to 40.3 dB.