# Requirements and Hardware Limitations of High-Frame-Rate 3-D Ultrasound Imaging Systems
## 4 Results and Discussion
Although fewer samples were beamformed, the saturation of B\({}_{\text{MC}}\) still limited FR\({}_{\text{MAX}}\). On the other hand, in the ring topology, reducing the RF samples by 33% and relaxing the requirements on the memories led to a 22% increase in FR\({}_{\text{MAX}}\) compared to Experiment III. Finally, Experiment V assessed the system performance for HFR imaging of a small volume composed of 960 lines. The results (Table 3 fifth column) show that, in the star topology, the maximum volume rate, FR\({}_{\text{MAX}}\), is \(\approx\)75 Hz in both DW1 and DW5 sequences. Here, the bottleneck was the saturation of B\({}_{\text{MC}}\). The ring topology enabled higher FR\({}_{\text{MAX}}\) values, up to 510 Hz in DW1 and 140 Hz in DW5 mode, respectively: here, the bottleneck was B\({}_{\text{BF}}\). Figure 4 shows sample images obtained when working at FR\({}_{\text{MAX}}\) for Experiments I, II, and IV on a cylindrical anechoic cyst phantom (Model 040, CIRS Inc., Norfolk, VA, USA). The top images highlight the different qualities obtained when 128 (Exp I--DW1) or 256 (Exp II--DW1) active elements were used. The bottom panels of Figure 4 show B-mode \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline  & & & \multicolumn{2}{c}{Exp. **II**} & \multicolumn{2}{c}{Exp. III} & \multicolumn{2}{c}{Exp. IV} & \multicolumn{2}{c}{Exp. V} \\ \cline{2-13}  & **N\({}_{\text{L}}\times\) N\({}_{\text{agents}}\)** & \multicolumn{2}{c}{**96 \(\times\) 1280**} & \multicolumn{2}{c}{**96 \(\times\) 1280**} & \multicolumn{2}{c}{**(96 \(\times\) 2) \(\times\) 1280**} & \multicolumn{2}{c}{**(96 \(\times\) 2) \(\times\) 896**} & \multicolumn{2}{c}{**(32 \(\times\) 30) \(\times\) 896**} \\  & **N\({}_{\text{CH}}\)** & \multicolumn{2}{c}{**128**} & \multicolumn{2}{c}{**256**} & \multicolumn{2}{c}{**256**} & \multicolumn{2}{c}{**256**} & \multicolumn{2}{c}{**256**} & \multicolumn{2}{c}{**256**} \\ \hline  & & Mode & DW1 & DW3 & DW5 & DW1 & DW3 & DW5 & DW1 & DW5 & DW1 & DW5 & DW1 & DW5 \\ \hline \multirow{4}{*}{**F\({}_{\text{MAX}}\)**} & **FR\({}_{\text{MAX}}\) [Hz]** & **1500** & **1500** & **1000** & **750** & **733** & **740** & **360** & **370** & **360** & **370** & **75** & **74** \\  & **B\({}_{\text{BC}}\) [MS]** & 184 & 553 & 614 & 92 & 270 & 455 & 88 & 455 & 65 & 318 & 65 & 318 \\  & **B\({}_{\text{BC}}\) [GB/s]** & 177 & 177 & 1.18 & **1.77** & **1.73** & **178** & **170** & **175** & **177** & **175** & **177** & **177** \\ \hline \multirow{4}{*}{**F\({}_{\text{MAX}}\)**} & **FR\({}_{\text{MAX}}\) [Hz]** & 4200 & **1700** & 1020 & 4400 & 1667 & 1000 & 2200 & 500 & 2700 & 650 & **510** & **140** \\  & **B\({}_{\text{BF}}\) [MSP]** & 516 & **627** & **627** & 541 & 614 & 614 & 541 & 614 & 464 & 568 & 439 & 602 \\  & **B\({}_{\text{MC}}\) [GB/s]** & 1.24 & 0.50 & 0.30 & 1.30 & 0.49 & 0.29 & 1.30 & 0.29 & 1.59 & 0.39 & 1.50 & 0.41 \\ \hline \multirow{4}{*}{**F\({}_{\text{MAX}}\)**} & **FR\({}_{\text{MAX}}\) inc.** & **+180\%** & **+13\%** & **+2\%** & **+487\%** & **+127\%** & **+35\%** & **+529\%** & **+35\%** & **+620\%** & **+78\%** & **+580\%** & **+89\%** \\ \cline{1-1} \cline{2-13}  & **FR\({}_{\text{MAX}}\) inc.** & **+180\%** & **+13\%** & **+2\%** & **+487\%** & **+127\%** & **+35\%** & **+529\%** & **+35\%** & **+620\%** & **+78\%** & **+580\%** & **+89\%** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: System performance achieved during experiments I–V. images obtained over two perpendicular planes in Experiment IV--DW5. The images show the cross (left) and longitudinal (right) sections of the cylindrical anechoic cyst.