## Materials and Methods
### Initial Experimental Acquisitions for Validation of the Platform  
The 4 Vantage systems were synchronized together for data acquisitions in 6 different array configurations allowed by the US probe. The validation of the setup was performed on a standard phantom (Figure 2) by using PW and DW. The used US acquisition parameters are described in Table 1.  
Table 2 presents all tested matrix configurations of the US probe for data acquired both with transmissions of plane waves (PW) and diverging waves (DW). The numbers of the connectors (C) are from 1 to 8, while the Verasonics (V) systems are numbered from 1 to 4. For symmetry reasons regarding the center of the probe along the \(y\) direction, for the presented examples, the connectors are plugged as follows: C4 and C5 on V1, C3 and C6 on V2, C2 and C7 on V3, while C1 and C8 on V4. For the validation of the US platform, serial experiments were performed with PW and DW with 9 transmission waves (9 in the \(x\) and \(y\) direction, resulting in a total of 81 transmissions) by using the matrix \begin{table}
\begin{tabular}{c c c} \hline
**Parameters** & **Value** \\ \hline _Probe parameters_ & & 32 \(\times\) 32 \\ Matrix probe number of elements & & \\ \hline Pitch & 0.3 mm \\ \hline Center frequency & 3 MHz \\ \hline _Imaging parameters_ & & \\ Transmit center frequency & & \\ \hline Sampling frequency & 12 MHz \\ \hline Max imaging depth & 60 mm \\ \hline Transmit full aperture & 4 \(\times\) 256 elements \\ Pulse Repetition Frequency (PRF) & 200–2000 Hz \\ \hline Frame-rate & 200–2000 fps \\ \hline \end{tabular}
\end{table} 
Table 1: US acquisition parameters. \begin{table}
\begin{tabular}{c c c c c} \hline
**Array Configuration** & **Matrix** & **No. of Active** & **Connectors (C)** & **No. of Verasonics (V)** \\  & **\# Columns \(\times\) \#Rows** & **Elements** & **Used** & **Systems** \\ \hline Full array & \(32\times 32\) & 1024 & C1:C8 & V1:V4 \\ \(1\) line ON/\(1\) line OFF & \(32\times 16\) & 512 & C2:C4,C5,C7 & V1, V3 \\ \(2\) lines ON/\(2\) lines OFF & \(32\times 16\) & 512 & C2:C4,C5,C7 & V1, V2 \\ \(4\) lines ON/\(4\) lines OFF & \(32\times 16\) & 512 & C1:C8 & V1:V4 \\ Middle ON & \(32\times 16\) & 512 & C1:C8 & V1:V4 \\ \(1\) line ON/\(3\) lines OFF & \(32\times 8\) & 256 & C2,C7 & V2 \\ \hline \end{tabular}
\end{table} 
Table 2: US probe matrix configurations and Verasonics combinations. Figure 2: (a) Validation setup on a standard cyst phantom; (b) The diagram of the standard phantom used for experiments. 1 and 2 indicates 2 possible positions of the probe. configurations described before. An excitation of 30 V was applied in all cases. The US probe was maintained in a fixed position in order to strictly image the same volume of the phantom for a correct comparison of the image quality obtained with the different configurations. Further image quality analysis and the presence of secondary lobes were carried out to compare the results obtained with all configurations. For a qualitative evaluation of the results, the axial and lateral resolution was measured in (\(x\), \(z\)) and (\(y\), \(z\)) central slices of the phantoms. The full width at half maximum (FWHM) for 3 different wires positioned at 10, 20 and 30 mm was computed and the obtained values analyzed. Moreover, the contrast ratio (CR) and the contrast to noise ratio (CNR) were also analyzed, transformed to decibel (dB) scale. The CNR is a measure of the signal level in the presence of noise, expressing the fact that detectability increases with increasing object contrast and decreasing acoustic noise. An inside region was defined in a (\(y\), \(z\)) plane as a circle of radius 6.6 mm edge inside the cyst (8 mm diameter cyst), while an outside region of the same dimensions was chosen above the cyst. The same inside and outside regions were preserved for all the measurements.