PROJECT II BEAM FORMING OF A US PHASED ARRAY SYSTEM

Project II Beam forming of a US phased array system

You will construct a B-mode image of a cyst phantom using a phased array setup for this assignment. 128 rectangular elements are grouped in a linear shape within the phased array. Table 1 displays the system’s specifications.

With the use of 100,000-point scatterers of various amplitudes, a target resembling a cyst was simulated. Circular areas where the scattering amplitude is assumed to be zero define nine “cysts.” In order to replicate speckle, the amplitudes are assumed to be spread uniformly elsewhere in the phantom. The ghost is shown in Figure 2.

For 127 RF (radio-frequency) lines, the time-domain scattered field produced by this target was simulated. These RF lines physically depict the pressure field that each element of the array “hears.” A single focal depth of 70 mm was used to steer the beam from -25 degrees to 25 degrees in relation to the normal array. The 128 components’ raw RF lines for each steering angle were saved as mat files.
An 8192 by 128 matrix can be found in each of the 127 mat files, which you can download using a portable hard drive (I’ll try to make the CDs as well). The column represents the 128 elements in the phased array, while the 8192-time samples, taken at 50 MHz, are represented by the rows.

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Your job is to create a B-mode image from the RF data. As a result, you will accomplish in software what a primate B-mode scanner achieves in technology. There are four steps in this process:
1. Use a single broadcast focus and a single reception focus to beamform the raw RF data.
2. Employ a discrete Hilbert transform to extract the envelopes of the beamformed data.
3. Scan the envelopes and convert them to a Cartesian grid.
4. Logarithmically reduce the results’ dynamic range to 45 dB for the intended display.

In Figure 2, this procedure is displayed.

The provided data is in MATLAB 7 format. Use MATLAB to put your solution into practice. Please include your code in your report as an Appendix (see example below). The signal/image processing chain consists of four steps. Thus, you should create four unique functions or scripts for each one. This method will simplify debugging. Then, you may create a master script that calls all four of the functions/subscripts.

Your findings will be summarized in a brief technical report. Although there are no length limits, your report has to contain the following information:

1. Introduction: Describe the problem, the data, and the strategy in one or two pages. DO NOT copy any part of this document verbatim.
2. Methods: Detailed explanations of the algorithms used to carry out each stage of the signal and picture processing. It should be possible for another engineer to duplicate your findings with enough information provided.
3. Results: This section of the report is the longest. Include at least three intermediate results in addition to the finished B-mode image. Examples of results include undelayed and delayed A-lines (waveplots), example envelopes, images exhibited before and after scan conversion, log compression displayed with various dynamics ranges, and images displayed in step 3 and step 4. Describe every figure in the report.
4. Conclusions: Summarize your study and findings in one or two paragraphs. You should also identify any flaws in the strategy and make recommendations for future work that could enhance your outcomes.
5. References: List any books or papers that were cited.
Your MATLAB code is in the Appendix.

The phased array geometry employed in the imaging investigation is shown in Figure 1.

Table 1 lists the features of phased arrays.

Note 1: With regard to ‘theta, RF lines are uniformly sampled. Note 2: Each RF trace’s start time is 0 seconds. Note 3: The x coordinates of all 128 receive elements in the array ‘ri and the directions for all 127 scan angles (corresponding to each file) in the array ‘theta are both contained in the file ‘cystdata. mat, which is located in the same directory as the file containing this ultrasound project description.
Cyst-Phantom, which produced the RF data on the supplemental CD or hard disk, is shown in Figure 2.
Diagram illustrating the signal and image processing required to produce a B-mode image from RF data in Figure 3.

 

 

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