Resolution of Delay Multiply And Sum on FI data from an UFF file

by Ole Marius Hoel Rindal olemarius@olemarius.net 28.05.2017

Setting up file path
Reading channel data from UFF file
Define Scan
Set up the processing pipeline
Define the DAS beamformer
Create the DMAS image using the delay_multiply_and_sum postprocess
Beamform DAS image
Plot both images in same plot
Compare resolution

Setting up file path

To read data from a UFF file the first we need is, you guessed it, a UFF file. We check if it is on the current path and download it from the USTB websever.

clear all; close all;

% data location
url='http://ustb.no/datasets/';      % if not found downloaded from here
local_path = [ustb_path(),'/data/']; % location of example data


% Choose dataset
filename='Alpinion_L3-8_FI_hyperechoic_scatterers.uff';

% check if the file is available in the local path or downloads otherwise
tools.download(filename, url, local_path);

Reading channel data from UFF file

channel_data=uff.read_object([local_path filename],'/channel_data');
% Check that the user have the correct version of the dataset
if(strcmp(channel_data.version{1},'1.0.2')~=1)
    error(['Wrong version of the dataset. Please delete ',local_path,...
                                        filename,' and rerun script.']);
end

UFF: reading channel_data [uff.channel_data]
UFF: reading sequence [uff.wave] [====================] 100%

%Print info about the dataset
channel_data.print_authorship

Name: 		 FI dataset of hyperechoic cyst and points  
		 scatterers recorded on an Alpinion scanner with a  
		 L3-8 Probe from a CIRS General Purpose Ultrasound  
		 Phantom 
Reference: 	 www.ultrasoundtoolbox.com 
Author(s): 	 Ole Marius Hoel Rindal <olemarius@olemarius.net> 
		 Muyinatu Lediju Bell <mledijubell@jhu.edu> 
Version: 	 1.0.2

Define Scan

Define the image coordinates we want to beamform in the scan object. Notice that we need to use quite a lot of samples in the z-direction. This is because the DMAS creates an "artificial" second harmonic signal, so we need high enough sampling frequency in the image to get a second harmonic signal.

z_axis=linspace(25e-3,45e-3,1024).';
x_axis=zeros(channel_data.N_waves,1);
for n=1:channel_data.N_waves
    x_axis(n) = channel_data.sequence(n).source.x;
end

scan=uff.linear_scan('x_axis',x_axis,'z_axis',z_axis);

Set up the processing pipeline

pipe=pipeline();
pipe.channel_data=channel_data;
pipe.scan=scan;

pipe.transmit_apodization.window=uff.window.scanline;

pipe.receive_apodization.window=uff.window.none;
pipe.receive_apodization.f_number=1.7;

Define the DAS beamformer

das = midprocess.das();
%Sum only on transmit, so that we can do DMAS on receice
das.dimension = dimension.transmit();

Create the DMAS image using the delay_multiply_and_sum postprocess

dmas = postprocess.delay_multiply_and_sum();
dmas.dimension = dimension.receive;
dmas.channel_data = channel_data;
dmas.receive_apodization = pipe.receive_apodization;

b_data_dmas=pipe.go({das dmas});

% beamforming
b_data_dmas.plot(100,'DMAS');

USTB MEX C beamformer...Completed in 0.97 seconds.

f_stop =

  single

    10913708

Warning: If the result looks funky, you might need to tune the filter paramters
of DMAS using the filter_freqs property. Use the plot to check that everything
is OK.

Beamform DAS image

Notice that I redefine the beamformer to summing on both transmit and receive.

das.dimension = dimension.both();

b_data_das=pipe.go({das});
b_data_das.plot([],'DAS');

USTB MEX C beamformer...Completed in 0.51 seconds.

Plot both images in same plot

Plot both in same plot with connected axes, try to zoom!

f3 = figure(3);clf
b_data_dmas.plot(subplot(2,1,1),'DMAS'); % Display image
ax(1) = gca;
b_data_das.plot(subplot(2,1,2),'DAS'); % Display image
ax(2) = gca;
linkaxes(ax);

Compare resolution

Plot the lateral line through some of the scatterers

% Let's get the images as a N_z_axis x N_x_axis image
dmas_img = b_data_dmas.get_image();
das_img = b_data_das.get_image();

So that we can plot the line through the group of scatterers

line_idx = 250;
figure(4);clf;
plot(b_data_dmas.scan.x_axis*10^3,dmas_img(line_idx,:),...
                               'DisplayName','DMAS','LineWidth',2);hold on;
plot(b_data_das.scan.x_axis*10^3,das_img(line_idx,:),...
                               'DisplayName','DAS','LineWidth',2);
xlabel('x [mm]');xlim([0 20]);ylabel('Amplitude [dB]');legend show
title(sprintf('Lateral line through %.2f mm',...
                                  b_data_dmas.scan.z_axis(line_idx)*10^3));

%So that we can plot the line through the aingle scatterer
line_idx = 747;
figure(5);clf;
plot(b_data_dmas.scan.x_axis*10^3,dmas_img(line_idx,:),...
                                'DisplayName','DMAS','LineWidth',2);hold on;
plot(b_data_das.scan.x_axis*10^3,das_img(line_idx,:),...
                                'DisplayName','DAS','LineWidth',2);
xlabel('x [mm]');xlim([-15 5]);ylabel('Amplitude [dB]');legend show
title(sprintf('Lateral line through %.2f mm',...
                                  b_data_dmas.scan.z_axis(line_idx)*10^3));