Insana Lab: Ultrasonic Imaging - The University of Illinois at Urbana-Champaign
Insana Lab: Ultrasound Research Interface (URI)Tutorials | B-Mode | 2D Color Doppler | More Color Doppler | Scan Conversion | M-mode | Spectral Doppler | Misc. Functions
Ultrasound B-mode images are 2-D displays of echo signal amplitudes. The RF data are demodulated, the amplitudes are logarithmically compressed, and a scan converter algorithm is applied to correctly place echoes. TGC (time-gain compensatioin) should be applied at the system before recording data.
You can generate B-mode images from a recorded data file by using the URIBmode.m program in Matlab. It can display all or only the specified frames from the stored data file as still images in separate figures.
To run the B-mode program, first start up Matlab and go to the directory where you have unzipped the URI Offline Processing Tools files.
For example, enter the following at Matlab command prompt if you stored the files in 'C:\URI programs\':
>> cd 'c:\URI programs'
(Note: use the quotation marks if the directory name contains spaces.)
Then to start the program:
(Note: Matlab programs names are usually not case-sensitive, whereas its workspace variables are.)
The user will be prompted to select a URI RF file.
User will then be prompted to enter some parameters here:
|← Select the first frame out of the data file to be displayed.
|← Specify how many frame(s) to skip between image formation (e.g., every other frame).
|← Select the last frame out of the data file to be displayed
|← Select type of bandpass filter (None, Hamming window FIR, Butterworth IIR).
|← Bandpass filter lower cut-off frequency, in MHz. Enter 0 to use filter as lowpass filter.
|← Bandpass filter higer cut-off frequency, in MHz. Enter 0 to use filter as highpass filter.
|← Filter order
|← Scan-conversion (Leave this field as "1" for automatic scan-conversion,
or input "0" to skip scan-conversion for faster rectangular display only.).
|← Spatial blending (Input "1" when data were acquired with multiple transmit focal zones).
|← Confirm or cancel. Press OK to Proceed.|
Matlab will start processing the B-mode image(s). This would take few seconds depending on the data size and filter used.
When Matlab has finished processing a single frame, a new figure with the image will pop up.
If "1" was entered in the scan-conversion field of the prompt window, a second image will be displayed in a new figure with the correct dimensions in mm using the the beam geometries information available in the file header.
If the image was acquired with curved or phased array, scan-conversion will display the image in a sector (fan-like) view.
When the processing is done, there will be some variables available in the Matlab workspace.
These variables can be used by users for further analysis:
(Note: These are case-sensitive, unlike most of the Matlab functions.)
BmodeArray: double precision 2D matrix of log-compressed envelop of of the echo data.
FileHeader: file header structure which contains information about the echo data.
RfDataFilt: double precision 2D matrix of filtered RF echo data.
UserInput: structure containing the parameters entered by user.
VectorArray: structure containing VectorArray.RfData and VectorArray.Header.
VectorArray.RfData is 16-bit integer 2D matrix of RF data.
VectorArray.Header is unsigned 8-bit integer 2D matrix of vector header.
For more information, please also look at the function URIBmodeF.m on how B-mode is processed in URI-OPT.
URIBmodeF.m is the functional form of URIBmode.m. It does not use graphical-user-interface, but is convenient for user to modify and test out new codes.
Effect of Bandpass Filtering in B-mode
The following are images processed from a single data frame of a gelatin-graphite phantom containing a circular inclusion. The original B-mode data was acquired with a linear array transducer at 10 MHz. Setting different bandpass filtering parameters in the post-processing can greatly affect the image quality.
IIR Bandpass filter, 5-7 MHz, order = 4
IIR Bandpass filter, 11-13 MHz, order = 4