Gammex 405 GSX LE, User Manual

19

Quantitative Measurement

A target’s brightness level can be most accurately measured using electronic methods. 
The user defines a region of interest and the scanner determines the average pixel 
value. To reduce the effect of speckle and small variations in the targets, several 
measurements are taken and averaged.

Note

:  If your system does not have a region of interest (ROI) tool, you will not be able 

to perform this test. As an alternative, refer to the Qualitative Measurement section of 
this document (on page 21).

Note

:  All values determined by the quantitative measurement test depend on scanning 

technique. Great care should be taken to perform the test in the same manner each 
time.

Method

Define a region of interest and measure the average echo level.

Procedure

Baseline Test

1. 

Scan the grey scale targets and display them as large as possible. Freeze the 
image.

2. 

Measure the echo level of the anechoic target. Adjust the system gain so that the 
measurement is approximately 1. This ensures that the system’s noise floor is 
barely reaching the visible level.

3. 

Record this setting and reuse for all subsequent tests.

Subsequent Tests

1. 

Scan the grey scale targets and display them as large as possible. Adjust the 
system control settings as recorded on the data sheet.

2. 

Freeze the image and place the region of interest (ROI) tool completely inside 
the grey scale target image. The ROI should be approximately 2/3 – 3/4 the 
diameter of the circle, and it should be centered in the circle.