Table of Contents
Advertisement
GE MEDICAL SYSTEMS
REV 2
5–2–3 Ultrasound Displays
See Illustration 5–1. Once an ultrasound echo has returned to the transducer, it is converted into an electronic pulse
which is used to calculate the distance between the transducer and the echo producing body organ. Echoes can be
displayed as a function of distance by three methods:
Amplitude Mode:
one–dimensional oscilloscope type display showing echo return amplitude on the vertical axis versus body
depth on the horizontal axis. (See Illustration 5–1a). If transducers were only equipped with one
piezoelectric element and no mechanical positioners, this would be the only display available. However,
transducers usually contain piezoelectric element arrays to develop the B–Mode and M–Mode displays.
Brightness (B) Mode: (Available on RTfino/RT3200 Advantage/RT–x200). This two dimensional display
mode permits the operator to see ultrasound images of body tissue, bones and organs. These are the
standard displays shown in Illustration 5–1b. They are cross sectional views of the body organs beneath
the transducer displayed at their relative depth as measured in centimeters. (The deepest area scanned
appears at the bottom of the CRT; the skin next to the probe appears at the top.)
The display is obtained by plotting, or mapping, echo source locations and intensities as display pixels. The brightness
of each pixel represents the strength or amplitude of the returning echoes; in the normal display mode, the brighter the
pixel, the stronger the returning signal.
This display method requires a transducer with an array of piezoelectric elements. The elements in the array are
sequentially pulsed and the returning echoes are processed to obtain an image.
Motion (M) Mode: (Available on RTfino/RT3200 Advantage/RT–x200). This display is formed by plotting
brightness mode information on the vertical axis versus time on the horizontal axis. (See Illustration 5–1c).
Motion studies are used to detect fetal heart rates, heart valve functions and other cardiac functions.
5–2–4 Beam Focusing
Ultrasound energy from a group of elements is formed into a beam for scanning purposes. This beam must be
focused, or narrowed down, in a specific area called the focal zone to obtain a sharp image at the body depth under
examination. Focal zone depth depends on four factors:
Ultrasound signal frequency;
Aperture Size of Transducer Array (the number of piezoelectric transducer elements);
Radius of curvature for each group of piezoelectric elements. (Each element grouping is shaped like a
parabola to focus its beam at a certain body depth).
The type of electronic focusing method employed. These methods utilize various phase delay techniques
to optimize focus at a specific body depth.
RTfino/RT3200 Advantage–II/RT–x200 SERVICE MANUAL
(Not available on RTfino/RT3200 Advantage–II/RT–x200).
5–4
P9030GX
This is simply a
THEORY
Advertisement
Table of Contents
