ultra sound imaging
Post on 13-Aug-2015
74 Views
Preview:
TRANSCRIPT
1
ULTRA SOUND IMAGING
Prepared by : Abhijith Prabha , L6A ,roll no : 6 ,
ECE Department , SNGCE.
Abhijith Prabha2
INTRODUCTION An ultrasound imaging device is a machine that is
commonly used to examine underlying features of the human body.
Its advantages are that no surgery is needed in order to obtain a clear picture of entities such as kidney stones.
The main parts of an ultrasound equipment are the ultrasound transducer or probe, the electrical control of the probe (including "beam former") and the visualization system. This section will focus particularly on the visualization system.
Abhijith Prabha3
Principle The ultrasound machine transmits high-frequency
(1 to 5 megahertz) sound pulses into your body using a probe.
The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone).
Some of the sound waves get reflect back to the probe, while some travel on further until they reach another boundary and get reflected.
Abhijith Prabha4
Fig : schematic diagram of principle of Ultra Sound imaging
5
Principle The reflected waves are picked up by the probe
and relayed to the machine. The machine calculates the distance from the
probe to the tissue or organ (boundaries) using the speed of sound in tissue (5,005 ft/s or1,540 m/s) and the time of the each echo's return (usually on the order of millionths of a second).
The machine displays the distances and intensities of the echoes on the screen, forming a two dimensional image
Abhijith Prabha
Abhijith Prabha6
Relation between attenuation and frequency in body.
Abhijith Prabha7
Attenuation coefficient of different body tissues
Abhijith Prabha8
Ultra Sound Machine
Abhijith Prabha9
The Ultrasound Machine
A basic ultrasound machine has the following parts:
transducer probe - probe that sends and receives the sound waves
central processing unit (CPU) - computer that does all of the calculations and contains the electrical power supplies for itself and the transducer probe
transducer pulse controls - changes the amplitude, frequency and duration of the pulses emitted from the transducer probe
Abhijith Prabha10
display - displays the image from the ultrasound data processed by the CPU
keyboard/cursor - inputs data and takes measurements from the display
disk storage device (hard, floppy, CD) - stores the acquired images
printer - prints the image from the displayed data
Abhijith Prabha11
Fig : working of Ultrasonic Machine
Abhijith Prabha12
Ultrasound generator
.
Abhijith Prabha13
Fig: block diagram of Ultra Sound generator
Abhijith Prabha14
Ultrasound receiver
Abhijith Prabha15
Fig : ckt diagram of a typical Ultrasound Receiver
Abhijith Prabha16
Modes of operation A MODE A stands for Amplitude. Information of the
reflected signal in a single ultrasound beam is continually displayed distance from the transducer and intensity are shown by position and amplitude in a line on an oscilloscope. This mode is mainly of historical interest, may be rarely used in gynaecology or ophthalmology.
Abhijith Prabha17
Modes of operation B MODE
B stands for Brightness. In this case A-mode information from many beams, typically forming a sector in a plane of the body, is shown as pixel intensity on a monitor. B mode is often referred to as 2D, and is the most important modality for anatomic assessment and orientation in the body, also for localising and as a background for display of other information such as Doppler signals.
Abhijith Prabha18
Abhijith Prabha19
Modes of operation
M MODE M stands for motion. This approach is used
for the analysis of moving organs. It is based on A-mode data from a single ultrasound beam that are represented as function of time. This does not require a sweep through many ultrasound beams which allows for high temporal resolution.
Abhijith Prabha20Fig : illustration of Ultrasound image in Mode M
Abhijith Prabha21
Modes of operation
Doppler mode Doppler mode exploits the frequency shift due to
relative motion between two objects. With this approach information regarding blood velocity and cardiac valves can be obtained.
Doppler mode can be obtained by continuous or pulsed wave (PW); in addition, velocity data can be shown as overlaying colour on B-mode images (colour Doppler, power Doppler and Tissue Doppler).
Abhijith Prabha22
Transducers Mechanical Probe: seldom used now. Electronic Probe: – Linear array transducers • piezoelectric elements linearly arranged • sequentially activated to produce an image – Phased array transducers • smaller scanning surface (foot print) • good for echocardiography • more expensive • elements are activated with phase
differences to allow steering of the ultrasound signal
Abhijith Prabha23
Applications Obstetrics and Gynaecology
measuring the size of the foetus to determine the due date
determining the position of the foetus to see if it is in the normal head down position or breech
checking the position of the placenta to see if it is improperly developing over the opening to the uterus (cervix)
seeing the number of foetuses in the uterus checking the sex of the baby (if the genital area
can be clearly seen) checking the foetus's growth rate by making many
measurements over time
Abhijith Prabha24
Applications Cardiology
seeing the inside of the heart to identify abnormal structures or functions
measuring blood flow through the heart and major blood vessels
Urology measuring blood flow through the kidney seeing kidney stones detecting prostate cancer early
Abhijith Prabha25
Advantages Ultrasonic can be easily focused, i.e., they
are directional. They are inaudible. It is possible to investigate the properties
of very small structures. Information obtained by US , particularly in
dynamic studies, cannot be acquired by other more convenient technique.
Abhijith Prabha26
Limitations development of heat - tissues or water absorb the
ultrasound energy which increases their temperature locally
formation of bubbles (cavitations) - when dissolved gases come out of solution due to local heat caused by ultrasound
Abhijith Prabha27
END
top related