Real Time p1 - Articles defining Medical Ultrasound Imaging

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4D Ultrasound

As far as ultrasound is concerned, 4D ultrasound (also referred to as live 3D ultrasound or 4B-mode) is the latest ultrasound technology - the fourth dimension means length, width, and depth over time. 4D Ultrasound takes 3D ultrasound images and adds the element of time to the progress so that a moving three-dimensional image is seen on the monitor. A 4D scan takes the same amounts of time as a 2D or 3D scan; the difference is the ultrasound equipment being used. One advantage of a 4D fetal ultrasound to a 2D-mode is that parents can see how their baby will generally look like. However, there are different opinions over the medical advantages.
To scan a 3D ultrasound image, the probe is swept over the maternal abdomen. A computer takes multiple images and renders the 3D picture. With 4D imaging, the computer takes the images as multiple pictures while the probe is hold still and a 3D image is simultaneously rendered in real time on a monitor.
In most cases, the standard 2D ultrasound is taken, and then the 3D/4D scan capability is added if an abnormality is detected or suspected. The 3D/4D sonogram is then focused on a specific area, to provide the details needed to assess and diagnose a suspected problem. A quick 4D scan of the face of the fetus may be performed at the end of a routine exam, providing the parents with a photo.

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Doppler Ultrasound

Doppler ultrasound is a medical imaging technique for calculating the relative velocity between two points by measuring the frequency shift of a sound wave transmitted from one point to the other, based on the Doppler effect. Continuous or pulsed Doppler is frequently used to examine cardiovascular blood flow. The combination of routine 2D-mode and Doppler ultrasound allows a complete evaluation of the heart's anatomy and function (including the fetal heart). See also Doppler Fluximetry in Pregnancy.
Doppler ultrasound depends on the fact that if a moving object reflects the ultrasound waves, the echo frequencies are changed. A higher frequency is created if the object is moving toward the probe//transducer and a lower frequency if it is moving away from it. How much the frequency is changed depends upon how fast the object is moving. Doppler ultrasound shows the different rates of blood flow in different colors on a monitor in real time.
The major Doppler parameters are the peak systolic velocity and the end-diastolic velocity. The peak systolic velocity ratio compensates the variability between different patients and instrumentations.

Different Doppler and duplex techniques:

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color Doppler;

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color power Doppler;

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continuous wave Doppler;

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contrast enhanced Doppler imaging;

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directional color power Doppler;

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duplex;

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harmonic power Doppler;

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pulse inversion Doppler;

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pulsed wave Doppler;

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spectral Doppler;

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transcranial Doppler.

Further Reading:

News & More:

Evaluation of lower extremity bypass grafts with use of color duplex sonography
Thursday, 30 June 2005 by radiographics.rsna.org

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Duplex Scanner

Duplex systems often combine a pulsed Doppler with a spectral display and a real time imaging system. A duplex scanner has usually an imaging transducer or a separate transducer used to collect continuous wave or pulsed Doppler signals, either simultaneously with imaging or sequentially.

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M-Mode Echocardiography

M-mode (Motion-mode) ultrasound shows the motion of cardiac structures. M-mode echocardiography records the amplitude and rate of motion of a moving structure in real time by repeatedly measuring the distance of the object from the single transducer at a given moment. The single sound beam is transmitted and reflected signals are displayed as dots of varying intensities, creating lines across the screen. It yields a one-dimensional image, sometimes called an 'ice pick' view of the heart.
M-mode echocardiography is used to detect valvulopathies (calcifications, etc.) and cardiomyopathies (dyskinesis, aneurysm, etc.).

See also Bicycle Stress Echocardiography, Transthoracic Echocardiography, and Transesophageal Echocardiography.

Further Reading:

News & More:

Placental insufficiency and fetal heart: Doppler ultrasonographic and biochemical markers of fetal cardiac dysfunction
by herkules.oulu.fi

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Pelvic Ultrasound

As far as ultrasound is concerned, 4D ultrasound (also referred to as live 3D ultrasound or 4B-mode) is the latest ultrasound technology - the fourth dimension means length, width, and depth over time. 4D Ultrasound takes 3D ultrasound images and adds the element of time to the progress so that a moving three-dimensional image is seen on the monitor. A 4D scan takes the same amounts of time as a 2D or 3D scan; the difference is the ultrasound equipment being used. One advantage of a 4D fetal ultrasound to a 2D-mode is that parents can see how their baby will generally look like. However, there are different opinions over the medical advantages.
To scan a 3D ultrasound image, the probe is swept over the maternal abdomen. A computer takes multiple images and renders the 3D picture. With 4D imaging, the computer takes the images as multiple pictures while the probe is hold still and a 3D image is simultaneously rendered in real time on a monitor.
In most cases, the standard 2D ultrasound is taken, and then the 3D/4D scan capability is added if an abnormality is detected or suspected. The 3D/4D sonogram is then focused on a specific area, to provide the details needed to assess and diagnose a suspected problem. A quick 4D scan of the face of the fetus may be performed at the end of a routine exam, providing the parents with a photo.
See also Obstetric and Gynecologic Ultrasound, Pregnancy Ultrasound, Fetal Ultrasound and Abdominal Ultrasound.