Yes, during reception,m when reflected sound arrives at the transducer, multiple neighboring elements in the probe are excited. These elements create electrical signals that return to the system's receiver via multiple channels.

A more accurate image can be created when the ultrasound receiver introduces variable time delays to some of the electrical signals during reception. The optimal time delays used during receive focusing depend upon the depth at which the reflection was created. Therefore, the delay patterns during receive-focusing change continuously as the transducer listens for reflections.

A technique called dynamic aperture can be used to make a sound beam narrow over a greater range of depths and thus optimize lateral resolution.

When an array transducer is used, the US system may change the number of crystals along the face of the probe used to transmit pulses and receive reflections. This process is called changing the aperture, variable aperture, or dynamic aperture.

(Don't think of the footprint of the transducer as the aperture. Only a portion of the footprint is used to send and receive signals. The portion active is the aperture.)

As the returning sound beam strikes the transducer, the size of the transducer surface listening for echoes is varied. This accomplished by varying the number of elements used to receive the reflected signal.

Echoes arising early (from superficial structures) are received using only a few crystals from the array.

As the echoes return from deeper structures, the aperture is increased. More and more elements in the array are used to listen.

This allows the receive beam to be as narrow as possible at all depths, and optimizes lateral resolution.

With dynamic frequency tuning, due to a wide range of frequencies (wide bandwith or broadband) transmitted, higher frequencies create shallow parts of the image and lower frequencies create deeper parts.

Echoes arising from superficial structures are filtered to process only higher frequencies because higher frequencies make better images.

Lower frequency signals are used to image deeper structures, because they higher frequencies have attenuated and are no longer present.

• time gain compensation
• log compression
• write magnification
• persistence
• spatial compounding
• edge enhancement
• fill-in interpolation

• any change after freeze frame
• black/white inversion
• read magnification
• contrast variation
• 3D rendering

Also known as Zoom, the sonographer can improve visualization of anatomic detail by enlarging a portion of tan image to fill the entire screen.

The selected part of the image is known as the region of interest, or ROI

Two;

Read magnification

Write magnification

1. The US system scans the anatomy
2. The image is converted from analog to digital form and is stored in the scan converter
3. The sonographer identifies the region of interest, and the system reads and displays only the original data that pertains to the region of interest. The ROI is not rescanned.

• The number of pixels or scan lines in the magnified image is the same as in the original image.
• Spatial resolution does not change because the number of pixels in the ROI is unchanged. However, the pixels are larger in the zoomed image.

1. The US system scans the anatomy and creates an image.
2. The image is converted from analog to digital form and is stored in the scan converter.
3. The sonographer identifies the region of interest. At that moment, the system discards all the existing data in the scan converter.
4. The US system then rescans on the region of interest and writes new data into the scan converter.

• The image used to identify the ROI is discarded and all new image information aquired.
• The number of pixels or scan lines in the ROI image is greater than that in the ROI's portion of the orininal image.
• The increased number of pixels in the region of interest improves spatial resolution. The pixels are the same sizze in both the old and the zoomed image.

Traditional imaging uses a very short pulse to create images; whereas, coded excitation creates long sound pulses that contain a wide range of frequencies (bandwidth or broadband) and special patterns. Special mathematical techniques alter the long reflections into a form suitable for high quality images.

Coded excitation takes places in the pulser.

Increases or improves signal-to-noise ratio.

Improves penetration, axial resolution, spatial resolution, and contrast resolution.

Compounding images starts by acquiring multiple frames from different angles. The frames are combined (overlapped or compounded) to form a single real-time image.

The number of frames and steering angles varies, depending om the transducer characteristics and the clinical application. In general, the more frames in the compound acquisition sequence, the better the compound image quality.

Fill-in interpolation is a method of constructing new simulated data points to fill in the gaps. The goal of fill-in interpolation is to fill in the gaps of missing data in a way that cannot be detected by the observer. 

Two-dimensional US images are created from multiple US pulses directed into the body. With sector-shaped images, the scan lines separate at increasing depths. Gaps, or missing data, exist between the scan lines, especially as the lines spread apart.