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The technology of diagnostic ultrasonography is developing rapidly. Advances in new technologies, new transducer types, and new system designs are delivered every year by the diagnostic ultrasonography companies. Even for experts in ultrasonography it is difficult to follow this progress. Knowledge of the different types of transducer and their respective advantages, together with an understanding of the tools available to improve the image during an ultrasonographic examination are essential. This chapter covers transducers; image processing during examination; image documentation and storage; equipment and transducer care; and choosing an ultrasound machine. This chapter includes five video clips.

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2.1 Control panel of a high-end ultrasound machine. The ergonomic and intuitive set-up of this unit make it easy to use.
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2.2 Types of transducer. Microcurved array. Curved array. Linear array. Phased array. Note the different sizes of the footprints of the transducers.
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2.3 Ultrasonograms of the head of the spleen using a transcostal window. With the linear array transducer the ribs (R) hamper the image, and the contact between the skin and transducer in this case was insufficient. With the microcurved array transducer the window is more appropriate due to the small footprint of the transducer fitting in between a rib pair (R).
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2.4 Ultrasonograms of the liver. Transducer frequency is set relatively low at 5 MHz. Transducer frequency is set at 10 MHz. Note the improvement in axial resolution: the image appears less grainy and the detail of the fine echotexture of the liver is clearer.
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2.5 Stand-off pad for linear array transducers.
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2.6 Low acoustic power is selected. Note: the power is displayed as 20% of the maximum available (top right). The image appears dark, representing an insufficient amount of returning echoes. The power is set to 95% of the maximum available (using the same gain settings), resulting in a better image. See also clip on DVD.
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2.7 The gain is set for optimal image quality. Increasing the gain results in an overall increase in image brightness, and oversampling, creating a worsened signal-to-noise ratio. See also , and clips on DVD.
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2.8 The difference between and is the depth selection. In (b) the region of interest in the near-field is enlarged. Note that the frame rate (upper right, Hz) is increased by selecting a lower depth.
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2.9 Changes in sector angle. Maximum field of view for this transducer. More narrow field of view. Note the increase in frame rate (upper right, Hz) in (b) compared with (a).


Changing acoustic power.

The acoustic output of the unit is altered during this clip. This can be followed in the upper right-hand corner of the image, where the output power is displayed as a percentage. Note the decrease in overall brightness and the lost of image information as the power is decreased.

Changing gain.

The overall gain is changed during this clip. The gain level is displayed in the lower left part of the image, denoted by ‘G’. Note the overall increase in image brightness, leading to increased noise due to over sampling, as the gain is increased.

Applying the ‘image optimizer’.

As the clip begins, the time–gain compensation (TGC) controls have been set wrongly, resulting in very dark superficial and deep bands, and a very bright middle band. When the ‘image optimizer’ is applied the optimal settings are restored without touching the TGC controls.

Time–gain compensation controls.

Time–gain compensation (TGC) controls are adjusted during this clip. Note the change in image brightness (gain) at the different axial levels.

Changing the number of focal zones.

At the right of the image, small green arrowheads are visible showing the focal zone(s). At the start of this clip, one focal zone is selected, then later two focal zones are chosen. Note the decrease in frame rate (shown at the top right-hand corner of the image) as soon as two focal zones are selected.

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