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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice small aNimal abDomiNal UlTrasoNograPhy Peer reviewed 23 Preset Controls A preset is a specifc combination of control settings that have been adjusted and set by the sonographer. The machine comes with factory presets, but the basic and advanced settings are usually changed to refect the personal preference of the sonographer. After establishing these settings, the sonographer should be able to store a preset; then, any time the machine is turned on, the preset engages and automatically applies the selected settings. Table 1 provides defnitions of the controls discussed in this section. Use of Controls The sonographer must take time to learn how all the controls affect the image. The easiest way to do so is to set aside several hours with a patient that is easy to image, such as a medium size (14 kg) dog that is not obese and has a good temperament. 1. Obtain a uniform image of the liver from near feld to far feld (about 6 cm) on the screen. 2. Once this is accomplished, take the controls individually through their ranges. 3. Abdomen settings usually are adjusted in the middle of the specifc control range that you are evaluating. 4. B or gray maps are set to the sonographer's personal preference based on the individual image manipulations. Choosing a good B map from the start is an important part of establishing the presets to ensure overall image quality. OPERATING THE ULTRASOUND MACHINE 1. Patient Data After turning on the US machine, enter the patient data. Take care to use a specifc/unique medical record number to ensure that all images related to the patient are stored. In addition, use a unique accession number that is specifc to the study (individual, date, and time) being performed. 2. Probe & Settings Selection Choose the probe and preset for imaging the patient. Most patients can initially be imaged with a microconvex curved array transducer. If using a linear array transducer, the coupling gel becomes more critical as the overall footprint that contacts the skin is longer (sometimes up to 5 cm); see Step 3. After choosing a given preset, the patient is ready to scan. Table 1. Guide to Ultrasound Controls CONTROLS PURPOSE Basic Controls Probe adjustment Controls which ultrasound probe or transducer is used Frequency adjustment Increases resolution at expense of penetration Depth adjustment Increases or decreases depth of US beam Focal zone adjustment Depth at which the image has the highest resolution Gain adjustment Adjusts overall brightness of the image Time gain compensation Depth gain compensation Adjusts gain in specifc areas of the image Dynamic range (compression) Increases or decreases number of gray shades displayed Additional Control Options B color map Shades of a color are used rather than grayscale Gray maps Adjusts the number of different shades of gray in the image Persistence Combines, or averages, multiple image frames into single image Line density Adjusts number of scan lines in image Harmonics Allows high resolution identifcation of tissues in the near feld and artifact reduction Image compounding Combines 3 or more slices from different steering angles into a single slice