Today's Veterinary Practice

JAN-FEB 2016

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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com imaging essenTiaLs Peer reviewed 110 BASICS OF DRIVING THE TRANSDUCER Hold the transducer as you would a pen. you should be able to rotate the transducer 90 degrees by rolling the transducer between your fngers and thumb without applying undue pressure on your wrist. you do not need to grip the transducer tightly, and you do not need to push the transducer into the dog or cat's abdomen to produce good-quality images. There are 3 different types of transducer motions: 1. With distance motion, the transducer moves across a physical distance on the patient. The transducer can move in cranial, caudal, right- sided, or left-sided directions. 2. With nondistance angle motion , the transducer is angled in different directions but stays in the same position (Figure 1, page 109). For example, the transducer is placed caudal to the xiphoid process and then angled cranially to visualize the liver. 3. By using nondistance, rotational motion, the transducer is fxed in its position and rotated in a clockwise or counterclockwise direction. in fnalizing an image of a specifc organ, a combination of these motions is often used. Us waves that refect from organs that are perpendicular to the probe provide optimal images; therefore, always try to put the organ of interest in the near feld and perpendicular to the probe. PROBE ORIENTATION Probe orientation and orientation of the image relative to the transducer can be confusing during abdominal ultrasonography. a notch on the probe has a "logo" that corresponds with the image display screen, identifying which way you are driving. With regard to the patient, the notch should always be pointing in the cranial direction (Figure 2), to the patient's right when on midline, and toward the dorsal direction when the lateral aspect of the animal is being imaged. The "logo" orientation should always be on the left side of the screen as the sonographer is facing the display. IDENTIFICATION OF ABNORMALITIES Look for abnormalities in the described size, shape, margins/contours, location/position, number, and echogenicity (a feature that replaces opacity for radiographic changes). Echogenicity & Echotexture The hardest and most subjective aspect to evaluate is the relative echogenicity of a given organ or structure. it is easy to turn the gain too high or too low, resulting in images that are hyperechoic or hypoechoic overall, respectively (see Basics of Imaging Optimization—How to Obtain High- Quality Scans in the november/december 2015 issue). in addition to the overall gray scale or echogenicity, the echotexture of the organ or structure of interest is also important ( Table). TABlE. Ultrasound Features of Each Organ/ Structure to Describe Normal Attributes 1. Size 2. Shape 3. Margins/contour 4. Location/position 5. Number 6. echogenicity (gray-scale appearance) • Fluid • Medulla (renal) • Cortex (renal) • liver • Spleen • Prostate (with benign prostatic hypertrophy) • Peritonitis 7. echotexture (internal echo appearance) • Uniform change • Mottled/mixed/multifocal • Heteroechoic • Target (alternating hyper- and hypoechoic concentric rings) Figure 2. The transducer notch is placed in a cranial direction when in long axis on the abdomen of a dog (as in this case) or cat. As a result the cranial direction is toward the viewer's left (cranial) as seen in this corresponding image of the liver. The hyperechoic margin of the diaphragm–lung interface is noted along the viewer's left of the image (arrows). Memorizing echogenicities The relative echogenicities can be remembered using the mnemonic For Most Cats Love Sunny Places , which designates a progressive increase in echogenicity: F luid (anechoic or black) M edulla (renal) C ortex (renal) L iver Spleen Prostate gland with benign prostatic hypertrophy P eritonitis (the mesentery becomes hyperechoic or white and hyperattenuating) M e m

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