when it was recorded may make no sense when under review two days or even two hours later. One of the most common mistakes sonographers make is not labeling their images. Label the organ or structure of interest and label your orientation as longitudinal versus transverse, if it is not evident from the image. There will be times when there are no anatomical landmarks evident on the image and labeling is your only guide (Figure 4.12).
Most ultrasound machines have some sort of body pattern that can be placed on the image with an icon to show the approximate location of the probe (see Chapter 2). Put all labels outside the image, too. Placing words across the image can potentially hide diagnostic information. If you must write across the ultrasound image, first save a picture of the unadulterated image and then save a second picture of the annotated image. Short (3–10 second) video clips can also be saved on most ultrasound machines.
For recording ultrasound findings in medical records, see suggested goal‐directed templates in the respective chapters throughout the textbook.
Figure 4.12. Labeling the image. The same image in (A) and (B) of a liver mass. The location cannot be determined by the image itself and thus the use of the body icon helps point out where the image was taken. The mass itself is circled using the various measurement features of the ultrasound machine. The measurements of the mass are displayed in the upper right of image (B). Source: Courtesy of Robert M. Fulton, DVM, Richmond, VA.
Ultrasound Machine and Probe Care
Not all ultrasound machines were designed for the battlefield with parts that can sustain a six‐foot drop. Most were designed for the relative quiet and safety of a hospital. Ultrasound machines and their components can be easily damaged or broken by rough handling and improper use, and replacement can be costly, especially if you drop an ultrasound probe and damage its crystals. Dropping the probe is the most common cause of probe damage and machine misuse.
The second most common form of misuse involves probe head damage (Figure 4.13). There are two major forms of probe head abuse: needle damage and chemical damage. With the use of POCUS as standard of care for many invasive procedures on the human side, now fast spilling over into veterinary medicine, needle damage, in other words stabbing or catching the rubber probe head with the point of the needle, quickly leads to severe probe head damage. In the haste of the moment, the attending sonographer will often grab a bottle of isopropyl alcohol, wet down the fur with only the alcohol, and apply the probe, leading over time to chemical damage. Many ultrasound manufacturers list alcohol as an inappropriate liquid to place in direct contact with the probe head because alcohol, over time through desiccation, can cause probe head damage.
Figure 4.13. Probe head damage. The damage to the surface of this probe was attributed to a combination of repeated or prolonged contact with isopropyl alcohol and needle trauma. The contact layer is clearly lost over a portion of this probe, negating its ability to serve as an electrical insulator between the probe and patient. It is possible for potentially serious electric shock to occur through the damaged area.
Source: Courtesy of Robert M. Fulton, DVM, Richmond, VA.
Pearl: Always use acoustic coupling gel on the probe head and be familiar with the guidelines provided by the ultrasound machine's manufacturer.
Importantly, it should be noted that the rubber probe head accomplishes two things. First, it acts as a coupling medium to transmit the sound wave out of the probe. Second, it is part of an electrical insulator serving as an electrical ground between the patient and the electricity being sent from the ultrasound machine to the transducer's crystals. There are currently no reports of electrocution via a damaged ultrasound probe but theoretically it's possible.
Pearl: Avoid probe head damage by using an acoustic coupling medium on the probe head as a barrier to alcohol, and avoid stabbing the probe head with needles during ultrasound‐guided procedures.
Deciding on an Ultrasound Machine
Selecting the Machine
There are three main types of ultrasound machine: consoles, portables, and hand‐helds. The console machines are big and bulky, but they have stronger processors and thus give a better image. The portables, often laptop format, are easy to move to the exam table or cage side and their image quality is constantly improving. There are several small hand‐held machines now on the market. Some have adequate depth and resolution capabilities. Just make sure they don't “walk out of your clinic” or get tossed into the laundry or dropped or stepped on. It's very easy to put these hand‐held devices in a lab jacket pocket and forget about them.
You may be limited to whatever you currently have in your veterinary practice, but if you are thinking of buying a new unit, consider what your main use is going to be and get the best ultrasound machine you can afford for that purpose. The axiom holds true: the better the machine, the better the image, and hence the better the diagnostic information.
Selecting the Probe: Linear, Curvilinear, and Phased‐array
Probes, or transducers, come in two basic types, mechanical and electronic. Mechanical probes are on many counts considered outdated but there are still some around with their working parts visibly rotating or rocking under their translucent covers. Newer ultrasounds have electronic probes as standard. Electronic probes come in various arrangements. Probes are generally described by the size and shape of their face, referred to as their “footprint,” which is represented by the gray rubber probe covering (see Figure 4.13). Selecting the right probe is essential to getting good images, although there may be times when more than one probe may be appropriate for a given exam.
Three basic types of probes are used in general practice, emergency, and critical care POCUS: linear, curvilinear, and phased‐array (also known as sector) (see Figure 4.4). Linear probes are typically of higher frequency and have a rectangular footprint. Curvilinear probes are arranged along a convex face and are typically of lower frequency than linear probes. A phased‐array (sector) probe generates an image from an electronically steered beam in a close array, generating an image that comes from a point and is good for getting between ribs, such as in cardiac ultrasound. Both curvilinear and phased‐array probes generate sector or pie‐shaped images, narrow in the near‐field and wide in the far‐field. Phased‐array probes are typically lower frequency. Because of their smaller footprint, “pie‐shaped” image, and commonly used frequencies, curvilinear probes are generally the most versatile and ideal for POCUS and FAST studies.
Probes are generally named for the primary frequency they emit. For example, a General Electric (GE) 8C probe indicates that 8 MHz is its primary frequency and the C represents the probe’s curvilinear footprint. A GE 9L probe indicates a 9 MHz primary frequency in a linear (L) probe, and a GE 7S has 7 MHz as its primary frequency in a sector (S) probe.
