style="font-size:15px;"> This artifact occurs where there is a curve within a fluid‐filled structure and is especially associated with the urinary bladder and gallbladder mimicking sediment and a mass. To differentiate artifact from sediment, consider where the gravity‐dependent region is within the lumen of these structures. If “sediment” appears in nongravity‐dependent regions, you should consider the possibility of artifact. Other techniques to differentiate artifact from true pathology include eliminating the artifact by turning down the gain and ballottement or changing the patient’s position. Finally, some hasty sonographers will misinterpret an artifact for a mass. Simply place color flow Doppler on the suspect region for differentiation because a mass generally has pulsatile blood flow and an artifact (and thrombus) does not. See Chapter 3 for more explanation and examples.
Edge Shadowing
The edge shadowing artifact is created when the ultrasound beam strikes a curved surface, creating a dark shadow that extends from that curved surface through the far‐field. Edge shadowing most commonly occurs at the curved surfaces of stomach wall, renal cortex, gallbladder and urinary bladder and can be mistaken for free fluid along the stomach wall and renal cortex or defects in the wall of the gallbladder and urinary bladder, the latter especially when ascites is present on the AFAST CC view. See Chapter 3 for more explanation and examples.
Pearls, Pitfalls, and The Final Say
The paradigm change of POCUS and FAST rests on expediting the learning process and we hope that this chapter will help accelerate your learning process by highlighting factors in a different way from other chapters in this textbook. The material in the chapter is based on training more than 1000 veterinarians in these techniques over the past 15 years as well as leading in clinical studies.
Take the time to go through the major knobs on the machine ‐ depth, gain (TGC and overall), focus cursor, frequency, and preset. Know where these buttons are located and play with images to get used to how to efficiently adjust their settings. Using stickers on your machine is another way to train yourself on where these buttons are located.
Use our algorithm for trouble shooting. By doing so, you will have a way to efficiently review the most common image optimization features of your machine. Depth, frequency, preset, focus cursor, gain (TGC and overall), probe–skin contact, direction of the beam, then default back to original settings.
Save images and then go through the views and play the artifact game; look through AFAST studies and see how many mirror image artifacts you see and then choose another artifact and do the same.
References
1 Boysen SR, Rozanski EA, Tidwell AS, et al. 2004. Evaluation of a focused assessment with sonography for trauma protocol to detect free abdominal fluid in dogs involved in motor vehicle accidents. J Am Vet Med Assoc 225(8):1198–1204.
2 Walker C, Mohabir PK. 2014. Orientation. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 25–31.
Further Reading
1 Blanco P, Volpicelli G. 2016. Common pitfalls in point‐of‐care ultrasound: a practical guide for emergency and critical care physicians. Crit Ultrasound J 8(1):15.
2 Boivin M. 2014. Basic operation of an ultrasound machine. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 32–37.
3 Brietkrutz R, Uddin S, Steiger H, et al. 2009. Focused echocardiography entry level: new concept of a 1‐day training course. Minerva Anesth 75(2):285–292.
4 Chiem AT. 2014. Transducers. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 19–24.
5 Goodgame B, Debesa O, Lee A, et al. 2014. Imaging artifacts. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 38–48.
6 Hempel D, Stenger T, Campo Dell Orto M, et al. 2014. Analysis of trainees' memory after classroom presentations of didactical ultrasound courses. Crit Ultrasound J 6(1):10.
7 Hock GH, Widmer WR. 2010. Apearance of common ultrasound artifacts in conventional vs. spatial compound imaging. Vet Radiol Ultrasound 51(6):621–627.
8 Mattoon JS, Nyland TG. 2015. Fundamentals of diagnostic ultrasound. In: Small Animal Diagnostic Ultrasound, 3rd edition, edited by Mattoon JS and Nyland TG. St Louis: Elsevier, pp 1–49.
9 Mayette M, Mohabir PK. 2014. Ultrasound physics. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 9–18.
Chapter Six POCUS: AFAST – Introduction and Image Acquisition
Gregory R. Lisciandro
Introduction
In 2004, a focused assessment with sonography for trauma (FAST) exam was prospectively validated in traumatized dogs, translating the four acoustic windows described in human medicine (Boysen et al. 2004) (Figure 6.1). Interestingly, intraabdominal injury, more specifically hemoabdomen, was far more prevalent than previously reported with a prevalence of 38–45% versus a pre‐FAST rate of 12–23% (Boysen et al. 2004).
In 2005, the original FAST examination was modified in the following ways, including renaming the study AFAST (Lisciandro et al. 2009) (Table 6.1).
The probe was directed into the gravity‐dependent regions of each acoustic window.
The views were renamed by their target organs rather than external anatomy.
The probe was maneuvered differently, making the major orientation longitudinal with fanning and rocking of the probe at each AFAST acoustic window without rotating.
The patient was not shaved but rather the hair was parted to maximize probe–skin contact.
A simple AFAST‐applied fluid scoring system (0–4) was developed for semiquantitating volume of the effusion, with more recent modifications.
Serial AFAST examinations were performed as standard of care for all admitted patients four hours post admission and sooner if questionable or unstable patient status.
AFAST investigated many important clinical questions rather than a single binary question of fluid positive or negative.
The AFAST study documented that its simple abdominal fluid scoring system (0–4) reliably predicted the degree of anticipated anemia in dogs with hemoabdomen. The abdominal fluid score (AFS) differentiated lower scoring small‐volume bleeders (AFS 1 and
