Page 426 - Libro 2

406 PART 6 — MISCELLANEOUS
AB
Figure 27-1 Use of agitated saline as an ultrasound contrast agent. This patient previously had a stoke and an echocardio- gram and was ordered to rule out a patent foramen ovale (PFO). On the grayscale examination, (A) no obvious PFO was visu- alized. After intravenous injection of 10 mL of agitated sterile saline (B), bubbles can be seen filling in the right heart but no bubbles were visualized on the left side of the heart. No PFO was identified. (Image courtesy of Kara Lopresti, RDCS, Thomas Jefferson University Hospital, Philadelphia, PA.)
administration, microbubbles within agitated saline do not persist through passage of the pulmonary and cardiac circulations, which makes this technique un- suitable for sonographic evaluations of the left heart and systemic circulation.
Numerous attempts have been made to encap- sulate gas in order to make a more suitable mi- crobubble-based UCA that can be administered intravenously for CES examinations. For a UCA to be clinically useful, it should be nontoxic; have micro- bubbles or microparticles that are small enough to traverse the pulmonary capillary beds (i.e., less than 8 􏰀m in size) but large enough to reflect US signals; and be stable enough to provide multiple recircu- lations. A number of agents posses these desirable traits and are commercially available worldwide. Table 27-1 summarizes some of the current clinically available UCAs.
TABLE 27-1
Ultrasound Contrast Agents
ULTRASOUND CONTRAST AGENT ADMINISTRATION
Typically, contrast is administered in small (􏰁3mL) intravenous (IV) bolus injections via an upper ex- tremity vein which, depending on the agent admin- istered and the patient’s characteristics, typically provide several minutes of enhancement. When nec- essary, a second administration of contrast can be performed. US contrast media can also be adminis- tered via slow IV infusion to provide prolonged en- hancement. Albrecht and colleagues found that the infusion of contrast-provided enhancement lasting as much as 12 minutes or more compared to just over 2 minutes with a bolus injection.4 The addi- tional enhancement time provided by the infusion of contrast is useful for difficult and time-consuming evaluations of vessels, such as the renal arteries.
Contrast Agent
Optison Definity SonoVue
Manufacturer
GE Healthcare, Princeton, NJ
Lantheus Medical Imaging, N. Billerica, MA
Bracco Imaging SpA, Milan, Italy
Microbubble Shell
Human serum albumin Lipid
Phospholipid
Microbubble Gas
Octafluoropropane (C3F8) Octafluoropropane (C3F8) Sulfur hexafluoride (SF6)