Potential role of PFOB enhanced sonography of the kidney. II. Detection of partial infarction

Abstract

Aside from its ability to assess flow velocity within vessels, color Doppler and gray-scale sonography cannot distinguish perfused from non-perfused tissues. In this study we evaluated whether Perfluorooctylbromide (PFOB), a sonographic contrast agent given i.v., could aid sonography with this recognition. Partial renal infarction was produced by a 1 mm bead embolized in the right, the left, or both renal arteries of 20 normal rabbits. The sonographer, unaware of rabbit assignment, attempted to diagnose the infarct 24 hours later. All 20 rabbits were studied with gray-scale and color Doppler sonography, 10 before and after PFOB and 10 only after PFOB. Angiography and post-mortem examination were done for confirmation. Of the 20 kidneys evaluated before PFOB, the sonographer was unable to diagnose the 10 partial infarctions. Color Doppler identified five of the ten infarcted kidneys, but accurately localized the infarction in only two. Of the 40 kidneys evaluated after PFOB infusion, 20 scanned before and 20 scanned only after PFOB, all 20 partial infarctions were accurately diagnosed with both gray-scale and color Doppler. PFOB enhanced the echogenicity of perfused renal tissue allowing the easy detection of the unenhanced infarct. Because of the increased signal from vessels after PFOB, color Doppler displayed the entire vascular tree, allowing the detection of the truncated embolized branch. The ability of PFOB to enhance Doppler signals and the echogenicity of perfused tissues improved the diagnostic accuracy of sonography when used to detect partial renal infarctions.

Detection of focal renal perfusion defects in rabbits after sulphur hexafluoride-filled microbubble injection at low transmission power ultrasound insonation

“…Microbubble-based US contrast agents were employed to enhance the sensitivity of colour/power Doppler US to slow flows, even though the presence of blooming and flash artefacts penalizes the assessment of renal vessels [6][7][8].…”

Ultrasound contrast agents and their use in urogenital radiology: status and prospects

“…Also Albunex (Molecular Biosystems, San Diego, Calif.) helped quantify renal flow in mongrel dogs after injections directly into aorta by means of analysing time-intensity curves of the aorta and renal cortex [21]. Intravenous injections of perfluoro-octylbromide (PFOB) enhanced the renal parenchyma on grey-scale images, and helped to depict hypovascular tumours in rabbit kidneys [22], as well as renal infarcts [23]. Of special interest is that PFOB caused increased reflectivity from the normal papilla.…”

Sonographic enhancement of renal cortex by contrast media.

“…Therefore, the signal So at the transducer from the volume element A is So= Kap2oe-2at'X+L> e-2a<X+LJ = Kap2oe-4at'X+U (3) where K is the proportionality constant and includes the characteristic properties of the imaging transducer. If the signal compression and amplification during the data processing are log functions, the brightness B 0 of the image can be described as Bo = log CJ + 2 log Po -4a(X + L) + log K (4) If aa(t) and .1a(t) represent the change in backscatter and attenuation coefficients, respectively, the backscatter I, from the volume element A in the presence of contrast media is I,(t) = [cr + acr(t)] (pcrlaX +fa +.6-a(l)JLJ )2 (5) or the signal S, at the receiver is S,(t) = K[a + aa(t)] <P2oe-4a(X+L> e-4Aa(tlL) (6) and the image brightness B,(t) is Bc<t> = log [a +Acr(t)] + 2 log Po-4a(X + L) -4.1a(t)…”