Comparison of standard and second harmonic B-mode sonography in the detection of segmental renal infarction with sonographic contrast in a rabbit model

This study compares contrast-enhanced fundamental and second harmonic B-mode sonography using a rabbit renal infarct model. Segmental renal infarctions were produced in 13 rabbits by embolizing a 0.7 mm bead into the renal artery 1 day prior to imaging. An ultrasonographic unit equipped with an L10-5 transducer and second harmonic imaging capability was used. Real-time recordings were made during the injection of 0.5 ml of an experimental formulation of a perfluorohexane vapor-stabilized microbubble (AF0145) given into the ear vein, and the imaging technique alternated between standard and harmonic imaging every 20 s. Each rabbit received two injections 1 h apart. To control for the effect of peak bolus enhancement, the initial imaging technique used for the first injection was randomized, and the other technique was used initially for the second injection. The videointensity difference between the infarcted and the normal cortex was then calculated and evaluated as a function of time. The infarcted segment could not be seen before administration of contrast agent with either technique. Although the infarction could be seen after injection of contrast agent with either technique, image contrast and contrast duration were nearly 75% greater for the harmonic technique than for the standard technique. AF0145 allows the visualization of segmental renal infarction on standard B-mode imaging. The second harmonic B-mode technique significantly increases image contrast and contrast duration.