Contrast-enhanced, real-time volumetric imaging of tissue perfusion

Although conventional contrast-enhanced harmonic US imaging is typically employed in subjective assessments, quantitative analysis is not widely performed. We have been developing a 3D mapping technique that may offer such assessment by recording transient changes in backscatter over a volume during controlled constant infusion of contrast. Unlike perfusion-refill techniques, the approach does not require pulse-inversion imaging, nor does it perform bubble destruction using a high-intensity pulse. The goal of the present study is to correlate the method with a gold-standard in vivo. Experiments were performed in 20 rabbits during intravenous infusion of Definity^® before and after unilateral testicular torsion and contralateral orchiopexy. The use of the testicular model allowed the unconstricted testicle to serve as a control. The degree of torsion was 0° in 4 (sham surgery), 180° in 4, 360° in 4, 540° in 4, and 720° in 4. Signals were recorded using a 3D imaging array and analyzed offline. For comparison radiolabeled microsphere measurements, an accepted reference standard, were also acquired. Correlation of all US testicular signal intensity ratios versus all radiolabeled microsphere perfusion ratios demonstrated a correlation coefficient of .79 (p <; 0.0001), while postoperative values revealed a coefficient of .90 (p <; 0.0001).