Arrival time parametric imaging: A new ultrasound technique for quantifying perfusion of kidney grafts

Purpose: Evaluation of a new standardised ultrasound (US) technique for diagnosis of acute rejection of kidney grafts. Materials and Methods: Twenty-two kidney recipients underwent US examination following administration of 1.6 ml US contrast medium (USCM, SonoVue (TM)) 6 days after kidney transplantation. The examinations were performed with the Aplio US system (Toshiba (TM)). The difference in time to the first increase in signal intensity between the renal artery and the renal cortex was determined. Subsequently, the temporal course of contrast enhancement in the area of the renal artery following the first peak was recorded over 10 sec and depicted in colour using a Windows-based software. The resulting colour-time-images were evaluated by three readers who rated the images on an analogue scale from 1 (normal) to 5 (abnormal). Results: 12 of the 22 patients had an uneventful clinical course. US demonstrated rapid inflow of the USCM into the renal cortex. The calculated time difference was 1.0 +/- 0.4 sec. The score assigned to the parametric images was 1.7 +/- 0.8. 8 of the 22 patients underwent biopsy and showed histologically proven rejection. The time difference in the rejection group was twice as high as in the normal group (2.2 +/- 0.7 sec, p < 0.05). The scores were in the abnormal range (3.7 +/- 1.6, p < 0.05). Two patients with perirenal haematoma also had high scores, without rejection. Conclusions: Acute rejection and perirenal haematoma are associated with a delayed signal increase in the renal cortex. This information can be provided with a single image with standardised colour display of the temporal course of USCM inflow.