The "iodine-derived perfusion" model applied to abdominal tissues with high arterial vascularization: pancreas, kidney cortex, and hepatocellular carcinoma

We investigated the relationship between enhancement and perfusion of abdominal tissues with high arterial vascularization, testing the hypothesis that in pancreas, kidney cortex, and HCC the iodine accumulated be proportional to the fraction of cardiac output (CO).

Computed tomography perfusion scans (every 1.5 s, 40 frames) of 11 patients with HCC (aged 69 ± 9 years, 8 males) were retrospectively analysed. Regions of interest (ROIs) were drawn on aorta, HCC, pancreas, and kidney cortex. Perfusion was computed: (1) using the enhancement-to-time maximum slope (MS) method; and (2) based on the amount of iodine at the end of the bolus, when most of contrast is in the extravascular compartment. Consequently, the amount of iodine divided by total iodine injected represents the CO fraction perfusing the tissue encompassed by the ROI; this value multiplied by CO gives the "iodine-derived perfusion" as blood volume per unit of volume per unit of time.

Values of iodine-derived perfusion was related with that computed from the MS method: iodine-derived perfusion (mL/s/mL) = 0.57 + 0.8 × MS perfusion (r2 = 0.82, P ≤ .001, Bland-Altman bias -0.01). Iodine-derived perfusion was 1.5 ± 0.3, 1.4 ± 0.5, and 2.7 ± 0.3 mL/s/mL while MS-derived perfusion was 1.1 ± 0.56, 1.3 ± 0.65, and 3.1 ± 0.91 mL/s/mL for HCC, pancreas, and kidney cortex, respectively. The results from the 2 methods were not different (P = .92). Kidney cortex perfusion was greater than those of HCC and pancreas (P ≤ .001).

Tissue enhancement in late arterial phase is well related to organ perfusion computed with the MS method.

CE in late arterial phase is a proxy for organ perfusion and can be expressed quantitatively if the amount of iodine injected is considered or cardiac output is estimated.