Page 267 - Computational Modeling in Biomedical Engineering and Medical Physics

256 Computational Modeling in Biomedical Engineering and Medical Physics

Figure 8.1 Qualitative view of the kidney, its vascularization, and the RF antenna: (A) medical scans
reconstruction; (B) and (C) CAD construct. RF, Radio frequency.

Murray, 1926) and the constructal law predictions (Bejan, 2000; Bejan and Zane,
2012). The arterial segment belongs to the group of resistance vessels, Fig. 8.2.
Kidneys filter the blood and regulate the arterial pressure. Arterial blood flows
through nephrons to glomeruli where tubules collect the toxins eventually drained
through the urine (NIH, 2019). The venous system returns the filtered blood. In
humans, depending on the resting heart rate, the whole content of the circulatory sys-
tem (B5 L for an adult) is filtered every 1/2 1 hour. The renal pelvis of the ureter,
comprising the calyces (cuplike extensions) that collect the urine before it flows on into
the urinary bladder, is considered here too, Fig. 8.1. Considering that the EMF expo-
sure lasts, perhaps, up to 10 min, on one hand, and for 1 L of filtered blood, B0.01 L
of urine is produced, on the other hand, the fluid loss to urine generation may be
neglected. Although it seems reasonable to assume that the volume fluid intake of the
renal pelvis is stagnant, it may however absorb some RF-produced heat. Consistent
with available experimental data, urine thermal properties are those of the water (ITIS,
2019; Putnam, 1971).