Page 191 - Computational Modeling in Biomedical Engineering and Medical Physics

180 Computational Modeling in Biomedical Engineering and Medical Physics

Figure 6.4 The magnetic drug is injected and eventually mixes with the blood. Uniform velocity
profiles at inlets, pressure uniform profile at the outlet and no-slip boundary conditions are set.

reconstruction, in the form of segmentation algorithms of ROIs (Osher and Sethian,
1988).
Stationary flow is relevant to the study of this mixing process as the MD injection
(at 1 m/s) concerns a vein, Fig. 6.4. Besides, the mixing length is apparently short
enough such that in B0.5 s (half of the cycle for 60 bpm flow dynamics) the MAF is
observed to materialize, Fig. 6.5 (Dobre, 2012).
The time scale of this mixing process is related to the size (caliber) of the vessel, the
injection flow rate and the blood flow rate. Here, the distance from the injection loca-
tion to the point where the MAF sets in is 5 6 times the hydraulic diameter of the ves-
sel, and the time scale is less than the cardiovascular period, that is, 1 s for 60 bpm.
More complex models, constructed, for instance, using fused computational domains
(Chapter 3: Computational Domains), may be of interest for more realistic, perhaps
patient-related evaluation. However, the outlining features of this mixing process are fairly
well presented by this 2D analysis, based on which it may be conjectured that the MD
(carried on by MNPs) and the blood may be modeled as a MAF in the circulatory system
of the ROI.

6.5 Magnetic drug targeting, from the blood vessel to the targeted
region
MNPs with usual dimensions less than 400 600 nm can protrude the walls of the
blood vessels walls into the adjacent tissue that contains the targeted ROI. MNPs with
characteristic size below 25 nm can also be used, but the smaller they are, the harder