Page 178 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

176 CHAPTER 7 Application of magnetic and electric fields for cancer therapy

significant and limited to tumor surface (less than 3.2% of tumor thickness, about
0.314 mm for 50 nm MDCs). This is because in absence of external magnet the dif-
fusion is single penetration mechanism and also MDCs diffusion coefficient in endo-
thelium layer and tumor tissue is low and also decreases as MDCs become greater.
Furthermore, for MDCs greater than 50 nm, the penetration depth increases exponen-
tially as the external magnet flux density (B) increases. However, the external magnet
flux density increases from 0 to 3 T, penetration depth of 250 and 345 nm MDCs
multiplied about 56 and 90, respectively. This means that the magnetic penetration
becomes dominant penetration mechanism as external magnet becomes strong. This
is due to the magnetic field intensity (H), and so magnetic force acting upon the
MDCs increases as the external magnet flux density (B ) increases.
0
Also it is observed that the penetration depth of 345 nm MDCs is about 10 times
of 50 nm MDCs while external magnet flux density is 2 T. This means that the greater
MDCs are more penetrative while strong external magnet is applied. This is because
magnetic force acting on the MDCs exponentially increases as MDCs radius increases.
Also the DMCs reached into the whole tumor as well as the concentration of great MDCs
is high. This result provides the better drug delivery with minimum side effects [ paper].
Figs. 7.10 and 7.11 represent the time variation of MDCs penetration depth with-
out and with external magnet, respectively.

FIGURE 7.10 MDCs penetration depth in the absence of external magnet (porosity = 0.3,
z = 5 mm).