Page 169 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

7.5 Hyperthermia 167

7.5.1 The application of MNPs in hyperthermia therapy
The activation of MNPs by an alternating magnetic field (AMF) is currently being
explored as a technique for targeted therapeutic heating of tumors. Various types of
superparamagnetic and ferromagnetic particles, with different coatings and targeting
agents, allow for tumor site and type specificity [25]. Alternative magnetic fields are
among the methods, such as ultrasound, radio waves, microwave waves, and infrared
waves that generate the needed heat for hyperthermia treatment. MNP hyperthermia is
also being studied as an adjuvant to conventional chemotherapy and radiation therapy.
In this method, the targeted cancerous tissue is heated by the induced electromag-
netic field. The rise in the body temperature during the MRI imaging is an example
of heat produced by electromagnetic field [26].
Hyperthermia like other medical treatments have some side effect for human
body. The most common limitation of conventional hyperthermia therapy is as fol-
lows [27]:
1. Increases the healthy tissue temperature as well
2. Does not raise the temperature high enough in areas with high blood flow or
thick tissue coverage
3. Penetration of the wave into the deep tissue is limited
To overcome the above-mentioned limitation, some MNPs are injected into the
targeted tissue during the hyperthermia therapy. The injected MNPs due to their
metallic base produce more heat in external magnetic field and increase the tempera-
ture of the tissue [23]. Ho et al. investigated the effect of the MNP injections on the
growth of the cancerous tumor in mice during the hyperthermia therapy [28]. They
reported that the patient’s recovery is much higher with nanoparticle injection com-
pare to without nanoparticle injection.

7.5.2 Sources of heat production in MNP
MNPs produce heat when they are placed in an alternative magnetic fields. The gen-
erated heat is the sum of the three sources; eddy current heat loss, the hysteresis loss
and the residual loss [29].
7.5.2.1 Eddy current heat loss
Based on electrical conductivity, alternative magnetic field produces electrical poten-
tial in MNPs. The produces electric potential creates electric vortex current at the
surface of the nanoparticles and then the vortex current is converted to eddy current
heat loss. The amount of the eddy current heat loss (P ) for spherical nanoparticles
e
is calculated by [30]:
π 2
2
2
P = × B d σ f 2 (7.21)
2
e 20 m Pe=π 20×Bm2d σf 2
2
The diameter of the nanoparticle is d, the conductivity of the nanoparticle is σ,
the frequency of the field is f, and the magnitude of the magnetic field induced in the