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heating of magnetite particles and heat-induced phase transition in the lipid membrane
(Katagiri, Nakamura, and Koumoto 2010). Selective heating of magnetic particles allows
maintaining low bulk temperatures outside the target region (McGill et al. 2009). As an
example, cytotoxicity of magnetic paclitaxel nanoparticles (MPNPs) against glioma was
studied in glioma-bearing rats. After intravenous injection and magnetic targeting with
a 500 mT magnet, drug content in glioma and its antitumor activity was increased, and
hence, the advantage of magnetic targeting for local chemotherapy of malignant glioma
was demonstrated (Zhao et al. 2010).
Superparamagnetic nanoparticles encapsulated in aerosols and guided by external
magnetic fields were also applied to treat lung carcinomas (Hallmark et al. 2010). With
these, drug-carrying magnetic aerosols were delivered through pulmonary pathways
directly to the tumor cells. This allowed drug deposition only in target cells, while
healthy lung regions remained unaltered and consequently protected from side effects
(Dahmani et al. 2009).
6.2.4 Magnetic Navigation
Magnetic navigation systems consist of two external electromagnets placed on opposite
sides of the patient, which guide, for example, an ablation catheter. A small magnet at its
tip allows navigating it to the target area, for example, in the heart. The accuracy of this
procedure is higher than that with manual navigation (Chen et al. 2010).
The development of magnetically controlled medical devices (e.g., catheters) and
anchored intracorporal surgical instruments, retractors, and cameras have helped
advance surgical practice. Magnetic anchoring guidance systems (MAGS) are composed
of an internal surgical instrument controlled by an external handheld magnet. Because
they do not require a dedicated surgical port, invasiveness is reduced. The application
of a swallowable pill camera used also in capsule endoscopy results in fewer instrument
collisions, improves surgical working space, and provides an image comparable to that
in standard laparoscopy. Therefore, the use of MAGS has further enhanced the use of
minimally invasive techniques.
As an example, it allows meeting or exceeding the benefits of current-day fixed-trocar
laparoscopy (Cadeddu et al. 2009; Scott and Cadeddu 2009). It allows reducing the number of transabdominal trocars to a single site and thus minimizing surgery invasiveness
of laparoscopic surgery to a single port.
6.2.5 Electronic Implants
Due to the position of electronic implants inside the body and hence because of their
immediate contact to tissue, active electronic implants may lead to different kinds of tissue exposure to EMF. This exposure may be generated for the following reasons:
• Direct exposure to ELF and/or direct current (DC) magnetic fields generated during operation by internal electric currents
• Exposure to RF EMF continuous transmission of energy via transmitting coils
placed on the body surface and exposing the interjacent tissue