Page 12 - Computational Modeling in Biomedical Engineering and Medical Physics

Preface xiii

are constructed using medical images or CADs. These are then Finite Element Method
(FEM)-discretized to become computational domains.

Modeling multidisciplinary processes and interactions
The cardiovascular system is a prominent subject. It balances complex linked electro-
mechanical processes and energy interactions that concur in ensuring the hemody-
namic flow. The electrical activity of the heart—action potentials traveling through
atria and ventricles—elicits the myocardium contraction and relaxation, which provide
the pressure field that drives the hemodynamic flow. From the nonlinear dynamics of
the excitable cardiac strand to the electric field diffusion through the thorax—that
charts the electrical activity of the heart measured noninvasively on the thorax
surface—numerical modeling is the evocative, insightful support of choice that predic-
tively complements the usual diagnosis of the cardiovascular system’s state and
condition.
More likely to be used as a first stage, expressive, general measurement principle,
bioimpedance (BI), may be used per se or complemented with several other techni-
ques, from surface plasmons to echography. BI measurements recast the complexity of
multiphysics processes into time series and signal spectra. It provides concise and
meaningful information that, sometimes, is difficult (if possible) to retrieve otherwise.
There is considerable interest in modeling the BI applied to monitor the cardiovascular
activity at the scale of the system, body, or parts of it, and “Gedanken” experiments
are key to understanding the physics insights perceived through a global, dynamic
quantity—an impedance.
Much attention is devoted to magnetic nanoparticles, useful in various processes—
separation and purification of cell and macromolecule, immunoassays, controlled drug
delivery, electromagnetic hyperthermia, magnetic resonance imaging, gene therapy,
etc. Magnetic drug targeting is among them, and selected models are discussed in the
context, to identify their potential and possible adverse effects.
Magnetic stimulation is used for noninvasive nerve stimulation, transcranial mag-
netic stimulation, motor evoked potentials, and neuropsychiatric applications.
Although its physics are simple, magnetic stimulation is still a sensitive procedure, as it
requires the precise location of the envisaged targeted region inside the body, good
focus strength of the magnetic stimulus, while minimizing its side effects. The knowl-
edge of the EMF stimuli distribution inside the body and the optimization of the mag-
netic applicators helps the progress of this medical procedure. Several analytic and
numerical models for the stimulation of peripheral nerves and the transcranial and
lumbar magnetic stimulation are presented. These add to some considerations on the
magnetotherapy known in physical therapy for its multiple curative effects and
reduced costs.